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Diffstat (limited to 'gcc/cp/constexpr.cc')
| -rw-r--r-- | gcc/cp/constexpr.cc | 9561 |
1 files changed, 9561 insertions, 0 deletions
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc new file mode 100644 index 0000000..d0da4a7 --- /dev/null +++ b/gcc/cp/constexpr.cc @@ -0,0 +1,9561 @@ +/* Perform -*- C++ -*- constant expression evaluation, including calls to + constexpr functions. These routines are used both during actual parsing + and during the instantiation of template functions. + + Copyright (C) 1998-2022 Free Software Foundation, Inc. + + This file is part of GCC. + + GCC is free software; you can redistribute it and/or modify it + under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3, or (at your option) + any later version. + + GCC is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING3. If not see +<http://www.gnu.org/licenses/>. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "cp-tree.h" +#include "varasm.h" +#include "c-family/c-objc.h" +#include "tree-iterator.h" +#include "gimplify.h" +#include "builtins.h" +#include "tree-inline.h" +#include "ubsan.h" +#include "gimple-fold.h" +#include "timevar.h" +#include "fold-const-call.h" +#include "stor-layout.h" +#include "cgraph.h" +#include "opts.h" +#include "stringpool.h" +#include "attribs.h" + +static bool verify_constant (tree, bool, bool *, bool *); +#define VERIFY_CONSTANT(X) \ +do { \ + if (verify_constant ((X), ctx->quiet, non_constant_p, overflow_p)) \ + return t; \ + } while (0) + +static HOST_WIDE_INT find_array_ctor_elt (tree ary, tree dindex, + bool insert = false); +static int array_index_cmp (tree key, tree index); + +/* Returns true iff FUN is an instantiation of a constexpr function + template or a defaulted constexpr function. */ + +bool +is_instantiation_of_constexpr (tree fun) +{ + return ((DECL_TEMPLOID_INSTANTIATION (fun) + && DECL_DECLARED_CONSTEXPR_P (DECL_TI_TEMPLATE (fun))) + || (DECL_DEFAULTED_FN (fun) + && DECL_DECLARED_CONSTEXPR_P (fun))); +} + +/* Return true if T is a literal type. */ + +bool +literal_type_p (tree t) +{ + if (SCALAR_TYPE_P (t) + || VECTOR_TYPE_P (t) + || TYPE_REF_P (t) + || (VOID_TYPE_P (t) && cxx_dialect >= cxx14)) + return true; + if (CLASS_TYPE_P (t)) + { + t = complete_type (t); + gcc_assert (COMPLETE_TYPE_P (t) || errorcount); + return CLASSTYPE_LITERAL_P (t); + } + if (TREE_CODE (t) == ARRAY_TYPE) + return literal_type_p (strip_array_types (t)); + return false; +} + +/* If DECL is a variable declared `constexpr', require its type + be literal. Return error_mark_node if we give an error, the + DECL otherwise. */ + +tree +ensure_literal_type_for_constexpr_object (tree decl) +{ + tree type = TREE_TYPE (decl); + if (VAR_P (decl) + && (DECL_DECLARED_CONSTEXPR_P (decl) + || var_in_constexpr_fn (decl)) + && !processing_template_decl) + { + tree stype = strip_array_types (type); + if (CLASS_TYPE_P (stype) && !COMPLETE_TYPE_P (complete_type (stype))) + /* Don't complain here, we'll complain about incompleteness + when we try to initialize the variable. */; + else if (!literal_type_p (type)) + { + if (DECL_DECLARED_CONSTEXPR_P (decl)) + { + auto_diagnostic_group d; + error_at (DECL_SOURCE_LOCATION (decl), + "the type %qT of %<constexpr%> variable %qD " + "is not literal", type, decl); + explain_non_literal_class (type); + decl = error_mark_node; + } + else if (cxx_dialect < cxx23) + { + if (!is_instantiation_of_constexpr (current_function_decl)) + { + auto_diagnostic_group d; + error_at (DECL_SOURCE_LOCATION (decl), + "variable %qD of non-literal type %qT in " + "%<constexpr%> function only available with " + "%<-std=c++2b%> or %<-std=gnu++2b%>", decl, type); + explain_non_literal_class (type); + decl = error_mark_node; + } + cp_function_chain->invalid_constexpr = true; + } + } + else if (DECL_DECLARED_CONSTEXPR_P (decl) + && variably_modified_type_p (type, NULL_TREE)) + { + error_at (DECL_SOURCE_LOCATION (decl), + "%<constexpr%> variable %qD has variably-modified " + "type %qT", decl, type); + decl = error_mark_node; + } + } + return decl; +} + +struct constexpr_fundef_hasher : ggc_ptr_hash<constexpr_fundef> +{ + static hashval_t hash (const constexpr_fundef *); + static bool equal (const constexpr_fundef *, const constexpr_fundef *); +}; + +/* This table holds all constexpr function definitions seen in + the current translation unit. */ + +static GTY (()) hash_table<constexpr_fundef_hasher> *constexpr_fundef_table; + +/* Utility function used for managing the constexpr function table. + Return true if the entries pointed to by P and Q are for the + same constexpr function. */ + +inline bool +constexpr_fundef_hasher::equal (const constexpr_fundef *lhs, + const constexpr_fundef *rhs) +{ + return lhs->decl == rhs->decl; +} + +/* Utility function used for managing the constexpr function table. + Return a hash value for the entry pointed to by Q. */ + +inline hashval_t +constexpr_fundef_hasher::hash (const constexpr_fundef *fundef) +{ + return DECL_UID (fundef->decl); +} + +/* Return a previously saved definition of function FUN. */ + +constexpr_fundef * +retrieve_constexpr_fundef (tree fun) +{ + if (constexpr_fundef_table == NULL) + return NULL; + + constexpr_fundef fundef = { fun, NULL_TREE, NULL_TREE, NULL_TREE }; + return constexpr_fundef_table->find (&fundef); +} + +/* Check whether the parameter and return types of FUN are valid for a + constexpr function, and complain if COMPLAIN. */ + +bool +is_valid_constexpr_fn (tree fun, bool complain) +{ + bool ret = true; + + if (DECL_INHERITED_CTOR (fun) + && TREE_CODE (fun) == TEMPLATE_DECL) + { + ret = false; + if (complain) + error ("inherited constructor %qD is not %<constexpr%>", + DECL_INHERITED_CTOR (fun)); + } + else + { + for (tree parm = FUNCTION_FIRST_USER_PARM (fun); + parm != NULL_TREE; parm = TREE_CHAIN (parm)) + if (!literal_type_p (TREE_TYPE (parm))) + { + ret = false; + if (complain) + { + auto_diagnostic_group d; + error ("invalid type for parameter %d of %<constexpr%> " + "function %q+#D", DECL_PARM_INDEX (parm), fun); + explain_non_literal_class (TREE_TYPE (parm)); + } + } + } + + if (LAMBDA_TYPE_P (CP_DECL_CONTEXT (fun)) && cxx_dialect < cxx17) + { + ret = false; + if (complain) + inform (DECL_SOURCE_LOCATION (fun), + "lambdas are implicitly %<constexpr%> only in C++17 and later"); + } + else if (DECL_DESTRUCTOR_P (fun)) + { + if (cxx_dialect < cxx20) + { + ret = false; + if (complain) + error_at (DECL_SOURCE_LOCATION (fun), + "%<constexpr%> destructors only available" + " with %<-std=c++20%> or %<-std=gnu++20%>"); + } + } + else if (!DECL_CONSTRUCTOR_P (fun)) + { + tree rettype = TREE_TYPE (TREE_TYPE (fun)); + if (!literal_type_p (rettype)) + { + ret = false; + if (complain) + { + auto_diagnostic_group d; + error ("invalid return type %qT of %<constexpr%> function %q+D", + rettype, fun); + explain_non_literal_class (rettype); + } + } + + /* C++14 DR 1684 removed this restriction. */ + if (cxx_dialect < cxx14 + && DECL_NONSTATIC_MEMBER_FUNCTION_P (fun) + && !CLASSTYPE_LITERAL_P (DECL_CONTEXT (fun))) + { + ret = false; + if (complain) + { + auto_diagnostic_group d; + if (pedwarn (DECL_SOURCE_LOCATION (fun), OPT_Wpedantic, + "enclosing class of %<constexpr%> non-static" + " member function %q+#D is not a literal type", + fun)) + explain_non_literal_class (DECL_CONTEXT (fun)); + } + } + } + else if (CLASSTYPE_VBASECLASSES (DECL_CONTEXT (fun))) + { + ret = false; + if (complain) + error ("%q#T has virtual base classes", DECL_CONTEXT (fun)); + } + + return ret; +} + +/* Subroutine of build_data_member_initialization. MEMBER is a COMPONENT_REF + for a member of an anonymous aggregate, INIT is the initializer for that + member, and VEC_OUTER is the vector of constructor elements for the class + whose constructor we are processing. Add the initializer to the vector + and return true to indicate success. */ + +static bool +build_anon_member_initialization (tree member, tree init, + vec<constructor_elt, va_gc> **vec_outer) +{ + /* MEMBER presents the relevant fields from the inside out, but we need + to build up the initializer from the outside in so that we can reuse + previously built CONSTRUCTORs if this is, say, the second field in an + anonymous struct. So we use a vec as a stack. */ + auto_vec<tree, 2> fields; + do + { + fields.safe_push (TREE_OPERAND (member, 1)); + member = TREE_OPERAND (member, 0); + } + while (ANON_AGGR_TYPE_P (TREE_TYPE (member)) + && TREE_CODE (member) == COMPONENT_REF); + + /* VEC has the constructor elements vector for the context of FIELD. + If FIELD is an anonymous aggregate, we will push inside it. */ + vec<constructor_elt, va_gc> **vec = vec_outer; + tree field; + while (field = fields.pop(), + ANON_AGGR_TYPE_P (TREE_TYPE (field))) + { + tree ctor; + /* If there is already an outer constructor entry for the anonymous + aggregate FIELD, use it; otherwise, insert one. */ + if (vec_safe_is_empty (*vec) + || (*vec)->last().index != field) + { + ctor = build_constructor (TREE_TYPE (field), NULL); + CONSTRUCTOR_APPEND_ELT (*vec, field, ctor); + } + else + ctor = (*vec)->last().value; + vec = &CONSTRUCTOR_ELTS (ctor); + } + + /* Now we're at the innermost field, the one that isn't an anonymous + aggregate. Add its initializer to the CONSTRUCTOR and we're done. */ + gcc_assert (fields.is_empty()); + CONSTRUCTOR_APPEND_ELT (*vec, field, init); + + return true; +} + +/* Subroutine of build_constexpr_constructor_member_initializers. + The expression tree T represents a data member initialization + in a (constexpr) constructor definition. Build a pairing of + the data member with its initializer, and prepend that pair + to the existing initialization pair INITS. */ + +static bool +build_data_member_initialization (tree t, vec<constructor_elt, va_gc> **vec) +{ + tree member, init; + if (TREE_CODE (t) == CLEANUP_POINT_EXPR) + t = TREE_OPERAND (t, 0); + if (TREE_CODE (t) == EXPR_STMT) + t = TREE_OPERAND (t, 0); + if (t == error_mark_node) + return false; + if (TREE_CODE (t) == STATEMENT_LIST) + { + for (tree stmt : tsi_range (t)) + if (! build_data_member_initialization (stmt, vec)) + return false; + return true; + } + if (TREE_CODE (t) == CLEANUP_STMT) + { + /* We can't see a CLEANUP_STMT in a constructor for a literal class, + but we can in a constexpr constructor for a non-literal class. Just + ignore it; either all the initialization will be constant, in which + case the cleanup can't run, or it can't be constexpr. + Still recurse into CLEANUP_BODY. */ + return build_data_member_initialization (CLEANUP_BODY (t), vec); + } + if (TREE_CODE (t) == CONVERT_EXPR) + t = TREE_OPERAND (t, 0); + if (TREE_CODE (t) == INIT_EXPR + /* vptr initialization shows up as a MODIFY_EXPR. In C++14 we only + use what this function builds for cx_check_missing_mem_inits, and + assignment in the ctor body doesn't count. */ + || (cxx_dialect < cxx14 && TREE_CODE (t) == MODIFY_EXPR)) + { + member = TREE_OPERAND (t, 0); + init = break_out_target_exprs (TREE_OPERAND (t, 1)); + } + else if (TREE_CODE (t) == CALL_EXPR) + { + tree fn = get_callee_fndecl (t); + if (!fn || !DECL_CONSTRUCTOR_P (fn)) + /* We're only interested in calls to subobject constructors. */ + return true; + member = CALL_EXPR_ARG (t, 0); + /* We don't use build_cplus_new here because it complains about + abstract bases. Leaving the call unwrapped means that it has the + wrong type, but cxx_eval_constant_expression doesn't care. */ + init = break_out_target_exprs (t); + } + else if (TREE_CODE (t) == BIND_EXPR) + return build_data_member_initialization (BIND_EXPR_BODY (t), vec); + else + /* Don't add anything else to the CONSTRUCTOR. */ + return true; + if (INDIRECT_REF_P (member)) + member = TREE_OPERAND (member, 0); + if (TREE_CODE (member) == NOP_EXPR) + { + tree op = member; + STRIP_NOPS (op); + if (TREE_CODE (op) == ADDR_EXPR) + { + gcc_assert (same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (TREE_TYPE (op)), + TREE_TYPE (TREE_TYPE (member)))); + /* Initializing a cv-qualified member; we need to look through + the const_cast. */ + member = op; + } + else if (op == current_class_ptr + && (same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (TREE_TYPE (member)), + current_class_type))) + /* Delegating constructor. */ + member = op; + else + { + /* This is an initializer for an empty base; keep it for now so + we can check it in cxx_eval_bare_aggregate. */ + gcc_assert (is_empty_class (TREE_TYPE (TREE_TYPE (member)))); + } + } + if (TREE_CODE (member) == ADDR_EXPR) + member = TREE_OPERAND (member, 0); + if (TREE_CODE (member) == COMPONENT_REF) + { + tree aggr = TREE_OPERAND (member, 0); + if (TREE_CODE (aggr) == VAR_DECL) + /* Initializing a local variable, don't add anything. */ + return true; + if (TREE_CODE (aggr) != COMPONENT_REF) + /* Normal member initialization. */ + member = TREE_OPERAND (member, 1); + else if (ANON_AGGR_TYPE_P (TREE_TYPE (aggr))) + /* Initializing a member of an anonymous union. */ + return build_anon_member_initialization (member, init, vec); + else + /* We're initializing a vtable pointer in a base. Leave it as + COMPONENT_REF so we remember the path to get to the vfield. */ + gcc_assert (TREE_TYPE (member) == vtbl_ptr_type_node); + } + + /* Value-initialization can produce multiple initializers for the + same field; use the last one. */ + if (!vec_safe_is_empty (*vec) && (*vec)->last().index == member) + (*vec)->last().value = init; + else + CONSTRUCTOR_APPEND_ELT (*vec, member, init); + return true; +} + +/* Subroutine of check_constexpr_ctor_body_1 and constexpr_fn_retval. + In C++11 mode checks that the TYPE_DECLs in the BIND_EXPR_VARS of a + BIND_EXPR conform to 7.1.5/3/4 on typedef and alias declarations. */ + +static bool +check_constexpr_bind_expr_vars (tree t) +{ + gcc_assert (TREE_CODE (t) == BIND_EXPR); + + for (tree var = BIND_EXPR_VARS (t); var; var = DECL_CHAIN (var)) + if (TREE_CODE (var) == TYPE_DECL + && DECL_IMPLICIT_TYPEDEF_P (var) + && !LAMBDA_TYPE_P (TREE_TYPE (var))) + return false; + return true; +} + +/* Subroutine of check_constexpr_ctor_body. */ + +static bool +check_constexpr_ctor_body_1 (tree last, tree list) +{ + switch (TREE_CODE (list)) + { + case DECL_EXPR: + if (TREE_CODE (DECL_EXPR_DECL (list)) == USING_DECL + || TREE_CODE (DECL_EXPR_DECL (list)) == TYPE_DECL) + return true; + return false; + + case CLEANUP_POINT_EXPR: + return check_constexpr_ctor_body (last, TREE_OPERAND (list, 0), + /*complain=*/false); + + case BIND_EXPR: + if (!check_constexpr_bind_expr_vars (list) + || !check_constexpr_ctor_body (last, BIND_EXPR_BODY (list), + /*complain=*/false)) + return false; + return true; + + case USING_STMT: + case STATIC_ASSERT: + case DEBUG_BEGIN_STMT: + return true; + + default: + return false; + } +} + +/* Make sure that there are no statements after LAST in the constructor + body represented by LIST. */ + +bool +check_constexpr_ctor_body (tree last, tree list, bool complain) +{ + /* C++14 doesn't require a constexpr ctor to have an empty body. */ + if (cxx_dialect >= cxx14) + return true; + + bool ok = true; + if (TREE_CODE (list) == STATEMENT_LIST) + { + tree_stmt_iterator i = tsi_last (list); + for (; !tsi_end_p (i); tsi_prev (&i)) + { + tree t = tsi_stmt (i); + if (t == last) + break; + if (!check_constexpr_ctor_body_1 (last, t)) + { + ok = false; + break; + } + } + } + else if (list != last + && !check_constexpr_ctor_body_1 (last, list)) + ok = false; + if (!ok) + { + if (complain) + error ("%<constexpr%> constructor does not have empty body"); + DECL_DECLARED_CONSTEXPR_P (current_function_decl) = false; + } + return ok; +} + +/* V is a vector of constructor elements built up for the base and member + initializers of a constructor for TYPE. They need to be in increasing + offset order, which they might not be yet if TYPE has a primary base + which is not first in the base-clause or a vptr and at least one base + all of which are non-primary. */ + +static vec<constructor_elt, va_gc> * +sort_constexpr_mem_initializers (tree type, vec<constructor_elt, va_gc> *v) +{ + tree pri = CLASSTYPE_PRIMARY_BINFO (type); + tree field_type; + unsigned i; + constructor_elt *ce; + + if (pri) + field_type = BINFO_TYPE (pri); + else if (TYPE_CONTAINS_VPTR_P (type)) + field_type = vtbl_ptr_type_node; + else + return v; + + /* Find the element for the primary base or vptr and move it to the + beginning of the vec. */ + for (i = 0; vec_safe_iterate (v, i, &ce); ++i) + if (TREE_TYPE (ce->index) == field_type) + break; + + if (i > 0 && i < vec_safe_length (v)) + { + vec<constructor_elt, va_gc> &vref = *v; + constructor_elt elt = vref[i]; + for (; i > 0; --i) + vref[i] = vref[i-1]; + vref[0] = elt; + } + + return v; +} + +/* Build compile-time evalable representations of member-initializer list + for a constexpr constructor. */ + +static tree +build_constexpr_constructor_member_initializers (tree type, tree body) +{ + vec<constructor_elt, va_gc> *vec = NULL; + bool ok = true; + while (true) + switch (TREE_CODE (body)) + { + case MUST_NOT_THROW_EXPR: + case EH_SPEC_BLOCK: + body = TREE_OPERAND (body, 0); + break; + + case STATEMENT_LIST: + for (tree stmt : tsi_range (body)) + { + body = stmt; + if (TREE_CODE (body) == BIND_EXPR) + break; + } + break; + + case BIND_EXPR: + body = BIND_EXPR_BODY (body); + goto found; + + default: + gcc_unreachable (); + } + found: + if (TREE_CODE (body) == TRY_BLOCK) + { + body = TREE_OPERAND (body, 0); + if (TREE_CODE (body) == BIND_EXPR) + body = BIND_EXPR_BODY (body); + } + if (TREE_CODE (body) == CLEANUP_POINT_EXPR) + { + body = TREE_OPERAND (body, 0); + if (TREE_CODE (body) == EXPR_STMT) + body = TREE_OPERAND (body, 0); + if (TREE_CODE (body) == INIT_EXPR + && (same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (TREE_OPERAND (body, 0)), + current_class_type))) + { + /* Trivial copy. */ + return TREE_OPERAND (body, 1); + } + ok = build_data_member_initialization (body, &vec); + } + else if (TREE_CODE (body) == STATEMENT_LIST) + { + for (tree stmt : tsi_range (body)) + { + ok = build_data_member_initialization (stmt, &vec); + if (!ok) + break; + } + } + else if (EXPR_P (body)) + ok = build_data_member_initialization (body, &vec); + else + gcc_assert (errorcount > 0); + if (ok) + { + if (vec_safe_length (vec) > 0) + { + /* In a delegating constructor, return the target. */ + constructor_elt *ce = &(*vec)[0]; + if (ce->index == current_class_ptr) + { + body = ce->value; + vec_free (vec); + return body; + } + } + vec = sort_constexpr_mem_initializers (type, vec); + return build_constructor (type, vec); + } + else + return error_mark_node; +} + +/* We have an expression tree T that represents a call, either CALL_EXPR + or AGGR_INIT_EXPR. If the call is lexically to a named function, + retrun the _DECL for that function. */ + +static tree +get_function_named_in_call (tree t) +{ + tree fun = cp_get_callee (t); + if (fun && TREE_CODE (fun) == ADDR_EXPR + && TREE_CODE (TREE_OPERAND (fun, 0)) == FUNCTION_DECL) + fun = TREE_OPERAND (fun, 0); + return fun; +} + +/* Subroutine of check_constexpr_fundef. BODY is the body of a function + declared to be constexpr, or a sub-statement thereof. Returns the + return value if suitable, error_mark_node for a statement not allowed in + a constexpr function, or NULL_TREE if no return value was found. */ + +tree +constexpr_fn_retval (tree body) +{ + switch (TREE_CODE (body)) + { + case STATEMENT_LIST: + { + tree expr = NULL_TREE; + for (tree stmt : tsi_range (body)) + { + tree s = constexpr_fn_retval (stmt); + if (s == error_mark_node) + return error_mark_node; + else if (s == NULL_TREE) + /* Keep iterating. */; + else if (expr) + /* Multiple return statements. */ + return error_mark_node; + else + expr = s; + } + return expr; + } + + case RETURN_EXPR: + return break_out_target_exprs (TREE_OPERAND (body, 0)); + + case DECL_EXPR: + { + tree decl = DECL_EXPR_DECL (body); + if (TREE_CODE (decl) == USING_DECL + /* Accept __func__, __FUNCTION__, and __PRETTY_FUNCTION__. */ + || DECL_ARTIFICIAL (decl)) + return NULL_TREE; + return error_mark_node; + } + + case CLEANUP_POINT_EXPR: + return constexpr_fn_retval (TREE_OPERAND (body, 0)); + + case BIND_EXPR: + if (!check_constexpr_bind_expr_vars (body)) + return error_mark_node; + return constexpr_fn_retval (BIND_EXPR_BODY (body)); + + case USING_STMT: + case DEBUG_BEGIN_STMT: + return NULL_TREE; + + case CALL_EXPR: + { + tree fun = get_function_named_in_call (body); + if (fun != NULL_TREE + && fndecl_built_in_p (fun, BUILT_IN_UNREACHABLE)) + return NULL_TREE; + } + /* Fallthru. */ + + default: + return error_mark_node; + } +} + +/* Subroutine of check_constexpr_fundef. BODY is the DECL_SAVED_TREE of + FUN; do the necessary transformations to turn it into a single expression + that we can store in the hash table. */ + +static tree +massage_constexpr_body (tree fun, tree body) +{ + if (DECL_CONSTRUCTOR_P (fun)) + body = build_constexpr_constructor_member_initializers + (DECL_CONTEXT (fun), body); + else if (cxx_dialect < cxx14) + { + if (TREE_CODE (body) == EH_SPEC_BLOCK) + body = EH_SPEC_STMTS (body); + if (TREE_CODE (body) == MUST_NOT_THROW_EXPR) + body = TREE_OPERAND (body, 0); + body = constexpr_fn_retval (body); + } + return body; +} + +/* CTYPE is a type constructed from BODY. Return true if some + bases/fields are uninitialized, and complain if COMPLAIN. */ + +static bool +cx_check_missing_mem_inits (tree ctype, tree body, bool complain) +{ + /* We allow uninitialized bases/fields in C++20. */ + if (cxx_dialect >= cxx20) + return false; + + unsigned nelts = 0; + + if (body) + { + if (TREE_CODE (body) != CONSTRUCTOR) + return false; + nelts = CONSTRUCTOR_NELTS (body); + } + tree field = TYPE_FIELDS (ctype); + + if (TREE_CODE (ctype) == UNION_TYPE) + { + if (nelts == 0 && next_initializable_field (field)) + { + if (complain) + error ("%<constexpr%> constructor for union %qT must " + "initialize exactly one non-static data member", ctype); + return true; + } + return false; + } + + /* Iterate over the CONSTRUCTOR, checking any missing fields don't + need an explicit initialization. */ + bool bad = false; + for (unsigned i = 0; i <= nelts; ++i) + { + tree index = NULL_TREE; + if (i < nelts) + { + index = CONSTRUCTOR_ELT (body, i)->index; + /* Skip base and vtable inits. */ + if (TREE_CODE (index) != FIELD_DECL + || DECL_ARTIFICIAL (index)) + continue; + } + + for (; field != index; field = DECL_CHAIN (field)) + { + tree ftype; + if (TREE_CODE (field) != FIELD_DECL) + continue; + if (DECL_UNNAMED_BIT_FIELD (field)) + continue; + if (DECL_ARTIFICIAL (field)) + continue; + if (ANON_AGGR_TYPE_P (TREE_TYPE (field))) + { + /* Recurse to check the anonymous aggregate member. */ + bad |= cx_check_missing_mem_inits + (TREE_TYPE (field), NULL_TREE, complain); + if (bad && !complain) + return true; + continue; + } + ftype = TREE_TYPE (field); + if (!ftype || !TYPE_P (ftype) || !COMPLETE_TYPE_P (ftype)) + /* A flexible array can't be intialized here, so don't complain + that it isn't. */ + continue; + if (is_empty_field (field)) + /* An empty field doesn't need an initializer. */ + continue; + ftype = strip_array_types (ftype); + if (type_has_constexpr_default_constructor (ftype)) + { + /* It's OK to skip a member with a trivial constexpr ctor. + A constexpr ctor that isn't trivial should have been + added in by now. */ + gcc_checking_assert (!TYPE_HAS_COMPLEX_DFLT (ftype) + || errorcount != 0); + continue; + } + if (!complain) + return true; + auto_diagnostic_group d; + error ("member %qD must be initialized by mem-initializer " + "in %<constexpr%> constructor", field); + inform (DECL_SOURCE_LOCATION (field), "declared here"); + bad = true; + } + if (field == NULL_TREE) + break; + + if (ANON_AGGR_TYPE_P (TREE_TYPE (index))) + { + /* Check the anonymous aggregate initializer is valid. */ + bad |= cx_check_missing_mem_inits + (TREE_TYPE (index), CONSTRUCTOR_ELT (body, i)->value, complain); + if (bad && !complain) + return true; + } + field = DECL_CHAIN (field); + } + + return bad; +} + +/* We are processing the definition of the constexpr function FUN. + Check that its body fulfills the apropriate requirements and + enter it in the constexpr function definition table. */ + +void +maybe_save_constexpr_fundef (tree fun) +{ + if (processing_template_decl + || cp_function_chain->invalid_constexpr + || (DECL_CLONED_FUNCTION_P (fun) && !DECL_DELETING_DESTRUCTOR_P (fun))) + return; + + /* With -fimplicit-constexpr, try to make inlines constexpr. We'll + actually set DECL_DECLARED_CONSTEXPR_P below if the checks pass. */ + bool implicit = false; + if (flag_implicit_constexpr) + { + if (DECL_DELETING_DESTRUCTOR_P (fun) + && decl_implicit_constexpr_p (DECL_CLONED_FUNCTION (fun))) + /* Don't inherit implicit constexpr from the non-deleting + destructor. */ + DECL_DECLARED_CONSTEXPR_P (fun) = false; + + if (!DECL_DECLARED_CONSTEXPR_P (fun) + && DECL_DECLARED_INLINE_P (fun) + && !lookup_attribute ("noinline", DECL_ATTRIBUTES (fun))) + implicit = true; + } + + if (!DECL_DECLARED_CONSTEXPR_P (fun) && !implicit) + return; + + bool complain = !DECL_GENERATED_P (fun) && !implicit; + + if (!is_valid_constexpr_fn (fun, complain)) + return; + + tree massaged = massage_constexpr_body (fun, DECL_SAVED_TREE (fun)); + if (massaged == NULL_TREE || massaged == error_mark_node) + { + if (!DECL_CONSTRUCTOR_P (fun) && complain) + error ("body of %<constexpr%> function %qD not a return-statement", + fun); + return; + } + + bool potential = potential_rvalue_constant_expression (massaged); + if (!potential && complain) + require_potential_rvalue_constant_expression (massaged); + + if (DECL_CONSTRUCTOR_P (fun) && potential) + { + if (cx_check_missing_mem_inits (DECL_CONTEXT (fun), + massaged, complain)) + potential = false; + else if (cxx_dialect > cxx11) + { + /* What we got from massage_constexpr_body is pretty much just the + ctor-initializer, also check the body. */ + massaged = DECL_SAVED_TREE (fun); + potential = potential_rvalue_constant_expression (massaged); + if (!potential && complain) + require_potential_rvalue_constant_expression (massaged); + } + } + + if (!potential && complain) + return; + + if (implicit) + { + if (potential) + { + DECL_DECLARED_CONSTEXPR_P (fun) = true; + DECL_LANG_SPECIFIC (fun)->u.fn.implicit_constexpr = true; + if (DECL_CONSTRUCTOR_P (fun)) + TYPE_HAS_CONSTEXPR_CTOR (DECL_CONTEXT (fun)) = true; + } + else + /* Don't bother keeping the pre-generic body of unsuitable functions + not explicitly declared constexpr. */ + return; + } + + constexpr_fundef entry = {fun, NULL_TREE, NULL_TREE, NULL_TREE}; + bool clear_ctx = false; + if (DECL_RESULT (fun) && DECL_CONTEXT (DECL_RESULT (fun)) == NULL_TREE) + { + clear_ctx = true; + DECL_CONTEXT (DECL_RESULT (fun)) = fun; + } + tree saved_fn = current_function_decl; + current_function_decl = fun; + entry.body = copy_fn (entry.decl, entry.parms, entry.result); + current_function_decl = saved_fn; + if (clear_ctx) + DECL_CONTEXT (DECL_RESULT (entry.decl)) = NULL_TREE; + if (!potential) + /* For a template instantiation, we want to remember the pre-generic body + for explain_invalid_constexpr_fn, but do tell cxx_eval_call_expression + that it doesn't need to bother trying to expand the function. */ + entry.result = error_mark_node; + + register_constexpr_fundef (entry); +} + +/* BODY is a validated and massaged definition of a constexpr + function. Register it in the hash table. */ + +void +register_constexpr_fundef (const constexpr_fundef &value) +{ + /* Create the constexpr function table if necessary. */ + if (constexpr_fundef_table == NULL) + constexpr_fundef_table + = hash_table<constexpr_fundef_hasher>::create_ggc (101); + + constexpr_fundef **slot = constexpr_fundef_table->find_slot + (const_cast<constexpr_fundef *> (&value), INSERT); + + gcc_assert (*slot == NULL); + *slot = ggc_alloc<constexpr_fundef> (); + **slot = value; +} + +/* FUN is a non-constexpr function called in a context that requires a + constant expression. If it comes from a constexpr template, explain why + the instantiation isn't constexpr. */ + +void +explain_invalid_constexpr_fn (tree fun) +{ + static hash_set<tree> *diagnosed; + tree body; + /* Only diagnose defaulted functions, lambdas, or instantiations. */ + if (!DECL_DEFAULTED_FN (fun) + && !LAMBDA_TYPE_P (CP_DECL_CONTEXT (fun)) + && !is_instantiation_of_constexpr (fun)) + { + inform (DECL_SOURCE_LOCATION (fun), "%qD declared here", fun); + return; + } + if (diagnosed == NULL) + diagnosed = new hash_set<tree>; + if (diagnosed->add (fun)) + /* Already explained. */ + return; + + iloc_sentinel ils = input_location; + if (!lambda_static_thunk_p (fun)) + { + /* Diagnostics should completely ignore the static thunk, so leave + input_location set to our caller's location. */ + input_location = DECL_SOURCE_LOCATION (fun); + inform (input_location, + "%qD is not usable as a %<constexpr%> function because:", fun); + } + /* First check the declaration. */ + if (is_valid_constexpr_fn (fun, true)) + { + /* Then if it's OK, the body. */ + if (!DECL_DECLARED_CONSTEXPR_P (fun) + && DECL_DEFAULTED_FN (fun)) + explain_implicit_non_constexpr (fun); + else + { + if (constexpr_fundef *fd = retrieve_constexpr_fundef (fun)) + body = fd->body; + else + body = DECL_SAVED_TREE (fun); + body = massage_constexpr_body (fun, body); + require_potential_rvalue_constant_expression (body); + if (DECL_CONSTRUCTOR_P (fun)) + cx_check_missing_mem_inits (DECL_CONTEXT (fun), body, true); + } + } +} + +/* Objects of this type represent calls to constexpr functions + along with the bindings of parameters to their arguments, for + the purpose of compile time evaluation. */ + +struct GTY((for_user)) constexpr_call { + /* Description of the constexpr function definition. */ + constexpr_fundef *fundef; + /* Parameter bindings environment. A TREE_VEC of arguments. */ + tree bindings; + /* Result of the call. + NULL means the call is being evaluated. + error_mark_node means that the evaluation was erroneous; + otherwise, the actuall value of the call. */ + tree result; + /* The hash of this call; we remember it here to avoid having to + recalculate it when expanding the hash table. */ + hashval_t hash; + /* Whether __builtin_is_constant_evaluated() should evaluate to true. */ + bool manifestly_const_eval; +}; + +struct constexpr_call_hasher : ggc_ptr_hash<constexpr_call> +{ + static hashval_t hash (constexpr_call *); + static bool equal (constexpr_call *, constexpr_call *); +}; + +enum constexpr_switch_state { + /* Used when processing a switch for the first time by cxx_eval_switch_expr + and default: label for that switch has not been seen yet. */ + css_default_not_seen, + /* Used when processing a switch for the first time by cxx_eval_switch_expr + and default: label for that switch has been seen already. */ + css_default_seen, + /* Used when processing a switch for the second time by + cxx_eval_switch_expr, where default: label should match. */ + css_default_processing +}; + +/* The constexpr expansion context part which needs one instance per + cxx_eval_outermost_constant_expr invocation. VALUES is a map of values of + variables initialized within the expression. */ + +struct constexpr_global_ctx { + /* Values for any temporaries or local variables within the + constant-expression. */ + hash_map<tree,tree> values; + /* Number of cxx_eval_constant_expression calls (except skipped ones, + on simple constants or location wrappers) encountered during current + cxx_eval_outermost_constant_expr call. */ + HOST_WIDE_INT constexpr_ops_count; + /* Heap VAR_DECLs created during the evaluation of the outermost constant + expression. */ + auto_vec<tree, 16> heap_vars; + /* Cleanups that need to be evaluated at the end of CLEANUP_POINT_EXPR. */ + vec<tree> *cleanups; + /* Number of heap VAR_DECL deallocations. */ + unsigned heap_dealloc_count; + /* Constructor. */ + constexpr_global_ctx () + : constexpr_ops_count (0), cleanups (NULL), heap_dealloc_count (0) {} +}; + +/* The constexpr expansion context. CALL is the current function + expansion, CTOR is the current aggregate initializer, OBJECT is the + object being initialized by CTOR, either a VAR_DECL or a _REF. */ + +struct constexpr_ctx { + /* The part of the context that needs to be unique to the whole + cxx_eval_outermost_constant_expr invocation. */ + constexpr_global_ctx *global; + /* The innermost call we're evaluating. */ + constexpr_call *call; + /* SAVE_EXPRs and TARGET_EXPR_SLOT vars of TARGET_EXPRs that we've seen + within the current LOOP_EXPR. NULL if we aren't inside a loop. */ + vec<tree> *save_exprs; + /* The CONSTRUCTOR we're currently building up for an aggregate + initializer. */ + tree ctor; + /* The object we're building the CONSTRUCTOR for. */ + tree object; + /* If inside SWITCH_EXPR. */ + constexpr_switch_state *css_state; + /* The aggregate initialization context inside which this one is nested. This + is used by lookup_placeholder to resolve PLACEHOLDER_EXPRs. */ + const constexpr_ctx *parent; + + /* Whether we should error on a non-constant expression or fail quietly. + This flag needs to be here, but some of the others could move to global + if they get larger than a word. */ + bool quiet; + /* Whether we are strictly conforming to constant expression rules or + trying harder to get a constant value. */ + bool strict; + /* Whether __builtin_is_constant_evaluated () should be true. */ + bool manifestly_const_eval; +}; + +/* This internal flag controls whether we should avoid doing anything during + constexpr evaluation that would cause extra DECL_UID generation, such as + template instantiation and function body copying. */ + +static bool uid_sensitive_constexpr_evaluation_value; + +/* An internal counter that keeps track of the number of times + uid_sensitive_constexpr_evaluation_p returned true. */ + +static unsigned uid_sensitive_constexpr_evaluation_true_counter; + +/* The accessor for uid_sensitive_constexpr_evaluation_value which also + increments the corresponding counter. */ + +static bool +uid_sensitive_constexpr_evaluation_p () +{ + if (uid_sensitive_constexpr_evaluation_value) + { + ++uid_sensitive_constexpr_evaluation_true_counter; + return true; + } + else + return false; +} + +/* The default constructor for uid_sensitive_constexpr_evaluation_sentinel + enables the internal flag for uid_sensitive_constexpr_evaluation_p + during the lifetime of the sentinel object. Upon its destruction, the + previous value of uid_sensitive_constexpr_evaluation_p is restored. */ + +uid_sensitive_constexpr_evaluation_sentinel +::uid_sensitive_constexpr_evaluation_sentinel () + : ovr (uid_sensitive_constexpr_evaluation_value, true) +{ +} + +/* The default constructor for uid_sensitive_constexpr_evaluation_checker + records the current number of times that uid_sensitive_constexpr_evaluation_p + has been called and returned true. */ + +uid_sensitive_constexpr_evaluation_checker +::uid_sensitive_constexpr_evaluation_checker () + : saved_counter (uid_sensitive_constexpr_evaluation_true_counter) +{ +} + +/* Returns true iff uid_sensitive_constexpr_evaluation_p is true, and + some constexpr evaluation was restricted due to u_s_c_e_p being called + and returning true during the lifetime of this checker object. */ + +bool +uid_sensitive_constexpr_evaluation_checker::evaluation_restricted_p () const +{ + return (uid_sensitive_constexpr_evaluation_value + && saved_counter != uid_sensitive_constexpr_evaluation_true_counter); +} + + +/* A table of all constexpr calls that have been evaluated by the + compiler in this translation unit. */ + +static GTY (()) hash_table<constexpr_call_hasher> *constexpr_call_table; + +static tree cxx_eval_constant_expression (const constexpr_ctx *, tree, + bool, bool *, bool *, tree * = NULL); + +/* Compute a hash value for a constexpr call representation. */ + +inline hashval_t +constexpr_call_hasher::hash (constexpr_call *info) +{ + return info->hash; +} + +/* Return true if the objects pointed to by P and Q represent calls + to the same constexpr function with the same arguments. + Otherwise, return false. */ + +bool +constexpr_call_hasher::equal (constexpr_call *lhs, constexpr_call *rhs) +{ + if (lhs == rhs) + return true; + if (lhs->hash != rhs->hash) + return false; + if (lhs->manifestly_const_eval != rhs->manifestly_const_eval) + return false; + if (!constexpr_fundef_hasher::equal (lhs->fundef, rhs->fundef)) + return false; + return cp_tree_equal (lhs->bindings, rhs->bindings); +} + +/* Initialize the constexpr call table, if needed. */ + +static void +maybe_initialize_constexpr_call_table (void) +{ + if (constexpr_call_table == NULL) + constexpr_call_table = hash_table<constexpr_call_hasher>::create_ggc (101); +} + +/* During constexpr CALL_EXPR evaluation, to avoid issues with sharing when + a function happens to get called recursively, we unshare the callee + function's body and evaluate this unshared copy instead of evaluating the + original body. + + FUNDEF_COPIES_TABLE is a per-function freelist of these unshared function + copies. The underlying data structure of FUNDEF_COPIES_TABLE is a hash_map + that's keyed off of the original FUNCTION_DECL and whose value is a + TREE_LIST of this function's unused copies awaiting reuse. + + This is not GC-deletable to avoid GC affecting UID generation. */ + +static GTY(()) decl_tree_map *fundef_copies_table; + +/* Reuse a copy or create a new unshared copy of the function FUN. + Return this copy. We use a TREE_LIST whose PURPOSE is body, VALUE + is parms, TYPE is result. */ + +static tree +get_fundef_copy (constexpr_fundef *fundef) +{ + tree copy; + bool existed; + tree *slot = &(hash_map_safe_get_or_insert<hm_ggc> + (fundef_copies_table, fundef->decl, &existed, 127)); + + if (!existed) + { + /* There is no cached function available, or in use. We can use + the function directly. That the slot is now created records + that this function is now in use. */ + copy = build_tree_list (fundef->body, fundef->parms); + TREE_TYPE (copy) = fundef->result; + } + else if (*slot == NULL_TREE) + { + if (uid_sensitive_constexpr_evaluation_p ()) + return NULL_TREE; + + /* We've already used the function itself, so make a copy. */ + copy = build_tree_list (NULL, NULL); + tree saved_body = DECL_SAVED_TREE (fundef->decl); + tree saved_parms = DECL_ARGUMENTS (fundef->decl); + tree saved_result = DECL_RESULT (fundef->decl); + tree saved_fn = current_function_decl; + DECL_SAVED_TREE (fundef->decl) = fundef->body; + DECL_ARGUMENTS (fundef->decl) = fundef->parms; + DECL_RESULT (fundef->decl) = fundef->result; + current_function_decl = fundef->decl; + TREE_PURPOSE (copy) = copy_fn (fundef->decl, TREE_VALUE (copy), + TREE_TYPE (copy)); + current_function_decl = saved_fn; + DECL_RESULT (fundef->decl) = saved_result; + DECL_ARGUMENTS (fundef->decl) = saved_parms; + DECL_SAVED_TREE (fundef->decl) = saved_body; + } + else + { + /* We have a cached function available. */ + copy = *slot; + *slot = TREE_CHAIN (copy); + } + + return copy; +} + +/* Save the copy COPY of function FUN for later reuse by + get_fundef_copy(). By construction, there will always be an entry + to find. */ + +static void +save_fundef_copy (tree fun, tree copy) +{ + tree *slot = fundef_copies_table->get (fun); + TREE_CHAIN (copy) = *slot; + *slot = copy; +} + +/* We have an expression tree T that represents a call, either CALL_EXPR + or AGGR_INIT_EXPR. Return the Nth argument. */ + +static inline tree +get_nth_callarg (tree t, int n) +{ + switch (TREE_CODE (t)) + { + case CALL_EXPR: + return CALL_EXPR_ARG (t, n); + + case AGGR_INIT_EXPR: + return AGGR_INIT_EXPR_ARG (t, n); + + default: + gcc_unreachable (); + return NULL; + } +} + +/* Attempt to evaluate T which represents a call to a builtin function. + We assume here that all builtin functions evaluate to scalar types + represented by _CST nodes. */ + +static tree +cxx_eval_builtin_function_call (const constexpr_ctx *ctx, tree t, tree fun, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + const int nargs = call_expr_nargs (t); + tree *args = (tree *) alloca (nargs * sizeof (tree)); + tree new_call; + int i; + + /* Don't fold __builtin_constant_p within a constexpr function. */ + bool bi_const_p = DECL_IS_BUILTIN_CONSTANT_P (fun); + + /* If we aren't requiring a constant expression, defer __builtin_constant_p + in a constexpr function until we have values for the parameters. */ + if (bi_const_p + && !ctx->manifestly_const_eval + && current_function_decl + && DECL_DECLARED_CONSTEXPR_P (current_function_decl)) + { + *non_constant_p = true; + return t; + } + + /* For __builtin_is_constant_evaluated, defer it if not + ctx->manifestly_const_eval (as sometimes we try to constant evaluate + without manifestly_const_eval even expressions or parts thereof which + will later be manifestly const_eval evaluated), otherwise fold it to + true. */ + if (fndecl_built_in_p (fun, CP_BUILT_IN_IS_CONSTANT_EVALUATED, + BUILT_IN_FRONTEND)) + { + if (!ctx->manifestly_const_eval) + { + *non_constant_p = true; + return t; + } + return boolean_true_node; + } + + if (fndecl_built_in_p (fun, CP_BUILT_IN_SOURCE_LOCATION, BUILT_IN_FRONTEND)) + { + temp_override<tree> ovr (current_function_decl); + if (ctx->call && ctx->call->fundef) + current_function_decl = ctx->call->fundef->decl; + return fold_builtin_source_location (EXPR_LOCATION (t)); + } + + int strops = 0; + int strret = 0; + if (fndecl_built_in_p (fun, BUILT_IN_NORMAL)) + switch (DECL_FUNCTION_CODE (fun)) + { + case BUILT_IN_STRLEN: + case BUILT_IN_STRNLEN: + strops = 1; + break; + case BUILT_IN_MEMCHR: + case BUILT_IN_STRCHR: + case BUILT_IN_STRRCHR: + strops = 1; + strret = 1; + break; + case BUILT_IN_MEMCMP: + case BUILT_IN_STRCMP: + strops = 2; + break; + case BUILT_IN_STRSTR: + strops = 2; + strret = 1; + break; + case BUILT_IN_ASAN_POINTER_COMPARE: + case BUILT_IN_ASAN_POINTER_SUBTRACT: + /* These builtins shall be ignored during constant expression + evaluation. */ + return void_node; + default: + break; + } + + /* Be permissive for arguments to built-ins; __builtin_constant_p should + return constant false for a non-constant argument. */ + constexpr_ctx new_ctx = *ctx; + new_ctx.quiet = true; + for (i = 0; i < nargs; ++i) + { + tree arg = CALL_EXPR_ARG (t, i); + tree oarg = arg; + + /* To handle string built-ins we need to pass ADDR_EXPR<STRING_CST> since + expand_builtin doesn't know how to look in the values table. */ + bool strop = i < strops; + if (strop) + { + STRIP_NOPS (arg); + if (TREE_CODE (arg) == ADDR_EXPR) + arg = TREE_OPERAND (arg, 0); + else + strop = false; + } + + /* If builtin_valid_in_constant_expr_p is true, + potential_constant_expression_1 has not recursed into the arguments + of the builtin, verify it here. */ + if (!builtin_valid_in_constant_expr_p (fun) + || potential_constant_expression (arg)) + { + bool dummy1 = false, dummy2 = false; + arg = cxx_eval_constant_expression (&new_ctx, arg, false, + &dummy1, &dummy2); + } + + if (bi_const_p) + /* For __builtin_constant_p, fold all expressions with constant values + even if they aren't C++ constant-expressions. */ + arg = cp_fold_rvalue (arg); + else if (strop) + { + if (TREE_CODE (arg) == CONSTRUCTOR) + arg = braced_lists_to_strings (TREE_TYPE (arg), arg); + if (TREE_CODE (arg) == STRING_CST) + arg = build_address (arg); + else + arg = oarg; + } + + args[i] = arg; + } + + bool save_ffbcp = force_folding_builtin_constant_p; + force_folding_builtin_constant_p |= ctx->manifestly_const_eval; + tree save_cur_fn = current_function_decl; + /* Return name of ctx->call->fundef->decl for __builtin_FUNCTION (). */ + if (fndecl_built_in_p (fun, BUILT_IN_FUNCTION) + && ctx->call + && ctx->call->fundef) + current_function_decl = ctx->call->fundef->decl; + if (fndecl_built_in_p (fun, + CP_BUILT_IN_IS_POINTER_INTERCONVERTIBLE_WITH_CLASS, + BUILT_IN_FRONTEND)) + { + location_t loc = EXPR_LOCATION (t); + if (nargs >= 1) + VERIFY_CONSTANT (args[0]); + new_call + = fold_builtin_is_pointer_inverconvertible_with_class (loc, nargs, + args); + } + else if (fndecl_built_in_p (fun, + CP_BUILT_IN_IS_CORRESPONDING_MEMBER, + BUILT_IN_FRONTEND)) + { + location_t loc = EXPR_LOCATION (t); + if (nargs >= 2) + { + VERIFY_CONSTANT (args[0]); + VERIFY_CONSTANT (args[1]); + } + new_call = fold_builtin_is_corresponding_member (loc, nargs, args); + } + else + new_call = fold_builtin_call_array (EXPR_LOCATION (t), TREE_TYPE (t), + CALL_EXPR_FN (t), nargs, args); + current_function_decl = save_cur_fn; + force_folding_builtin_constant_p = save_ffbcp; + if (new_call == NULL) + { + if (!*non_constant_p && !ctx->quiet) + { + /* Do not allow__builtin_unreachable in constexpr function. + The __builtin_unreachable call with BUILTINS_LOCATION + comes from cp_maybe_instrument_return. */ + if (fndecl_built_in_p (fun, BUILT_IN_UNREACHABLE) + && EXPR_LOCATION (t) == BUILTINS_LOCATION) + error ("%<constexpr%> call flows off the end of the function"); + else + { + new_call = build_call_array_loc (EXPR_LOCATION (t), TREE_TYPE (t), + CALL_EXPR_FN (t), nargs, args); + error ("%q+E is not a constant expression", new_call); + } + } + *non_constant_p = true; + return t; + } + + if (!potential_constant_expression (new_call)) + { + if (!*non_constant_p && !ctx->quiet) + error ("%q+E is not a constant expression", new_call); + *non_constant_p = true; + return t; + } + + if (strret) + { + /* memchr returns a pointer into the first argument, but we replaced the + argument above with a STRING_CST; put it back it now. */ + tree op = CALL_EXPR_ARG (t, strret-1); + STRIP_NOPS (new_call); + if (TREE_CODE (new_call) == POINTER_PLUS_EXPR) + TREE_OPERAND (new_call, 0) = op; + else if (TREE_CODE (new_call) == ADDR_EXPR) + new_call = op; + } + + return cxx_eval_constant_expression (&new_ctx, new_call, lval, + non_constant_p, overflow_p); +} + +/* TEMP is the constant value of a temporary object of type TYPE. Adjust + the type of the value to match. */ + +static tree +adjust_temp_type (tree type, tree temp) +{ + if (same_type_p (TREE_TYPE (temp), type)) + return temp; + /* Avoid wrapping an aggregate value in a NOP_EXPR. */ + if (TREE_CODE (temp) == CONSTRUCTOR) + { + /* build_constructor wouldn't retain various CONSTRUCTOR flags. */ + tree t = copy_node (temp); + TREE_TYPE (t) = type; + return t; + } + if (TREE_CODE (temp) == EMPTY_CLASS_EXPR) + return build0 (EMPTY_CLASS_EXPR, type); + gcc_assert (scalarish_type_p (type)); + /* Now we know we're dealing with a scalar, and a prvalue of non-class + type is cv-unqualified. */ + return cp_fold_convert (cv_unqualified (type), temp); +} + +/* If T is a CONSTRUCTOR, return an unshared copy of T and any + sub-CONSTRUCTORs. Otherwise return T. + + We use this whenever we initialize an object as a whole, whether it's a + parameter, a local variable, or a subobject, so that subsequent + modifications don't affect other places where it was used. */ + +tree +unshare_constructor (tree t MEM_STAT_DECL) +{ + if (!t || TREE_CODE (t) != CONSTRUCTOR) + return t; + auto_vec <tree*, 4> ptrs; + ptrs.safe_push (&t); + while (!ptrs.is_empty ()) + { + tree *p = ptrs.pop (); + tree n = copy_node (*p PASS_MEM_STAT); + CONSTRUCTOR_ELTS (n) = vec_safe_copy (CONSTRUCTOR_ELTS (*p) PASS_MEM_STAT); + *p = n; + vec<constructor_elt, va_gc> *v = CONSTRUCTOR_ELTS (n); + constructor_elt *ce; + for (HOST_WIDE_INT i = 0; vec_safe_iterate (v, i, &ce); ++i) + if (ce->value && TREE_CODE (ce->value) == CONSTRUCTOR) + ptrs.safe_push (&ce->value); + } + return t; +} + +/* If T is a CONSTRUCTOR, ggc_free T and any sub-CONSTRUCTORs. */ + +static void +free_constructor (tree t) +{ + if (!t || TREE_CODE (t) != CONSTRUCTOR) + return; + releasing_vec ctors; + vec_safe_push (ctors, t); + while (!ctors->is_empty ()) + { + tree c = ctors->pop (); + if (vec<constructor_elt, va_gc> *elts = CONSTRUCTOR_ELTS (c)) + { + constructor_elt *ce; + for (HOST_WIDE_INT i = 0; vec_safe_iterate (elts, i, &ce); ++i) + if (TREE_CODE (ce->value) == CONSTRUCTOR) + vec_safe_push (ctors, ce->value); + ggc_free (elts); + } + ggc_free (c); + } +} + +/* Helper function of cxx_bind_parameters_in_call. Return non-NULL + if *TP is address of a static variable (or part of it) currently being + constructed or of a heap artificial variable. */ + +static tree +addr_of_non_const_var (tree *tp, int *walk_subtrees, void *data) +{ + if (TREE_CODE (*tp) == ADDR_EXPR) + if (tree var = get_base_address (TREE_OPERAND (*tp, 0))) + if (VAR_P (var) && TREE_STATIC (var)) + { + if (DECL_NAME (var) == heap_uninit_identifier + || DECL_NAME (var) == heap_identifier + || DECL_NAME (var) == heap_vec_uninit_identifier + || DECL_NAME (var) == heap_vec_identifier) + return var; + + constexpr_global_ctx *global = (constexpr_global_ctx *) data; + if (global->values.get (var)) + return var; + } + if (TYPE_P (*tp)) + *walk_subtrees = false; + return NULL_TREE; +} + +/* Subroutine of cxx_eval_call_expression. + We are processing a call expression (either CALL_EXPR or + AGGR_INIT_EXPR) in the context of CTX. Evaluate + all arguments and bind their values to correspondings + parameters, making up the NEW_CALL context. */ + +static tree +cxx_bind_parameters_in_call (const constexpr_ctx *ctx, tree t, tree fun, + bool *non_constant_p, bool *overflow_p, + bool *non_constant_args) +{ + const int nargs = call_expr_nargs (t); + tree parms = DECL_ARGUMENTS (fun); + int i; + /* We don't record ellipsis args below. */ + int nparms = list_length (parms); + int nbinds = nargs < nparms ? nargs : nparms; + tree binds = make_tree_vec (nbinds); + for (i = 0; i < nargs; ++i) + { + tree x, arg; + tree type = parms ? TREE_TYPE (parms) : void_type_node; + if (parms && DECL_BY_REFERENCE (parms)) + type = TREE_TYPE (type); + x = get_nth_callarg (t, i); + /* For member function, the first argument is a pointer to the implied + object. For a constructor, it might still be a dummy object, in + which case we get the real argument from ctx. */ + if (i == 0 && DECL_CONSTRUCTOR_P (fun) + && is_dummy_object (x)) + { + x = ctx->object; + x = build_address (x); + } + if (TREE_ADDRESSABLE (type)) + /* Undo convert_for_arg_passing work here. */ + x = convert_from_reference (x); + /* Normally we would strip a TARGET_EXPR in an initialization context + such as this, but here we do the elision differently: we keep the + TARGET_EXPR, and use its CONSTRUCTOR as the value of the parm. */ + arg = cxx_eval_constant_expression (ctx, x, /*lval=*/false, + non_constant_p, overflow_p); + /* Don't VERIFY_CONSTANT here. */ + if (*non_constant_p && ctx->quiet) + break; + /* Just discard ellipsis args after checking their constantitude. */ + if (!parms) + continue; + + if (!*non_constant_p) + { + /* Make sure the binding has the same type as the parm. But + only for constant args. */ + if (!TYPE_REF_P (type)) + arg = adjust_temp_type (type, arg); + if (!TREE_CONSTANT (arg)) + *non_constant_args = true; + else if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type)) + /* The destructor needs to see any modifications the callee makes + to the argument. */ + *non_constant_args = true; + /* If arg is or contains address of a heap artificial variable or + of a static variable being constructed, avoid caching the + function call, as those variables might be modified by the + function, or might be modified by the callers in between + the cached function and just read by the function. */ + else if (!*non_constant_args + && cp_walk_tree (&arg, addr_of_non_const_var, ctx->global, + NULL)) + *non_constant_args = true; + + /* For virtual calls, adjust the this argument, so that it is + the object on which the method is called, rather than + one of its bases. */ + if (i == 0 && DECL_VIRTUAL_P (fun)) + { + tree addr = arg; + STRIP_NOPS (addr); + if (TREE_CODE (addr) == ADDR_EXPR) + { + tree obj = TREE_OPERAND (addr, 0); + while (TREE_CODE (obj) == COMPONENT_REF + && DECL_FIELD_IS_BASE (TREE_OPERAND (obj, 1)) + && !same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (obj), DECL_CONTEXT (fun))) + obj = TREE_OPERAND (obj, 0); + if (obj != TREE_OPERAND (addr, 0)) + arg = build_fold_addr_expr_with_type (obj, + TREE_TYPE (arg)); + } + } + TREE_VEC_ELT (binds, i) = arg; + } + parms = TREE_CHAIN (parms); + } + + return binds; +} + +/* Variables and functions to manage constexpr call expansion context. + These do not need to be marked for PCH or GC. */ + +/* FIXME remember and print actual constant arguments. */ +static vec<tree> call_stack; +static int call_stack_tick; +static int last_cx_error_tick; + +static int +push_cx_call_context (tree call) +{ + ++call_stack_tick; + if (!EXPR_HAS_LOCATION (call)) + SET_EXPR_LOCATION (call, input_location); + call_stack.safe_push (call); + int len = call_stack.length (); + if (len > max_constexpr_depth) + return false; + return len; +} + +static void +pop_cx_call_context (void) +{ + ++call_stack_tick; + call_stack.pop (); +} + +vec<tree> +cx_error_context (void) +{ + vec<tree> r = vNULL; + if (call_stack_tick != last_cx_error_tick + && !call_stack.is_empty ()) + r = call_stack; + last_cx_error_tick = call_stack_tick; + return r; +} + +/* Evaluate a call T to a GCC internal function when possible and return + the evaluated result or, under the control of CTX, give an error, set + NON_CONSTANT_P, and return the unevaluated call T otherwise. */ + +static tree +cxx_eval_internal_function (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + enum tree_code opcode = ERROR_MARK; + + switch (CALL_EXPR_IFN (t)) + { + case IFN_UBSAN_NULL: + case IFN_UBSAN_BOUNDS: + case IFN_UBSAN_VPTR: + case IFN_FALLTHROUGH: + return void_node; + + case IFN_ADD_OVERFLOW: + opcode = PLUS_EXPR; + break; + case IFN_SUB_OVERFLOW: + opcode = MINUS_EXPR; + break; + case IFN_MUL_OVERFLOW: + opcode = MULT_EXPR; + break; + + case IFN_LAUNDER: + return cxx_eval_constant_expression (ctx, CALL_EXPR_ARG (t, 0), + false, non_constant_p, overflow_p); + + case IFN_VEC_CONVERT: + { + tree arg = cxx_eval_constant_expression (ctx, CALL_EXPR_ARG (t, 0), + false, non_constant_p, + overflow_p); + if (TREE_CODE (arg) == VECTOR_CST) + return fold_const_call (CFN_VEC_CONVERT, TREE_TYPE (t), arg); + else + { + *non_constant_p = true; + return t; + } + } + + default: + if (!ctx->quiet) + error_at (cp_expr_loc_or_input_loc (t), + "call to internal function %qE", t); + *non_constant_p = true; + return t; + } + + /* Evaluate constant arguments using OPCODE and return a complex + number containing the result and the overflow bit. */ + tree arg0 = cxx_eval_constant_expression (ctx, CALL_EXPR_ARG (t, 0), lval, + non_constant_p, overflow_p); + tree arg1 = cxx_eval_constant_expression (ctx, CALL_EXPR_ARG (t, 1), lval, + non_constant_p, overflow_p); + + if (TREE_CODE (arg0) == INTEGER_CST && TREE_CODE (arg1) == INTEGER_CST) + { + location_t loc = cp_expr_loc_or_input_loc (t); + tree type = TREE_TYPE (TREE_TYPE (t)); + tree result = fold_binary_loc (loc, opcode, type, + fold_convert_loc (loc, type, arg0), + fold_convert_loc (loc, type, arg1)); + tree ovf + = build_int_cst (type, arith_overflowed_p (opcode, type, arg0, arg1)); + /* Reset TREE_OVERFLOW to avoid warnings for the overflow. */ + if (TREE_OVERFLOW (result)) + TREE_OVERFLOW (result) = 0; + + return build_complex (TREE_TYPE (t), result, ovf); + } + + *non_constant_p = true; + return t; +} + +/* Clean CONSTRUCTOR_NO_CLEARING from CTOR and its sub-aggregates. */ + +static void +clear_no_implicit_zero (tree ctor) +{ + if (CONSTRUCTOR_NO_CLEARING (ctor)) + { + CONSTRUCTOR_NO_CLEARING (ctor) = false; + for (auto &e: CONSTRUCTOR_ELTS (ctor)) + if (TREE_CODE (e.value) == CONSTRUCTOR) + clear_no_implicit_zero (e.value); + } +} + +/* Complain about a const object OBJ being modified in a constant expression. + EXPR is the MODIFY_EXPR expression performing the modification. */ + +static void +modifying_const_object_error (tree expr, tree obj) +{ + location_t loc = cp_expr_loc_or_input_loc (expr); + auto_diagnostic_group d; + error_at (loc, "modifying a const object %qE is not allowed in " + "a constant expression", TREE_OPERAND (expr, 0)); + inform (location_of (obj), "originally declared %<const%> here"); +} + +/* Return true if FNDECL is a replaceable global allocation function that + should be useable during constant expression evaluation. */ + +static inline bool +cxx_replaceable_global_alloc_fn (tree fndecl) +{ + return (cxx_dialect >= cxx20 + && IDENTIFIER_NEWDEL_OP_P (DECL_NAME (fndecl)) + && CP_DECL_CONTEXT (fndecl) == global_namespace + && (DECL_IS_REPLACEABLE_OPERATOR_NEW_P (fndecl) + || DECL_IS_OPERATOR_DELETE_P (fndecl))); +} + +/* Return true if FNDECL is a placement new function that should be + useable during constant expression evaluation of std::construct_at. */ + +static inline bool +cxx_placement_new_fn (tree fndecl) +{ + if (cxx_dialect >= cxx20 + && IDENTIFIER_NEW_OP_P (DECL_NAME (fndecl)) + && CP_DECL_CONTEXT (fndecl) == global_namespace + && !DECL_IS_REPLACEABLE_OPERATOR_NEW_P (fndecl) + && TREE_CODE (TREE_TYPE (fndecl)) == FUNCTION_TYPE) + { + tree first_arg = TREE_CHAIN (TYPE_ARG_TYPES (TREE_TYPE (fndecl))); + if (TREE_VALUE (first_arg) == ptr_type_node + && TREE_CHAIN (first_arg) == void_list_node) + return true; + } + return false; +} + +/* Return true if FNDECL is std::construct_at. */ + +static inline bool +is_std_construct_at (tree fndecl) +{ + if (!decl_in_std_namespace_p (fndecl)) + return false; + + tree name = DECL_NAME (fndecl); + return name && id_equal (name, "construct_at"); +} + +/* Overload for the above taking constexpr_call*. */ + +static inline bool +is_std_construct_at (const constexpr_call *call) +{ + return (call + && call->fundef + && is_std_construct_at (call->fundef->decl)); +} + +/* Return true if FNDECL is std::allocator<T>::{,de}allocate. */ + +static inline bool +is_std_allocator_allocate (tree fndecl) +{ + tree name = DECL_NAME (fndecl); + if (name == NULL_TREE + || !(id_equal (name, "allocate") || id_equal (name, "deallocate"))) + return false; + + tree ctx = DECL_CONTEXT (fndecl); + if (ctx == NULL_TREE || !CLASS_TYPE_P (ctx) || !TYPE_MAIN_DECL (ctx)) + return false; + + tree decl = TYPE_MAIN_DECL (ctx); + name = DECL_NAME (decl); + if (name == NULL_TREE || !id_equal (name, "allocator")) + return false; + + return decl_in_std_namespace_p (decl); +} + +/* Overload for the above taking constexpr_call*. */ + +static inline bool +is_std_allocator_allocate (const constexpr_call *call) +{ + return (call + && call->fundef + && is_std_allocator_allocate (call->fundef->decl)); +} + +/* Return true if FNDECL is __dynamic_cast. */ + +static inline bool +cxx_dynamic_cast_fn_p (tree fndecl) +{ + return (cxx_dialect >= cxx20 + && id_equal (DECL_NAME (fndecl), "__dynamic_cast") + && CP_DECL_CONTEXT (fndecl) == global_namespace); +} + +/* Often, we have an expression in the form of address + offset, e.g. + "&_ZTV1A + 16". Extract the object from it, i.e. "_ZTV1A". */ + +static tree +extract_obj_from_addr_offset (tree expr) +{ + if (TREE_CODE (expr) == POINTER_PLUS_EXPR) + expr = TREE_OPERAND (expr, 0); + STRIP_NOPS (expr); + if (TREE_CODE (expr) == ADDR_EXPR) + expr = TREE_OPERAND (expr, 0); + return expr; +} + +/* Given a PATH like + + g.D.2181.D.2154.D.2102.D.2093 + + find a component with type TYPE. Return NULL_TREE if not found, and + error_mark_node if the component is not accessible. If STOP is non-null, + this function will return NULL_TREE if STOP is found before TYPE. */ + +static tree +get_component_with_type (tree path, tree type, tree stop) +{ + while (true) + { + if (same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (path), type)) + /* Found it. */ + return path; + else if (stop + && (same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (path), + stop))) + return NULL_TREE; + else if (TREE_CODE (path) == COMPONENT_REF + && DECL_FIELD_IS_BASE (TREE_OPERAND (path, 1))) + { + /* We need to check that the component we're accessing is in fact + accessible. */ + if (TREE_PRIVATE (TREE_OPERAND (path, 1)) + || TREE_PROTECTED (TREE_OPERAND (path, 1))) + return error_mark_node; + path = TREE_OPERAND (path, 0); + } + else + return NULL_TREE; + } +} + +/* Evaluate a call to __dynamic_cast (permitted by P1327R1). + + The declaration of __dynamic_cast is: + + void* __dynamic_cast (const void* __src_ptr, + const __class_type_info* __src_type, + const __class_type_info* __dst_type, + ptrdiff_t __src2dst); + + where src2dst has the following possible values + + >-1: src_type is a unique public non-virtual base of dst_type + dst_ptr + src2dst == src_ptr + -1: unspecified relationship + -2: src_type is not a public base of dst_type + -3: src_type is a multiple public non-virtual base of dst_type + + Since literal types can't have virtual bases, we only expect hint >=0, + -2, or -3. */ + +static tree +cxx_eval_dynamic_cast_fn (const constexpr_ctx *ctx, tree call, + bool *non_constant_p, bool *overflow_p) +{ + /* T will be something like + __dynamic_cast ((B*) b, &_ZTI1B, &_ZTI1D, 8) + dismantle it. */ + gcc_assert (call_expr_nargs (call) == 4); + tsubst_flags_t complain = ctx->quiet ? tf_none : tf_warning_or_error; + tree obj = CALL_EXPR_ARG (call, 0); + tree type = CALL_EXPR_ARG (call, 2); + HOST_WIDE_INT hint = int_cst_value (CALL_EXPR_ARG (call, 3)); + location_t loc = cp_expr_loc_or_input_loc (call); + + /* Get the target type of the dynamic_cast. */ + gcc_assert (TREE_CODE (type) == ADDR_EXPR); + type = TREE_OPERAND (type, 0); + type = TREE_TYPE (DECL_NAME (type)); + + /* TYPE can only be either T* or T&. We can't know which of these it + is by looking at TYPE, but OBJ will be "(T*) x" in the first case, + and something like "(T*)(T&)(T*) x" in the second case. */ + bool reference_p = false; + while (CONVERT_EXPR_P (obj) || TREE_CODE (obj) == SAVE_EXPR) + { + reference_p |= TYPE_REF_P (TREE_TYPE (obj)); + obj = TREE_OPERAND (obj, 0); + } + + /* Evaluate the object so that we know its dynamic type. */ + obj = cxx_eval_constant_expression (ctx, obj, /*lval*/false, non_constant_p, + overflow_p); + if (*non_constant_p) + return call; + + /* We expect OBJ to be in form of &d.D.2102 when HINT == 0, + but when HINT is > 0, it can also be something like + &d.D.2102 + 18446744073709551608, which includes the BINFO_OFFSET. */ + obj = extract_obj_from_addr_offset (obj); + const tree objtype = TREE_TYPE (obj); + /* If OBJ doesn't refer to a base field, we're done. */ + if (tree t = (TREE_CODE (obj) == COMPONENT_REF + ? TREE_OPERAND (obj, 1) : obj)) + if (TREE_CODE (t) != FIELD_DECL || !DECL_FIELD_IS_BASE (t)) + { + if (reference_p) + { + if (!ctx->quiet) + { + error_at (loc, "reference %<dynamic_cast%> failed"); + inform (loc, "dynamic type %qT of its operand does " + "not have a base class of type %qT", + objtype, type); + } + *non_constant_p = true; + } + return integer_zero_node; + } + + /* [class.cdtor] When a dynamic_cast is used in a constructor ... + or in a destructor ... if the operand of the dynamic_cast refers + to the object under construction or destruction, this object is + considered to be a most derived object that has the type of the + constructor or destructor's class. */ + tree vtable = build_vfield_ref (obj, objtype); + vtable = cxx_eval_constant_expression (ctx, vtable, /*lval*/false, + non_constant_p, overflow_p); + if (*non_constant_p) + return call; + /* With -fsanitize=vptr, we initialize all vtable pointers to null, + so it's possible that we got a null pointer now. */ + if (integer_zerop (vtable)) + { + if (!ctx->quiet) + error_at (loc, "virtual table pointer is used uninitialized"); + *non_constant_p = true; + return integer_zero_node; + } + /* VTABLE will be &_ZTV1A + 16 or similar, get _ZTV1A. */ + vtable = extract_obj_from_addr_offset (vtable); + const tree mdtype = DECL_CONTEXT (vtable); + + /* Given dynamic_cast<T>(v), + + [expr.dynamic.cast] If C is the class type to which T points or refers, + the runtime check logically executes as follows: + + If, in the most derived object pointed (referred) to by v, v points + (refers) to a public base class subobject of a C object, and if only + one object of type C is derived from the subobject pointed (referred) + to by v the result points (refers) to that C object. + + In this case, HINT >= 0 or -3. */ + if (hint >= 0 || hint == -3) + { + /* Look for a component with type TYPE. */ + tree t = get_component_with_type (obj, type, mdtype); + /* If not accessible, give an error. */ + if (t == error_mark_node) + { + if (reference_p) + { + if (!ctx->quiet) + { + error_at (loc, "reference %<dynamic_cast%> failed"); + inform (loc, "static type %qT of its operand is a " + "non-public base class of dynamic type %qT", + objtype, type); + + } + *non_constant_p = true; + } + return integer_zero_node; + } + else if (t) + /* The result points to the TYPE object. */ + return cp_build_addr_expr (t, complain); + /* Else, TYPE was not found, because the HINT turned out to be wrong. + Fall through to the normal processing. */ + } + + /* Otherwise, if v points (refers) to a public base class subobject of the + most derived object, and the type of the most derived object has a base + class, of type C, that is unambiguous and public, the result points + (refers) to the C subobject of the most derived object. + + But it can also be an invalid case. */ + + /* Get the most derived object. */ + obj = get_component_with_type (obj, mdtype, NULL_TREE); + if (obj == error_mark_node) + { + if (reference_p) + { + if (!ctx->quiet) + { + error_at (loc, "reference %<dynamic_cast%> failed"); + inform (loc, "static type %qT of its operand is a non-public" + " base class of dynamic type %qT", objtype, mdtype); + } + *non_constant_p = true; + } + return integer_zero_node; + } + else + gcc_assert (obj); + + /* Check that the type of the most derived object has a base class + of type TYPE that is unambiguous and public. */ + base_kind b_kind; + tree binfo = lookup_base (mdtype, type, ba_check, &b_kind, tf_none); + if (!binfo || binfo == error_mark_node) + { + if (reference_p) + { + if (!ctx->quiet) + { + error_at (loc, "reference %<dynamic_cast%> failed"); + if (b_kind == bk_ambig) + inform (loc, "%qT is an ambiguous base class of dynamic " + "type %qT of its operand", type, mdtype); + else + inform (loc, "dynamic type %qT of its operand does not " + "have an unambiguous public base class %qT", + mdtype, type); + } + *non_constant_p = true; + } + return integer_zero_node; + } + /* If so, return the TYPE subobject of the most derived object. */ + obj = convert_to_base_statically (obj, binfo); + return cp_build_addr_expr (obj, complain); +} + +/* Data structure used by replace_decl and replace_decl_r. */ + +struct replace_decl_data +{ + /* The _DECL we want to replace. */ + tree decl; + /* The replacement for DECL. */ + tree replacement; + /* Trees we've visited. */ + hash_set<tree> *pset; + /* Whether we've performed any replacements. */ + bool changed; +}; + +/* Helper function for replace_decl, called through cp_walk_tree. */ + +static tree +replace_decl_r (tree *tp, int *walk_subtrees, void *data) +{ + replace_decl_data *d = (replace_decl_data *) data; + + if (*tp == d->decl) + { + *tp = unshare_expr (d->replacement); + d->changed = true; + *walk_subtrees = 0; + } + else if (TYPE_P (*tp) + || d->pset->add (*tp)) + *walk_subtrees = 0; + + return NULL_TREE; +} + +/* Replace every occurrence of DECL with (an unshared copy of) + REPLACEMENT within the expression *TP. Returns true iff a + replacement was performed. */ + +bool +replace_decl (tree *tp, tree decl, tree replacement) +{ + gcc_checking_assert (same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (decl), TREE_TYPE (replacement))); + hash_set<tree> pset; + replace_decl_data data = { decl, replacement, &pset, false }; + cp_walk_tree (tp, replace_decl_r, &data, NULL); + return data.changed; +} + +/* Evaluate the call T to virtual function thunk THUNK_FNDECL. */ + +static tree +cxx_eval_thunk_call (const constexpr_ctx *ctx, tree t, tree thunk_fndecl, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree function = THUNK_TARGET (thunk_fndecl); + + if (THUNK_VIRTUAL_OFFSET (thunk_fndecl)) + { + if (!ctx->quiet) + { + if (!DECL_DECLARED_CONSTEXPR_P (function)) + { + error ("call to non-%<constexpr%> function %qD", function); + explain_invalid_constexpr_fn (function); + } + else + /* virtual_offset is only set for virtual bases, which make the + class non-literal, so we don't need to handle it here. */ + error ("calling constexpr member function %qD through virtual " + "base subobject", function); + } + *non_constant_p = true; + return t; + } + + tree new_call = copy_node (t); + CALL_EXPR_FN (new_call) = function; + TREE_TYPE (new_call) = TREE_TYPE (TREE_TYPE (function)); + + tree offset = size_int (THUNK_FIXED_OFFSET (thunk_fndecl)); + + if (DECL_THIS_THUNK_P (thunk_fndecl)) + { + /* 'this'-adjusting thunk. */ + tree this_arg = CALL_EXPR_ARG (t, 0); + this_arg = build2 (POINTER_PLUS_EXPR, TREE_TYPE (this_arg), + this_arg, offset); + CALL_EXPR_ARG (new_call, 0) = this_arg; + } + else + /* Return-adjusting thunk. */ + new_call = build2 (POINTER_PLUS_EXPR, TREE_TYPE (new_call), + new_call, offset); + + return cxx_eval_constant_expression (ctx, new_call, lval, + non_constant_p, overflow_p); +} + +/* If OBJECT is of const class type, evaluate it to a CONSTRUCTOR and set + its TREE_READONLY flag according to READONLY_P. Used for constexpr + 'tors to detect modifying const objects in a constexpr context. */ + +static void +cxx_set_object_constness (const constexpr_ctx *ctx, tree object, + bool readonly_p, bool *non_constant_p, + bool *overflow_p) +{ + if (CLASS_TYPE_P (TREE_TYPE (object)) + && CP_TYPE_CONST_P (TREE_TYPE (object))) + { + /* Subobjects might not be stored in ctx->global->values but we + can get its CONSTRUCTOR by evaluating *this. */ + tree e = cxx_eval_constant_expression (ctx, object, /*lval*/false, + non_constant_p, overflow_p); + if (TREE_CODE (e) == CONSTRUCTOR && !*non_constant_p) + TREE_READONLY (e) = readonly_p; + } +} + +/* Subroutine of cxx_eval_constant_expression. + Evaluate the call expression tree T in the context of OLD_CALL expression + evaluation. */ + +static tree +cxx_eval_call_expression (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + /* Handle concept checks separately. */ + if (concept_check_p (t)) + return evaluate_concept_check (t); + + location_t loc = cp_expr_loc_or_input_loc (t); + tree fun = get_function_named_in_call (t); + constexpr_call new_call + = { NULL, NULL, NULL, 0, ctx->manifestly_const_eval }; + int depth_ok; + + if (fun == NULL_TREE) + return cxx_eval_internal_function (ctx, t, lval, + non_constant_p, overflow_p); + + if (TREE_CODE (fun) != FUNCTION_DECL) + { + /* Might be a constexpr function pointer. */ + fun = cxx_eval_constant_expression (ctx, fun, + /*lval*/false, non_constant_p, + overflow_p); + STRIP_NOPS (fun); + if (TREE_CODE (fun) == ADDR_EXPR) + fun = TREE_OPERAND (fun, 0); + /* For TARGET_VTABLE_USES_DESCRIPTORS targets, there is no + indirection, the called expression is a pointer into the + virtual table which should contain FDESC_EXPR. Extract the + FUNCTION_DECL from there. */ + else if (TARGET_VTABLE_USES_DESCRIPTORS + && TREE_CODE (fun) == POINTER_PLUS_EXPR + && TREE_CODE (TREE_OPERAND (fun, 0)) == ADDR_EXPR + && TREE_CODE (TREE_OPERAND (fun, 1)) == INTEGER_CST) + { + tree d = TREE_OPERAND (TREE_OPERAND (fun, 0), 0); + if (VAR_P (d) + && DECL_VTABLE_OR_VTT_P (d) + && TREE_CODE (TREE_TYPE (d)) == ARRAY_TYPE + && TREE_TYPE (TREE_TYPE (d)) == vtable_entry_type + && DECL_INITIAL (d) + && TREE_CODE (DECL_INITIAL (d)) == CONSTRUCTOR) + { + tree i = int_const_binop (TRUNC_DIV_EXPR, TREE_OPERAND (fun, 1), + TYPE_SIZE_UNIT (vtable_entry_type)); + HOST_WIDE_INT idx = find_array_ctor_elt (DECL_INITIAL (d), i); + if (idx >= 0) + { + tree fdesc + = (*CONSTRUCTOR_ELTS (DECL_INITIAL (d)))[idx].value; + if (TREE_CODE (fdesc) == FDESC_EXPR + && integer_zerop (TREE_OPERAND (fdesc, 1))) + fun = TREE_OPERAND (fdesc, 0); + } + } + } + } + if (TREE_CODE (fun) != FUNCTION_DECL) + { + if (!ctx->quiet && !*non_constant_p) + error_at (loc, "expression %qE does not designate a %<constexpr%> " + "function", fun); + *non_constant_p = true; + return t; + } + if (DECL_CLONED_FUNCTION_P (fun) && !DECL_DELETING_DESTRUCTOR_P (fun)) + fun = DECL_CLONED_FUNCTION (fun); + + if (is_ubsan_builtin_p (fun)) + return void_node; + + if (fndecl_built_in_p (fun)) + return cxx_eval_builtin_function_call (ctx, t, fun, + lval, non_constant_p, overflow_p); + if (DECL_THUNK_P (fun)) + return cxx_eval_thunk_call (ctx, t, fun, lval, non_constant_p, overflow_p); + if (!maybe_constexpr_fn (fun)) + { + if (TREE_CODE (t) == CALL_EXPR + && cxx_replaceable_global_alloc_fn (fun) + && (CALL_FROM_NEW_OR_DELETE_P (t) + || is_std_allocator_allocate (ctx->call))) + { + const int nargs = call_expr_nargs (t); + tree arg0 = NULL_TREE; + for (int i = 0; i < nargs; ++i) + { + tree arg = CALL_EXPR_ARG (t, i); + arg = cxx_eval_constant_expression (ctx, arg, false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (arg); + if (i == 0) + arg0 = arg; + } + gcc_assert (arg0); + if (IDENTIFIER_NEW_OP_P (DECL_NAME (fun))) + { + tree type = build_array_type_nelts (char_type_node, + tree_to_uhwi (arg0)); + tree var = build_decl (loc, VAR_DECL, + (IDENTIFIER_OVL_OP_FLAGS (DECL_NAME (fun)) + & OVL_OP_FLAG_VEC) + ? heap_vec_uninit_identifier + : heap_uninit_identifier, + type); + DECL_ARTIFICIAL (var) = 1; + TREE_STATIC (var) = 1; + // Temporarily register the artificial var in varpool, + // so that comparisons of its address against NULL are folded + // through nonzero_address even with + // -fno-delete-null-pointer-checks or that comparison of + // addresses of different heap artificial vars is folded too. + // See PR98988 and PR99031. + varpool_node::finalize_decl (var); + ctx->global->heap_vars.safe_push (var); + ctx->global->values.put (var, NULL_TREE); + return fold_convert (ptr_type_node, build_address (var)); + } + else + { + STRIP_NOPS (arg0); + if (TREE_CODE (arg0) == ADDR_EXPR + && VAR_P (TREE_OPERAND (arg0, 0))) + { + tree var = TREE_OPERAND (arg0, 0); + if (DECL_NAME (var) == heap_uninit_identifier + || DECL_NAME (var) == heap_identifier) + { + if (IDENTIFIER_OVL_OP_FLAGS (DECL_NAME (fun)) + & OVL_OP_FLAG_VEC) + { + if (!ctx->quiet) + { + error_at (loc, "array deallocation of object " + "allocated with non-array " + "allocation"); + inform (DECL_SOURCE_LOCATION (var), + "allocation performed here"); + } + *non_constant_p = true; + return t; + } + DECL_NAME (var) = heap_deleted_identifier; + ctx->global->values.remove (var); + ctx->global->heap_dealloc_count++; + return void_node; + } + else if (DECL_NAME (var) == heap_vec_uninit_identifier + || DECL_NAME (var) == heap_vec_identifier) + { + if ((IDENTIFIER_OVL_OP_FLAGS (DECL_NAME (fun)) + & OVL_OP_FLAG_VEC) == 0) + { + if (!ctx->quiet) + { + error_at (loc, "non-array deallocation of " + "object allocated with array " + "allocation"); + inform (DECL_SOURCE_LOCATION (var), + "allocation performed here"); + } + *non_constant_p = true; + return t; + } + DECL_NAME (var) = heap_deleted_identifier; + ctx->global->values.remove (var); + ctx->global->heap_dealloc_count++; + return void_node; + } + else if (DECL_NAME (var) == heap_deleted_identifier) + { + if (!ctx->quiet) + error_at (loc, "deallocation of already deallocated " + "storage"); + *non_constant_p = true; + return t; + } + } + if (!ctx->quiet) + error_at (loc, "deallocation of storage that was " + "not previously allocated"); + *non_constant_p = true; + return t; + } + } + /* Allow placement new in std::construct_at, just return the second + argument. */ + if (TREE_CODE (t) == CALL_EXPR + && cxx_placement_new_fn (fun) + && is_std_construct_at (ctx->call)) + { + const int nargs = call_expr_nargs (t); + tree arg1 = NULL_TREE; + for (int i = 0; i < nargs; ++i) + { + tree arg = CALL_EXPR_ARG (t, i); + arg = cxx_eval_constant_expression (ctx, arg, false, + non_constant_p, overflow_p); + if (i == 1) + arg1 = arg; + else + VERIFY_CONSTANT (arg); + } + gcc_assert (arg1); + return arg1; + } + else if (cxx_dynamic_cast_fn_p (fun)) + return cxx_eval_dynamic_cast_fn (ctx, t, non_constant_p, overflow_p); + + if (!ctx->quiet) + { + if (!lambda_static_thunk_p (fun)) + error_at (loc, "call to non-%<constexpr%> function %qD", fun); + explain_invalid_constexpr_fn (fun); + } + *non_constant_p = true; + return t; + } + + constexpr_ctx new_ctx = *ctx; + if (DECL_CONSTRUCTOR_P (fun) && !ctx->object + && TREE_CODE (t) == AGGR_INIT_EXPR) + { + /* We want to have an initialization target for an AGGR_INIT_EXPR. + If we don't already have one in CTX, use the AGGR_INIT_EXPR_SLOT. */ + new_ctx.object = AGGR_INIT_EXPR_SLOT (t); + tree ctor = new_ctx.ctor = build_constructor (DECL_CONTEXT (fun), NULL); + CONSTRUCTOR_NO_CLEARING (ctor) = true; + ctx->global->values.put (new_ctx.object, ctor); + ctx = &new_ctx; + } + + /* Shortcut trivial constructor/op=. */ + if (trivial_fn_p (fun)) + { + tree init = NULL_TREE; + if (call_expr_nargs (t) == 2) + init = convert_from_reference (get_nth_callarg (t, 1)); + else if (TREE_CODE (t) == AGGR_INIT_EXPR + && AGGR_INIT_ZERO_FIRST (t)) + init = build_zero_init (DECL_CONTEXT (fun), NULL_TREE, false); + if (init) + { + tree op = get_nth_callarg (t, 0); + if (is_dummy_object (op)) + op = ctx->object; + else + op = build1 (INDIRECT_REF, TREE_TYPE (TREE_TYPE (op)), op); + tree set = build2 (MODIFY_EXPR, TREE_TYPE (op), op, init); + new_ctx.call = &new_call; + return cxx_eval_constant_expression (&new_ctx, set, lval, + non_constant_p, overflow_p); + } + } + + bool non_constant_args = false; + new_call.bindings + = cxx_bind_parameters_in_call (ctx, t, fun, non_constant_p, + overflow_p, &non_constant_args); + + /* We build up the bindings list before we know whether we already have this + call cached. If we don't end up saving these bindings, ggc_free them when + this function exits. */ + class free_bindings + { + tree *bindings; + public: + free_bindings (tree &b): bindings (&b) { } + ~free_bindings () { if (bindings) ggc_free (*bindings); } + void preserve () { bindings = NULL; } + } fb (new_call.bindings); + + if (*non_constant_p) + return t; + + /* We can't defer instantiating the function any longer. */ + if (!DECL_INITIAL (fun) + && DECL_TEMPLOID_INSTANTIATION (fun) + && !uid_sensitive_constexpr_evaluation_p ()) + { + location_t save_loc = input_location; + input_location = loc; + ++function_depth; + if (ctx->manifestly_const_eval) + FNDECL_MANIFESTLY_CONST_EVALUATED (fun) = true; + instantiate_decl (fun, /*defer_ok*/false, /*expl_inst*/false); + --function_depth; + input_location = save_loc; + } + + /* If in direct recursive call, optimize definition search. */ + if (ctx && ctx->call && ctx->call->fundef && ctx->call->fundef->decl == fun) + new_call.fundef = ctx->call->fundef; + else + { + new_call.fundef = retrieve_constexpr_fundef (fun); + if (new_call.fundef == NULL || new_call.fundef->body == NULL + || new_call.fundef->result == error_mark_node + || fun == current_function_decl) + { + if (!ctx->quiet) + { + /* We need to check for current_function_decl here in case we're + being called during cp_fold_function, because at that point + DECL_INITIAL is set properly and we have a fundef but we + haven't lowered invisirefs yet (c++/70344). */ + if (DECL_INITIAL (fun) == error_mark_node + || fun == current_function_decl) + error_at (loc, "%qD called in a constant expression before its " + "definition is complete", fun); + else if (DECL_INITIAL (fun)) + { + /* The definition of fun was somehow unsuitable. But pretend + that lambda static thunks don't exist. */ + if (!lambda_static_thunk_p (fun)) + error_at (loc, "%qD called in a constant expression", fun); + explain_invalid_constexpr_fn (fun); + } + else + error_at (loc, "%qD used before its definition", fun); + } + *non_constant_p = true; + return t; + } + } + + depth_ok = push_cx_call_context (t); + + /* Remember the object we are constructing or destructing. */ + tree new_obj = NULL_TREE; + if (DECL_CONSTRUCTOR_P (fun) || DECL_DESTRUCTOR_P (fun)) + { + /* In a cdtor, it should be the first `this' argument. + At this point it has already been evaluated in the call + to cxx_bind_parameters_in_call. */ + new_obj = TREE_VEC_ELT (new_call.bindings, 0); + STRIP_NOPS (new_obj); + if (TREE_CODE (new_obj) == ADDR_EXPR) + new_obj = TREE_OPERAND (new_obj, 0); + + if (ctx->call && ctx->call->fundef + && DECL_CONSTRUCTOR_P (ctx->call->fundef->decl)) + { + tree cur_obj = TREE_VEC_ELT (ctx->call->bindings, 0); + STRIP_NOPS (cur_obj); + if (TREE_CODE (cur_obj) == ADDR_EXPR) + cur_obj = TREE_OPERAND (cur_obj, 0); + if (new_obj == cur_obj) + /* We're calling the target constructor of a delegating + constructor, or accessing a base subobject through a + NOP_EXPR as part of a call to a base constructor, so + there is no new (sub)object. */ + new_obj = NULL_TREE; + } + } + + tree result = NULL_TREE; + + constexpr_call *entry = NULL; + if (depth_ok && !non_constant_args && ctx->strict) + { + new_call.hash = constexpr_fundef_hasher::hash (new_call.fundef); + new_call.hash + = iterative_hash_template_arg (new_call.bindings, new_call.hash); + new_call.hash + = iterative_hash_object (ctx->manifestly_const_eval, new_call.hash); + + /* If we have seen this call before, we are done. */ + maybe_initialize_constexpr_call_table (); + constexpr_call **slot + = constexpr_call_table->find_slot (&new_call, INSERT); + entry = *slot; + if (entry == NULL) + { + /* Only cache up to constexpr_cache_depth to limit memory use. */ + if (depth_ok < constexpr_cache_depth) + { + /* We need to keep a pointer to the entry, not just the slot, as + the slot can move during evaluation of the body. */ + *slot = entry = ggc_alloc<constexpr_call> (); + *entry = new_call; + fb.preserve (); + } + } + /* Calls that are in progress have their result set to NULL, so that we + can detect circular dependencies. Now that we only cache up to + constexpr_cache_depth this won't catch circular dependencies that + start deeper, but they'll hit the recursion or ops limit. */ + else if (entry->result == NULL) + { + if (!ctx->quiet) + error ("call has circular dependency"); + *non_constant_p = true; + entry->result = result = error_mark_node; + } + else + result = entry->result; + } + + if (!depth_ok) + { + if (!ctx->quiet) + error ("%<constexpr%> evaluation depth exceeds maximum of %d (use " + "%<-fconstexpr-depth=%> to increase the maximum)", + max_constexpr_depth); + *non_constant_p = true; + result = error_mark_node; + } + else + { + bool cacheable = true; + if (result && result != error_mark_node) + /* OK */; + else if (!DECL_SAVED_TREE (fun)) + { + /* When at_eof >= 2, cgraph has started throwing away + DECL_SAVED_TREE, so fail quietly. FIXME we get here because of + late code generation for VEC_INIT_EXPR, which needs to be + completely reconsidered. */ + gcc_assert (at_eof >= 2 && ctx->quiet); + *non_constant_p = true; + } + else if (tree copy = get_fundef_copy (new_call.fundef)) + { + tree body, parms, res; + releasing_vec ctors; + + /* Reuse or create a new unshared copy of this function's body. */ + body = TREE_PURPOSE (copy); + parms = TREE_VALUE (copy); + res = TREE_TYPE (copy); + + /* Associate the bindings with the remapped parms. */ + tree bound = new_call.bindings; + tree remapped = parms; + for (int i = 0; i < TREE_VEC_LENGTH (bound); ++i) + { + tree arg = TREE_VEC_ELT (bound, i); + if (entry) + { + /* Unshare args going into the hash table to separate them + from the caller's context, for better GC and to avoid + problems with verify_gimple. */ + arg = unshare_expr_without_location (arg); + TREE_VEC_ELT (bound, i) = arg; + + /* And then unshare again so the callee doesn't change the + argument values in the hash table. XXX Could we unshare + lazily in cxx_eval_store_expression? */ + arg = unshare_constructor (arg); + if (TREE_CODE (arg) == CONSTRUCTOR) + vec_safe_push (ctors, arg); + } + ctx->global->values.put (remapped, arg); + remapped = DECL_CHAIN (remapped); + } + /* Add the RESULT_DECL to the values map, too. */ + gcc_assert (!DECL_BY_REFERENCE (res)); + ctx->global->values.put (res, NULL_TREE); + + /* Track the callee's evaluated SAVE_EXPRs and TARGET_EXPRs so that + we can forget their values after the call. */ + constexpr_ctx ctx_with_save_exprs = *ctx; + auto_vec<tree, 10> save_exprs; + ctx_with_save_exprs.save_exprs = &save_exprs; + ctx_with_save_exprs.call = &new_call; + unsigned save_heap_alloc_count = ctx->global->heap_vars.length (); + unsigned save_heap_dealloc_count = ctx->global->heap_dealloc_count; + + /* If this is a constexpr destructor, the object's const and volatile + semantics are no longer in effect; see [class.dtor]p5. */ + if (new_obj && DECL_DESTRUCTOR_P (fun)) + cxx_set_object_constness (ctx, new_obj, /*readonly_p=*/false, + non_constant_p, overflow_p); + + tree jump_target = NULL_TREE; + cxx_eval_constant_expression (&ctx_with_save_exprs, body, + lval, non_constant_p, overflow_p, + &jump_target); + + if (DECL_CONSTRUCTOR_P (fun)) + { + /* This can be null for a subobject constructor call, in + which case what we care about is the initialization + side-effects rather than the value. We could get at the + value by evaluating *this, but we don't bother; there's + no need to put such a call in the hash table. */ + result = lval ? ctx->object : ctx->ctor; + + /* If we've just evaluated a subobject constructor call for an + empty union member, it might not have produced a side effect + that actually activated the union member. So produce such a + side effect now to ensure the union appears initialized. */ + if (!result && new_obj + && TREE_CODE (new_obj) == COMPONENT_REF + && TREE_CODE (TREE_TYPE + (TREE_OPERAND (new_obj, 0))) == UNION_TYPE + && is_really_empty_class (TREE_TYPE (new_obj), + /*ignore_vptr*/false)) + { + tree activate = build2 (MODIFY_EXPR, TREE_TYPE (new_obj), + new_obj, + build_constructor (TREE_TYPE (new_obj), + NULL)); + cxx_eval_constant_expression (ctx, activate, lval, + non_constant_p, overflow_p); + ggc_free (activate); + } + } + else if (VOID_TYPE_P (TREE_TYPE (res))) + result = void_node; + else + { + result = *ctx->global->values.get (res); + if (result == NULL_TREE && !*non_constant_p) + { + if (!ctx->quiet) + error ("%<constexpr%> call flows off the end " + "of the function"); + *non_constant_p = true; + } + } + + /* At this point, the object's constructor will have run, so + the object is no longer under construction, and its possible + 'const' semantics now apply. Make a note of this fact by + marking the CONSTRUCTOR TREE_READONLY. */ + if (new_obj && DECL_CONSTRUCTOR_P (fun)) + cxx_set_object_constness (ctx, new_obj, /*readonly_p=*/true, + non_constant_p, overflow_p); + + /* Forget the saved values of the callee's SAVE_EXPRs and + TARGET_EXPRs. */ + for (tree save_expr : save_exprs) + ctx->global->values.remove (save_expr); + + /* Remove the parms/result from the values map. Is it worth + bothering to do this when the map itself is only live for + one constexpr evaluation? If so, maybe also clear out + other vars from call, maybe in BIND_EXPR handling? */ + ctx->global->values.remove (res); + for (tree parm = parms; parm; parm = TREE_CHAIN (parm)) + ctx->global->values.remove (parm); + + /* Free any parameter CONSTRUCTORs we aren't returning directly. */ + while (!ctors->is_empty ()) + { + tree c = ctors->pop (); + if (c != result) + free_constructor (c); + } + + /* Make the unshared function copy we used available for re-use. */ + save_fundef_copy (fun, copy); + + /* If the call allocated some heap object that hasn't been + deallocated during the call, or if it deallocated some heap + object it has not allocated, the call isn't really stateless + for the constexpr evaluation and should not be cached. + It is fine if the call allocates something and deallocates it + too. */ + if (entry + && (save_heap_alloc_count != ctx->global->heap_vars.length () + || (save_heap_dealloc_count + != ctx->global->heap_dealloc_count))) + { + tree heap_var; + unsigned int i; + if ((ctx->global->heap_vars.length () + - ctx->global->heap_dealloc_count) + != save_heap_alloc_count - save_heap_dealloc_count) + cacheable = false; + else + FOR_EACH_VEC_ELT_FROM (ctx->global->heap_vars, i, heap_var, + save_heap_alloc_count) + if (DECL_NAME (heap_var) != heap_deleted_identifier) + { + cacheable = false; + break; + } + } + + /* Rewrite all occurrences of the function's RESULT_DECL with the + current object under construction. */ + if (!*non_constant_p && ctx->object + && CLASS_TYPE_P (TREE_TYPE (res)) + && !is_empty_class (TREE_TYPE (res))) + if (replace_decl (&result, res, ctx->object)) + cacheable = false; + } + else + /* Couldn't get a function copy to evaluate. */ + *non_constant_p = true; + + if (result == error_mark_node) + *non_constant_p = true; + if (*non_constant_p || *overflow_p) + result = error_mark_node; + else if (!result) + result = void_node; + if (entry) + entry->result = cacheable ? result : error_mark_node; + } + + /* The result of a constexpr function must be completely initialized. + + However, in C++20, a constexpr constructor doesn't necessarily have + to initialize all the fields, so we don't clear CONSTRUCTOR_NO_CLEARING + in order to detect reading an unitialized object in constexpr instead + of value-initializing it. (reduced_constant_expression_p is expected to + take care of clearing the flag.) */ + if (TREE_CODE (result) == CONSTRUCTOR + && (cxx_dialect < cxx20 + || !DECL_CONSTRUCTOR_P (fun))) + clear_no_implicit_zero (result); + + pop_cx_call_context (); + return result; +} + +/* Return true if T is a valid constant initializer. If a CONSTRUCTOR + initializes all the members, the CONSTRUCTOR_NO_CLEARING flag will be + cleared. + FIXME speed this up, it's taking 16% of compile time on sieve testcase. */ + +bool +reduced_constant_expression_p (tree t) +{ + if (t == NULL_TREE) + return false; + + switch (TREE_CODE (t)) + { + case PTRMEM_CST: + /* Even if we can't lower this yet, it's constant. */ + return true; + + case CONSTRUCTOR: + /* And we need to handle PTRMEM_CST wrapped in a CONSTRUCTOR. */ + tree field; + if (CONSTRUCTOR_NO_CLEARING (t)) + { + if (TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE) + /* An initialized vector would have a VECTOR_CST. */ + return false; + else if (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE) + { + /* There must be a valid constant initializer at every array + index. */ + tree min = TYPE_MIN_VALUE (TYPE_DOMAIN (TREE_TYPE (t))); + tree max = TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (t))); + tree cursor = min; + for (auto &e: CONSTRUCTOR_ELTS (t)) + { + if (!reduced_constant_expression_p (e.value)) + return false; + if (array_index_cmp (cursor, e.index) != 0) + return false; + if (TREE_CODE (e.index) == RANGE_EXPR) + cursor = TREE_OPERAND (e.index, 1); + cursor = int_const_binop (PLUS_EXPR, cursor, size_one_node); + } + if (find_array_ctor_elt (t, max) == -1) + return false; + goto ok; + } + else if (cxx_dialect >= cxx20 + && TREE_CODE (TREE_TYPE (t)) == UNION_TYPE) + { + if (CONSTRUCTOR_NELTS (t) == 0) + /* An initialized union has a constructor element. */ + return false; + /* And it only initializes one member. */ + field = NULL_TREE; + } + else + field = next_initializable_field (TYPE_FIELDS (TREE_TYPE (t))); + } + else + field = NULL_TREE; + for (auto &e: CONSTRUCTOR_ELTS (t)) + { + /* If VAL is null, we're in the middle of initializing this + element. */ + if (!reduced_constant_expression_p (e.value)) + return false; + /* Empty class field may or may not have an initializer. */ + for (; field && e.index != field; + field = next_initializable_field (DECL_CHAIN (field))) + if (!is_really_empty_class (TREE_TYPE (field), + /*ignore_vptr*/false)) + return false; + if (field) + field = next_initializable_field (DECL_CHAIN (field)); + } + /* There could be a non-empty field at the end. */ + for (; field; field = next_initializable_field (DECL_CHAIN (field))) + if (!is_really_empty_class (TREE_TYPE (field), /*ignore_vptr*/false)) + return false; +ok: + if (CONSTRUCTOR_NO_CLEARING (t)) + /* All the fields are initialized. */ + CONSTRUCTOR_NO_CLEARING (t) = false; + return true; + + default: + /* FIXME are we calling this too much? */ + return initializer_constant_valid_p (t, TREE_TYPE (t)) != NULL_TREE; + } +} + +/* Some expressions may have constant operands but are not constant + themselves, such as 1/0. Call this function to check for that + condition. + + We only call this in places that require an arithmetic constant, not in + places where we might have a non-constant expression that can be a + component of a constant expression, such as the address of a constexpr + variable that might be dereferenced later. */ + +static bool +verify_constant (tree t, bool allow_non_constant, bool *non_constant_p, + bool *overflow_p) +{ + if (!*non_constant_p && !reduced_constant_expression_p (t) + && t != void_node) + { + if (!allow_non_constant) + error ("%q+E is not a constant expression", t); + *non_constant_p = true; + } + if (TREE_OVERFLOW_P (t)) + { + if (!allow_non_constant) + { + permerror (input_location, "overflow in constant expression"); + /* If we're being permissive (and are in an enforcing + context), ignore the overflow. */ + if (flag_permissive) + return *non_constant_p; + } + *overflow_p = true; + } + return *non_constant_p; +} + +/* Check whether the shift operation with code CODE and type TYPE on LHS + and RHS is undefined. If it is, give an error with an explanation, + and return true; return false otherwise. */ + +static bool +cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx, + enum tree_code code, tree type, tree lhs, tree rhs) +{ + if ((code != LSHIFT_EXPR && code != RSHIFT_EXPR) + || TREE_CODE (lhs) != INTEGER_CST + || TREE_CODE (rhs) != INTEGER_CST) + return false; + + tree lhstype = TREE_TYPE (lhs); + unsigned HOST_WIDE_INT uprec = TYPE_PRECISION (TREE_TYPE (lhs)); + + /* [expr.shift] The behavior is undefined if the right operand + is negative, or greater than or equal to the length in bits + of the promoted left operand. */ + if (tree_int_cst_sgn (rhs) == -1) + { + if (!ctx->quiet) + permerror (loc, "right operand of shift expression %q+E is negative", + build2_loc (loc, code, type, lhs, rhs)); + return (!flag_permissive || ctx->quiet); + } + if (compare_tree_int (rhs, uprec) >= 0) + { + if (!ctx->quiet) + permerror (loc, "right operand of shift expression %q+E is greater " + "than or equal to the precision %wu of the left operand", + build2_loc (loc, code, type, lhs, rhs), uprec); + return (!flag_permissive || ctx->quiet); + } + + /* The value of E1 << E2 is E1 left-shifted E2 bit positions; [...] + if E1 has a signed type and non-negative value, and E1x2^E2 is + representable in the corresponding unsigned type of the result type, + then that value, converted to the result type, is the resulting value; + otherwise, the behavior is undefined. + For C++20: + The value of E1 << E2 is the unique value congruent to E1 x 2^E2 modulo + 2^N, where N is the range exponent of the type of the result. */ + if (code == LSHIFT_EXPR + && !TYPE_UNSIGNED (lhstype) + && cxx_dialect >= cxx11 + && cxx_dialect < cxx20) + { + if (tree_int_cst_sgn (lhs) == -1) + { + if (!ctx->quiet) + permerror (loc, + "left operand of shift expression %q+E is negative", + build2_loc (loc, code, type, lhs, rhs)); + return (!flag_permissive || ctx->quiet); + } + /* For signed x << y the following: + (unsigned) x >> ((prec (lhs) - 1) - y) + if > 1, is undefined. The right-hand side of this formula + is the highest bit of the LHS that can be set (starting from 0), + so that the shift doesn't overflow. We then right-shift the LHS + to see whether any other bit is set making the original shift + undefined -- the result is not representable in the corresponding + unsigned type. */ + tree t = build_int_cst (unsigned_type_node, uprec - 1); + t = fold_build2 (MINUS_EXPR, unsigned_type_node, t, rhs); + tree ulhs = fold_convert (unsigned_type_for (lhstype), lhs); + t = fold_build2 (RSHIFT_EXPR, TREE_TYPE (ulhs), ulhs, t); + if (tree_int_cst_lt (integer_one_node, t)) + { + if (!ctx->quiet) + permerror (loc, "shift expression %q+E overflows", + build2_loc (loc, code, type, lhs, rhs)); + return (!flag_permissive || ctx->quiet); + } + } + return false; +} + +/* Subroutine of cxx_eval_constant_expression. + Attempt to reduce the unary expression tree T to a compile time value. + If successful, return the value. Otherwise issue a diagnostic + and return error_mark_node. */ + +static tree +cxx_eval_unary_expression (const constexpr_ctx *ctx, tree t, + bool /*lval*/, + bool *non_constant_p, bool *overflow_p) +{ + tree r; + tree orig_arg = TREE_OPERAND (t, 0); + tree arg = cxx_eval_constant_expression (ctx, orig_arg, /*lval*/false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (arg); + location_t loc = EXPR_LOCATION (t); + enum tree_code code = TREE_CODE (t); + tree type = TREE_TYPE (t); + r = fold_unary_loc (loc, code, type, arg); + if (r == NULL_TREE) + { + if (arg == orig_arg) + r = t; + else + r = build1_loc (loc, code, type, arg); + } + VERIFY_CONSTANT (r); + return r; +} + +/* Helper function for cxx_eval_binary_expression. Try to optimize + original POINTER_PLUS_EXPR T, LHS p+ RHS, return NULL_TREE if the + generic folding should be used. */ + +static tree +cxx_fold_pointer_plus_expression (const constexpr_ctx *ctx, tree t, + tree lhs, tree rhs, bool *non_constant_p, + bool *overflow_p) +{ + STRIP_NOPS (lhs); + if (TREE_CODE (lhs) != ADDR_EXPR) + return NULL_TREE; + + lhs = TREE_OPERAND (lhs, 0); + + /* &A[i] p+ j => &A[i + j] */ + if (TREE_CODE (lhs) == ARRAY_REF + && TREE_CODE (TREE_OPERAND (lhs, 1)) == INTEGER_CST + && TREE_CODE (rhs) == INTEGER_CST + && TYPE_SIZE_UNIT (TREE_TYPE (lhs)) + && TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (lhs))) == INTEGER_CST) + { + tree orig_type = TREE_TYPE (t); + location_t loc = EXPR_LOCATION (t); + tree type = TREE_TYPE (lhs); + + t = fold_convert_loc (loc, ssizetype, TREE_OPERAND (lhs, 1)); + tree nelts = array_type_nelts_top (TREE_TYPE (TREE_OPERAND (lhs, 0))); + nelts = cxx_eval_constant_expression (ctx, nelts, false, non_constant_p, + overflow_p); + if (*non_constant_p) + return NULL_TREE; + /* Don't fold an out-of-bound access. */ + if (!tree_int_cst_le (t, nelts)) + return NULL_TREE; + rhs = cp_fold_convert (ssizetype, rhs); + /* Don't fold if rhs can't be divided exactly by TYPE_SIZE_UNIT. + constexpr int A[1]; ... (char *)&A[0] + 1 */ + if (!integer_zerop (fold_build2_loc (loc, TRUNC_MOD_EXPR, sizetype, + rhs, TYPE_SIZE_UNIT (type)))) + return NULL_TREE; + /* Make sure to treat the second operand of POINTER_PLUS_EXPR + as signed. */ + rhs = fold_build2_loc (loc, EXACT_DIV_EXPR, ssizetype, rhs, + TYPE_SIZE_UNIT (type)); + t = size_binop_loc (loc, PLUS_EXPR, rhs, t); + t = build4_loc (loc, ARRAY_REF, type, TREE_OPERAND (lhs, 0), + t, NULL_TREE, NULL_TREE); + t = cp_build_addr_expr (t, tf_warning_or_error); + t = cp_fold_convert (orig_type, t); + return cxx_eval_constant_expression (ctx, t, /*lval*/false, + non_constant_p, overflow_p); + } + + return NULL_TREE; +} + +/* Try to fold expressions like + (struct S *) (&a[0].D.2378 + 12) + into + &MEM <struct T> [(void *)&a + 12B] + This is something normally done by gimple_fold_stmt_to_constant_1 + on GIMPLE, but is undesirable on GENERIC if we are e.g. going to + dereference the address because some details are lost. + For pointer comparisons we want such folding though so that + match.pd address_compare optimization works. */ + +static tree +cxx_maybe_fold_addr_pointer_plus (tree t) +{ + while (CONVERT_EXPR_P (t) + && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (t, 0)))) + t = TREE_OPERAND (t, 0); + if (TREE_CODE (t) != POINTER_PLUS_EXPR) + return NULL_TREE; + tree op0 = TREE_OPERAND (t, 0); + tree op1 = TREE_OPERAND (t, 1); + if (TREE_CODE (op1) != INTEGER_CST) + return NULL_TREE; + while (CONVERT_EXPR_P (op0) + && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (op0, 0)))) + op0 = TREE_OPERAND (op0, 0); + if (TREE_CODE (op0) != ADDR_EXPR) + return NULL_TREE; + op1 = fold_convert (ptr_type_node, op1); + tree r = fold_build2 (MEM_REF, TREE_TYPE (TREE_TYPE (op0)), op0, op1); + return build1_loc (EXPR_LOCATION (t), ADDR_EXPR, TREE_TYPE (op0), r); +} + +/* Subroutine of cxx_eval_constant_expression. + Like cxx_eval_unary_expression, except for binary expressions. */ + +static tree +cxx_eval_binary_expression (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree r = NULL_TREE; + tree orig_lhs = TREE_OPERAND (t, 0); + tree orig_rhs = TREE_OPERAND (t, 1); + tree lhs, rhs; + lhs = cxx_eval_constant_expression (ctx, orig_lhs, /*lval*/false, + non_constant_p, overflow_p); + /* Don't VERIFY_CONSTANT here, it's unnecessary and will break pointer + subtraction. */ + if (*non_constant_p) + return t; + rhs = cxx_eval_constant_expression (ctx, orig_rhs, /*lval*/false, + non_constant_p, overflow_p); + if (*non_constant_p) + return t; + + location_t loc = EXPR_LOCATION (t); + enum tree_code code = TREE_CODE (t); + tree type = TREE_TYPE (t); + + if (code == EQ_EXPR || code == NE_EXPR) + { + bool is_code_eq = (code == EQ_EXPR); + + if (TREE_CODE (lhs) == PTRMEM_CST + && TREE_CODE (rhs) == PTRMEM_CST) + { + tree lmem = PTRMEM_CST_MEMBER (lhs); + tree rmem = PTRMEM_CST_MEMBER (rhs); + bool eq; + if (TREE_CODE (lmem) == TREE_CODE (rmem) + && TREE_CODE (lmem) == FIELD_DECL + && TREE_CODE (DECL_CONTEXT (lmem)) == UNION_TYPE + && same_type_p (DECL_CONTEXT (lmem), + DECL_CONTEXT (rmem))) + /* If both refer to (possibly different) members of the same union + (12.3), they compare equal. */ + eq = true; + else + eq = cp_tree_equal (lhs, rhs); + r = constant_boolean_node (eq == is_code_eq, type); + } + else if ((TREE_CODE (lhs) == PTRMEM_CST + || TREE_CODE (rhs) == PTRMEM_CST) + && (null_member_pointer_value_p (lhs) + || null_member_pointer_value_p (rhs))) + r = constant_boolean_node (!is_code_eq, type); + else if (TREE_CODE (lhs) == PTRMEM_CST) + lhs = cplus_expand_constant (lhs); + else if (TREE_CODE (rhs) == PTRMEM_CST) + rhs = cplus_expand_constant (rhs); + } + if (r == NULL_TREE + && TREE_CODE_CLASS (code) == tcc_comparison + && POINTER_TYPE_P (TREE_TYPE (lhs))) + { + if (tree lhso = cxx_maybe_fold_addr_pointer_plus (lhs)) + lhs = fold_convert (TREE_TYPE (lhs), lhso); + if (tree rhso = cxx_maybe_fold_addr_pointer_plus (rhs)) + rhs = fold_convert (TREE_TYPE (rhs), rhso); + } + if (code == POINTER_PLUS_EXPR && !*non_constant_p + && integer_zerop (lhs) && !integer_zerop (rhs)) + { + if (!ctx->quiet) + error ("arithmetic involving a null pointer in %qE", lhs); + *non_constant_p = true; + return t; + } + else if (code == POINTER_PLUS_EXPR) + r = cxx_fold_pointer_plus_expression (ctx, t, lhs, rhs, non_constant_p, + overflow_p); + else if (code == SPACESHIP_EXPR) + { + r = genericize_spaceship (loc, type, lhs, rhs); + return cxx_eval_constant_expression (ctx, r, lval, non_constant_p, + overflow_p); + } + + if (r == NULL_TREE) + { + if (ctx->manifestly_const_eval + && (flag_constexpr_fp_except + || TREE_CODE (type) != REAL_TYPE)) + r = fold_binary_initializer_loc (loc, code, type, lhs, rhs); + else + r = fold_binary_loc (loc, code, type, lhs, rhs); + } + + if (r == NULL_TREE + && (code == LSHIFT_EXPR || code == RSHIFT_EXPR) + && TREE_CODE (lhs) == INTEGER_CST + && TREE_CODE (rhs) == INTEGER_CST + && wi::neg_p (wi::to_wide (rhs))) + { + /* For diagnostics and -fpermissive emulate previous behavior of + handling shifts by negative amount. */ + tree nrhs = const_unop (NEGATE_EXPR, TREE_TYPE (rhs), rhs); + if (nrhs) + r = fold_binary_loc (loc, + code == LSHIFT_EXPR ? RSHIFT_EXPR : LSHIFT_EXPR, + type, lhs, nrhs); + } + + if (r == NULL_TREE) + { + if (lhs == orig_lhs && rhs == orig_rhs) + r = t; + else + r = build2_loc (loc, code, type, lhs, rhs); + } + else if (cxx_eval_check_shift_p (loc, ctx, code, type, lhs, rhs)) + *non_constant_p = true; + /* Don't VERIFY_CONSTANT if this might be dealing with a pointer to + a local array in a constexpr function. */ + bool ptr = INDIRECT_TYPE_P (TREE_TYPE (lhs)); + if (!ptr) + VERIFY_CONSTANT (r); + return r; +} + +/* Subroutine of cxx_eval_constant_expression. + Attempt to evaluate condition expressions. Dead branches are not + looked into. */ + +static tree +cxx_eval_conditional_expression (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p, + tree *jump_target) +{ + tree val = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), + /*lval*/false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (val); + if (TREE_CODE (t) == IF_STMT && IF_STMT_CONSTEVAL_P (t)) + { + /* Evaluate the condition as if it was + if (__builtin_is_constant_evaluated ()), i.e. defer it if not + ctx->manifestly_const_eval (as sometimes we try to constant evaluate + without manifestly_const_eval even expressions or parts thereof which + will later be manifestly const_eval evaluated), otherwise fold it to + true. */ + if (ctx->manifestly_const_eval) + val = boolean_true_node; + else + { + *non_constant_p = true; + return t; + } + } + /* Don't VERIFY_CONSTANT the other operands. */ + if (integer_zerop (val)) + val = TREE_OPERAND (t, 2); + else + val = TREE_OPERAND (t, 1); + if (TREE_CODE (t) == IF_STMT && !val) + val = void_node; + return cxx_eval_constant_expression (ctx, val, lval, non_constant_p, + overflow_p, jump_target); +} + +/* Subroutine of cxx_eval_constant_expression. + Attempt to evaluate vector condition expressions. Unlike + cxx_eval_conditional_expression, VEC_COND_EXPR acts like a normal + ternary arithmetics operation, where all 3 arguments have to be + evaluated as constants and then folding computes the result from + them. */ + +static tree +cxx_eval_vector_conditional_expression (const constexpr_ctx *ctx, tree t, + bool *non_constant_p, bool *overflow_p) +{ + tree arg1 = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), + /*lval*/false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (arg1); + tree arg2 = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 1), + /*lval*/false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (arg2); + tree arg3 = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 2), + /*lval*/false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (arg3); + location_t loc = EXPR_LOCATION (t); + tree type = TREE_TYPE (t); + tree r = fold_ternary_loc (loc, VEC_COND_EXPR, type, arg1, arg2, arg3); + if (r == NULL_TREE) + { + if (arg1 == TREE_OPERAND (t, 0) + && arg2 == TREE_OPERAND (t, 1) + && arg3 == TREE_OPERAND (t, 2)) + r = t; + else + r = build3_loc (loc, VEC_COND_EXPR, type, arg1, arg2, arg3); + } + VERIFY_CONSTANT (r); + return r; +} + +/* Returns less than, equal to, or greater than zero if KEY is found to be + less than, to match, or to be greater than the constructor_elt's INDEX. */ + +static int +array_index_cmp (tree key, tree index) +{ + gcc_assert (TREE_CODE (key) == INTEGER_CST); + + switch (TREE_CODE (index)) + { + case INTEGER_CST: + return tree_int_cst_compare (key, index); + case RANGE_EXPR: + { + tree lo = TREE_OPERAND (index, 0); + tree hi = TREE_OPERAND (index, 1); + if (tree_int_cst_lt (key, lo)) + return -1; + else if (tree_int_cst_lt (hi, key)) + return 1; + else + return 0; + } + default: + gcc_unreachable (); + } +} + +/* Returns the index of the constructor_elt of ARY which matches DINDEX, or -1 + if none. If INSERT is true, insert a matching element rather than fail. */ + +static HOST_WIDE_INT +find_array_ctor_elt (tree ary, tree dindex, bool insert) +{ + if (tree_int_cst_sgn (dindex) < 0) + return -1; + + unsigned HOST_WIDE_INT i = tree_to_uhwi (dindex); + vec<constructor_elt, va_gc> *elts = CONSTRUCTOR_ELTS (ary); + unsigned HOST_WIDE_INT len = vec_safe_length (elts); + + unsigned HOST_WIDE_INT end = len; + unsigned HOST_WIDE_INT begin = 0; + + /* If the last element of the CONSTRUCTOR has its own index, we can assume + that the same is true of the other elements and index directly. */ + if (end > 0) + { + tree cindex = (*elts)[end - 1].index; + if (cindex == NULL_TREE) + { + /* Verify that if the last index is missing, all indexes + are missing. */ + if (flag_checking) + for (unsigned int j = 0; j < len - 1; ++j) + gcc_assert ((*elts)[j].index == NULL_TREE); + if (i < end) + return i; + else + { + begin = end; + if (i == end) + /* If the element is to be added right at the end, + make sure it is added with cleared index too. */ + dindex = NULL_TREE; + else if (insert) + /* Otherwise, in order not to break the assumption + that CONSTRUCTOR either has all indexes or none, + we need to add indexes to all elements. */ + for (unsigned int j = 0; j < len; ++j) + (*elts)[j].index = build_int_cst (TREE_TYPE (dindex), j); + } + } + else if (TREE_CODE (cindex) == INTEGER_CST + && compare_tree_int (cindex, end - 1) == 0) + { + if (i < end) + return i; + else + begin = end; + } + } + + /* Otherwise, find a matching index by means of a binary search. */ + while (begin != end) + { + unsigned HOST_WIDE_INT middle = (begin + end) / 2; + constructor_elt &elt = (*elts)[middle]; + tree idx = elt.index; + + int cmp = array_index_cmp (dindex, idx); + if (cmp < 0) + end = middle; + else if (cmp > 0) + begin = middle + 1; + else + { + if (insert && TREE_CODE (idx) == RANGE_EXPR) + { + /* We need to split the range. */ + constructor_elt e; + tree lo = TREE_OPERAND (idx, 0); + tree hi = TREE_OPERAND (idx, 1); + tree value = elt.value; + dindex = fold_convert (sizetype, dindex); + if (tree_int_cst_lt (lo, dindex)) + { + /* There are still some lower elts; shorten the range. */ + tree new_hi = int_const_binop (MINUS_EXPR, dindex, + size_one_node); + if (tree_int_cst_equal (lo, new_hi)) + /* Only one element left, no longer a range. */ + elt.index = lo; + else + TREE_OPERAND (idx, 1) = new_hi; + /* Append the element we want to insert. */ + ++middle; + e.index = dindex; + e.value = unshare_constructor (value); + vec_safe_insert (CONSTRUCTOR_ELTS (ary), middle, e); + } + else + /* No lower elts, the range elt is now ours. */ + elt.index = dindex; + + if (tree_int_cst_lt (dindex, hi)) + { + /* There are still some higher elts; append a range. */ + tree new_lo = int_const_binop (PLUS_EXPR, dindex, + size_one_node); + if (tree_int_cst_equal (new_lo, hi)) + e.index = hi; + else + e.index = build2 (RANGE_EXPR, sizetype, new_lo, hi); + e.value = unshare_constructor (value); + vec_safe_insert (CONSTRUCTOR_ELTS (ary), middle + 1, e); + } + } + return middle; + } + } + + if (insert) + { + constructor_elt e = { dindex, NULL_TREE }; + vec_safe_insert (CONSTRUCTOR_ELTS (ary), end, e); + return end; + } + + return -1; +} + +/* Return a pointer to the constructor_elt of CTOR which matches INDEX. If no + matching constructor_elt exists, then add one to CTOR. + + As an optimization, if POS_HINT is non-negative then it is used as a guess + for the (integer) index of the matching constructor_elt within CTOR. */ + +static constructor_elt * +get_or_insert_ctor_field (tree ctor, tree index, int pos_hint = -1) +{ + /* Check the hint first. */ + if (pos_hint >= 0 && (unsigned)pos_hint < CONSTRUCTOR_NELTS (ctor) + && CONSTRUCTOR_ELT (ctor, pos_hint)->index == index) + return CONSTRUCTOR_ELT (ctor, pos_hint); + + tree type = TREE_TYPE (ctor); + if (TREE_CODE (type) == VECTOR_TYPE && index == NULL_TREE) + { + CONSTRUCTOR_APPEND_ELT (CONSTRUCTOR_ELTS (ctor), index, NULL_TREE); + return &CONSTRUCTOR_ELTS (ctor)->last(); + } + else if (TREE_CODE (type) == ARRAY_TYPE || TREE_CODE (type) == VECTOR_TYPE) + { + if (TREE_CODE (index) == RANGE_EXPR) + { + /* Support for RANGE_EXPR index lookups is currently limited to + accessing an existing element via POS_HINT, or appending a new + element to the end of CTOR. ??? Support for other access + patterns may also be needed. */ + vec<constructor_elt, va_gc> *elts = CONSTRUCTOR_ELTS (ctor); + if (vec_safe_length (elts)) + { + tree lo = TREE_OPERAND (index, 0); + gcc_assert (array_index_cmp (elts->last().index, lo) < 0); + } + CONSTRUCTOR_APPEND_ELT (elts, index, NULL_TREE); + return &elts->last(); + } + + HOST_WIDE_INT i = find_array_ctor_elt (ctor, index, /*insert*/true); + gcc_assert (i >= 0); + constructor_elt *cep = CONSTRUCTOR_ELT (ctor, i); + gcc_assert (cep->index == NULL_TREE + || TREE_CODE (cep->index) != RANGE_EXPR); + return cep; + } + else + { + gcc_assert (TREE_CODE (index) == FIELD_DECL + && (same_type_ignoring_top_level_qualifiers_p + (DECL_CONTEXT (index), TREE_TYPE (ctor)))); + + /* We must keep the CONSTRUCTOR's ELTS in FIELD order. + Usually we meet initializers in that order, but it is + possible for base types to be placed not in program + order. */ + tree fields = TYPE_FIELDS (DECL_CONTEXT (index)); + unsigned HOST_WIDE_INT idx = 0; + constructor_elt *cep = NULL; + + /* Check if we're changing the active member of a union. */ + if (TREE_CODE (type) == UNION_TYPE && CONSTRUCTOR_NELTS (ctor) + && CONSTRUCTOR_ELT (ctor, 0)->index != index) + vec_safe_truncate (CONSTRUCTOR_ELTS (ctor), 0); + /* If the bit offset of INDEX is larger than that of the last + constructor_elt, then we can just immediately append a new + constructor_elt to the end of CTOR. */ + else if (CONSTRUCTOR_NELTS (ctor) + && tree_int_cst_compare (bit_position (index), + bit_position (CONSTRUCTOR_ELTS (ctor) + ->last().index)) > 0) + { + idx = CONSTRUCTOR_NELTS (ctor); + goto insert; + } + + /* Otherwise, we need to iterate over CTOR to find or insert INDEX + appropriately. */ + + for (; vec_safe_iterate (CONSTRUCTOR_ELTS (ctor), idx, &cep); + idx++, fields = DECL_CHAIN (fields)) + { + if (index == cep->index) + goto found; + + /* The field we're initializing must be on the field + list. Look to see if it is present before the + field the current ELT initializes. */ + for (; fields != cep->index; fields = DECL_CHAIN (fields)) + if (index == fields) + goto insert; + } + /* We fell off the end of the CONSTRUCTOR, so insert a new + entry at the end. */ + + insert: + { + constructor_elt ce = { index, NULL_TREE }; + + vec_safe_insert (CONSTRUCTOR_ELTS (ctor), idx, ce); + cep = CONSTRUCTOR_ELT (ctor, idx); + } + found:; + + return cep; + } +} + +/* Under the control of CTX, issue a detailed diagnostic for + an out-of-bounds subscript INDEX into the expression ARRAY. */ + +static void +diag_array_subscript (location_t loc, const constexpr_ctx *ctx, tree array, tree index) +{ + if (!ctx->quiet) + { + tree arraytype = TREE_TYPE (array); + + /* Convert the unsigned array subscript to a signed integer to avoid + printing huge numbers for small negative values. */ + tree sidx = fold_convert (ssizetype, index); + STRIP_ANY_LOCATION_WRAPPER (array); + if (DECL_P (array)) + { + if (TYPE_DOMAIN (arraytype)) + error_at (loc, "array subscript value %qE is outside the bounds " + "of array %qD of type %qT", sidx, array, arraytype); + else + error_at (loc, "nonzero array subscript %qE is used with array %qD of " + "type %qT with unknown bounds", sidx, array, arraytype); + inform (DECL_SOURCE_LOCATION (array), "declared here"); + } + else if (TYPE_DOMAIN (arraytype)) + error_at (loc, "array subscript value %qE is outside the bounds " + "of array type %qT", sidx, arraytype); + else + error_at (loc, "nonzero array subscript %qE is used with array of type %qT " + "with unknown bounds", sidx, arraytype); + } +} + +/* Return the number of elements for TYPE (which is an ARRAY_TYPE or + a VECTOR_TYPE). */ + +static tree +get_array_or_vector_nelts (const constexpr_ctx *ctx, tree type, + bool *non_constant_p, bool *overflow_p) +{ + tree nelts; + if (TREE_CODE (type) == ARRAY_TYPE) + { + if (TYPE_DOMAIN (type)) + nelts = array_type_nelts_top (type); + else + nelts = size_zero_node; + } + else if (VECTOR_TYPE_P (type)) + nelts = size_int (TYPE_VECTOR_SUBPARTS (type)); + else + gcc_unreachable (); + + /* For VLAs, the number of elements won't be an integer constant. */ + nelts = cxx_eval_constant_expression (ctx, nelts, false, + non_constant_p, overflow_p); + return nelts; +} + +/* Extract element INDEX consisting of CHARS_PER_ELT chars from + STRING_CST STRING. */ + +static tree +extract_string_elt (tree string, unsigned chars_per_elt, unsigned index) +{ + tree type = cv_unqualified (TREE_TYPE (TREE_TYPE (string))); + tree r; + + if (chars_per_elt == 1) + r = build_int_cst (type, TREE_STRING_POINTER (string)[index]); + else + { + const unsigned char *ptr + = ((const unsigned char *)TREE_STRING_POINTER (string) + + index * chars_per_elt); + r = native_interpret_expr (type, ptr, chars_per_elt); + } + return r; +} + +/* Subroutine of cxx_eval_array_reference. T is an ARRAY_REF; evaluate the + subscript, diagnose any problems with it, and return the result. */ + +static tree +eval_and_check_array_index (const constexpr_ctx *ctx, + tree t, bool allow_one_past, + bool *non_constant_p, bool *overflow_p) +{ + location_t loc = cp_expr_loc_or_input_loc (t); + tree ary = TREE_OPERAND (t, 0); + t = TREE_OPERAND (t, 1); + tree index = cxx_eval_constant_expression (ctx, t, false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (index); + + if (!tree_fits_shwi_p (index) + || tree_int_cst_sgn (index) < 0) + { + diag_array_subscript (loc, ctx, ary, index); + *non_constant_p = true; + return t; + } + + tree nelts = get_array_or_vector_nelts (ctx, TREE_TYPE (ary), non_constant_p, + overflow_p); + VERIFY_CONSTANT (nelts); + if (allow_one_past + ? !tree_int_cst_le (index, nelts) + : !tree_int_cst_lt (index, nelts)) + { + diag_array_subscript (loc, ctx, ary, index); + *non_constant_p = true; + return t; + } + + return index; +} + +/* Subroutine of cxx_eval_constant_expression. + Attempt to reduce a reference to an array slot. */ + +static tree +cxx_eval_array_reference (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree oldary = TREE_OPERAND (t, 0); + tree ary = cxx_eval_constant_expression (ctx, oldary, + lval, + non_constant_p, overflow_p); + if (*non_constant_p) + return t; + if (!lval + && TREE_CODE (ary) == VIEW_CONVERT_EXPR + && VECTOR_TYPE_P (TREE_TYPE (TREE_OPERAND (ary, 0))) + && TREE_TYPE (t) == TREE_TYPE (TREE_TYPE (TREE_OPERAND (ary, 0)))) + ary = TREE_OPERAND (ary, 0); + + tree oldidx = TREE_OPERAND (t, 1); + tree index = eval_and_check_array_index (ctx, t, lval, + non_constant_p, overflow_p); + if (*non_constant_p) + return t; + + if (lval && ary == oldary && index == oldidx) + return t; + else if (lval) + return build4 (ARRAY_REF, TREE_TYPE (t), ary, index, NULL, NULL); + + unsigned len = 0, elem_nchars = 1; + tree elem_type = TREE_TYPE (TREE_TYPE (ary)); + if (TREE_CODE (ary) == CONSTRUCTOR) + len = CONSTRUCTOR_NELTS (ary); + else if (TREE_CODE (ary) == STRING_CST) + { + elem_nchars = (TYPE_PRECISION (elem_type) + / TYPE_PRECISION (char_type_node)); + len = (unsigned) TREE_STRING_LENGTH (ary) / elem_nchars; + } + else if (TREE_CODE (ary) == VECTOR_CST) + /* We don't create variable-length VECTOR_CSTs. */ + len = VECTOR_CST_NELTS (ary).to_constant (); + else + { + /* We can't do anything with other tree codes, so use + VERIFY_CONSTANT to complain and fail. */ + VERIFY_CONSTANT (ary); + gcc_unreachable (); + } + + bool found; + HOST_WIDE_INT i = 0; + if (TREE_CODE (ary) == CONSTRUCTOR) + { + HOST_WIDE_INT ix = find_array_ctor_elt (ary, index); + found = (ix >= 0); + if (found) + i = ix; + } + else + { + i = tree_to_shwi (index); + found = (i < len); + } + + if (found) + { + tree r; + if (TREE_CODE (ary) == CONSTRUCTOR) + r = (*CONSTRUCTOR_ELTS (ary))[i].value; + else if (TREE_CODE (ary) == VECTOR_CST) + r = VECTOR_CST_ELT (ary, i); + else + r = extract_string_elt (ary, elem_nchars, i); + + if (r) + /* Don't VERIFY_CONSTANT here. */ + return r; + + /* Otherwise the element doesn't have a value yet. */ + } + + /* Not found. */ + + if (TREE_CODE (ary) == CONSTRUCTOR + && CONSTRUCTOR_NO_CLEARING (ary)) + { + /* 'ary' is part of the aggregate initializer we're currently + building; if there's no initializer for this element yet, + that's an error. */ + if (!ctx->quiet) + error ("accessing uninitialized array element"); + *non_constant_p = true; + return t; + } + + /* If it's within the array bounds but doesn't have an explicit + initializer, it's initialized from {}. But use build_value_init + directly for non-aggregates to avoid creating a garbage CONSTRUCTOR. */ + tree val; + constexpr_ctx new_ctx; + if (is_really_empty_class (elem_type, /*ignore_vptr*/false)) + return build_constructor (elem_type, NULL); + else if (CP_AGGREGATE_TYPE_P (elem_type)) + { + tree empty_ctor = build_constructor (init_list_type_node, NULL); + val = digest_init (elem_type, empty_ctor, tf_warning_or_error); + } + else + val = build_value_init (elem_type, tf_warning_or_error); + + if (!SCALAR_TYPE_P (elem_type)) + { + new_ctx = *ctx; + if (ctx->object) + /* If there was no object, don't add one: it could confuse us + into thinking we're modifying a const object. */ + new_ctx.object = t; + new_ctx.ctor = build_constructor (elem_type, NULL); + ctx = &new_ctx; + } + t = cxx_eval_constant_expression (ctx, val, lval, non_constant_p, + overflow_p); + if (!SCALAR_TYPE_P (elem_type) && t != ctx->ctor) + free_constructor (ctx->ctor); + return t; +} + +/* Subroutine of cxx_eval_constant_expression. + Attempt to reduce a field access of a value of class type. */ + +static tree +cxx_eval_component_reference (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + unsigned HOST_WIDE_INT i; + tree field; + tree value; + tree part = TREE_OPERAND (t, 1); + tree orig_whole = TREE_OPERAND (t, 0); + tree whole = cxx_eval_constant_expression (ctx, orig_whole, + lval, + non_constant_p, overflow_p); + if (INDIRECT_REF_P (whole) + && integer_zerop (TREE_OPERAND (whole, 0))) + { + if (!ctx->quiet) + error ("dereferencing a null pointer in %qE", orig_whole); + *non_constant_p = true; + return t; + } + + if (TREE_CODE (whole) == PTRMEM_CST) + whole = cplus_expand_constant (whole); + if (whole == orig_whole) + return t; + if (lval) + return fold_build3 (COMPONENT_REF, TREE_TYPE (t), + whole, part, NULL_TREE); + /* Don't VERIFY_CONSTANT here; we only want to check that we got a + CONSTRUCTOR. */ + if (!*non_constant_p && TREE_CODE (whole) != CONSTRUCTOR) + { + if (!ctx->quiet) + error ("%qE is not a constant expression", orig_whole); + *non_constant_p = true; + } + if (DECL_MUTABLE_P (part)) + { + if (!ctx->quiet) + error ("mutable %qD is not usable in a constant expression", part); + *non_constant_p = true; + } + if (*non_constant_p) + return t; + bool pmf = TYPE_PTRMEMFUNC_P (TREE_TYPE (whole)); + FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (whole), i, field, value) + { + /* Use name match for PMF fields, as a variant will have a + different FIELD_DECL with a different type. */ + if (pmf ? DECL_NAME (field) == DECL_NAME (part) + : field == part) + { + if (value) + { + STRIP_ANY_LOCATION_WRAPPER (value); + return value; + } + else + /* We're in the middle of initializing it. */ + break; + } + } + if (TREE_CODE (TREE_TYPE (whole)) == UNION_TYPE + && CONSTRUCTOR_NELTS (whole) > 0) + { + /* DR 1188 says we don't have to deal with this. */ + if (!ctx->quiet) + { + constructor_elt *cep = CONSTRUCTOR_ELT (whole, 0); + if (cep->value == NULL_TREE) + error ("accessing uninitialized member %qD", part); + else + error ("accessing %qD member instead of initialized %qD member in " + "constant expression", part, cep->index); + } + *non_constant_p = true; + return t; + } + + /* We only create a CONSTRUCTOR for a subobject when we modify it, so empty + classes never get represented; throw together a value now. */ + if (is_really_empty_class (TREE_TYPE (t), /*ignore_vptr*/false)) + return build_constructor (TREE_TYPE (t), NULL); + + gcc_assert (DECL_CONTEXT (part) == TYPE_MAIN_VARIANT (TREE_TYPE (whole))); + + if (CONSTRUCTOR_NO_CLEARING (whole)) + { + /* 'whole' is part of the aggregate initializer we're currently + building; if there's no initializer for this member yet, that's an + error. */ + if (!ctx->quiet) + error ("accessing uninitialized member %qD", part); + *non_constant_p = true; + return t; + } + + /* If there's no explicit init for this field, it's value-initialized. */ + value = build_value_init (TREE_TYPE (t), tf_warning_or_error); + return cxx_eval_constant_expression (ctx, value, + lval, + non_constant_p, overflow_p); +} + +/* Subroutine of cxx_eval_constant_expression. + Attempt to reduce a field access of a value of class type that is + expressed as a BIT_FIELD_REF. */ + +static tree +cxx_eval_bit_field_ref (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree orig_whole = TREE_OPERAND (t, 0); + tree retval, fldval, utype, mask; + bool fld_seen = false; + HOST_WIDE_INT istart, isize; + tree whole = cxx_eval_constant_expression (ctx, orig_whole, + lval, + non_constant_p, overflow_p); + tree start, field, value; + unsigned HOST_WIDE_INT i; + + if (whole == orig_whole) + return t; + /* Don't VERIFY_CONSTANT here; we only want to check that we got a + CONSTRUCTOR. */ + if (!*non_constant_p + && TREE_CODE (whole) != VECTOR_CST + && TREE_CODE (whole) != CONSTRUCTOR) + { + if (!ctx->quiet) + error ("%qE is not a constant expression", orig_whole); + *non_constant_p = true; + } + if (*non_constant_p) + return t; + + if (TREE_CODE (whole) == VECTOR_CST) + return fold_ternary (BIT_FIELD_REF, TREE_TYPE (t), whole, + TREE_OPERAND (t, 1), TREE_OPERAND (t, 2)); + + start = TREE_OPERAND (t, 2); + istart = tree_to_shwi (start); + isize = tree_to_shwi (TREE_OPERAND (t, 1)); + utype = TREE_TYPE (t); + if (!TYPE_UNSIGNED (utype)) + utype = build_nonstandard_integer_type (TYPE_PRECISION (utype), 1); + retval = build_int_cst (utype, 0); + FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (whole), i, field, value) + { + tree bitpos = bit_position (field); + STRIP_ANY_LOCATION_WRAPPER (value); + if (bitpos == start && DECL_SIZE (field) == TREE_OPERAND (t, 1)) + return value; + if (TREE_CODE (TREE_TYPE (field)) == INTEGER_TYPE + && TREE_CODE (value) == INTEGER_CST + && tree_fits_shwi_p (bitpos) + && tree_fits_shwi_p (DECL_SIZE (field))) + { + HOST_WIDE_INT bit = tree_to_shwi (bitpos); + HOST_WIDE_INT sz = tree_to_shwi (DECL_SIZE (field)); + HOST_WIDE_INT shift; + if (bit >= istart && bit + sz <= istart + isize) + { + fldval = fold_convert (utype, value); + mask = build_int_cst_type (utype, -1); + mask = fold_build2 (LSHIFT_EXPR, utype, mask, + size_int (TYPE_PRECISION (utype) - sz)); + mask = fold_build2 (RSHIFT_EXPR, utype, mask, + size_int (TYPE_PRECISION (utype) - sz)); + fldval = fold_build2 (BIT_AND_EXPR, utype, fldval, mask); + shift = bit - istart; + if (BYTES_BIG_ENDIAN) + shift = TYPE_PRECISION (utype) - shift - sz; + fldval = fold_build2 (LSHIFT_EXPR, utype, fldval, + size_int (shift)); + retval = fold_build2 (BIT_IOR_EXPR, utype, retval, fldval); + fld_seen = true; + } + } + } + if (fld_seen) + return fold_convert (TREE_TYPE (t), retval); + gcc_unreachable (); + return error_mark_node; +} + +/* Helper for cxx_eval_bit_cast. + Check [bit.cast]/3 rules, bit_cast is constexpr only if the To and From + types and types of all subobjects have is_union_v<T>, is_pointer_v<T>, + is_member_pointer_v<T>, is_volatile_v<T> false and has no non-static + data members of reference type. */ + +static bool +check_bit_cast_type (const constexpr_ctx *ctx, location_t loc, tree type, + tree orig_type) +{ + if (TREE_CODE (type) == UNION_TYPE) + { + if (!ctx->quiet) + { + if (type == orig_type) + error_at (loc, "%qs is not a constant expression because %qT is " + "a union type", "__builtin_bit_cast", type); + else + error_at (loc, "%qs is not a constant expression because %qT " + "contains a union type", "__builtin_bit_cast", + orig_type); + } + return true; + } + if (TREE_CODE (type) == POINTER_TYPE) + { + if (!ctx->quiet) + { + if (type == orig_type) + error_at (loc, "%qs is not a constant expression because %qT is " + "a pointer type", "__builtin_bit_cast", type); + else + error_at (loc, "%qs is not a constant expression because %qT " + "contains a pointer type", "__builtin_bit_cast", + orig_type); + } + return true; + } + if (TREE_CODE (type) == REFERENCE_TYPE) + { + if (!ctx->quiet) + { + if (type == orig_type) + error_at (loc, "%qs is not a constant expression because %qT is " + "a reference type", "__builtin_bit_cast", type); + else + error_at (loc, "%qs is not a constant expression because %qT " + "contains a reference type", "__builtin_bit_cast", + orig_type); + } + return true; + } + if (TYPE_PTRMEM_P (type)) + { + if (!ctx->quiet) + { + if (type == orig_type) + error_at (loc, "%qs is not a constant expression because %qT is " + "a pointer to member type", "__builtin_bit_cast", + type); + else + error_at (loc, "%qs is not a constant expression because %qT " + "contains a pointer to member type", + "__builtin_bit_cast", orig_type); + } + return true; + } + if (TYPE_VOLATILE (type)) + { + if (!ctx->quiet) + { + if (type == orig_type) + error_at (loc, "%qs is not a constant expression because %qT is " + "volatile", "__builtin_bit_cast", type); + else + error_at (loc, "%qs is not a constant expression because %qT " + "contains a volatile subobject", + "__builtin_bit_cast", orig_type); + } + return true; + } + if (TREE_CODE (type) == RECORD_TYPE) + for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field)) + if (TREE_CODE (field) == FIELD_DECL + && check_bit_cast_type (ctx, loc, TREE_TYPE (field), orig_type)) + return true; + return false; +} + +/* Helper function for cxx_eval_bit_cast. For unsigned char or + std::byte members of CONSTRUCTOR (recursively) if they contain + some indeterminate bits (as set in MASK), remove the ctor elts, + mark the CONSTRUCTOR as CONSTRUCTOR_NO_CLEARING and clear the + bits in MASK. */ + +static void +clear_uchar_or_std_byte_in_mask (location_t loc, tree t, unsigned char *mask) +{ + if (TREE_CODE (t) != CONSTRUCTOR) + return; + + unsigned i, j = 0; + tree index, value; + FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (t), i, index, value) + { + tree type = TREE_TYPE (value); + if (TREE_CODE (TREE_TYPE (t)) != ARRAY_TYPE + && DECL_BIT_FIELD_TYPE (index) != NULL_TREE) + { + if (is_byte_access_type_not_plain_char (DECL_BIT_FIELD_TYPE (index))) + { + HOST_WIDE_INT fldsz = TYPE_PRECISION (TREE_TYPE (index)); + gcc_assert (fldsz != 0); + HOST_WIDE_INT pos = int_byte_position (index); + HOST_WIDE_INT bpos + = tree_to_uhwi (DECL_FIELD_BIT_OFFSET (index)); + bpos %= BITS_PER_UNIT; + HOST_WIDE_INT end + = ROUND_UP (bpos + fldsz, BITS_PER_UNIT) / BITS_PER_UNIT; + gcc_assert (end == 1 || end == 2); + unsigned char *p = mask + pos; + unsigned char mask_save[2]; + mask_save[0] = mask[pos]; + mask_save[1] = end == 2 ? mask[pos + 1] : 0; + if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN) + sorry_at (loc, "PDP11 bit-field handling unsupported" + " in %qs", "__builtin_bit_cast"); + else if (BYTES_BIG_ENDIAN) + { + /* Big endian. */ + if (bpos + fldsz <= BITS_PER_UNIT) + *p &= ~(((1 << fldsz) - 1) + << (BITS_PER_UNIT - bpos - fldsz)); + else + { + gcc_assert (bpos); + *p &= ~(((1U << BITS_PER_UNIT) - 1) >> bpos); + p++; + fldsz -= BITS_PER_UNIT - bpos; + gcc_assert (fldsz && fldsz < BITS_PER_UNIT); + *p &= ((1U << BITS_PER_UNIT) - 1) >> fldsz; + } + } + else + { + /* Little endian. */ + if (bpos + fldsz <= BITS_PER_UNIT) + *p &= ~(((1 << fldsz) - 1) << bpos); + else + { + gcc_assert (bpos); + *p &= ~(((1 << BITS_PER_UNIT) - 1) << bpos); + p++; + fldsz -= BITS_PER_UNIT - bpos; + gcc_assert (fldsz && fldsz < BITS_PER_UNIT); + *p &= ~((1 << fldsz) - 1); + } + } + if (mask_save[0] != mask[pos] + || (end == 2 && mask_save[1] != mask[pos + 1])) + { + CONSTRUCTOR_NO_CLEARING (t) = 1; + continue; + } + } + } + else if (is_byte_access_type_not_plain_char (type)) + { + HOST_WIDE_INT pos; + if (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE) + pos = tree_to_shwi (index); + else + pos = int_byte_position (index); + if (mask[pos]) + { + CONSTRUCTOR_NO_CLEARING (t) = 1; + mask[pos] = 0; + continue; + } + } + if (TREE_CODE (value) == CONSTRUCTOR) + { + HOST_WIDE_INT pos; + if (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE) + pos = tree_to_shwi (index) + * tree_to_shwi (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (t)))); + else + pos = int_byte_position (index); + clear_uchar_or_std_byte_in_mask (loc, value, mask + pos); + } + if (i != j) + { + CONSTRUCTOR_ELT (t, j)->index = index; + CONSTRUCTOR_ELT (t, j)->value = value; + } + ++j; + } + if (CONSTRUCTOR_NELTS (t) != j) + vec_safe_truncate (CONSTRUCTOR_ELTS (t), j); +} + +/* Subroutine of cxx_eval_constant_expression. + Attempt to evaluate a BIT_CAST_EXPR. */ + +static tree +cxx_eval_bit_cast (const constexpr_ctx *ctx, tree t, bool *non_constant_p, + bool *overflow_p) +{ + if (check_bit_cast_type (ctx, EXPR_LOCATION (t), TREE_TYPE (t), + TREE_TYPE (t)) + || check_bit_cast_type (ctx, cp_expr_loc_or_loc (TREE_OPERAND (t, 0), + EXPR_LOCATION (t)), + TREE_TYPE (TREE_OPERAND (t, 0)), + TREE_TYPE (TREE_OPERAND (t, 0)))) + { + *non_constant_p = true; + return t; + } + + tree op = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), false, + non_constant_p, overflow_p); + if (*non_constant_p) + return t; + + location_t loc = EXPR_LOCATION (t); + if (BITS_PER_UNIT != 8 || CHAR_BIT != 8) + { + if (!ctx->quiet) + sorry_at (loc, "%qs cannot be constant evaluated on the target", + "__builtin_bit_cast"); + *non_constant_p = true; + return t; + } + + if (!tree_fits_shwi_p (TYPE_SIZE_UNIT (TREE_TYPE (t)))) + { + if (!ctx->quiet) + sorry_at (loc, "%qs cannot be constant evaluated because the " + "type is too large", "__builtin_bit_cast"); + *non_constant_p = true; + return t; + } + + HOST_WIDE_INT len = tree_to_shwi (TYPE_SIZE_UNIT (TREE_TYPE (t))); + if (len < 0 || (int) len != len) + { + if (!ctx->quiet) + sorry_at (loc, "%qs cannot be constant evaluated because the " + "type is too large", "__builtin_bit_cast"); + *non_constant_p = true; + return t; + } + + unsigned char buf[64]; + unsigned char *ptr, *mask; + size_t alen = (size_t) len * 2; + if (alen <= sizeof (buf)) + ptr = buf; + else + ptr = XNEWVEC (unsigned char, alen); + mask = ptr + (size_t) len; + /* At the beginning consider everything indeterminate. */ + memset (mask, ~0, (size_t) len); + + if (native_encode_initializer (op, ptr, len, 0, mask) != len) + { + if (!ctx->quiet) + sorry_at (loc, "%qs cannot be constant evaluated because the " + "argument cannot be encoded", "__builtin_bit_cast"); + *non_constant_p = true; + if (ptr != buf) + XDELETE (ptr); + return t; + } + + tree r = NULL_TREE; + if (can_native_interpret_type_p (TREE_TYPE (t))) + { + r = native_interpret_expr (TREE_TYPE (t), ptr, len); + if (is_byte_access_type_not_plain_char (TREE_TYPE (t))) + { + gcc_assert (len == 1); + if (mask[0]) + { + memset (mask, 0, len); + r = build_constructor (TREE_TYPE (r), NULL); + CONSTRUCTOR_NO_CLEARING (r) = 1; + } + } + } + else if (TREE_CODE (TREE_TYPE (t)) == RECORD_TYPE) + { + r = native_interpret_aggregate (TREE_TYPE (t), ptr, 0, len); + if (r != NULL_TREE) + { + clear_type_padding_in_mask (TREE_TYPE (t), mask); + clear_uchar_or_std_byte_in_mask (loc, r, mask); + } + } + + if (r != NULL_TREE) + { + for (int i = 0; i < len; i++) + if (mask[i]) + { + if (!ctx->quiet) + error_at (loc, "%qs accessing uninitialized byte at offset %d", + "__builtin_bit_cast", i); + *non_constant_p = true; + r = t; + break; + } + if (ptr != buf) + XDELETE (ptr); + return r; + } + + if (!ctx->quiet) + sorry_at (loc, "%qs cannot be constant evaluated because the " + "argument cannot be interpreted", "__builtin_bit_cast"); + *non_constant_p = true; + if (ptr != buf) + XDELETE (ptr); + return t; +} + +/* Subroutine of cxx_eval_constant_expression. + Evaluate a short-circuited logical expression T in the context + of a given constexpr CALL. BAILOUT_VALUE is the value for + early return. CONTINUE_VALUE is used here purely for + sanity check purposes. */ + +static tree +cxx_eval_logical_expression (const constexpr_ctx *ctx, tree t, + tree bailout_value, tree continue_value, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree r; + tree lhs = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), + lval, + non_constant_p, overflow_p); + VERIFY_CONSTANT (lhs); + if (tree_int_cst_equal (lhs, bailout_value)) + return lhs; + gcc_assert (tree_int_cst_equal (lhs, continue_value)); + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 1), + lval, non_constant_p, + overflow_p); + VERIFY_CONSTANT (r); + return r; +} + +/* REF is a COMPONENT_REF designating a particular field. V is a vector of + CONSTRUCTOR elements to initialize (part of) an object containing that + field. Return a pointer to the constructor_elt corresponding to the + initialization of the field. */ + +static constructor_elt * +base_field_constructor_elt (vec<constructor_elt, va_gc> *v, tree ref) +{ + tree aggr = TREE_OPERAND (ref, 0); + tree field = TREE_OPERAND (ref, 1); + HOST_WIDE_INT i; + constructor_elt *ce; + + gcc_assert (TREE_CODE (ref) == COMPONENT_REF); + + if (TREE_CODE (aggr) == COMPONENT_REF) + { + constructor_elt *base_ce + = base_field_constructor_elt (v, aggr); + v = CONSTRUCTOR_ELTS (base_ce->value); + } + + for (i = 0; vec_safe_iterate (v, i, &ce); ++i) + if (ce->index == field) + return ce; + + gcc_unreachable (); + return NULL; +} + +/* Some of the expressions fed to the constexpr mechanism are calls to + constructors, which have type void. In that case, return the type being + initialized by the constructor. */ + +static tree +initialized_type (tree t) +{ + if (TYPE_P (t)) + return t; + tree type = TREE_TYPE (t); + if (TREE_CODE (t) == CALL_EXPR) + { + /* A constructor call has void type, so we need to look deeper. */ + tree fn = get_function_named_in_call (t); + if (fn && TREE_CODE (fn) == FUNCTION_DECL + && DECL_CXX_CONSTRUCTOR_P (fn)) + type = DECL_CONTEXT (fn); + } + else if (TREE_CODE (t) == COMPOUND_EXPR) + return initialized_type (TREE_OPERAND (t, 1)); + else if (TREE_CODE (t) == AGGR_INIT_EXPR) + type = TREE_TYPE (AGGR_INIT_EXPR_SLOT (t)); + return cv_unqualified (type); +} + +/* We're about to initialize element INDEX of an array or class from VALUE. + Set up NEW_CTX appropriately by adjusting .object to refer to the + subobject and creating a new CONSTRUCTOR if the element is itself + a class or array. */ + +static void +init_subob_ctx (const constexpr_ctx *ctx, constexpr_ctx &new_ctx, + tree index, tree &value) +{ + new_ctx = *ctx; + + if (index && TREE_CODE (index) != INTEGER_CST + && TREE_CODE (index) != FIELD_DECL + && TREE_CODE (index) != RANGE_EXPR) + /* This won't have an element in the new CONSTRUCTOR. */ + return; + + tree type = initialized_type (value); + if (!AGGREGATE_TYPE_P (type) && !VECTOR_TYPE_P (type)) + /* A non-aggregate member doesn't get its own CONSTRUCTOR. */ + return; + + /* The sub-aggregate initializer might contain a placeholder; + update object to refer to the subobject and ctor to refer to + the (newly created) sub-initializer. */ + if (ctx->object) + { + if (index == NULL_TREE || TREE_CODE (index) == RANGE_EXPR) + /* There's no well-defined subobject for this index. */ + new_ctx.object = NULL_TREE; + else + new_ctx.object = build_ctor_subob_ref (index, type, ctx->object); + } + tree elt = build_constructor (type, NULL); + CONSTRUCTOR_NO_CLEARING (elt) = true; + new_ctx.ctor = elt; + + if (TREE_CODE (value) == TARGET_EXPR) + /* Avoid creating another CONSTRUCTOR when we expand the TARGET_EXPR. */ + value = TARGET_EXPR_INITIAL (value); +} + +/* We're about to process an initializer for a class or array TYPE. Make + sure that CTX is set up appropriately. */ + +static void +verify_ctor_sanity (const constexpr_ctx *ctx, tree type) +{ + /* We don't bother building a ctor for an empty base subobject. */ + if (is_empty_class (type)) + return; + + /* We're in the middle of an initializer that might involve placeholders; + our caller should have created a CONSTRUCTOR for us to put the + initializer into. We will either return that constructor or T. */ + gcc_assert (ctx->ctor); + gcc_assert (same_type_ignoring_top_level_qualifiers_p + (type, TREE_TYPE (ctx->ctor))); + /* We used to check that ctx->ctor was empty, but that isn't the case when + the object is zero-initialized before calling the constructor. */ + if (ctx->object) + { + tree otype = TREE_TYPE (ctx->object); + gcc_assert (same_type_ignoring_top_level_qualifiers_p (type, otype) + /* Handle flexible array members. */ + || (TREE_CODE (otype) == ARRAY_TYPE + && TYPE_DOMAIN (otype) == NULL_TREE + && TREE_CODE (type) == ARRAY_TYPE + && (same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (type), TREE_TYPE (otype))))); + } + gcc_assert (!ctx->object || !DECL_P (ctx->object) + || *(ctx->global->values.get (ctx->object)) == ctx->ctor); +} + +/* Subroutine of cxx_eval_constant_expression. + The expression tree T denotes a C-style array or a C-style + aggregate. Reduce it to a constant expression. */ + +static tree +cxx_eval_bare_aggregate (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + vec<constructor_elt, va_gc> *v = CONSTRUCTOR_ELTS (t); + bool changed = false; + gcc_assert (!BRACE_ENCLOSED_INITIALIZER_P (t)); + tree type = TREE_TYPE (t); + + constexpr_ctx new_ctx; + if (TYPE_PTRMEMFUNC_P (type) || VECTOR_TYPE_P (type)) + { + /* We don't really need the ctx->ctor business for a PMF or + vector, but it's simpler to use the same code. */ + new_ctx = *ctx; + new_ctx.ctor = build_constructor (type, NULL); + new_ctx.object = NULL_TREE; + ctx = &new_ctx; + }; + verify_ctor_sanity (ctx, type); + vec<constructor_elt, va_gc> **p = &CONSTRUCTOR_ELTS (ctx->ctor); + vec_alloc (*p, vec_safe_length (v)); + + if (CONSTRUCTOR_PLACEHOLDER_BOUNDARY (t)) + CONSTRUCTOR_PLACEHOLDER_BOUNDARY (ctx->ctor) = 1; + + unsigned i; + tree index, value; + bool constant_p = true; + bool side_effects_p = false; + FOR_EACH_CONSTRUCTOR_ELT (v, i, index, value) + { + tree orig_value = value; + /* Like in cxx_eval_store_expression, omit entries for empty fields. */ + bool no_slot = TREE_CODE (type) == RECORD_TYPE && is_empty_field (index); + if (no_slot) + new_ctx = *ctx; + else + init_subob_ctx (ctx, new_ctx, index, value); + int pos_hint = -1; + if (new_ctx.ctor != ctx->ctor) + { + /* If we built a new CONSTRUCTOR, attach it now so that other + initializers can refer to it. */ + constructor_elt *cep = get_or_insert_ctor_field (ctx->ctor, index); + cep->value = new_ctx.ctor; + pos_hint = cep - (*p)->begin(); + } + else if (TREE_CODE (type) == UNION_TYPE) + /* Otherwise if we're constructing a non-aggregate union member, set + the active union member now so that we can later detect and diagnose + if its initializer attempts to activate another member. */ + get_or_insert_ctor_field (ctx->ctor, index); + tree elt = cxx_eval_constant_expression (&new_ctx, value, + lval, + non_constant_p, overflow_p); + /* Don't VERIFY_CONSTANT here. */ + if (ctx->quiet && *non_constant_p) + break; + if (elt != orig_value) + changed = true; + + if (!TREE_CONSTANT (elt)) + constant_p = false; + if (TREE_SIDE_EFFECTS (elt)) + side_effects_p = true; + if (index && TREE_CODE (index) == COMPONENT_REF) + { + /* This is an initialization of a vfield inside a base + subaggregate that we already initialized; push this + initialization into the previous initialization. */ + constructor_elt *inner = base_field_constructor_elt (*p, index); + inner->value = elt; + changed = true; + } + else if (index + && (TREE_CODE (index) == NOP_EXPR + || TREE_CODE (index) == POINTER_PLUS_EXPR)) + { + /* This is an initializer for an empty base; now that we've + checked that it's constant, we can ignore it. */ + gcc_assert (is_empty_class (TREE_TYPE (TREE_TYPE (index)))); + changed = true; + } + else if (no_slot) + changed = true; + else + { + if (TREE_CODE (type) == UNION_TYPE + && (*p)->last().index != index) + /* The initializer erroneously changed the active union member that + we're initializing. */ + gcc_assert (*non_constant_p); + else + { + /* The initializer might have mutated the underlying CONSTRUCTOR, + so recompute the location of the target constructer_elt. */ + constructor_elt *cep + = get_or_insert_ctor_field (ctx->ctor, index, pos_hint); + cep->value = elt; + } + + /* Adding or replacing an element might change the ctor's flags. */ + TREE_CONSTANT (ctx->ctor) = constant_p; + TREE_SIDE_EFFECTS (ctx->ctor) = side_effects_p; + } + } + if (*non_constant_p || !changed) + return t; + t = ctx->ctor; + /* We're done building this CONSTRUCTOR, so now we can interpret an + element without an explicit initializer as value-initialized. */ + CONSTRUCTOR_NO_CLEARING (t) = false; + TREE_CONSTANT (t) = constant_p; + TREE_SIDE_EFFECTS (t) = side_effects_p; + if (VECTOR_TYPE_P (type)) + t = fold (t); + return t; +} + +/* Subroutine of cxx_eval_constant_expression. + The expression tree T is a VEC_INIT_EXPR which denotes the desired + initialization of a non-static data member of array type. Reduce it to a + CONSTRUCTOR. + + Note that apart from value-initialization (when VALUE_INIT is true), + this is only intended to support value-initialization and the + initializations done by defaulted constructors for classes with + non-static data members of array type. In this case, VEC_INIT_EXPR_INIT + will either be NULL_TREE for the default constructor, or a COMPONENT_REF + for the copy/move constructor. */ + +static tree +cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init, + bool value_init, bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree elttype = TREE_TYPE (atype); + verify_ctor_sanity (ctx, atype); + vec<constructor_elt, va_gc> **p = &CONSTRUCTOR_ELTS (ctx->ctor); + bool pre_init = false; + unsigned HOST_WIDE_INT i; + tsubst_flags_t complain = ctx->quiet ? tf_none : tf_warning_or_error; + + if (init && TREE_CODE (init) == CONSTRUCTOR) + return cxx_eval_bare_aggregate (ctx, init, lval, + non_constant_p, overflow_p); + + /* For the default constructor, build up a call to the default + constructor of the element type. We only need to handle class types + here, as for a constructor to be constexpr, all members must be + initialized, which for a defaulted default constructor means they must + be of a class type with a constexpr default constructor. */ + if (TREE_CODE (elttype) == ARRAY_TYPE) + /* We only do this at the lowest level. */; + else if (value_init) + { + init = build_value_init (elttype, complain); + pre_init = true; + } + else if (!init) + { + releasing_vec argvec; + init = build_special_member_call (NULL_TREE, complete_ctor_identifier, + &argvec, elttype, LOOKUP_NORMAL, + complain); + init = build_aggr_init_expr (elttype, init); + pre_init = true; + } + + bool zeroed_out = false; + if (!CONSTRUCTOR_NO_CLEARING (ctx->ctor)) + { + /* We're initializing an array object that had been zero-initialized + earlier. Truncate ctx->ctor, and propagate its zeroed state by + clearing CONSTRUCTOR_NO_CLEARING on each of the aggregate element + initializers we append to it. */ + gcc_checking_assert (initializer_zerop (ctx->ctor)); + zeroed_out = true; + vec_safe_truncate (*p, 0); + } + + tree nelts = get_array_or_vector_nelts (ctx, atype, non_constant_p, + overflow_p); + unsigned HOST_WIDE_INT max = tree_to_uhwi (nelts); + for (i = 0; i < max; ++i) + { + tree idx = build_int_cst (size_type_node, i); + tree eltinit; + bool reuse = false; + constexpr_ctx new_ctx; + init_subob_ctx (ctx, new_ctx, idx, pre_init ? init : elttype); + if (new_ctx.ctor != ctx->ctor) + { + if (zeroed_out) + CONSTRUCTOR_NO_CLEARING (new_ctx.ctor) = false; + CONSTRUCTOR_APPEND_ELT (*p, idx, new_ctx.ctor); + } + if (TREE_CODE (elttype) == ARRAY_TYPE) + { + /* A multidimensional array; recurse. */ + if (value_init || init == NULL_TREE) + { + eltinit = NULL_TREE; + reuse = i == 0; + } + else + eltinit = cp_build_array_ref (input_location, init, idx, complain); + eltinit = cxx_eval_vec_init_1 (&new_ctx, elttype, eltinit, value_init, + lval, + non_constant_p, overflow_p); + } + else if (pre_init) + { + /* Initializing an element using value or default initialization + we just pre-built above. */ + if (init == void_node) + /* Trivial default-init, don't do anything to the CONSTRUCTOR. */ + return ctx->ctor; + eltinit = cxx_eval_constant_expression (&new_ctx, init, lval, + non_constant_p, overflow_p); + reuse = i == 0; + } + else + { + /* Copying an element. */ + gcc_assert (same_type_ignoring_top_level_qualifiers_p + (atype, TREE_TYPE (init))); + eltinit = cp_build_array_ref (input_location, init, idx, complain); + if (!lvalue_p (init)) + eltinit = move (eltinit); + eltinit = force_rvalue (eltinit, complain); + eltinit = cxx_eval_constant_expression (&new_ctx, eltinit, lval, + non_constant_p, overflow_p); + } + if (*non_constant_p) + break; + if (new_ctx.ctor != ctx->ctor) + { + /* We appended this element above; update the value. */ + gcc_assert ((*p)->last().index == idx); + (*p)->last().value = eltinit; + } + else + CONSTRUCTOR_APPEND_ELT (*p, idx, eltinit); + /* Reuse the result of cxx_eval_constant_expression call + from the first iteration to all others if it is a constant + initializer that doesn't require relocations. */ + if (reuse + && max > 1 + && (eltinit == NULL_TREE + || (initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit)) + == null_pointer_node))) + { + if (new_ctx.ctor != ctx->ctor) + eltinit = new_ctx.ctor; + tree range = build2 (RANGE_EXPR, size_type_node, + build_int_cst (size_type_node, 1), + build_int_cst (size_type_node, max - 1)); + CONSTRUCTOR_APPEND_ELT (*p, range, unshare_constructor (eltinit)); + break; + } + else if (i == 0) + vec_safe_reserve (*p, max); + } + + if (!*non_constant_p) + { + init = ctx->ctor; + CONSTRUCTOR_NO_CLEARING (init) = false; + } + return init; +} + +static tree +cxx_eval_vec_init (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree atype = TREE_TYPE (t); + tree init = VEC_INIT_EXPR_INIT (t); + bool value_init = VEC_INIT_EXPR_VALUE_INIT (t); + if (!init || !BRACE_ENCLOSED_INITIALIZER_P (init)) + ; + else if (CONSTRUCTOR_NELTS (init) == 0) + { + /* Handle {} as value-init. */ + init = NULL_TREE; + value_init = true; + } + else + { + /* This is a more complicated case, like needing to loop over trailing + elements; call build_vec_init and evaluate the result. */ + tsubst_flags_t complain = ctx->quiet ? tf_none : tf_warning_or_error; + constexpr_ctx new_ctx = *ctx; + if (!ctx->object) + { + /* We want to have an initialization target for an VEC_INIT_EXPR. + If we don't already have one in CTX, use the VEC_INIT_EXPR_SLOT. */ + new_ctx.object = VEC_INIT_EXPR_SLOT (t); + tree ctor = new_ctx.ctor = build_constructor (atype, NULL); + CONSTRUCTOR_NO_CLEARING (ctor) = true; + ctx->global->values.put (new_ctx.object, ctor); + ctx = &new_ctx; + } + init = expand_vec_init_expr (ctx->object, t, complain); + return cxx_eval_constant_expression (ctx, init, lval, non_constant_p, + overflow_p); + } + tree r = cxx_eval_vec_init_1 (ctx, atype, init, value_init, + lval, non_constant_p, overflow_p); + if (*non_constant_p) + return t; + else + return r; +} + +/* Like same_type_ignoring_top_level_qualifiers_p, but also handle the case + where the desired type is an array of unknown bounds because the variable + has had its bounds deduced since the wrapping expression was created. */ + +static bool +same_type_ignoring_tlq_and_bounds_p (tree type1, tree type2) +{ + while (TREE_CODE (type1) == ARRAY_TYPE + && TREE_CODE (type2) == ARRAY_TYPE + && (!TYPE_DOMAIN (type1) || !TYPE_DOMAIN (type2))) + { + type1 = TREE_TYPE (type1); + type2 = TREE_TYPE (type2); + } + return same_type_ignoring_top_level_qualifiers_p (type1, type2); +} + +/* Try to determine the currently active union member for an expression + with UNION_TYPE. If it can be determined, return the FIELD_DECL, + otherwise return NULL_TREE. */ + +static tree +cxx_union_active_member (const constexpr_ctx *ctx, tree t) +{ + constexpr_ctx new_ctx = *ctx; + new_ctx.quiet = true; + bool non_constant_p = false, overflow_p = false; + tree ctor = cxx_eval_constant_expression (&new_ctx, t, false, + &non_constant_p, + &overflow_p); + if (TREE_CODE (ctor) == CONSTRUCTOR + && CONSTRUCTOR_NELTS (ctor) == 1 + && CONSTRUCTOR_ELT (ctor, 0)->index + && TREE_CODE (CONSTRUCTOR_ELT (ctor, 0)->index) == FIELD_DECL) + return CONSTRUCTOR_ELT (ctor, 0)->index; + return NULL_TREE; +} + +/* Helper function for cxx_fold_indirect_ref_1, called recursively. */ + +static tree +cxx_fold_indirect_ref_1 (const constexpr_ctx *ctx, location_t loc, tree type, + tree op, unsigned HOST_WIDE_INT off, bool *empty_base) +{ + tree optype = TREE_TYPE (op); + unsigned HOST_WIDE_INT const_nunits; + if (off == 0 && similar_type_p (optype, type)) + return op; + else if (TREE_CODE (optype) == COMPLEX_TYPE + && similar_type_p (type, TREE_TYPE (optype))) + { + /* *(foo *)&complexfoo => __real__ complexfoo */ + if (off == 0) + return build1_loc (loc, REALPART_EXPR, type, op); + /* ((foo*)&complexfoo)[1] => __imag__ complexfoo */ + else if (tree_to_uhwi (TYPE_SIZE_UNIT (type)) == off) + return build1_loc (loc, IMAGPART_EXPR, type, op); + } + /* ((foo*)&vectorfoo)[x] => BIT_FIELD_REF<vectorfoo,...> */ + else if (VECTOR_TYPE_P (optype) + && similar_type_p (type, TREE_TYPE (optype)) + && TYPE_VECTOR_SUBPARTS (optype).is_constant (&const_nunits)) + { + unsigned HOST_WIDE_INT part_width = tree_to_uhwi (TYPE_SIZE_UNIT (type)); + unsigned HOST_WIDE_INT max_offset = part_width * const_nunits; + if (off < max_offset && off % part_width == 0) + { + tree index = bitsize_int (off * BITS_PER_UNIT); + return build3_loc (loc, BIT_FIELD_REF, type, op, + TYPE_SIZE (type), index); + } + } + /* ((foo *)&fooarray)[x] => fooarray[x] */ + else if (TREE_CODE (optype) == ARRAY_TYPE + && tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (optype))) + && !integer_zerop (TYPE_SIZE_UNIT (TREE_TYPE (optype)))) + { + tree type_domain = TYPE_DOMAIN (optype); + tree min_val = size_zero_node; + if (type_domain && TYPE_MIN_VALUE (type_domain)) + min_val = TYPE_MIN_VALUE (type_domain); + unsigned HOST_WIDE_INT el_sz + = tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (optype))); + unsigned HOST_WIDE_INT idx = off / el_sz; + unsigned HOST_WIDE_INT rem = off % el_sz; + if (tree_fits_uhwi_p (min_val)) + { + tree index = size_int (idx + tree_to_uhwi (min_val)); + op = build4_loc (loc, ARRAY_REF, TREE_TYPE (optype), op, index, + NULL_TREE, NULL_TREE); + return cxx_fold_indirect_ref_1 (ctx, loc, type, op, rem, + empty_base); + } + } + /* ((foo *)&struct_with_foo_field)[x] => COMPONENT_REF */ + else if (TREE_CODE (optype) == RECORD_TYPE + || TREE_CODE (optype) == UNION_TYPE) + { + if (TREE_CODE (optype) == UNION_TYPE) + /* For unions prefer the currently active member. */ + if (tree field = cxx_union_active_member (ctx, op)) + { + unsigned HOST_WIDE_INT el_sz + = tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (field))); + if (off < el_sz) + { + tree cop = build3 (COMPONENT_REF, TREE_TYPE (field), + op, field, NULL_TREE); + if (tree ret = cxx_fold_indirect_ref_1 (ctx, loc, type, cop, + off, empty_base)) + return ret; + } + } + for (tree field = TYPE_FIELDS (optype); + field; field = DECL_CHAIN (field)) + if (TREE_CODE (field) == FIELD_DECL + && TREE_TYPE (field) != error_mark_node + && tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (field)))) + { + tree pos = byte_position (field); + if (!tree_fits_uhwi_p (pos)) + continue; + unsigned HOST_WIDE_INT upos = tree_to_uhwi (pos); + unsigned HOST_WIDE_INT el_sz + = tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (field))); + if (upos <= off && off < upos + el_sz) + { + tree cop = build3 (COMPONENT_REF, TREE_TYPE (field), + op, field, NULL_TREE); + if (tree ret = cxx_fold_indirect_ref_1 (ctx, loc, type, cop, + off - upos, + empty_base)) + return ret; + } + } + /* Also handle conversion to an empty base class, which + is represented with a NOP_EXPR. */ + if (is_empty_class (type) + && CLASS_TYPE_P (optype) + && DERIVED_FROM_P (type, optype)) + { + *empty_base = true; + return op; + } + } + + return NULL_TREE; +} + +/* A less strict version of fold_indirect_ref_1, which requires cv-quals to + match. We want to be less strict for simple *& folding; if we have a + non-const temporary that we access through a const pointer, that should + work. We handle this here rather than change fold_indirect_ref_1 + because we're dealing with things like ADDR_EXPR of INTEGER_CST which + don't really make sense outside of constant expression evaluation. Also + we want to allow folding to COMPONENT_REF, which could cause trouble + with TBAA in fold_indirect_ref_1. */ + +static tree +cxx_fold_indirect_ref (const constexpr_ctx *ctx, location_t loc, tree type, + tree op0, bool *empty_base) +{ + tree sub = op0; + tree subtype; + poly_uint64 const_op01; + + /* STRIP_NOPS, but stop if REINTERPRET_CAST_P. */ + while (CONVERT_EXPR_P (sub) || TREE_CODE (sub) == NON_LVALUE_EXPR + || TREE_CODE (sub) == VIEW_CONVERT_EXPR) + { + if (TREE_CODE (sub) == NOP_EXPR + && REINTERPRET_CAST_P (sub)) + return NULL_TREE; + sub = TREE_OPERAND (sub, 0); + } + + subtype = TREE_TYPE (sub); + if (!INDIRECT_TYPE_P (subtype)) + return NULL_TREE; + + /* Canonicalizes the given OBJ/OFF pair by iteratively absorbing + the innermost component into the offset until it would make the + offset positive, so that cxx_fold_indirect_ref_1 can identify + more folding opportunities. */ + auto canonicalize_obj_off = [] (tree& obj, tree& off) { + while (TREE_CODE (obj) == COMPONENT_REF + && (tree_int_cst_sign_bit (off) || integer_zerop (off))) + { + tree field = TREE_OPERAND (obj, 1); + tree pos = byte_position (field); + if (integer_zerop (off) && integer_nonzerop (pos)) + /* If the offset is already 0, keep going as long as the + component is at position 0. */ + break; + off = int_const_binop (PLUS_EXPR, off, pos); + obj = TREE_OPERAND (obj, 0); + } + }; + + if (TREE_CODE (sub) == ADDR_EXPR) + { + tree op = TREE_OPERAND (sub, 0); + tree optype = TREE_TYPE (op); + + /* *&CONST_DECL -> to the value of the const decl. */ + if (TREE_CODE (op) == CONST_DECL) + return DECL_INITIAL (op); + /* *&p => p; make sure to handle *&"str"[cst] here. */ + if (similar_type_p (optype, type)) + { + tree fop = fold_read_from_constant_string (op); + if (fop) + return fop; + else + return op; + } + else + { + tree off = integer_zero_node; + canonicalize_obj_off (op, off); + gcc_assert (integer_zerop (off)); + return cxx_fold_indirect_ref_1 (ctx, loc, type, op, 0, empty_base); + } + } + else if (TREE_CODE (sub) == POINTER_PLUS_EXPR + && tree_fits_uhwi_p (TREE_OPERAND (sub, 1))) + { + tree op00 = TREE_OPERAND (sub, 0); + tree off = TREE_OPERAND (sub, 1); + + STRIP_NOPS (op00); + if (TREE_CODE (op00) == ADDR_EXPR) + { + tree obj = TREE_OPERAND (op00, 0); + canonicalize_obj_off (obj, off); + return cxx_fold_indirect_ref_1 (ctx, loc, type, obj, + tree_to_uhwi (off), empty_base); + } + } + /* *(foo *)fooarrptr => (*fooarrptr)[0] */ + else if (TREE_CODE (TREE_TYPE (subtype)) == ARRAY_TYPE + && similar_type_p (type, TREE_TYPE (TREE_TYPE (subtype)))) + { + tree type_domain; + tree min_val = size_zero_node; + tree newsub + = cxx_fold_indirect_ref (ctx, loc, TREE_TYPE (subtype), sub, NULL); + if (newsub) + sub = newsub; + else + sub = build1_loc (loc, INDIRECT_REF, TREE_TYPE (subtype), sub); + type_domain = TYPE_DOMAIN (TREE_TYPE (sub)); + if (type_domain && TYPE_MIN_VALUE (type_domain)) + min_val = TYPE_MIN_VALUE (type_domain); + return build4_loc (loc, ARRAY_REF, type, sub, min_val, NULL_TREE, + NULL_TREE); + } + + return NULL_TREE; +} + +static tree +cxx_eval_indirect_ref (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + tree orig_op0 = TREE_OPERAND (t, 0); + bool empty_base = false; + + /* We can handle a MEM_REF like an INDIRECT_REF, if MEM_REF's second + operand is an integer-zero. Otherwise reject the MEM_REF for now. */ + + if (TREE_CODE (t) == MEM_REF + && (!TREE_OPERAND (t, 1) || !integer_zerop (TREE_OPERAND (t, 1)))) + { + gcc_assert (ctx->quiet); + *non_constant_p = true; + return t; + } + + /* First try to simplify it directly. */ + tree r = cxx_fold_indirect_ref (ctx, EXPR_LOCATION (t), TREE_TYPE (t), + orig_op0, &empty_base); + if (!r) + { + /* If that didn't work, evaluate the operand first. */ + tree op0 = cxx_eval_constant_expression (ctx, orig_op0, + /*lval*/false, non_constant_p, + overflow_p); + /* Don't VERIFY_CONSTANT here. */ + if (*non_constant_p) + return t; + + if (!lval && integer_zerop (op0)) + { + if (!ctx->quiet) + error ("dereferencing a null pointer"); + *non_constant_p = true; + return t; + } + + r = cxx_fold_indirect_ref (ctx, EXPR_LOCATION (t), TREE_TYPE (t), op0, + &empty_base); + if (r == NULL_TREE) + { + /* We couldn't fold to a constant value. Make sure it's not + something we should have been able to fold. */ + tree sub = op0; + STRIP_NOPS (sub); + if (TREE_CODE (sub) == ADDR_EXPR) + { + gcc_assert (!similar_type_p + (TREE_TYPE (TREE_TYPE (sub)), TREE_TYPE (t))); + /* DR 1188 says we don't have to deal with this. */ + if (!ctx->quiet) + error_at (cp_expr_loc_or_input_loc (t), + "accessing value of %qE through a %qT glvalue in a " + "constant expression", build_fold_indirect_ref (sub), + TREE_TYPE (t)); + *non_constant_p = true; + return t; + } + + if (lval && op0 != orig_op0) + return build1 (INDIRECT_REF, TREE_TYPE (t), op0); + if (!lval) + VERIFY_CONSTANT (t); + return t; + } + } + + r = cxx_eval_constant_expression (ctx, r, + lval, non_constant_p, overflow_p); + if (*non_constant_p) + return t; + + /* If we're pulling out the value of an empty base, just return an empty + CONSTRUCTOR. */ + if (empty_base && !lval) + { + r = build_constructor (TREE_TYPE (t), NULL); + TREE_CONSTANT (r) = true; + } + + return r; +} + +/* Complain about R, a VAR_DECL, not being usable in a constant expression. + Shared between potential_constant_expression and + cxx_eval_constant_expression. */ + +static void +non_const_var_error (location_t loc, tree r) +{ + auto_diagnostic_group d; + tree type = TREE_TYPE (r); + if (DECL_NAME (r) == heap_uninit_identifier + || DECL_NAME (r) == heap_identifier + || DECL_NAME (r) == heap_vec_uninit_identifier + || DECL_NAME (r) == heap_vec_identifier) + { + error_at (loc, "the content of uninitialized storage is not usable " + "in a constant expression"); + inform (DECL_SOURCE_LOCATION (r), "allocated here"); + return; + } + if (DECL_NAME (r) == heap_deleted_identifier) + { + error_at (loc, "use of allocated storage after deallocation in a " + "constant expression"); + inform (DECL_SOURCE_LOCATION (r), "allocated here"); + return; + } + error_at (loc, "the value of %qD is not usable in a constant " + "expression", r); + /* Avoid error cascade. */ + if (DECL_INITIAL (r) == error_mark_node) + return; + if (DECL_DECLARED_CONSTEXPR_P (r)) + inform (DECL_SOURCE_LOCATION (r), + "%qD used in its own initializer", r); + else if (INTEGRAL_OR_ENUMERATION_TYPE_P (type)) + { + if (!CP_TYPE_CONST_P (type)) + inform (DECL_SOURCE_LOCATION (r), + "%q#D is not const", r); + else if (CP_TYPE_VOLATILE_P (type)) + inform (DECL_SOURCE_LOCATION (r), + "%q#D is volatile", r); + else if (!DECL_INITIAL (r) + || !TREE_CONSTANT (DECL_INITIAL (r)) + || !DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (r)) + inform (DECL_SOURCE_LOCATION (r), + "%qD was not initialized with a constant " + "expression", r); + else + gcc_unreachable (); + } + else if (TYPE_REF_P (type)) + inform (DECL_SOURCE_LOCATION (r), + "%qD was not initialized with a constant " + "expression", r); + else + { + if (cxx_dialect >= cxx11 && !DECL_DECLARED_CONSTEXPR_P (r)) + inform (DECL_SOURCE_LOCATION (r), + "%qD was not declared %<constexpr%>", r); + else + inform (DECL_SOURCE_LOCATION (r), + "%qD does not have integral or enumeration type", + r); + } +} + +/* Subroutine of cxx_eval_constant_expression. + Like cxx_eval_unary_expression, except for trinary expressions. */ + +static tree +cxx_eval_trinary_expression (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + int i; + tree args[3]; + tree val; + + for (i = 0; i < 3; i++) + { + args[i] = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, i), + lval, + non_constant_p, overflow_p); + VERIFY_CONSTANT (args[i]); + } + + val = fold_ternary_loc (EXPR_LOCATION (t), TREE_CODE (t), TREE_TYPE (t), + args[0], args[1], args[2]); + if (val == NULL_TREE) + return t; + VERIFY_CONSTANT (val); + return val; +} + +/* True if T was declared in a function declared to be constexpr, and + therefore potentially constant in C++14. */ + +bool +var_in_constexpr_fn (tree t) +{ + tree ctx = DECL_CONTEXT (t); + return (ctx && TREE_CODE (ctx) == FUNCTION_DECL + && DECL_DECLARED_CONSTEXPR_P (ctx)); +} + +/* True if a function might be constexpr: either a function that was + declared constexpr, or a C++17 lambda op(). */ + +bool +maybe_constexpr_fn (tree t) +{ + return (DECL_DECLARED_CONSTEXPR_P (t) + || (cxx_dialect >= cxx17 && LAMBDA_FUNCTION_P (t)) + || (flag_implicit_constexpr + && DECL_DECLARED_INLINE_P (STRIP_TEMPLATE (t)))); +} + +/* True if T was declared in a function that might be constexpr: either a + function that was declared constexpr, or a C++17 lambda op(). */ + +bool +var_in_maybe_constexpr_fn (tree t) +{ + return (DECL_FUNCTION_SCOPE_P (t) + && maybe_constexpr_fn (DECL_CONTEXT (t))); +} + +/* We're assigning INIT to TARGET. In do_build_copy_constructor and + build_over_call we implement trivial copy of a class with tail padding using + assignment of character arrays, which is valid in normal code, but not in + constexpr evaluation. We don't need to worry about clobbering tail padding + in constexpr evaluation, so strip the type punning. */ + +static void +maybe_simplify_trivial_copy (tree &target, tree &init) +{ + if (TREE_CODE (target) == MEM_REF + && TREE_CODE (init) == MEM_REF + && TREE_TYPE (target) == TREE_TYPE (init) + && TREE_CODE (TREE_TYPE (target)) == ARRAY_TYPE + && TREE_TYPE (TREE_TYPE (target)) == unsigned_char_type_node) + { + target = build_fold_indirect_ref (TREE_OPERAND (target, 0)); + init = build_fold_indirect_ref (TREE_OPERAND (init, 0)); + } +} + +/* Returns true if REF, which is a COMPONENT_REF, has any fields + of constant type. This does not check for 'mutable', so the + caller is expected to be mindful of that. */ + +static bool +cref_has_const_field (tree ref) +{ + while (TREE_CODE (ref) == COMPONENT_REF) + { + if (CP_TYPE_CONST_P (TREE_TYPE (TREE_OPERAND (ref, 1)))) + return true; + ref = TREE_OPERAND (ref, 0); + } + return false; +} + +/* Return true if we are modifying something that is const during constant + expression evaluation. CODE is the code of the statement, OBJ is the + object in question, MUTABLE_P is true if one of the subobjects were + declared mutable. */ + +static bool +modifying_const_object_p (tree_code code, tree obj, bool mutable_p) +{ + /* If this is initialization, there's no problem. */ + if (code != MODIFY_EXPR) + return false; + + /* [basic.type.qualifier] "A const object is an object of type + const T or a non-mutable subobject of a const object." */ + if (mutable_p) + return false; + + if (TREE_READONLY (obj)) + return true; + + if (CP_TYPE_CONST_P (TREE_TYPE (obj))) + { + /* Although a COMPONENT_REF may have a const type, we should + only consider it modifying a const object when any of the + field components is const. This can happen when using + constructs such as const_cast<const T &>(m), making something + const even though it wasn't declared const. */ + if (TREE_CODE (obj) == COMPONENT_REF) + return cref_has_const_field (obj); + else + return true; + } + + return false; +} + +/* Evaluate an INIT_EXPR or MODIFY_EXPR. */ + +static tree +cxx_eval_store_expression (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + constexpr_ctx new_ctx = *ctx; + + tree init = TREE_OPERAND (t, 1); + if (TREE_CLOBBER_P (init)) + /* Just ignore clobbers. */ + return void_node; + + /* First we figure out where we're storing to. */ + tree target = TREE_OPERAND (t, 0); + + maybe_simplify_trivial_copy (target, init); + + tree type = TREE_TYPE (target); + bool preeval = SCALAR_TYPE_P (type) || TREE_CODE (t) == MODIFY_EXPR; + if (preeval) + { + /* Evaluate the value to be stored without knowing what object it will be + stored in, so that any side-effects happen first. */ + if (!SCALAR_TYPE_P (type)) + new_ctx.ctor = new_ctx.object = NULL_TREE; + init = cxx_eval_constant_expression (&new_ctx, init, false, + non_constant_p, overflow_p); + if (*non_constant_p) + return t; + } + + bool evaluated = false; + if (lval) + { + /* If we want to return a reference to the target, we need to evaluate it + as a whole; otherwise, only evaluate the innermost piece to avoid + building up unnecessary *_REFs. */ + target = cxx_eval_constant_expression (ctx, target, true, + non_constant_p, overflow_p); + evaluated = true; + if (*non_constant_p) + return t; + } + + /* Find the underlying variable. */ + releasing_vec refs; + tree object = NULL_TREE; + /* If we're modifying a const object, save it. */ + tree const_object_being_modified = NULL_TREE; + bool mutable_p = false; + for (tree probe = target; object == NULL_TREE; ) + { + switch (TREE_CODE (probe)) + { + case BIT_FIELD_REF: + case COMPONENT_REF: + case ARRAY_REF: + { + tree ob = TREE_OPERAND (probe, 0); + tree elt = TREE_OPERAND (probe, 1); + if (TREE_CODE (elt) == FIELD_DECL && DECL_MUTABLE_P (elt)) + mutable_p = true; + if (TREE_CODE (probe) == ARRAY_REF) + { + elt = eval_and_check_array_index (ctx, probe, false, + non_constant_p, overflow_p); + if (*non_constant_p) + return t; + } + /* We don't check modifying_const_object_p for ARRAY_REFs. Given + "int a[10]", an ARRAY_REF "a[2]" can be "const int", even though + the array isn't const. Instead, check "a" in the next iteration; + that will detect modifying "const int a[10]". */ + else if (evaluated + && modifying_const_object_p (TREE_CODE (t), probe, + mutable_p) + && const_object_being_modified == NULL_TREE) + const_object_being_modified = probe; + vec_safe_push (refs, elt); + vec_safe_push (refs, TREE_TYPE (probe)); + probe = ob; + } + break; + + default: + if (evaluated) + object = probe; + else + { + probe = cxx_eval_constant_expression (ctx, probe, true, + non_constant_p, overflow_p); + evaluated = true; + if (*non_constant_p) + return t; + } + break; + } + } + + if (modifying_const_object_p (TREE_CODE (t), object, mutable_p) + && const_object_being_modified == NULL_TREE) + const_object_being_modified = object; + + /* And then find/build up our initializer for the path to the subobject + we're initializing. */ + tree *valp; + if (DECL_P (object)) + valp = ctx->global->values.get (object); + else + valp = NULL; + if (!valp) + { + /* A constant-expression cannot modify objects from outside the + constant-expression. */ + if (!ctx->quiet) + error ("modification of %qE is not a constant expression", object); + *non_constant_p = true; + return t; + } + type = TREE_TYPE (object); + bool no_zero_init = true; + + releasing_vec ctors, indexes; + auto_vec<int> index_pos_hints; + bool activated_union_member_p = false; + while (!refs->is_empty ()) + { + if (*valp == NULL_TREE) + { + *valp = build_constructor (type, NULL); + CONSTRUCTOR_NO_CLEARING (*valp) = no_zero_init; + } + else if (TREE_CODE (*valp) == STRING_CST) + { + /* An array was initialized with a string constant, and now + we're writing into one of its elements. Explode the + single initialization into a set of element + initializations. */ + gcc_assert (TREE_CODE (type) == ARRAY_TYPE); + + tree string = *valp; + tree elt_type = TREE_TYPE (type); + unsigned chars_per_elt = (TYPE_PRECISION (elt_type) + / TYPE_PRECISION (char_type_node)); + unsigned num_elts = TREE_STRING_LENGTH (string) / chars_per_elt; + tree ary_ctor = build_constructor (type, NULL); + + vec_safe_reserve (CONSTRUCTOR_ELTS (ary_ctor), num_elts); + for (unsigned ix = 0; ix != num_elts; ix++) + { + constructor_elt elt = + { + build_int_cst (size_type_node, ix), + extract_string_elt (string, chars_per_elt, ix) + }; + CONSTRUCTOR_ELTS (ary_ctor)->quick_push (elt); + } + + *valp = ary_ctor; + } + + /* If the value of object is already zero-initialized, any new ctors for + subobjects will also be zero-initialized. */ + no_zero_init = CONSTRUCTOR_NO_CLEARING (*valp); + + enum tree_code code = TREE_CODE (type); + type = refs->pop(); + tree index = refs->pop(); + + if (code == RECORD_TYPE && is_empty_field (index)) + /* Don't build a sub-CONSTRUCTOR for an empty base or field, as they + have no data and might have an offset lower than previously declared + fields, which confuses the middle-end. The code below will notice + that we don't have a CONSTRUCTOR for our inner target and just + return init. */ + break; + + if (code == UNION_TYPE && CONSTRUCTOR_NELTS (*valp) + && CONSTRUCTOR_ELT (*valp, 0)->index != index) + { + if (cxx_dialect < cxx20) + { + if (!ctx->quiet) + error_at (cp_expr_loc_or_input_loc (t), + "change of the active member of a union " + "from %qD to %qD", + CONSTRUCTOR_ELT (*valp, 0)->index, + index); + *non_constant_p = true; + } + else if (TREE_CODE (t) == MODIFY_EXPR + && CONSTRUCTOR_NO_CLEARING (*valp)) + { + /* Diagnose changing the active union member while the union + is in the process of being initialized. */ + if (!ctx->quiet) + error_at (cp_expr_loc_or_input_loc (t), + "change of the active member of a union " + "from %qD to %qD during initialization", + CONSTRUCTOR_ELT (*valp, 0)->index, + index); + *non_constant_p = true; + } + no_zero_init = true; + } + + vec_safe_push (ctors, *valp); + vec_safe_push (indexes, index); + + constructor_elt *cep + = get_or_insert_ctor_field (*valp, index); + index_pos_hints.safe_push (cep - CONSTRUCTOR_ELTS (*valp)->begin()); + + if (code == UNION_TYPE) + activated_union_member_p = true; + + valp = &cep->value; + } + + /* Detect modifying a constant object in constexpr evaluation. + We have found a const object that is being modified. Figure out + if we need to issue an error. Consider + + struct A { + int n; + constexpr A() : n(1) { n = 2; } // #1 + }; + struct B { + const A a; + constexpr B() { a.n = 3; } // #2 + }; + constexpr B b{}; + + #1 is OK, since we're modifying an object under construction, but + #2 is wrong, since "a" is const and has been fully constructed. + To track it, we use the TREE_READONLY bit in the object's CONSTRUCTOR + which means that the object is read-only. For the example above, the + *ctors stack at the point of #2 will look like: + + ctors[0] = {.a={.n=2}} TREE_READONLY = 0 + ctors[1] = {.n=2} TREE_READONLY = 1 + + and we're modifying "b.a", so we search the stack and see if the + constructor for "b.a" has already run. */ + if (const_object_being_modified) + { + bool fail = false; + tree const_objtype + = strip_array_types (TREE_TYPE (const_object_being_modified)); + if (!CLASS_TYPE_P (const_objtype)) + fail = true; + else + { + /* [class.ctor]p5 "A constructor can be invoked for a const, + volatile, or const volatile object. const and volatile + semantics are not applied on an object under construction. + They come into effect when the constructor for the most + derived object ends." */ + for (tree elt : *ctors) + if (same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (const_object_being_modified), TREE_TYPE (elt))) + { + fail = TREE_READONLY (elt); + break; + } + } + if (fail) + { + if (!ctx->quiet) + modifying_const_object_error (t, const_object_being_modified); + *non_constant_p = true; + return t; + } + } + + if (!preeval) + { + /* We're handling an INIT_EXPR of class type, so the value of the + initializer can depend on the object it's initializing. */ + + /* Create a new CONSTRUCTOR in case evaluation of the initializer + wants to modify it. */ + if (*valp == NULL_TREE) + { + *valp = build_constructor (type, NULL); + CONSTRUCTOR_NO_CLEARING (*valp) = no_zero_init; + } + new_ctx.ctor = *valp; + new_ctx.object = target; + /* Avoid temporary materialization when initializing from a TARGET_EXPR. + We don't need to mess with AGGR_EXPR_SLOT/VEC_INIT_EXPR_SLOT because + expansion of those trees uses ctx instead. */ + if (TREE_CODE (init) == TARGET_EXPR) + if (tree tinit = TARGET_EXPR_INITIAL (init)) + init = tinit; + init = cxx_eval_constant_expression (&new_ctx, init, false, + non_constant_p, overflow_p); + /* The hash table might have moved since the get earlier, and the + initializer might have mutated the underlying CONSTRUCTORs, so we must + recompute VALP. */ + valp = ctx->global->values.get (object); + for (unsigned i = 0; i < vec_safe_length (indexes); i++) + { + constructor_elt *cep + = get_or_insert_ctor_field (*valp, indexes[i], index_pos_hints[i]); + valp = &cep->value; + } + } + + /* Don't share a CONSTRUCTOR that might be changed later. */ + init = unshare_constructor (init); + + if (*valp && TREE_CODE (*valp) == CONSTRUCTOR + && TREE_CODE (init) == CONSTRUCTOR) + { + /* An outer ctx->ctor might be pointing to *valp, so replace + its contents. */ + if (!same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (init), + TREE_TYPE (*valp))) + { + /* For initialization of an empty base, the original target will be + *(base*)this, evaluation of which resolves to the object + argument, which has the derived type rather than the base type. In + this situation, just evaluate the initializer and return, since + there's no actual data to store. */ + gcc_assert (is_empty_class (TREE_TYPE (init))); + return lval ? target : init; + } + CONSTRUCTOR_ELTS (*valp) = CONSTRUCTOR_ELTS (init); + TREE_CONSTANT (*valp) = TREE_CONSTANT (init); + TREE_SIDE_EFFECTS (*valp) = TREE_SIDE_EFFECTS (init); + CONSTRUCTOR_NO_CLEARING (*valp) + = CONSTRUCTOR_NO_CLEARING (init); + } + else if (TREE_CODE (init) == CONSTRUCTOR + && !same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (init), + type)) + { + /* See above on initialization of empty bases. */ + gcc_assert (is_empty_class (TREE_TYPE (init)) && !lval); + return init; + } + else + *valp = init; + + /* After initialization, 'const' semantics apply to the value of the + object. Make a note of this fact by marking the CONSTRUCTOR + TREE_READONLY. */ + if (TREE_CODE (t) == INIT_EXPR + && TREE_CODE (*valp) == CONSTRUCTOR + && TYPE_READONLY (type)) + { + if (INDIRECT_REF_P (target) + && (is_this_parameter + (tree_strip_nop_conversions (TREE_OPERAND (target, 0))))) + /* We've just initialized '*this' (perhaps via the target + constructor of a delegating constructor). Leave it up to the + caller that set 'this' to set TREE_READONLY appropriately. */ + gcc_checking_assert (same_type_ignoring_top_level_qualifiers_p + (TREE_TYPE (target), type)); + else + TREE_READONLY (*valp) = true; + } + + /* Update TREE_CONSTANT and TREE_SIDE_EFFECTS on enclosing + CONSTRUCTORs, if any. */ + bool c = TREE_CONSTANT (init); + bool s = TREE_SIDE_EFFECTS (init); + if (!c || s || activated_union_member_p) + for (tree elt : *ctors) + { + if (!c) + TREE_CONSTANT (elt) = false; + if (s) + TREE_SIDE_EFFECTS (elt) = true; + /* Clear CONSTRUCTOR_NO_CLEARING since we've activated a member of + this union. */ + if (TREE_CODE (TREE_TYPE (elt)) == UNION_TYPE) + CONSTRUCTOR_NO_CLEARING (elt) = false; + } + + if (*non_constant_p) + return t; + else if (lval) + return target; + else + return init; +} + +/* Evaluate a ++ or -- expression. */ + +static tree +cxx_eval_increment_expression (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p) +{ + enum tree_code code = TREE_CODE (t); + tree type = TREE_TYPE (t); + tree op = TREE_OPERAND (t, 0); + tree offset = TREE_OPERAND (t, 1); + gcc_assert (TREE_CONSTANT (offset)); + + /* OFFSET is constant, but perhaps not constant enough. We need to + e.g. bash FLOAT_EXPRs to REAL_CSTs. */ + offset = fold_simple (offset); + + /* The operand as an lvalue. */ + op = cxx_eval_constant_expression (ctx, op, true, + non_constant_p, overflow_p); + + /* The operand as an rvalue. */ + tree val + = cxx_eval_constant_expression (ctx, op, false, + non_constant_p, overflow_p); + /* Don't VERIFY_CONSTANT if this might be dealing with a pointer to + a local array in a constexpr function. */ + bool ptr = INDIRECT_TYPE_P (TREE_TYPE (val)); + if (!ptr) + VERIFY_CONSTANT (val); + + /* The modified value. */ + bool inc = (code == PREINCREMENT_EXPR || code == POSTINCREMENT_EXPR); + tree mod; + if (INDIRECT_TYPE_P (type)) + { + /* The middle end requires pointers to use POINTER_PLUS_EXPR. */ + offset = convert_to_ptrofftype (offset); + if (!inc) + offset = fold_build1 (NEGATE_EXPR, TREE_TYPE (offset), offset); + mod = fold_build2 (POINTER_PLUS_EXPR, type, val, offset); + } + else + mod = fold_build2 (inc ? PLUS_EXPR : MINUS_EXPR, type, val, offset); + if (!ptr) + VERIFY_CONSTANT (mod); + + /* Storing the modified value. */ + tree store = build2_loc (cp_expr_loc_or_loc (t, input_location), + MODIFY_EXPR, type, op, mod); + mod = cxx_eval_constant_expression (ctx, store, lval, + non_constant_p, overflow_p); + ggc_free (store); + if (*non_constant_p) + return t; + + /* And the value of the expression. */ + if (code == PREINCREMENT_EXPR || code == PREDECREMENT_EXPR) + /* Prefix ops are lvalues, but the caller might want an rvalue; + lval has already been taken into account in the store above. */ + return mod; + else + /* Postfix ops are rvalues. */ + return val; +} + +/* Predicates for the meaning of *jump_target. */ + +static bool +returns (tree *jump_target) +{ + return *jump_target + && (TREE_CODE (*jump_target) == RETURN_EXPR + || (TREE_CODE (*jump_target) == LABEL_DECL + && LABEL_DECL_CDTOR (*jump_target))); +} + +static bool +breaks (tree *jump_target) +{ + return *jump_target + && ((TREE_CODE (*jump_target) == LABEL_DECL + && LABEL_DECL_BREAK (*jump_target)) + || TREE_CODE (*jump_target) == BREAK_STMT + || TREE_CODE (*jump_target) == EXIT_EXPR); +} + +static bool +continues (tree *jump_target) +{ + return *jump_target + && ((TREE_CODE (*jump_target) == LABEL_DECL + && LABEL_DECL_CONTINUE (*jump_target)) + || TREE_CODE (*jump_target) == CONTINUE_STMT); + +} + +static bool +switches (tree *jump_target) +{ + return *jump_target + && TREE_CODE (*jump_target) == INTEGER_CST; +} + +/* Subroutine of cxx_eval_statement_list. Determine whether the statement + STMT matches *jump_target. If we're looking for a case label and we see + the default label, note it in ctx->css_state. */ + +static bool +label_matches (const constexpr_ctx *ctx, tree *jump_target, tree stmt) +{ + switch (TREE_CODE (*jump_target)) + { + case LABEL_DECL: + if (TREE_CODE (stmt) == LABEL_EXPR + && LABEL_EXPR_LABEL (stmt) == *jump_target) + return true; + break; + + case INTEGER_CST: + if (TREE_CODE (stmt) == CASE_LABEL_EXPR) + { + gcc_assert (ctx->css_state != NULL); + if (!CASE_LOW (stmt)) + { + /* default: should appear just once in a SWITCH_EXPR + body (excluding nested SWITCH_EXPR). */ + gcc_assert (*ctx->css_state != css_default_seen); + /* When evaluating SWITCH_EXPR body for the second time, + return true for the default: label. */ + if (*ctx->css_state == css_default_processing) + return true; + *ctx->css_state = css_default_seen; + } + else if (CASE_HIGH (stmt)) + { + if (tree_int_cst_le (CASE_LOW (stmt), *jump_target) + && tree_int_cst_le (*jump_target, CASE_HIGH (stmt))) + return true; + } + else if (tree_int_cst_equal (*jump_target, CASE_LOW (stmt))) + return true; + } + break; + + case BREAK_STMT: + case CONTINUE_STMT: + /* These two are handled directly in cxx_eval_loop_expr by testing + breaks (jump_target) or continues (jump_target). */ + break; + + default: + gcc_unreachable (); + } + return false; +} + +/* Evaluate a STATEMENT_LIST for side-effects. Handles various jump + semantics, for switch, break, continue, and return. */ + +static tree +cxx_eval_statement_list (const constexpr_ctx *ctx, tree t, + bool *non_constant_p, bool *overflow_p, + tree *jump_target) +{ + tree local_target; + /* In a statement-expression we want to return the last value. + For empty statement expression return void_node. */ + tree r = void_node; + if (!jump_target) + { + local_target = NULL_TREE; + jump_target = &local_target; + } + for (tree stmt : tsi_range (t)) + { + /* We've found a continue, so skip everything until we reach + the label its jumping to. */ + if (continues (jump_target)) + { + if (label_matches (ctx, jump_target, stmt)) + /* Found it. */ + *jump_target = NULL_TREE; + else + continue; + } + if (TREE_CODE (stmt) == DEBUG_BEGIN_STMT) + continue; + r = cxx_eval_constant_expression (ctx, stmt, false, + non_constant_p, overflow_p, + jump_target); + if (*non_constant_p) + break; + if (returns (jump_target) || breaks (jump_target)) + break; + } + if (*jump_target && jump_target == &local_target) + { + /* We aren't communicating the jump to our caller, so give up. We don't + need to support evaluation of jumps out of statement-exprs. */ + if (!ctx->quiet) + error_at (cp_expr_loc_or_input_loc (r), + "statement is not a constant expression"); + *non_constant_p = true; + } + return r; +} + +/* Evaluate a LOOP_EXPR for side-effects. Handles break and return + semantics; continue semantics are covered by cxx_eval_statement_list. */ + +static tree +cxx_eval_loop_expr (const constexpr_ctx *ctx, tree t, + bool *non_constant_p, bool *overflow_p, + tree *jump_target) +{ + constexpr_ctx new_ctx = *ctx; + tree local_target; + if (!jump_target) + { + local_target = NULL_TREE; + jump_target = &local_target; + } + + tree body, cond = NULL_TREE, expr = NULL_TREE; + int count = 0; + switch (TREE_CODE (t)) + { + case LOOP_EXPR: + body = LOOP_EXPR_BODY (t); + break; + case DO_STMT: + body = DO_BODY (t); + cond = DO_COND (t); + break; + case WHILE_STMT: + body = WHILE_BODY (t); + cond = WHILE_COND (t); + count = -1; + break; + case FOR_STMT: + if (FOR_INIT_STMT (t)) + cxx_eval_constant_expression (ctx, FOR_INIT_STMT (t), /*lval*/false, + non_constant_p, overflow_p, jump_target); + if (*non_constant_p) + return NULL_TREE; + body = FOR_BODY (t); + cond = FOR_COND (t); + expr = FOR_EXPR (t); + count = -1; + break; + default: + gcc_unreachable (); + } + auto_vec<tree, 10> save_exprs; + new_ctx.save_exprs = &save_exprs; + do + { + if (count != -1) + { + if (body) + cxx_eval_constant_expression (&new_ctx, body, /*lval*/false, + non_constant_p, overflow_p, + jump_target); + if (breaks (jump_target)) + { + *jump_target = NULL_TREE; + break; + } + + if (TREE_CODE (t) != LOOP_EXPR && continues (jump_target)) + *jump_target = NULL_TREE; + + if (expr) + cxx_eval_constant_expression (&new_ctx, expr, /*lval*/false, + non_constant_p, overflow_p, + jump_target); + } + + if (cond) + { + tree res + = cxx_eval_constant_expression (&new_ctx, cond, /*lval*/false, + non_constant_p, overflow_p, + jump_target); + if (res) + { + if (verify_constant (res, ctx->quiet, non_constant_p, + overflow_p)) + break; + if (integer_zerop (res)) + break; + } + else + gcc_assert (*jump_target); + } + + /* Forget saved values of SAVE_EXPRs and TARGET_EXPRs. */ + for (tree save_expr : save_exprs) + ctx->global->values.remove (save_expr); + save_exprs.truncate (0); + + if (++count >= constexpr_loop_limit) + { + if (!ctx->quiet) + error_at (cp_expr_loc_or_input_loc (t), + "%<constexpr%> loop iteration count exceeds limit of %d " + "(use %<-fconstexpr-loop-limit=%> to increase the limit)", + constexpr_loop_limit); + *non_constant_p = true; + break; + } + } + while (!returns (jump_target) + && !breaks (jump_target) + && !continues (jump_target) + && (!switches (jump_target) || count == 0) + && !*non_constant_p); + + /* Forget saved values of SAVE_EXPRs and TARGET_EXPRs. */ + for (tree save_expr : save_exprs) + ctx->global->values.remove (save_expr); + + return NULL_TREE; +} + +/* Evaluate a SWITCH_EXPR for side-effects. Handles switch and break jump + semantics. */ + +static tree +cxx_eval_switch_expr (const constexpr_ctx *ctx, tree t, + bool *non_constant_p, bool *overflow_p, + tree *jump_target) +{ + tree cond + = TREE_CODE (t) == SWITCH_STMT ? SWITCH_STMT_COND (t) : SWITCH_COND (t); + cond = cxx_eval_constant_expression (ctx, cond, false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (cond); + *jump_target = cond; + + tree body + = TREE_CODE (t) == SWITCH_STMT ? SWITCH_STMT_BODY (t) : SWITCH_BODY (t); + constexpr_ctx new_ctx = *ctx; + constexpr_switch_state css = css_default_not_seen; + new_ctx.css_state = &css; + cxx_eval_constant_expression (&new_ctx, body, false, + non_constant_p, overflow_p, jump_target); + if (switches (jump_target) && css == css_default_seen) + { + /* If the SWITCH_EXPR body has default: label, process it once again, + this time instructing label_matches to return true for default: + label on switches (jump_target). */ + css = css_default_processing; + cxx_eval_constant_expression (&new_ctx, body, false, + non_constant_p, overflow_p, jump_target); + } + if (breaks (jump_target) || switches (jump_target)) + *jump_target = NULL_TREE; + return NULL_TREE; +} + +/* Find the object of TYPE under initialization in CTX. */ + +static tree +lookup_placeholder (const constexpr_ctx *ctx, bool lval, tree type) +{ + if (!ctx) + return NULL_TREE; + + /* Prefer the outermost matching object, but don't cross + CONSTRUCTOR_PLACEHOLDER_BOUNDARY constructors. */ + if (ctx->ctor && !CONSTRUCTOR_PLACEHOLDER_BOUNDARY (ctx->ctor)) + if (tree outer_ob = lookup_placeholder (ctx->parent, lval, type)) + return outer_ob; + + /* We could use ctx->object unconditionally, but using ctx->ctor when we + can is a minor optimization. */ + if (!lval && ctx->ctor && same_type_p (TREE_TYPE (ctx->ctor), type)) + return ctx->ctor; + + if (!ctx->object) + return NULL_TREE; + + /* Since an object cannot have a field of its own type, we can search outward + from ctx->object to find the unique containing object of TYPE. */ + tree ob = ctx->object; + while (ob) + { + if (same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (ob), type)) + break; + if (handled_component_p (ob)) + ob = TREE_OPERAND (ob, 0); + else + ob = NULL_TREE; + } + + return ob; +} + +/* Complain about an attempt to evaluate inline assembly. */ + +static void +inline_asm_in_constexpr_error (location_t loc) +{ + auto_diagnostic_group d; + error_at (loc, "inline assembly is not a constant expression"); + inform (loc, "only unevaluated inline assembly is allowed in a " + "%<constexpr%> function in C++20"); +} + +/* We're getting the constant value of DECL in a manifestly constant-evaluated + context; maybe complain about that. */ + +static void +maybe_warn_about_constant_value (location_t loc, tree decl) +{ + static bool explained = false; + if (cxx_dialect >= cxx17 + && warn_interference_size + && !OPTION_SET_P (param_destruct_interfere_size) + && DECL_CONTEXT (decl) == std_node + && id_equal (DECL_NAME (decl), "hardware_destructive_interference_size") + && (LOCATION_FILE (input_location) != main_input_filename + || module_exporting_p ()) + && warning_at (loc, OPT_Winterference_size, "use of %qD", decl) + && !explained) + { + explained = true; + inform (loc, "its value can vary between compiler versions or " + "with different %<-mtune%> or %<-mcpu%> flags"); + inform (loc, "if this use is part of a public ABI, change it to " + "instead use a constant variable you define"); + inform (loc, "the default value for the current CPU tuning " + "is %d bytes", param_destruct_interfere_size); + inform (loc, "you can stabilize this value with %<--param " + "hardware_destructive_interference_size=%d%>, or disable " + "this warning with %<-Wno-interference-size%>", + param_destruct_interfere_size); + } +} + +/* Attempt to reduce the expression T to a constant value. + On failure, issue diagnostic and return error_mark_node. */ +/* FIXME unify with c_fully_fold */ +/* FIXME overflow_p is too global */ + +static tree +cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t, + bool lval, + bool *non_constant_p, bool *overflow_p, + tree *jump_target /* = NULL */) +{ + if (jump_target && *jump_target) + { + /* If we are jumping, ignore all statements/expressions except those + that could have LABEL_EXPR or CASE_LABEL_EXPR in their bodies. */ + switch (TREE_CODE (t)) + { + case BIND_EXPR: + case STATEMENT_LIST: + case LOOP_EXPR: + case COND_EXPR: + case IF_STMT: + case DO_STMT: + case WHILE_STMT: + case FOR_STMT: + break; + case LABEL_EXPR: + case CASE_LABEL_EXPR: + if (label_matches (ctx, jump_target, t)) + /* Found it. */ + *jump_target = NULL_TREE; + return NULL_TREE; + default: + return NULL_TREE; + } + } + if (error_operand_p (t)) + { + *non_constant_p = true; + return t; + } + + location_t loc = cp_expr_loc_or_input_loc (t); + + STRIP_ANY_LOCATION_WRAPPER (t); + + if (CONSTANT_CLASS_P (t)) + { + if (TREE_OVERFLOW (t)) + { + if (!ctx->quiet) + permerror (input_location, "overflow in constant expression"); + if (!flag_permissive || ctx->quiet) + *overflow_p = true; + } + + if (TREE_CODE (t) == INTEGER_CST + && TYPE_PTR_P (TREE_TYPE (t)) + /* INTEGER_CST with pointer-to-method type is only used + for a virtual method in a pointer to member function. + Don't reject those. */ + && TREE_CODE (TREE_TYPE (TREE_TYPE (t))) != METHOD_TYPE + && !integer_zerop (t)) + { + if (!ctx->quiet) + error ("value %qE of type %qT is not a constant expression", + t, TREE_TYPE (t)); + *non_constant_p = true; + } + + return t; + } + + /* Avoid excessively long constexpr evaluations. */ + if (++ctx->global->constexpr_ops_count >= constexpr_ops_limit) + { + if (!ctx->quiet) + error_at (loc, + "%<constexpr%> evaluation operation count exceeds limit of " + "%wd (use %<-fconstexpr-ops-limit=%> to increase the limit)", + constexpr_ops_limit); + ctx->global->constexpr_ops_count = INTTYPE_MINIMUM (HOST_WIDE_INT); + *non_constant_p = true; + return t; + } + + constexpr_ctx new_ctx; + tree r = t; + + tree_code tcode = TREE_CODE (t); + switch (tcode) + { + case RESULT_DECL: + if (lval) + return t; + /* We ask for an rvalue for the RESULT_DECL when indirecting + through an invisible reference, or in named return value + optimization. */ + if (tree *p = ctx->global->values.get (t)) + return *p; + else + { + if (!ctx->quiet) + error ("%qE is not a constant expression", t); + *non_constant_p = true; + } + break; + + case VAR_DECL: + if (DECL_HAS_VALUE_EXPR_P (t)) + { + if (is_normal_capture_proxy (t) + && current_function_decl == DECL_CONTEXT (t)) + { + /* Function parms aren't constexpr within the function + definition, so don't try to look at the closure. But if the + captured variable is constant, try to evaluate it directly. */ + r = DECL_CAPTURED_VARIABLE (t); + tree type = TREE_TYPE (t); + if (TYPE_REF_P (type) != TYPE_REF_P (TREE_TYPE (r))) + { + /* Adjust r to match the reference-ness of t. */ + if (TYPE_REF_P (type)) + r = build_address (r); + else + r = convert_from_reference (r); + } + } + else + r = DECL_VALUE_EXPR (t); + return cxx_eval_constant_expression (ctx, r, lval, non_constant_p, + overflow_p); + } + /* fall through */ + case CONST_DECL: + /* We used to not check lval for CONST_DECL, but darwin.c uses + CONST_DECL for aggregate constants. */ + if (lval) + return t; + else if (t == ctx->object) + return ctx->ctor; + if (VAR_P (t)) + if (tree *p = ctx->global->values.get (t)) + if (*p != NULL_TREE) + { + r = *p; + break; + } + if (ctx->manifestly_const_eval) + maybe_warn_about_constant_value (loc, t); + if (COMPLETE_TYPE_P (TREE_TYPE (t)) + && is_really_empty_class (TREE_TYPE (t), /*ignore_vptr*/false)) + { + /* If the class is empty, we aren't actually loading anything. */ + r = build_constructor (TREE_TYPE (t), NULL); + TREE_CONSTANT (r) = true; + } + else if (ctx->strict) + r = decl_really_constant_value (t, /*unshare_p=*/false); + else + r = decl_constant_value (t, /*unshare_p=*/false); + if (TREE_CODE (r) == TARGET_EXPR + && TREE_CODE (TARGET_EXPR_INITIAL (r)) == CONSTRUCTOR) + r = TARGET_EXPR_INITIAL (r); + if (DECL_P (r)) + { + if (!ctx->quiet) + non_const_var_error (loc, r); + *non_constant_p = true; + } + break; + + case DEBUG_BEGIN_STMT: + /* ??? It might be nice to retain this information somehow, so + as to be able to step into a constexpr function call. */ + /* Fall through. */ + + case FUNCTION_DECL: + case TEMPLATE_DECL: + case LABEL_DECL: + case LABEL_EXPR: + case CASE_LABEL_EXPR: + case PREDICT_EXPR: + return t; + + case PARM_DECL: + if (lval && !TYPE_REF_P (TREE_TYPE (t))) + /* glvalue use. */; + else if (tree *p = ctx->global->values.get (r)) + r = *p; + else if (lval) + /* Defer in case this is only used for its type. */; + else if (COMPLETE_TYPE_P (TREE_TYPE (t)) + && is_really_empty_class (TREE_TYPE (t), /*ignore_vptr*/false)) + { + /* If the class is empty, we aren't actually loading anything. */ + r = build_constructor (TREE_TYPE (t), NULL); + TREE_CONSTANT (r) = true; + } + else + { + if (!ctx->quiet) + error ("%qE is not a constant expression", t); + *non_constant_p = true; + } + break; + + case CALL_EXPR: + case AGGR_INIT_EXPR: + r = cxx_eval_call_expression (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case DECL_EXPR: + { + r = DECL_EXPR_DECL (t); + if (TREE_CODE (r) == USING_DECL) + { + r = void_node; + break; + } + + if (VAR_P (r) + && (TREE_STATIC (r) || CP_DECL_THREAD_LOCAL_P (r)) + /* Allow __FUNCTION__ etc. */ + && !DECL_ARTIFICIAL (r)) + { + gcc_assert (cxx_dialect >= cxx23); + if (!ctx->quiet) + { + if (CP_DECL_THREAD_LOCAL_P (r)) + error_at (loc, "control passes through declaration of %qD " + "with thread storage duration", r); + else + error_at (loc, "control passes through declaration of %qD " + "with static storage duration", r); + } + *non_constant_p = true; + break; + } + + if (AGGREGATE_TYPE_P (TREE_TYPE (r)) + || VECTOR_TYPE_P (TREE_TYPE (r))) + { + new_ctx = *ctx; + new_ctx.object = r; + new_ctx.ctor = build_constructor (TREE_TYPE (r), NULL); + CONSTRUCTOR_NO_CLEARING (new_ctx.ctor) = true; + ctx->global->values.put (r, new_ctx.ctor); + ctx = &new_ctx; + } + + if (tree init = DECL_INITIAL (r)) + { + init = cxx_eval_constant_expression (ctx, init, + false, + non_constant_p, overflow_p); + /* Don't share a CONSTRUCTOR that might be changed. */ + init = unshare_constructor (init); + /* Remember that a constant object's constructor has already + run. */ + if (CLASS_TYPE_P (TREE_TYPE (r)) + && CP_TYPE_CONST_P (TREE_TYPE (r))) + TREE_READONLY (init) = true; + ctx->global->values.put (r, init); + } + else if (ctx == &new_ctx) + /* We gave it a CONSTRUCTOR above. */; + else + ctx->global->values.put (r, NULL_TREE); + } + break; + + case TARGET_EXPR: + { + tree type = TREE_TYPE (t); + + if (!literal_type_p (type)) + { + if (!ctx->quiet) + { + auto_diagnostic_group d; + error ("temporary of non-literal type %qT in a " + "constant expression", type); + explain_non_literal_class (type); + } + *non_constant_p = true; + break; + } + gcc_checking_assert (!TARGET_EXPR_DIRECT_INIT_P (t)); + /* Avoid evaluating a TARGET_EXPR more than once. */ + tree slot = TARGET_EXPR_SLOT (t); + if (tree *p = ctx->global->values.get (slot)) + { + if (lval) + return slot; + r = *p; + break; + } + if ((AGGREGATE_TYPE_P (type) || VECTOR_TYPE_P (type))) + { + /* We're being expanded without an explicit target, so start + initializing a new object; expansion with an explicit target + strips the TARGET_EXPR before we get here. */ + new_ctx = *ctx; + /* Link CTX to NEW_CTX so that lookup_placeholder can resolve + any PLACEHOLDER_EXPR within the initializer that refers to the + former object under construction. */ + new_ctx.parent = ctx; + new_ctx.ctor = build_constructor (type, NULL); + CONSTRUCTOR_NO_CLEARING (new_ctx.ctor) = true; + new_ctx.object = slot; + ctx->global->values.put (new_ctx.object, new_ctx.ctor); + ctx = &new_ctx; + } + /* Pass false for 'lval' because this indicates + initialization of a temporary. */ + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 1), + false, + non_constant_p, overflow_p); + if (*non_constant_p) + break; + /* Adjust the type of the result to the type of the temporary. */ + r = adjust_temp_type (type, r); + if (TARGET_EXPR_CLEANUP (t) && !CLEANUP_EH_ONLY (t)) + ctx->global->cleanups->safe_push (TARGET_EXPR_CLEANUP (t)); + r = unshare_constructor (r); + ctx->global->values.put (slot, r); + if (ctx->save_exprs) + ctx->save_exprs->safe_push (slot); + if (lval) + return slot; + } + break; + + case INIT_EXPR: + case MODIFY_EXPR: + gcc_assert (jump_target == NULL || *jump_target == NULL_TREE); + r = cxx_eval_store_expression (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case SCOPE_REF: + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 1), + lval, + non_constant_p, overflow_p); + break; + + case RETURN_EXPR: + if (TREE_OPERAND (t, 0) != NULL_TREE) + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), + lval, + non_constant_p, overflow_p); + /* FALLTHRU */ + case BREAK_STMT: + case CONTINUE_STMT: + if (jump_target) + *jump_target = t; + else + { + /* Can happen with ({ return true; }) && false; passed to + maybe_constant_value. There is nothing to jump over in this + case, and the bug will be diagnosed later. */ + gcc_assert (ctx->quiet); + *non_constant_p = true; + } + break; + + case SAVE_EXPR: + /* Avoid evaluating a SAVE_EXPR more than once. */ + if (tree *p = ctx->global->values.get (t)) + r = *p; + else + { + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), false, + non_constant_p, overflow_p); + if (*non_constant_p) + break; + ctx->global->values.put (t, r); + if (ctx->save_exprs) + ctx->save_exprs->safe_push (t); + } + break; + + case TRY_CATCH_EXPR: + if (TREE_OPERAND (t, 0) == NULL_TREE) + { + r = void_node; + break; + } + /* FALLTHRU */ + case NON_LVALUE_EXPR: + case TRY_BLOCK: + case MUST_NOT_THROW_EXPR: + case EXPR_STMT: + case EH_SPEC_BLOCK: + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), + lval, + non_constant_p, overflow_p, + jump_target); + break; + + case CLEANUP_POINT_EXPR: + { + auto_vec<tree, 2> cleanups; + vec<tree> *prev_cleanups = ctx->global->cleanups; + ctx->global->cleanups = &cleanups; + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), + lval, + non_constant_p, overflow_p, + jump_target); + ctx->global->cleanups = prev_cleanups; + unsigned int i; + tree cleanup; + /* Evaluate the cleanups. */ + FOR_EACH_VEC_ELT_REVERSE (cleanups, i, cleanup) + cxx_eval_constant_expression (ctx, cleanup, false, + non_constant_p, overflow_p); + } + break; + + case TRY_FINALLY_EXPR: + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), lval, + non_constant_p, overflow_p, + jump_target); + if (!*non_constant_p) + /* Also evaluate the cleanup. */ + cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 1), true, + non_constant_p, overflow_p); + break; + + case CLEANUP_STMT: + r = cxx_eval_constant_expression (ctx, CLEANUP_BODY (t), lval, + non_constant_p, overflow_p, + jump_target); + if (!CLEANUP_EH_ONLY (t) && !*non_constant_p) + { + iloc_sentinel ils (loc); + /* Also evaluate the cleanup. */ + cxx_eval_constant_expression (ctx, CLEANUP_EXPR (t), true, + non_constant_p, overflow_p); + } + break; + + /* These differ from cxx_eval_unary_expression in that this doesn't + check for a constant operand or result; an address can be + constant without its operand being, and vice versa. */ + case MEM_REF: + case INDIRECT_REF: + r = cxx_eval_indirect_ref (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case ADDR_EXPR: + { + tree oldop = TREE_OPERAND (t, 0); + tree op = cxx_eval_constant_expression (ctx, oldop, + /*lval*/true, + non_constant_p, overflow_p); + /* Don't VERIFY_CONSTANT here. */ + if (*non_constant_p) + return t; + gcc_checking_assert (TREE_CODE (op) != CONSTRUCTOR); + /* This function does more aggressive folding than fold itself. */ + r = build_fold_addr_expr_with_type (op, TREE_TYPE (t)); + if (TREE_CODE (r) == ADDR_EXPR && TREE_OPERAND (r, 0) == oldop) + { + ggc_free (r); + return t; + } + break; + } + + case REALPART_EXPR: + case IMAGPART_EXPR: + if (lval) + { + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), lval, + non_constant_p, overflow_p); + if (r == error_mark_node) + ; + else if (r == TREE_OPERAND (t, 0)) + r = t; + else + r = fold_build1 (TREE_CODE (t), TREE_TYPE (t), r); + break; + } + /* FALLTHRU */ + case CONJ_EXPR: + case FIX_TRUNC_EXPR: + case FLOAT_EXPR: + case NEGATE_EXPR: + case ABS_EXPR: + case ABSU_EXPR: + case BIT_NOT_EXPR: + case TRUTH_NOT_EXPR: + case FIXED_CONVERT_EXPR: + r = cxx_eval_unary_expression (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case SIZEOF_EXPR: + r = fold_sizeof_expr (t); + /* In a template, fold_sizeof_expr may merely create a new SIZEOF_EXPR, + which could lead to an infinite recursion. */ + if (TREE_CODE (r) != SIZEOF_EXPR) + r = cxx_eval_constant_expression (ctx, r, lval, + non_constant_p, overflow_p, + jump_target); + else + { + *non_constant_p = true; + gcc_assert (ctx->quiet); + } + + break; + + case COMPOUND_EXPR: + { + /* check_return_expr sometimes wraps a TARGET_EXPR in a + COMPOUND_EXPR; don't get confused. Also handle EMPTY_CLASS_EXPR + introduced by build_call_a. */ + tree op0 = TREE_OPERAND (t, 0); + tree op1 = TREE_OPERAND (t, 1); + STRIP_NOPS (op1); + if ((TREE_CODE (op0) == TARGET_EXPR && op1 == TARGET_EXPR_SLOT (op0)) + || TREE_CODE (op1) == EMPTY_CLASS_EXPR) + r = cxx_eval_constant_expression (ctx, op0, + lval, non_constant_p, overflow_p, + jump_target); + else + { + /* Check that the LHS is constant and then discard it. */ + cxx_eval_constant_expression (ctx, op0, + true, non_constant_p, overflow_p, + jump_target); + if (*non_constant_p) + return t; + op1 = TREE_OPERAND (t, 1); + r = cxx_eval_constant_expression (ctx, op1, + lval, non_constant_p, overflow_p, + jump_target); + } + } + break; + + case POINTER_PLUS_EXPR: + case POINTER_DIFF_EXPR: + case PLUS_EXPR: + case MINUS_EXPR: + case MULT_EXPR: + case TRUNC_DIV_EXPR: + case CEIL_DIV_EXPR: + case FLOOR_DIV_EXPR: + case ROUND_DIV_EXPR: + case TRUNC_MOD_EXPR: + case CEIL_MOD_EXPR: + case ROUND_MOD_EXPR: + case RDIV_EXPR: + case EXACT_DIV_EXPR: + case MIN_EXPR: + case MAX_EXPR: + case LSHIFT_EXPR: + case RSHIFT_EXPR: + case LROTATE_EXPR: + case RROTATE_EXPR: + case BIT_IOR_EXPR: + case BIT_XOR_EXPR: + case BIT_AND_EXPR: + case TRUTH_XOR_EXPR: + case LT_EXPR: + case LE_EXPR: + case GT_EXPR: + case GE_EXPR: + case EQ_EXPR: + case NE_EXPR: + case SPACESHIP_EXPR: + case UNORDERED_EXPR: + case ORDERED_EXPR: + case UNLT_EXPR: + case UNLE_EXPR: + case UNGT_EXPR: + case UNGE_EXPR: + case UNEQ_EXPR: + case LTGT_EXPR: + case RANGE_EXPR: + case COMPLEX_EXPR: + r = cxx_eval_binary_expression (ctx, t, lval, + non_constant_p, overflow_p); + break; + + /* fold can introduce non-IF versions of these; still treat them as + short-circuiting. */ + case TRUTH_AND_EXPR: + case TRUTH_ANDIF_EXPR: + r = cxx_eval_logical_expression (ctx, t, boolean_false_node, + boolean_true_node, + lval, + non_constant_p, overflow_p); + break; + + case TRUTH_OR_EXPR: + case TRUTH_ORIF_EXPR: + r = cxx_eval_logical_expression (ctx, t, boolean_true_node, + boolean_false_node, + lval, + non_constant_p, overflow_p); + break; + + case ARRAY_REF: + r = cxx_eval_array_reference (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case COMPONENT_REF: + if (is_overloaded_fn (t)) + { + /* We can only get here in checking mode via + build_non_dependent_expr, because any expression that + calls or takes the address of the function will have + pulled a FUNCTION_DECL out of the COMPONENT_REF. */ + gcc_checking_assert (ctx->quiet || errorcount); + *non_constant_p = true; + return t; + } + r = cxx_eval_component_reference (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case BIT_FIELD_REF: + r = cxx_eval_bit_field_ref (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case COND_EXPR: + case IF_STMT: + if (jump_target && *jump_target) + { + tree orig_jump = *jump_target; + tree arg = ((TREE_CODE (t) != IF_STMT || TREE_OPERAND (t, 1)) + ? TREE_OPERAND (t, 1) : void_node); + /* When jumping to a label, the label might be either in the + then or else blocks, so process then block first in skipping + mode first, and if we are still in the skipping mode at its end, + process the else block too. */ + r = cxx_eval_constant_expression (ctx, arg, lval, non_constant_p, + overflow_p, jump_target); + /* It's possible that we found the label in the then block. But + it could have been followed by another jumping statement, e.g. + say we're looking for case 1: + if (cond) + { + // skipped statements + case 1:; // clears up *jump_target + return 1; // and sets it to a RETURN_EXPR + } + else { ... } + in which case we need not go looking to the else block. + (goto is not allowed in a constexpr function.) */ + if (*jump_target == orig_jump) + { + arg = ((TREE_CODE (t) != IF_STMT || TREE_OPERAND (t, 2)) + ? TREE_OPERAND (t, 2) : void_node); + r = cxx_eval_constant_expression (ctx, arg, lval, non_constant_p, + overflow_p, jump_target); + } + break; + } + r = cxx_eval_conditional_expression (ctx, t, lval, + non_constant_p, overflow_p, + jump_target); + break; + case VEC_COND_EXPR: + r = cxx_eval_vector_conditional_expression (ctx, t, non_constant_p, + overflow_p); + break; + + case CONSTRUCTOR: + if (TREE_CONSTANT (t) && reduced_constant_expression_p (t)) + { + /* Don't re-process a constant CONSTRUCTOR, but do fold it to + VECTOR_CST if applicable. */ + verify_constructor_flags (t); + if (TREE_CONSTANT (t)) + return fold (t); + } + r = cxx_eval_bare_aggregate (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case VEC_INIT_EXPR: + /* We can get this in a defaulted constructor for a class with a + non-static data member of array type. Either the initializer will + be NULL, meaning default-initialization, or it will be an lvalue + or xvalue of the same type, meaning direct-initialization from the + corresponding member. */ + r = cxx_eval_vec_init (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case VEC_PERM_EXPR: + r = cxx_eval_trinary_expression (ctx, t, lval, + non_constant_p, overflow_p); + break; + + case PAREN_EXPR: + gcc_assert (!REF_PARENTHESIZED_P (t)); + /* A PAREN_EXPR resulting from __builtin_assoc_barrier has no effect in + constant expressions since it's unaffected by -fassociative-math. */ + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), lval, + non_constant_p, overflow_p); + break; + + case NOP_EXPR: + if (REINTERPRET_CAST_P (t)) + { + if (!ctx->quiet) + error_at (loc, + "%<reinterpret_cast%> is not a constant expression"); + *non_constant_p = true; + return t; + } + /* FALLTHROUGH. */ + case CONVERT_EXPR: + case VIEW_CONVERT_EXPR: + case UNARY_PLUS_EXPR: + { + tree oldop = TREE_OPERAND (t, 0); + + tree op = cxx_eval_constant_expression (ctx, oldop, + lval, + non_constant_p, overflow_p); + if (*non_constant_p) + return t; + tree type = TREE_TYPE (t); + + if (VOID_TYPE_P (type)) + return void_node; + + if (TREE_CODE (t) == CONVERT_EXPR + && ARITHMETIC_TYPE_P (type) + && INDIRECT_TYPE_P (TREE_TYPE (op)) + && ctx->manifestly_const_eval) + { + if (!ctx->quiet) + error_at (loc, + "conversion from pointer type %qT to arithmetic type " + "%qT in a constant expression", TREE_TYPE (op), type); + *non_constant_p = true; + return t; + } + + /* [expr.const]: a conversion from type cv void* to a pointer-to-object + type cannot be part of a core constant expression as a resolution to + DR 1312. */ + if (TYPE_PTROB_P (type) + && TYPE_PTR_P (TREE_TYPE (op)) + && VOID_TYPE_P (TREE_TYPE (TREE_TYPE (op))) + /* Inside a call to std::construct_at or to + std::allocator<T>::{,de}allocate, we permit casting from void* + because that is compiler-generated code. */ + && !is_std_construct_at (ctx->call) + && !is_std_allocator_allocate (ctx->call)) + { + /* Likewise, don't error when casting from void* when OP is + &heap uninit and similar. */ + tree sop = tree_strip_nop_conversions (op); + if (TREE_CODE (sop) == ADDR_EXPR + && VAR_P (TREE_OPERAND (sop, 0)) + && DECL_ARTIFICIAL (TREE_OPERAND (sop, 0))) + /* OK */; + else + { + if (!ctx->quiet) + error_at (loc, "cast from %qT is not allowed", + TREE_TYPE (op)); + *non_constant_p = true; + return t; + } + } + + if (TREE_CODE (op) == PTRMEM_CST && !TYPE_PTRMEM_P (type)) + op = cplus_expand_constant (op); + + if (TREE_CODE (op) == PTRMEM_CST && tcode == NOP_EXPR) + { + if (!same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (op)) + && !can_convert_qual (type, op)) + op = cplus_expand_constant (op); + return cp_fold_convert (type, op); + } + + if (INDIRECT_TYPE_P (type) && TREE_CODE (op) == INTEGER_CST) + { + if (integer_zerop (op)) + { + if (TYPE_REF_P (type)) + { + if (!ctx->quiet) + error_at (loc, "dereferencing a null pointer"); + *non_constant_p = true; + return t; + } + } + else + { + /* This detects for example: + reinterpret_cast<void*>(sizeof 0) + */ + if (!ctx->quiet) + error_at (loc, "%<reinterpret_cast<%T>(%E)%> is not " + "a constant expression", + type, op); + *non_constant_p = true; + return t; + } + } + + if (INDIRECT_TYPE_P (type) + && TREE_CODE (op) == NOP_EXPR + && TREE_TYPE (op) == ptr_type_node + && TREE_CODE (TREE_OPERAND (op, 0)) == ADDR_EXPR + && VAR_P (TREE_OPERAND (TREE_OPERAND (op, 0), 0)) + && (DECL_NAME (TREE_OPERAND (TREE_OPERAND (op, 0), + 0)) == heap_uninit_identifier + || DECL_NAME (TREE_OPERAND (TREE_OPERAND (op, 0), + 0)) == heap_vec_uninit_identifier)) + { + tree var = TREE_OPERAND (TREE_OPERAND (op, 0), 0); + tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); + tree elt_type = TREE_TYPE (type); + tree cookie_size = NULL_TREE; + if (TREE_CODE (elt_type) == RECORD_TYPE + && TYPE_NAME (elt_type) == heap_identifier) + { + tree fld1 = TYPE_FIELDS (elt_type); + tree fld2 = DECL_CHAIN (fld1); + elt_type = TREE_TYPE (TREE_TYPE (fld2)); + cookie_size = TYPE_SIZE_UNIT (TREE_TYPE (fld1)); + } + DECL_NAME (var) + = (DECL_NAME (var) == heap_uninit_identifier + ? heap_identifier : heap_vec_identifier); + TREE_TYPE (var) + = build_new_constexpr_heap_type (elt_type, cookie_size, + var_size); + TREE_TYPE (TREE_OPERAND (op, 0)) + = build_pointer_type (TREE_TYPE (var)); + } + + if (op == oldop && tcode != UNARY_PLUS_EXPR) + /* We didn't fold at the top so we could check for ptr-int + conversion. */ + return fold (t); + + tree sop; + + /* Handle an array's bounds having been deduced after we built + the wrapping expression. */ + if (same_type_ignoring_tlq_and_bounds_p (type, TREE_TYPE (op))) + r = op; + else if (sop = tree_strip_nop_conversions (op), + sop != op && (same_type_ignoring_tlq_and_bounds_p + (type, TREE_TYPE (sop)))) + r = sop; + else if (tcode == UNARY_PLUS_EXPR) + r = fold_convert (TREE_TYPE (t), op); + else + r = fold_build1 (tcode, type, op); + + /* Conversion of an out-of-range value has implementation-defined + behavior; the language considers it different from arithmetic + overflow, which is undefined. */ + if (TREE_OVERFLOW_P (r) && !TREE_OVERFLOW_P (op)) + TREE_OVERFLOW (r) = false; + } + break; + + case EMPTY_CLASS_EXPR: + /* Handle EMPTY_CLASS_EXPR produced by build_call_a by lowering + it to an appropriate CONSTRUCTOR. */ + return build_constructor (TREE_TYPE (t), NULL); + + case STATEMENT_LIST: + new_ctx = *ctx; + new_ctx.ctor = new_ctx.object = NULL_TREE; + return cxx_eval_statement_list (&new_ctx, t, + non_constant_p, overflow_p, jump_target); + + case BIND_EXPR: + return cxx_eval_constant_expression (ctx, BIND_EXPR_BODY (t), + lval, + non_constant_p, overflow_p, + jump_target); + + case PREINCREMENT_EXPR: + case POSTINCREMENT_EXPR: + case PREDECREMENT_EXPR: + case POSTDECREMENT_EXPR: + return cxx_eval_increment_expression (ctx, t, + lval, non_constant_p, overflow_p); + + case LAMBDA_EXPR: + case NEW_EXPR: + case VEC_NEW_EXPR: + case DELETE_EXPR: + case VEC_DELETE_EXPR: + case THROW_EXPR: + case MODOP_EXPR: + /* GCC internal stuff. */ + case VA_ARG_EXPR: + case NON_DEPENDENT_EXPR: + case BASELINK: + case OFFSET_REF: + if (!ctx->quiet) + error_at (loc, "expression %qE is not a constant expression", t); + *non_constant_p = true; + break; + + case OBJ_TYPE_REF: + /* Virtual function lookup. We don't need to do anything fancy. */ + return cxx_eval_constant_expression (ctx, OBJ_TYPE_REF_EXPR (t), + lval, non_constant_p, overflow_p); + + case PLACEHOLDER_EXPR: + /* Use of the value or address of the current object. */ + if (tree ctor = lookup_placeholder (ctx, lval, TREE_TYPE (t))) + { + if (TREE_CODE (ctor) == CONSTRUCTOR) + return ctor; + else + return cxx_eval_constant_expression (ctx, ctor, lval, + non_constant_p, overflow_p); + } + /* A placeholder without a referent. We can get here when + checking whether NSDMIs are noexcept, or in massage_init_elt; + just say it's non-constant for now. */ + gcc_assert (ctx->quiet); + *non_constant_p = true; + break; + + case EXIT_EXPR: + { + tree cond = TREE_OPERAND (t, 0); + cond = cxx_eval_constant_expression (ctx, cond, /*lval*/false, + non_constant_p, overflow_p); + VERIFY_CONSTANT (cond); + if (integer_nonzerop (cond)) + *jump_target = t; + } + break; + + case GOTO_EXPR: + if (breaks (&TREE_OPERAND (t, 0)) + || continues (&TREE_OPERAND (t, 0)) + /* Allow for jumping to a cdtor_label. */ + || returns (&TREE_OPERAND (t, 0))) + *jump_target = TREE_OPERAND (t, 0); + else + { + gcc_assert (cxx_dialect >= cxx23); + if (!ctx->quiet) + error_at (loc, "%<goto%> is not a constant expression"); + *non_constant_p = true; + } + break; + + case LOOP_EXPR: + case DO_STMT: + case WHILE_STMT: + case FOR_STMT: + cxx_eval_loop_expr (ctx, t, + non_constant_p, overflow_p, jump_target); + break; + + case SWITCH_EXPR: + case SWITCH_STMT: + cxx_eval_switch_expr (ctx, t, + non_constant_p, overflow_p, jump_target); + break; + + case REQUIRES_EXPR: + /* It's possible to get a requires-expression in a constant + expression. For example: + + template<typename T> concept bool C() { + return requires (T t) { t; }; + } + + template<typename T> requires !C<T>() void f(T); + + Normalization leaves f with the associated constraint + '!requires (T t) { ... }' which is not transformed into + a constraint. */ + if (!processing_template_decl) + return evaluate_requires_expr (t); + else + *non_constant_p = true; + return t; + + case ANNOTATE_EXPR: + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0), + lval, + non_constant_p, overflow_p, + jump_target); + break; + + case USING_STMT: + r = void_node; + break; + + case TEMPLATE_ID_EXPR: + { + /* We can evaluate template-id that refers to a concept only if + the template arguments are non-dependent. */ + tree id = unpack_concept_check (t); + tree tmpl = TREE_OPERAND (id, 0); + if (!concept_definition_p (tmpl)) + internal_error ("unexpected template-id %qE", t); + + if (function_concept_p (tmpl)) + { + if (!ctx->quiet) + error_at (cp_expr_loc_or_input_loc (t), + "function concept must be called"); + r = error_mark_node; + break; + } + + if (!value_dependent_expression_p (t) + && !uid_sensitive_constexpr_evaluation_p ()) + r = evaluate_concept_check (t); + else + *non_constant_p = true; + + break; + } + + case ASM_EXPR: + if (!ctx->quiet) + inline_asm_in_constexpr_error (loc); + *non_constant_p = true; + return t; + + case BIT_CAST_EXPR: + if (lval) + { + if (!ctx->quiet) + error_at (EXPR_LOCATION (t), + "address of a call to %qs is not a constant expression", + "__builtin_bit_cast"); + *non_constant_p = true; + return t; + } + r = cxx_eval_bit_cast (ctx, t, non_constant_p, overflow_p); + break; + + default: + if (STATEMENT_CODE_P (TREE_CODE (t))) + { + /* This function doesn't know how to deal with pre-genericize + statements; this can only happen with statement-expressions, + so for now just fail. */ + if (!ctx->quiet) + error_at (EXPR_LOCATION (t), + "statement is not a constant expression"); + } + else + internal_error ("unexpected expression %qE of kind %s", t, + get_tree_code_name (TREE_CODE (t))); + *non_constant_p = true; + break; + } + + if (r == error_mark_node) + *non_constant_p = true; + + if (*non_constant_p) + return t; + else + return r; +} + +/* P0859: A function is needed for constant evaluation if it is a constexpr + function that is named by an expression ([basic.def.odr]) that is + potentially constant evaluated. + + So we need to instantiate any constexpr functions mentioned by the + expression even if the definition isn't needed for evaluating the + expression. */ + +static tree +instantiate_cx_fn_r (tree *tp, int *walk_subtrees, void */*data*/) +{ + if (TREE_CODE (*tp) == FUNCTION_DECL + && DECL_DECLARED_CONSTEXPR_P (*tp) + && !DECL_INITIAL (*tp) + && !trivial_fn_p (*tp) + && DECL_TEMPLOID_INSTANTIATION (*tp) + && !uid_sensitive_constexpr_evaluation_p ()) + { + ++function_depth; + instantiate_decl (*tp, /*defer_ok*/false, /*expl_inst*/false); + --function_depth; + } + else if (TREE_CODE (*tp) == CALL_EXPR + || TREE_CODE (*tp) == AGGR_INIT_EXPR) + { + if (EXPR_HAS_LOCATION (*tp)) + input_location = EXPR_LOCATION (*tp); + } + + if (!EXPR_P (*tp)) + *walk_subtrees = 0; + + return NULL_TREE; +} + +static void +instantiate_constexpr_fns (tree t) +{ + location_t loc = input_location; + cp_walk_tree_without_duplicates (&t, instantiate_cx_fn_r, NULL); + input_location = loc; +} + +/* Look for heap variables in the expression *TP. */ + +static tree +find_heap_var_refs (tree *tp, int *walk_subtrees, void */*data*/) +{ + if (VAR_P (*tp) + && (DECL_NAME (*tp) == heap_uninit_identifier + || DECL_NAME (*tp) == heap_identifier + || DECL_NAME (*tp) == heap_vec_uninit_identifier + || DECL_NAME (*tp) == heap_vec_identifier + || DECL_NAME (*tp) == heap_deleted_identifier)) + return *tp; + + if (TYPE_P (*tp)) + *walk_subtrees = 0; + return NULL_TREE; +} + +/* Find immediate function decls in *TP if any. */ + +static tree +find_immediate_fndecl (tree *tp, int */*walk_subtrees*/, void */*data*/) +{ + if (TREE_CODE (*tp) == FUNCTION_DECL && DECL_IMMEDIATE_FUNCTION_P (*tp)) + return *tp; + if (TREE_CODE (*tp) == PTRMEM_CST + && TREE_CODE (PTRMEM_CST_MEMBER (*tp)) == FUNCTION_DECL + && DECL_IMMEDIATE_FUNCTION_P (PTRMEM_CST_MEMBER (*tp))) + return PTRMEM_CST_MEMBER (*tp); + return NULL_TREE; +} + +/* ALLOW_NON_CONSTANT is false if T is required to be a constant expression. + STRICT has the same sense as for constant_value_1: true if we only allow + conforming C++ constant expressions, or false if we want a constant value + even if it doesn't conform. + MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated as + per P0595 even when ALLOW_NON_CONSTANT is true. + CONSTEXPR_DTOR is true when evaluating the dtor of a constexpr variable. + OBJECT must be non-NULL in that case. */ + +static tree +cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant, + bool strict = true, + bool manifestly_const_eval = false, + bool constexpr_dtor = false, + tree object = NULL_TREE) +{ + auto_timevar time (TV_CONSTEXPR); + + bool non_constant_p = false; + bool overflow_p = false; + + if (BRACE_ENCLOSED_INITIALIZER_P (t)) + { + gcc_checking_assert (allow_non_constant); + return t; + } + + constexpr_global_ctx global_ctx; + constexpr_ctx ctx = { &global_ctx, NULL, NULL, NULL, NULL, NULL, NULL, + allow_non_constant, strict, + manifestly_const_eval || !allow_non_constant }; + + /* Turn off -frounding-math for manifestly constant evaluation. */ + warning_sentinel rm (flag_rounding_math, ctx.manifestly_const_eval); + tree type = initialized_type (t); + tree r = t; + bool is_consteval = false; + if (VOID_TYPE_P (type)) + { + if (constexpr_dtor) + /* Used for destructors of array elements. */ + type = TREE_TYPE (object); + else + { + if (cxx_dialect < cxx20) + return t; + if (TREE_CODE (t) != CALL_EXPR && TREE_CODE (t) != AGGR_INIT_EXPR) + return t; + /* Calls to immediate functions returning void need to be + evaluated. */ + tree fndecl = cp_get_callee_fndecl_nofold (t); + if (fndecl == NULL_TREE || !DECL_IMMEDIATE_FUNCTION_P (fndecl)) + return t; + else + is_consteval = true; + } + } + else if (cxx_dialect >= cxx20 + && (TREE_CODE (t) == CALL_EXPR + || TREE_CODE (t) == AGGR_INIT_EXPR + || TREE_CODE (t) == TARGET_EXPR)) + { + /* For non-concept checks, determine if it is consteval. */ + if (!concept_check_p (t)) + { + tree x = t; + if (TREE_CODE (x) == TARGET_EXPR) + x = TARGET_EXPR_INITIAL (x); + tree fndecl = cp_get_callee_fndecl_nofold (x); + if (fndecl && DECL_IMMEDIATE_FUNCTION_P (fndecl)) + is_consteval = true; + } + } + if (AGGREGATE_TYPE_P (type) || VECTOR_TYPE_P (type)) + { + /* In C++14 an NSDMI can participate in aggregate initialization, + and can refer to the address of the object being initialized, so + we need to pass in the relevant VAR_DECL if we want to do the + evaluation in a single pass. The evaluation will dynamically + update ctx.values for the VAR_DECL. We use the same strategy + for C++11 constexpr constructors that refer to the object being + initialized. */ + if (constexpr_dtor) + { + gcc_assert (object && VAR_P (object)); + gcc_assert (DECL_DECLARED_CONSTEXPR_P (object)); + gcc_assert (DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (object)); + if (error_operand_p (DECL_INITIAL (object))) + return t; + ctx.ctor = unshare_expr (DECL_INITIAL (object)); + TREE_READONLY (ctx.ctor) = false; + /* Temporarily force decl_really_constant_value to return false + for it, we want to use ctx.ctor for the current value instead. */ + DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (object) = false; + } + else + { + ctx.ctor = build_constructor (type, NULL); + CONSTRUCTOR_NO_CLEARING (ctx.ctor) = true; + } + if (!object) + { + if (TREE_CODE (t) == TARGET_EXPR) + object = TARGET_EXPR_SLOT (t); + else if (TREE_CODE (t) == AGGR_INIT_EXPR) + object = AGGR_INIT_EXPR_SLOT (t); + } + ctx.object = object; + if (object) + gcc_assert (same_type_ignoring_top_level_qualifiers_p + (type, TREE_TYPE (object))); + if (object && DECL_P (object)) + global_ctx.values.put (object, ctx.ctor); + if (TREE_CODE (r) == TARGET_EXPR) + /* Avoid creating another CONSTRUCTOR when we expand the + TARGET_EXPR. */ + r = TARGET_EXPR_INITIAL (r); + } + + auto_vec<tree, 16> cleanups; + global_ctx.cleanups = &cleanups; + + if (manifestly_const_eval) + instantiate_constexpr_fns (r); + r = cxx_eval_constant_expression (&ctx, r, + false, &non_constant_p, &overflow_p); + + if (!constexpr_dtor) + verify_constant (r, allow_non_constant, &non_constant_p, &overflow_p); + else + DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (object) = true; + + unsigned int i; + tree cleanup; + /* Evaluate the cleanups. */ + FOR_EACH_VEC_ELT_REVERSE (cleanups, i, cleanup) + cxx_eval_constant_expression (&ctx, cleanup, false, + &non_constant_p, &overflow_p); + + /* Mutable logic is a bit tricky: we want to allow initialization of + constexpr variables with mutable members, but we can't copy those + members to another constexpr variable. */ + if (TREE_CODE (r) == CONSTRUCTOR && CONSTRUCTOR_MUTABLE_POISON (r)) + { + if (!allow_non_constant) + error ("%qE is not a constant expression because it refers to " + "mutable subobjects of %qT", t, type); + non_constant_p = true; + } + + if (TREE_CODE (r) == CONSTRUCTOR && CONSTRUCTOR_NO_CLEARING (r)) + { + if (!allow_non_constant) + error ("%qE is not a constant expression because it refers to " + "an incompletely initialized variable", t); + TREE_CONSTANT (r) = false; + non_constant_p = true; + } + + if (!global_ctx.heap_vars.is_empty ()) + { + tree heap_var = cp_walk_tree_without_duplicates (&r, find_heap_var_refs, + NULL); + unsigned int i; + if (heap_var) + { + if (!allow_non_constant && !non_constant_p) + error_at (DECL_SOURCE_LOCATION (heap_var), + "%qE is not a constant expression because it refers to " + "a result of %<operator new%>", t); + r = t; + non_constant_p = true; + } + FOR_EACH_VEC_ELT (global_ctx.heap_vars, i, heap_var) + { + if (DECL_NAME (heap_var) != heap_deleted_identifier) + { + if (!allow_non_constant && !non_constant_p) + error_at (DECL_SOURCE_LOCATION (heap_var), + "%qE is not a constant expression because allocated " + "storage has not been deallocated", t); + r = t; + non_constant_p = true; + } + varpool_node::get (heap_var)->remove (); + } + } + + /* Check that immediate invocation does not return an expression referencing + any immediate function decls. */ + if (is_consteval || in_immediate_context ()) + if (tree immediate_fndecl + = cp_walk_tree_without_duplicates (&r, find_immediate_fndecl, + NULL)) + { + if (!allow_non_constant && !non_constant_p) + error_at (cp_expr_loc_or_input_loc (t), + "immediate evaluation returns address of immediate " + "function %qD", immediate_fndecl); + r = t; + non_constant_p = true; + } + + if (non_constant_p) + /* If we saw something bad, go back to our argument. The wrapping below is + only for the cases of TREE_CONSTANT argument or overflow. */ + r = t; + + if (!non_constant_p && overflow_p) + non_constant_p = true; + + /* Unshare the result. */ + bool should_unshare = true; + if (r == t || (TREE_CODE (t) == TARGET_EXPR + && TARGET_EXPR_INITIAL (t) == r)) + should_unshare = false; + + if (non_constant_p && !allow_non_constant) + return error_mark_node; + else if (constexpr_dtor) + return r; + else if (non_constant_p && TREE_CONSTANT (r)) + { + /* This isn't actually constant, so unset TREE_CONSTANT. + Don't clear TREE_CONSTANT on ADDR_EXPR, as the middle-end requires + it to be set if it is invariant address, even when it is not + a valid C++ constant expression. Wrap it with a NOP_EXPR + instead. */ + if (EXPR_P (r) && TREE_CODE (r) != ADDR_EXPR) + r = copy_node (r); + else if (TREE_CODE (r) == CONSTRUCTOR) + r = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (r), r); + else + r = build_nop (TREE_TYPE (r), r); + TREE_CONSTANT (r) = false; + } + else if (non_constant_p) + return t; + + if (should_unshare) + r = unshare_expr (r); + + if (TREE_CODE (r) == CONSTRUCTOR && CLASS_TYPE_P (TREE_TYPE (r))) + { + r = adjust_temp_type (type, r); + if (TREE_CODE (t) == TARGET_EXPR + && TARGET_EXPR_INITIAL (t) == r) + return t; + else if (TREE_CODE (t) != CONSTRUCTOR) + { + r = get_target_expr_sfinae (r, tf_warning_or_error | tf_no_cleanup); + TREE_CONSTANT (r) = true; + } + } + + /* Remember the original location if that wouldn't need a wrapper. */ + if (location_t loc = EXPR_LOCATION (t)) + protected_set_expr_location (r, loc); + + return r; +} + +/* If T represents a constant expression returns its reduced value. + Otherwise return error_mark_node. If T is dependent, then + return NULL. */ + +tree +cxx_constant_value (tree t, tree decl) +{ + return cxx_eval_outermost_constant_expr (t, false, true, true, false, decl); +} + +/* As above, but respect SFINAE. */ + +tree +cxx_constant_value_sfinae (tree t, tsubst_flags_t complain) +{ + bool sfinae = !(complain & tf_error); + tree r = cxx_eval_outermost_constant_expr (t, sfinae, true, true); + if (sfinae && !TREE_CONSTANT (r)) + r = error_mark_node; + return r; +} + +/* Like cxx_constant_value, but used for evaluation of constexpr destructors + of constexpr variables. The actual initializer of DECL is not modified. */ + +void +cxx_constant_dtor (tree t, tree decl) +{ + cxx_eval_outermost_constant_expr (t, false, true, true, true, decl); +} + +/* Helper routine for fold_simple function. Either return simplified + expression T, otherwise NULL_TREE. + In contrast to cp_fully_fold, and to maybe_constant_value, we try to fold + even if we are within template-declaration. So be careful on call, as in + such case types can be undefined. */ + +static tree +fold_simple_1 (tree t) +{ + tree op1; + enum tree_code code = TREE_CODE (t); + + switch (code) + { + case INTEGER_CST: + case REAL_CST: + case VECTOR_CST: + case FIXED_CST: + case COMPLEX_CST: + return t; + + case SIZEOF_EXPR: + return fold_sizeof_expr (t); + + case ABS_EXPR: + case ABSU_EXPR: + case CONJ_EXPR: + case REALPART_EXPR: + case IMAGPART_EXPR: + case NEGATE_EXPR: + case BIT_NOT_EXPR: + case TRUTH_NOT_EXPR: + case NOP_EXPR: + case VIEW_CONVERT_EXPR: + case CONVERT_EXPR: + case FLOAT_EXPR: + case FIX_TRUNC_EXPR: + case FIXED_CONVERT_EXPR: + case ADDR_SPACE_CONVERT_EXPR: + + op1 = TREE_OPERAND (t, 0); + + t = const_unop (code, TREE_TYPE (t), op1); + if (!t) + return NULL_TREE; + + if (CONVERT_EXPR_CODE_P (code) + && TREE_OVERFLOW_P (t) && !TREE_OVERFLOW_P (op1)) + TREE_OVERFLOW (t) = false; + return t; + + default: + return NULL_TREE; + } +} + +/* If T is a simple constant expression, returns its simplified value. + Otherwise returns T. In contrast to maybe_constant_value we + simplify only few operations on constant-expressions, and we don't + try to simplify constexpressions. */ + +tree +fold_simple (tree t) +{ + if (processing_template_decl) + return t; + + tree r = fold_simple_1 (t); + if (r) + return r; + + return t; +} + +/* If T is a constant expression, returns its reduced value. + Otherwise, if T does not have TREE_CONSTANT set, returns T. + Otherwise, returns a version of T without TREE_CONSTANT. + MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated + as per P0595. */ + +static GTY((deletable)) hash_map<tree, tree> *cv_cache; + +tree +maybe_constant_value (tree t, tree decl, bool manifestly_const_eval) +{ + tree r; + + if (!is_nondependent_constant_expression (t)) + { + if (TREE_OVERFLOW_P (t)) + { + t = build_nop (TREE_TYPE (t), t); + TREE_CONSTANT (t) = false; + } + return t; + } + else if (CONSTANT_CLASS_P (t)) + /* No caching or evaluation needed. */ + return t; + + if (manifestly_const_eval) + return cxx_eval_outermost_constant_expr (t, true, true, true, false, decl); + + if (cv_cache == NULL) + cv_cache = hash_map<tree, tree>::create_ggc (101); + if (tree *cached = cv_cache->get (t)) + { + r = *cached; + if (r != t) + { + r = break_out_target_exprs (r, /*clear_loc*/true); + protected_set_expr_location (r, EXPR_LOCATION (t)); + } + return r; + } + + /* Don't evaluate an unevaluated operand. */ + if (cp_unevaluated_operand) + return t; + + uid_sensitive_constexpr_evaluation_checker c; + r = cxx_eval_outermost_constant_expr (t, true, true, false, false, decl); + gcc_checking_assert (r == t + || CONVERT_EXPR_P (t) + || TREE_CODE (t) == VIEW_CONVERT_EXPR + || (TREE_CONSTANT (t) && !TREE_CONSTANT (r)) + || !cp_tree_equal (r, t)); + if (!c.evaluation_restricted_p ()) + cv_cache->put (t, r); + return r; +} + +/* Dispose of the whole CV_CACHE. */ + +static void +clear_cv_cache (void) +{ + if (cv_cache != NULL) + cv_cache->empty (); +} + +/* Dispose of the whole CV_CACHE and FOLD_CACHE. */ + +void +clear_cv_and_fold_caches () +{ + clear_cv_cache (); + clear_fold_cache (); +} + +/* Internal function handling expressions in templates for + fold_non_dependent_expr and fold_non_dependent_init. + + If we're in a template, but T isn't value dependent, simplify + it. We're supposed to treat: + + template <typename T> void f(T[1 + 1]); + template <typename T> void f(T[2]); + + as two declarations of the same function, for example. */ + +static tree +fold_non_dependent_expr_template (tree t, tsubst_flags_t complain, + bool manifestly_const_eval, + tree object) +{ + gcc_assert (processing_template_decl); + + if (is_nondependent_constant_expression (t)) + { + processing_template_decl_sentinel s; + t = instantiate_non_dependent_expr_internal (t, complain); + + if (type_unknown_p (t) || BRACE_ENCLOSED_INITIALIZER_P (t)) + { + if (TREE_OVERFLOW_P (t)) + { + t = build_nop (TREE_TYPE (t), t); + TREE_CONSTANT (t) = false; + } + return t; + } + + if (cp_unevaluated_operand && !manifestly_const_eval) + return t; + + tree r = cxx_eval_outermost_constant_expr (t, true, true, + manifestly_const_eval, + false, object); + /* cp_tree_equal looks through NOPs, so allow them. */ + gcc_checking_assert (r == t + || CONVERT_EXPR_P (t) + || TREE_CODE (t) == VIEW_CONVERT_EXPR + || (TREE_CONSTANT (t) && !TREE_CONSTANT (r)) + || !cp_tree_equal (r, t)); + return r; + } + else if (TREE_OVERFLOW_P (t)) + { + t = build_nop (TREE_TYPE (t), t); + TREE_CONSTANT (t) = false; + } + + return t; +} + +/* Like maybe_constant_value but first fully instantiate the argument. + + Note: this is equivalent to instantiate_non_dependent_expr_sfinae + (t, complain) followed by maybe_constant_value but is more efficient, + because it calls instantiation_dependent_expression_p and + potential_constant_expression at most once. + The manifestly_const_eval argument is passed to maybe_constant_value. + + Callers should generally pass their active complain, or if they are in a + non-template, diagnosing context, they can use the default of + tf_warning_or_error. Callers that might be within a template context, don't + have a complain parameter, and aren't going to remember the result for long + (e.g. null_ptr_cst_p), can pass tf_none and deal with error_mark_node + appropriately. */ + +tree +fold_non_dependent_expr (tree t, + tsubst_flags_t complain /* = tf_warning_or_error */, + bool manifestly_const_eval /* = false */, + tree object /* = NULL_TREE */) +{ + if (t == NULL_TREE) + return NULL_TREE; + + if (processing_template_decl) + return fold_non_dependent_expr_template (t, complain, + manifestly_const_eval, object); + + return maybe_constant_value (t, object, manifestly_const_eval); +} + +/* Like fold_non_dependent_expr, but if EXPR couldn't be folded to a constant, + return the original expression. */ + +tree +maybe_fold_non_dependent_expr (tree expr, + tsubst_flags_t complain/*=tf_warning_or_error*/) +{ + tree t = fold_non_dependent_expr (expr, complain); + if (t && TREE_CONSTANT (t)) + return t; + + return expr; +} + +/* Like maybe_constant_init but first fully instantiate the argument. */ + +tree +fold_non_dependent_init (tree t, + tsubst_flags_t complain /*=tf_warning_or_error*/, + bool manifestly_const_eval /*=false*/, + tree object /* = NULL_TREE */) +{ + if (t == NULL_TREE) + return NULL_TREE; + + if (processing_template_decl) + { + t = fold_non_dependent_expr_template (t, complain, + manifestly_const_eval, object); + /* maybe_constant_init does this stripping, so do it here too. */ + if (TREE_CODE (t) == TARGET_EXPR) + { + tree init = TARGET_EXPR_INITIAL (t); + if (TREE_CODE (init) == CONSTRUCTOR) + t = init; + } + return t; + } + + return maybe_constant_init (t, object, manifestly_const_eval); +} + +/* Like maybe_constant_value, but returns a CONSTRUCTOR directly, rather + than wrapped in a TARGET_EXPR. + ALLOW_NON_CONSTANT is false if T is required to be a constant expression. + MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated as + per P0595 even when ALLOW_NON_CONSTANT is true. */ + +static tree +maybe_constant_init_1 (tree t, tree decl, bool allow_non_constant, + bool manifestly_const_eval) +{ + if (!t) + return t; + if (TREE_CODE (t) == EXPR_STMT) + t = TREE_OPERAND (t, 0); + if (TREE_CODE (t) == CONVERT_EXPR + && VOID_TYPE_P (TREE_TYPE (t))) + t = TREE_OPERAND (t, 0); + if (TREE_CODE (t) == INIT_EXPR) + t = TREE_OPERAND (t, 1); + if (TREE_CODE (t) == TARGET_EXPR) + t = TARGET_EXPR_INITIAL (t); + if (!is_nondependent_static_init_expression (t)) + /* Don't try to evaluate it. */; + else if (CONSTANT_CLASS_P (t) && allow_non_constant) + /* No evaluation needed. */; + else + t = cxx_eval_outermost_constant_expr (t, allow_non_constant, + /*strict*/false, + manifestly_const_eval, false, decl); + if (TREE_CODE (t) == TARGET_EXPR) + { + tree init = TARGET_EXPR_INITIAL (t); + if (TREE_CODE (init) == CONSTRUCTOR) + t = init; + } + return t; +} + +/* Wrapper for maybe_constant_init_1 which permits non constants. */ + +tree +maybe_constant_init (tree t, tree decl, bool manifestly_const_eval) +{ + return maybe_constant_init_1 (t, decl, true, manifestly_const_eval); +} + +/* Wrapper for maybe_constant_init_1 which does not permit non constants. */ + +tree +cxx_constant_init (tree t, tree decl) +{ + return maybe_constant_init_1 (t, decl, false, true); +} + +#if 0 +/* FIXME see ADDR_EXPR section in potential_constant_expression_1. */ +/* Return true if the object referred to by REF has automatic or thread + local storage. */ + +enum { ck_ok, ck_bad, ck_unknown }; +static int +check_automatic_or_tls (tree ref) +{ + machine_mode mode; + poly_int64 bitsize, bitpos; + tree offset; + int volatilep = 0, unsignedp = 0; + tree decl = get_inner_reference (ref, &bitsize, &bitpos, &offset, + &mode, &unsignedp, &volatilep, false); + duration_kind dk; + + /* If there isn't a decl in the middle, we don't know the linkage here, + and this isn't a constant expression anyway. */ + if (!DECL_P (decl)) + return ck_unknown; + dk = decl_storage_duration (decl); + return (dk == dk_auto || dk == dk_thread) ? ck_bad : ck_ok; +} +#endif + +/* Data structure for passing data from potential_constant_expression_1 + to check_for_return_continue via cp_walk_tree. */ +struct check_for_return_continue_data { + hash_set<tree> *pset; + tree continue_stmt; + tree break_stmt; +}; + +/* Helper function for potential_constant_expression_1 SWITCH_STMT handling, + called through cp_walk_tree. Return the first RETURN_EXPR found, or note + the first CONTINUE_STMT and/or BREAK_STMT if RETURN_EXPR is not found. */ +static tree +check_for_return_continue (tree *tp, int *walk_subtrees, void *data) +{ + tree t = *tp, s, b; + check_for_return_continue_data *d = (check_for_return_continue_data *) data; + switch (TREE_CODE (t)) + { + case RETURN_EXPR: + return t; + + case CONTINUE_STMT: + if (d->continue_stmt == NULL_TREE) + d->continue_stmt = t; + break; + + case BREAK_STMT: + if (d->break_stmt == NULL_TREE) + d->break_stmt = t; + break; + +#define RECUR(x) \ + if (tree r = cp_walk_tree (&x, check_for_return_continue, data, \ + d->pset)) \ + return r + + /* For loops, walk subtrees manually, so that continue stmts found + inside of the bodies of the loops are ignored. */ + case DO_STMT: + *walk_subtrees = 0; + RECUR (DO_COND (t)); + s = d->continue_stmt; + b = d->break_stmt; + RECUR (DO_BODY (t)); + d->continue_stmt = s; + d->break_stmt = b; + break; + + case WHILE_STMT: + *walk_subtrees = 0; + RECUR (WHILE_COND (t)); + s = d->continue_stmt; + b = d->break_stmt; + RECUR (WHILE_BODY (t)); + d->continue_stmt = s; + d->break_stmt = b; + break; + + case FOR_STMT: + *walk_subtrees = 0; + RECUR (FOR_INIT_STMT (t)); + RECUR (FOR_COND (t)); + RECUR (FOR_EXPR (t)); + s = d->continue_stmt; + b = d->break_stmt; + RECUR (FOR_BODY (t)); + d->continue_stmt = s; + d->break_stmt = b; + break; + + case RANGE_FOR_STMT: + *walk_subtrees = 0; + RECUR (RANGE_FOR_EXPR (t)); + s = d->continue_stmt; + b = d->break_stmt; + RECUR (RANGE_FOR_BODY (t)); + d->continue_stmt = s; + d->break_stmt = b; + break; + + case SWITCH_STMT: + *walk_subtrees = 0; + RECUR (SWITCH_STMT_COND (t)); + b = d->break_stmt; + RECUR (SWITCH_STMT_BODY (t)); + d->break_stmt = b; + break; +#undef RECUR + + case STATEMENT_LIST: + case CONSTRUCTOR: + break; + + default: + if (!EXPR_P (t)) + *walk_subtrees = 0; + break; + } + + return NULL_TREE; +} + +/* Return true if T denotes a potentially constant expression. Issue + diagnostic as appropriate under control of FLAGS. If WANT_RVAL is true, + an lvalue-rvalue conversion is implied. If NOW is true, we want to + consider the expression in the current context, independent of constexpr + substitution. + + C++0x [expr.const] used to say + + 6 An expression is a potential constant expression if it is + a constant expression where all occurrences of function + parameters are replaced by arbitrary constant expressions + of the appropriate type. + + 2 A conditional expression is a constant expression unless it + involves one of the following as a potentially evaluated + subexpression (3.2), but subexpressions of logical AND (5.14), + logical OR (5.15), and conditional (5.16) operations that are + not evaluated are not considered. */ + +static bool +potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, + tsubst_flags_t flags, tree *jump_target) +{ +#define RECUR(T,RV) \ + potential_constant_expression_1 ((T), (RV), strict, now, flags, jump_target) + + enum { any = false, rval = true }; + int i; + tree tmp; + + if (t == error_mark_node) + return false; + if (t == NULL_TREE) + return true; + location_t loc = cp_expr_loc_or_input_loc (t); + + if (*jump_target) + /* If we are jumping, ignore everything. This is simpler than the + cxx_eval_constant_expression handling because we only need to be + conservatively correct, and we don't necessarily have a constant value + available, so we don't bother with switch tracking. */ + return true; + + if (TREE_THIS_VOLATILE (t) && want_rval) + { + if (flags & tf_error) + error_at (loc, "lvalue-to-rvalue conversion of a volatile lvalue " + "%qE with type %qT", t, TREE_TYPE (t)); + return false; + } + if (CONSTANT_CLASS_P (t)) + return true; + if (CODE_CONTAINS_STRUCT (TREE_CODE (t), TS_TYPED) + && TREE_TYPE (t) == error_mark_node) + return false; + + switch (TREE_CODE (t)) + { + case FUNCTION_DECL: + case BASELINK: + case TEMPLATE_DECL: + case OVERLOAD: + case TEMPLATE_ID_EXPR: + case LABEL_DECL: + case CASE_LABEL_EXPR: + case PREDICT_EXPR: + case CONST_DECL: + case SIZEOF_EXPR: + case ALIGNOF_EXPR: + case OFFSETOF_EXPR: + case NOEXCEPT_EXPR: + case TEMPLATE_PARM_INDEX: + case TRAIT_EXPR: + case IDENTIFIER_NODE: + case USERDEF_LITERAL: + /* We can see a FIELD_DECL in a pointer-to-member expression. */ + case FIELD_DECL: + case RESULT_DECL: + case USING_DECL: + case USING_STMT: + case PLACEHOLDER_EXPR: + case REQUIRES_EXPR: + case STATIC_ASSERT: + case DEBUG_BEGIN_STMT: + return true; + + case RETURN_EXPR: + if (!RECUR (TREE_OPERAND (t, 0), any)) + return false; + /* FALLTHROUGH */ + + case BREAK_STMT: + case CONTINUE_STMT: + *jump_target = t; + return true; + + case PARM_DECL: + if (now && want_rval) + { + tree type = TREE_TYPE (t); + if ((processing_template_decl && !COMPLETE_TYPE_P (type)) + || dependent_type_p (type) + || is_really_empty_class (type, /*ignore_vptr*/false)) + /* An empty class has no data to read. */ + return true; + if (flags & tf_error) + error ("%qE is not a constant expression", t); + return false; + } + return true; + + case AGGR_INIT_EXPR: + case CALL_EXPR: + /* -- an invocation of a function other than a constexpr function + or a constexpr constructor. */ + { + tree fun = get_function_named_in_call (t); + const int nargs = call_expr_nargs (t); + i = 0; + + if (fun == NULL_TREE) + { + /* Reset to allow the function to continue past the end + of the block below. Otherwise return early. */ + bool bail = true; + + if (TREE_CODE (t) == CALL_EXPR + && CALL_EXPR_FN (t) == NULL_TREE) + switch (CALL_EXPR_IFN (t)) + { + /* These should be ignored, they are optimized away from + constexpr functions. */ + case IFN_UBSAN_NULL: + case IFN_UBSAN_BOUNDS: + case IFN_UBSAN_VPTR: + case IFN_FALLTHROUGH: + return true; + + case IFN_ADD_OVERFLOW: + case IFN_SUB_OVERFLOW: + case IFN_MUL_OVERFLOW: + case IFN_LAUNDER: + case IFN_VEC_CONVERT: + bail = false; + break; + + default: + break; + } + + if (bail) + { + /* fold_call_expr can't do anything with IFN calls. */ + if (flags & tf_error) + error_at (loc, "call to internal function %qE", t); + return false; + } + } + + if (fun && is_overloaded_fn (fun)) + { + if (TREE_CODE (fun) == FUNCTION_DECL) + { + if (builtin_valid_in_constant_expr_p (fun)) + return true; + if (!maybe_constexpr_fn (fun) + /* Allow any built-in function; if the expansion + isn't constant, we'll deal with that then. */ + && !fndecl_built_in_p (fun) + /* In C++20, replaceable global allocation functions + are constant expressions. */ + && (!cxx_replaceable_global_alloc_fn (fun) + || TREE_CODE (t) != CALL_EXPR + || (!CALL_FROM_NEW_OR_DELETE_P (t) + && (current_function_decl == NULL_TREE + || !is_std_allocator_allocate + (current_function_decl)))) + /* Allow placement new in std::construct_at. */ + && (!cxx_placement_new_fn (fun) + || TREE_CODE (t) != CALL_EXPR + || current_function_decl == NULL_TREE + || !is_std_construct_at (current_function_decl)) + && !cxx_dynamic_cast_fn_p (fun)) + { + if (flags & tf_error) + { + error_at (loc, "call to non-%<constexpr%> function %qD", + fun); + explain_invalid_constexpr_fn (fun); + } + return false; + } + /* A call to a non-static member function takes the address + of the object as the first argument. But in a constant + expression the address will be folded away, so look + through it now. */ + if (DECL_NONSTATIC_MEMBER_FUNCTION_P (fun) + && !DECL_CONSTRUCTOR_P (fun)) + { + tree x = get_nth_callarg (t, 0); + if (is_this_parameter (x)) + return true; + /* Don't require an immediately constant value, as + constexpr substitution might not use the value. */ + bool sub_now = false; + if (!potential_constant_expression_1 (x, rval, strict, + sub_now, flags, + jump_target)) + return false; + i = 1; + } + } + else + { + if (!RECUR (fun, true)) + return false; + fun = get_first_fn (fun); + } + /* Skip initial arguments to base constructors. */ + if (DECL_BASE_CONSTRUCTOR_P (fun)) + i = num_artificial_parms_for (fun); + fun = DECL_ORIGIN (fun); + } + else if (fun) + { + if (RECUR (fun, rval)) + /* Might end up being a constant function pointer. */; + else + return false; + } + for (; i < nargs; ++i) + { + tree x = get_nth_callarg (t, i); + /* In a template, reference arguments haven't been converted to + REFERENCE_TYPE and we might not even know if the parameter + is a reference, so accept lvalue constants too. */ + bool rv = processing_template_decl ? any : rval; + /* Don't require an immediately constant value, as constexpr + substitution might not use the value of the argument. */ + bool sub_now = false; + if (!potential_constant_expression_1 (x, rv, strict, + sub_now, flags, jump_target)) + return false; + } + return true; + } + + case NON_LVALUE_EXPR: + /* -- an lvalue-to-rvalue conversion (4.1) unless it is applied to + -- an lvalue of integral type that refers to a non-volatile + const variable or static data member initialized with + constant expressions, or + + -- an lvalue of literal type that refers to non-volatile + object defined with constexpr, or that refers to a + sub-object of such an object; */ + return RECUR (TREE_OPERAND (t, 0), rval); + + case VAR_DECL: + if (DECL_HAS_VALUE_EXPR_P (t)) + { + if (now && is_normal_capture_proxy (t)) + { + /* -- in a lambda-expression, a reference to this or to a + variable with automatic storage duration defined outside that + lambda-expression, where the reference would be an + odr-use. */ + + if (want_rval) + /* Since we're doing an lvalue-rvalue conversion, this might + not be an odr-use, so evaluate the variable directly. */ + return RECUR (DECL_CAPTURED_VARIABLE (t), rval); + + if (flags & tf_error) + { + tree cap = DECL_CAPTURED_VARIABLE (t); + error ("lambda capture of %qE is not a constant expression", + cap); + if (decl_constant_var_p (cap)) + inform (input_location, "because it is used as a glvalue"); + } + return false; + } + /* Treat __PRETTY_FUNCTION__ inside a template function as + potentially-constant. */ + else if (DECL_PRETTY_FUNCTION_P (t) + && DECL_VALUE_EXPR (t) == error_mark_node) + return true; + return RECUR (DECL_VALUE_EXPR (t), rval); + } + if (want_rval + && !var_in_maybe_constexpr_fn (t) + && !type_dependent_expression_p (t) + && !decl_maybe_constant_var_p (t) + && (strict + || !CP_TYPE_CONST_NON_VOLATILE_P (TREE_TYPE (t)) + || (DECL_INITIAL (t) + && !DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (t))) + && COMPLETE_TYPE_P (TREE_TYPE (t)) + && !is_really_empty_class (TREE_TYPE (t), /*ignore_vptr*/false)) + { + if (flags & tf_error) + non_const_var_error (loc, t); + return false; + } + return true; + + case NOP_EXPR: + if (REINTERPRET_CAST_P (t)) + { + if (flags & tf_error) + error_at (loc, "%<reinterpret_cast%> is not a constant expression"); + return false; + } + /* FALLTHRU */ + case CONVERT_EXPR: + case VIEW_CONVERT_EXPR: + /* -- a reinterpret_cast. FIXME not implemented, and this rule + may change to something more specific to type-punning (DR 1312). */ + { + tree from = TREE_OPERAND (t, 0); + if (location_wrapper_p (t)) + return (RECUR (from, want_rval)); + if (INDIRECT_TYPE_P (TREE_TYPE (t))) + { + STRIP_ANY_LOCATION_WRAPPER (from); + if (TREE_CODE (from) == INTEGER_CST + && !integer_zerop (from)) + { + if (flags & tf_error) + error_at (loc, + "%<reinterpret_cast%> from integer to pointer"); + return false; + } + } + return (RECUR (from, TREE_CODE (t) != VIEW_CONVERT_EXPR)); + } + + case ADDRESSOF_EXPR: + /* This is like ADDR_EXPR, except it won't form pointer-to-member. */ + t = TREE_OPERAND (t, 0); + goto handle_addr_expr; + + case ADDR_EXPR: + /* -- a unary operator & that is applied to an lvalue that + designates an object with thread or automatic storage + duration; */ + t = TREE_OPERAND (t, 0); + + if (TREE_CODE (t) == OFFSET_REF && PTRMEM_OK_P (t)) + /* A pointer-to-member constant. */ + return true; + + handle_addr_expr: +#if 0 + /* FIXME adjust when issue 1197 is fully resolved. For now don't do + any checking here, as we might dereference the pointer later. If + we remove this code, also remove check_automatic_or_tls. */ + i = check_automatic_or_tls (t); + if (i == ck_ok) + return true; + if (i == ck_bad) + { + if (flags & tf_error) + error ("address-of an object %qE with thread local or " + "automatic storage is not a constant expression", t); + return false; + } +#endif + return RECUR (t, any); + + case COMPONENT_REF: + case ARROW_EXPR: + case OFFSET_REF: + /* -- a class member access unless its postfix-expression is + of literal type or of pointer to literal type. */ + /* This test would be redundant, as it follows from the + postfix-expression being a potential constant expression. */ + if (type_unknown_p (t)) + return true; + if (is_overloaded_fn (t)) + /* In a template, a COMPONENT_REF of a function expresses ob.fn(), + which uses ob as an lvalue. */ + want_rval = false; + gcc_fallthrough (); + + case REALPART_EXPR: + case IMAGPART_EXPR: + case BIT_FIELD_REF: + return RECUR (TREE_OPERAND (t, 0), want_rval); + + case EXPR_PACK_EXPANSION: + return RECUR (PACK_EXPANSION_PATTERN (t), want_rval); + + case INDIRECT_REF: + { + tree x = TREE_OPERAND (t, 0); + STRIP_NOPS (x); + if (is_this_parameter (x) && !is_capture_proxy (x)) + { + if (!var_in_maybe_constexpr_fn (x)) + { + if (flags & tf_error) + error_at (loc, "use of %<this%> in a constant expression"); + return false; + } + return true; + } + return RECUR (x, rval); + } + + case STATEMENT_LIST: + for (tree stmt : tsi_range (t)) + if (!RECUR (stmt, any)) + return false; + return true; + + case MODIFY_EXPR: + if (cxx_dialect < cxx14) + goto fail; + if (!RECUR (TREE_OPERAND (t, 0), any)) + return false; + /* Just ignore clobbers. */ + if (TREE_CLOBBER_P (TREE_OPERAND (t, 1))) + return true; + if (!RECUR (TREE_OPERAND (t, 1), rval)) + return false; + return true; + + case MODOP_EXPR: + if (cxx_dialect < cxx14) + goto fail; + if (!RECUR (TREE_OPERAND (t, 0), rval)) + return false; + if (!RECUR (TREE_OPERAND (t, 2), rval)) + return false; + return true; + + case DO_STMT: + if (!RECUR (DO_COND (t), rval)) + return false; + if (!RECUR (DO_BODY (t), any)) + return false; + if (breaks (jump_target) || continues (jump_target)) + *jump_target = NULL_TREE; + return true; + + case FOR_STMT: + if (!RECUR (FOR_INIT_STMT (t), any)) + return false; + tmp = FOR_COND (t); + if (!RECUR (tmp, rval)) + return false; + if (tmp) + { + if (!processing_template_decl) + tmp = cxx_eval_outermost_constant_expr (tmp, true); + /* If we couldn't evaluate the condition, it might not ever be + true. */ + if (!integer_onep (tmp)) + { + /* Before returning true, check if the for body can contain + a return. */ + hash_set<tree> pset; + check_for_return_continue_data data = { &pset, NULL_TREE, + NULL_TREE }; + if (tree ret_expr + = cp_walk_tree (&FOR_BODY (t), check_for_return_continue, + &data, &pset)) + *jump_target = ret_expr; + return true; + } + } + if (!RECUR (FOR_EXPR (t), any)) + return false; + if (!RECUR (FOR_BODY (t), any)) + return false; + if (breaks (jump_target) || continues (jump_target)) + *jump_target = NULL_TREE; + return true; + + case RANGE_FOR_STMT: + if (!RECUR (RANGE_FOR_INIT_STMT (t), any)) + return false; + if (!RECUR (RANGE_FOR_EXPR (t), any)) + return false; + if (!RECUR (RANGE_FOR_BODY (t), any)) + return false; + if (breaks (jump_target) || continues (jump_target)) + *jump_target = NULL_TREE; + return true; + + case WHILE_STMT: + tmp = WHILE_COND (t); + if (!RECUR (tmp, rval)) + return false; + if (!processing_template_decl) + tmp = cxx_eval_outermost_constant_expr (tmp, true); + /* If we couldn't evaluate the condition, it might not ever be true. */ + if (!integer_onep (tmp)) + { + /* Before returning true, check if the while body can contain + a return. */ + hash_set<tree> pset; + check_for_return_continue_data data = { &pset, NULL_TREE, + NULL_TREE }; + if (tree ret_expr + = cp_walk_tree (&WHILE_BODY (t), check_for_return_continue, + &data, &pset)) + *jump_target = ret_expr; + return true; + } + if (!RECUR (WHILE_BODY (t), any)) + return false; + if (breaks (jump_target) || continues (jump_target)) + *jump_target = NULL_TREE; + return true; + + case SWITCH_STMT: + if (!RECUR (SWITCH_STMT_COND (t), rval)) + return false; + /* FIXME we don't check SWITCH_STMT_BODY currently, because even + unreachable labels would be checked and it is enough if there is + a single switch cond value for which it is a valid constant + expression. We need to check if there are any RETURN_EXPRs + or CONTINUE_STMTs inside of the body though, as in that case + we need to set *jump_target. */ + else + { + hash_set<tree> pset; + check_for_return_continue_data data = { &pset, NULL_TREE, + NULL_TREE }; + if (tree ret_expr + = cp_walk_tree (&SWITCH_STMT_BODY (t), check_for_return_continue, + &data, &pset)) + /* The switch might return. */ + *jump_target = ret_expr; + else if (data.continue_stmt) + /* The switch can't return, but might continue. */ + *jump_target = data.continue_stmt; + } + return true; + + case STMT_EXPR: + return RECUR (STMT_EXPR_STMT (t), rval); + + case LAMBDA_EXPR: + if (cxx_dialect >= cxx17) + /* In C++17 lambdas can be constexpr, don't give up yet. */ + return true; + else if (flags & tf_error) + error_at (loc, "lambda-expression is not a constant expression " + "before C++17"); + return false; + + case DYNAMIC_CAST_EXPR: + case PSEUDO_DTOR_EXPR: + case NEW_EXPR: + case VEC_NEW_EXPR: + case DELETE_EXPR: + case VEC_DELETE_EXPR: + case THROW_EXPR: + case OMP_PARALLEL: + case OMP_TASK: + case OMP_FOR: + case OMP_SIMD: + case OMP_DISTRIBUTE: + case OMP_TASKLOOP: + case OMP_LOOP: + case OMP_TEAMS: + case OMP_TARGET_DATA: + case OMP_TARGET: + case OMP_SECTIONS: + case OMP_ORDERED: + case OMP_CRITICAL: + case OMP_SINGLE: + case OMP_SECTION: + case OMP_MASTER: + case OMP_MASKED: + case OMP_TASKGROUP: + case OMP_TARGET_UPDATE: + case OMP_TARGET_ENTER_DATA: + case OMP_TARGET_EXIT_DATA: + case OMP_ATOMIC: + case OMP_ATOMIC_READ: + case OMP_ATOMIC_CAPTURE_OLD: + case OMP_ATOMIC_CAPTURE_NEW: + case OMP_DEPOBJ: + case OACC_PARALLEL: + case OACC_KERNELS: + case OACC_SERIAL: + case OACC_DATA: + case OACC_HOST_DATA: + case OACC_LOOP: + case OACC_CACHE: + case OACC_DECLARE: + case OACC_ENTER_DATA: + case OACC_EXIT_DATA: + case OACC_UPDATE: + /* GCC internal stuff. */ + case VA_ARG_EXPR: + case TRANSACTION_EXPR: + case AT_ENCODE_EXPR: + fail: + if (flags & tf_error) + error_at (loc, "expression %qE is not a constant expression", t); + return false; + + case ASM_EXPR: + if (flags & tf_error) + inline_asm_in_constexpr_error (loc); + return false; + + case OBJ_TYPE_REF: + if (cxx_dialect >= cxx20) + /* In C++20 virtual calls can be constexpr, don't give up yet. */ + return true; + else if (flags & tf_error) + error_at (loc, + "virtual functions cannot be %<constexpr%> before C++20"); + return false; + + case TYPEID_EXPR: + /* In C++20, a typeid expression whose operand is of polymorphic + class type can be constexpr. */ + { + tree e = TREE_OPERAND (t, 0); + if (cxx_dialect < cxx20 + && strict + && !TYPE_P (e) + && !type_dependent_expression_p (e) + && TYPE_POLYMORPHIC_P (TREE_TYPE (e))) + { + if (flags & tf_error) + error_at (loc, "%<typeid%> is not a constant expression " + "because %qE is of polymorphic type", e); + return false; + } + return true; + } + + case POINTER_DIFF_EXPR: + case MINUS_EXPR: + want_rval = true; + goto binary; + + case LT_EXPR: + case LE_EXPR: + case GT_EXPR: + case GE_EXPR: + case EQ_EXPR: + case NE_EXPR: + case SPACESHIP_EXPR: + want_rval = true; + goto binary; + + case PREINCREMENT_EXPR: + case POSTINCREMENT_EXPR: + case PREDECREMENT_EXPR: + case POSTDECREMENT_EXPR: + if (cxx_dialect < cxx14) + goto fail; + goto unary; + + case BIT_NOT_EXPR: + /* A destructor. */ + if (TYPE_P (TREE_OPERAND (t, 0))) + return true; + /* fall through. */ + + case CONJ_EXPR: + case SAVE_EXPR: + case FIX_TRUNC_EXPR: + case FLOAT_EXPR: + case NEGATE_EXPR: + case ABS_EXPR: + case ABSU_EXPR: + case TRUTH_NOT_EXPR: + case FIXED_CONVERT_EXPR: + case UNARY_PLUS_EXPR: + case UNARY_LEFT_FOLD_EXPR: + case UNARY_RIGHT_FOLD_EXPR: + unary: + return RECUR (TREE_OPERAND (t, 0), rval); + + case CAST_EXPR: + case CONST_CAST_EXPR: + case STATIC_CAST_EXPR: + case REINTERPRET_CAST_EXPR: + case IMPLICIT_CONV_EXPR: + if (cxx_dialect < cxx11 + && !dependent_type_p (TREE_TYPE (t)) + && !INTEGRAL_OR_ENUMERATION_TYPE_P (TREE_TYPE (t))) + /* In C++98, a conversion to non-integral type can't be part of a + constant expression. */ + { + if (flags & tf_error) + error_at (loc, + "cast to non-integral type %qT in a constant expression", + TREE_TYPE (t)); + return false; + } + /* This might be a conversion from a class to a (potentially) literal + type. Let's consider it potentially constant since the conversion + might be a constexpr user-defined conversion. */ + else if (cxx_dialect >= cxx11 + && (dependent_type_p (TREE_TYPE (t)) + || !COMPLETE_TYPE_P (TREE_TYPE (t)) + || literal_type_p (TREE_TYPE (t))) + && TREE_OPERAND (t, 0)) + { + tree type = TREE_TYPE (TREE_OPERAND (t, 0)); + /* If this is a dependent type, it could end up being a class + with conversions. */ + if (type == NULL_TREE || WILDCARD_TYPE_P (type)) + return true; + /* Or a non-dependent class which has conversions. */ + else if (CLASS_TYPE_P (type) + && (TYPE_HAS_CONVERSION (type) || dependent_scope_p (type))) + return true; + } + + return (RECUR (TREE_OPERAND (t, 0), + !TYPE_REF_P (TREE_TYPE (t)))); + + case BIND_EXPR: + return RECUR (BIND_EXPR_BODY (t), want_rval); + + case CLEANUP_POINT_EXPR: + case MUST_NOT_THROW_EXPR: + case TRY_CATCH_EXPR: + case TRY_BLOCK: + case EH_SPEC_BLOCK: + case EXPR_STMT: + case PAREN_EXPR: + case NON_DEPENDENT_EXPR: + /* For convenience. */ + case LOOP_EXPR: + case EXIT_EXPR: + return RECUR (TREE_OPERAND (t, 0), want_rval); + + case DECL_EXPR: + tmp = DECL_EXPR_DECL (t); + if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp)) + { + if (CP_DECL_THREAD_LOCAL_P (tmp)) + { + if (flags & tf_error) + error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared " + "%<thread_local%> in %<constexpr%> context", tmp); + return false; + } + else if (TREE_STATIC (tmp)) + { + if (flags & tf_error) + error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared " + "%<static%> in %<constexpr%> context", tmp); + return false; + } + else if (!check_for_uninitialized_const_var + (tmp, /*constexpr_context_p=*/true, flags)) + return false; + } + return RECUR (tmp, want_rval); + + case TRY_FINALLY_EXPR: + return (RECUR (TREE_OPERAND (t, 0), want_rval) + && RECUR (TREE_OPERAND (t, 1), any)); + + case SCOPE_REF: + return RECUR (TREE_OPERAND (t, 1), want_rval); + + case TARGET_EXPR: + if (!TARGET_EXPR_DIRECT_INIT_P (t) + && !literal_type_p (TREE_TYPE (t))) + { + if (flags & tf_error) + { + auto_diagnostic_group d; + error_at (loc, "temporary of non-literal type %qT in a " + "constant expression", TREE_TYPE (t)); + explain_non_literal_class (TREE_TYPE (t)); + } + return false; + } + /* FALLTHRU */ + case INIT_EXPR: + return RECUR (TREE_OPERAND (t, 1), rval); + + case CONSTRUCTOR: + { + vec<constructor_elt, va_gc> *v = CONSTRUCTOR_ELTS (t); + constructor_elt *ce; + for (i = 0; vec_safe_iterate (v, i, &ce); ++i) + if (!RECUR (ce->value, want_rval)) + return false; + return true; + } + + case TREE_LIST: + { + gcc_assert (TREE_PURPOSE (t) == NULL_TREE + || DECL_P (TREE_PURPOSE (t))); + if (!RECUR (TREE_VALUE (t), want_rval)) + return false; + if (TREE_CHAIN (t) == NULL_TREE) + return true; + return RECUR (TREE_CHAIN (t), want_rval); + } + + case TRUNC_DIV_EXPR: + case CEIL_DIV_EXPR: + case FLOOR_DIV_EXPR: + case ROUND_DIV_EXPR: + case TRUNC_MOD_EXPR: + case CEIL_MOD_EXPR: + case ROUND_MOD_EXPR: + { + tree denom = TREE_OPERAND (t, 1); + if (!RECUR (denom, rval)) + return false; + /* We can't call cxx_eval_outermost_constant_expr on an expression + that hasn't been through instantiate_non_dependent_expr yet. */ + if (!processing_template_decl) + denom = cxx_eval_outermost_constant_expr (denom, true); + if (integer_zerop (denom)) + { + if (flags & tf_error) + error ("division by zero is not a constant expression"); + return false; + } + else + { + want_rval = true; + return RECUR (TREE_OPERAND (t, 0), want_rval); + } + } + + case COMPOUND_EXPR: + { + /* check_return_expr sometimes wraps a TARGET_EXPR in a + COMPOUND_EXPR; don't get confused. */ + tree op0 = TREE_OPERAND (t, 0); + tree op1 = TREE_OPERAND (t, 1); + STRIP_NOPS (op1); + if (TREE_CODE (op0) == TARGET_EXPR && op1 == TARGET_EXPR_SLOT (op0)) + return RECUR (op0, want_rval); + else + goto binary; + } + + /* If the first operand is the non-short-circuit constant, look at + the second operand; otherwise we only care about the first one for + potentiality. */ + case TRUTH_AND_EXPR: + case TRUTH_ANDIF_EXPR: + tmp = boolean_true_node; + goto truth; + case TRUTH_OR_EXPR: + case TRUTH_ORIF_EXPR: + tmp = boolean_false_node; + truth: + { + tree op0 = TREE_OPERAND (t, 0); + tree op1 = TREE_OPERAND (t, 1); + if (!RECUR (op0, rval)) + return false; + if (!(flags & tf_error) && RECUR (op1, rval)) + /* When quiet, try to avoid expensive trial evaluation by first + checking potentiality of the second operand. */ + return true; + if (!processing_template_decl) + op0 = cxx_eval_outermost_constant_expr (op0, true); + if (tree_int_cst_equal (op0, tmp)) + return (flags & tf_error) ? RECUR (op1, rval) : false; + else + return true; + } + + case PLUS_EXPR: + case MULT_EXPR: + case POINTER_PLUS_EXPR: + case RDIV_EXPR: + case EXACT_DIV_EXPR: + case MIN_EXPR: + case MAX_EXPR: + case LSHIFT_EXPR: + case RSHIFT_EXPR: + case LROTATE_EXPR: + case RROTATE_EXPR: + case BIT_IOR_EXPR: + case BIT_XOR_EXPR: + case BIT_AND_EXPR: + case TRUTH_XOR_EXPR: + case UNORDERED_EXPR: + case ORDERED_EXPR: + case UNLT_EXPR: + case UNLE_EXPR: + case UNGT_EXPR: + case UNGE_EXPR: + case UNEQ_EXPR: + case LTGT_EXPR: + case RANGE_EXPR: + case COMPLEX_EXPR: + want_rval = true; + /* Fall through. */ + case ARRAY_REF: + case ARRAY_RANGE_REF: + case MEMBER_REF: + case DOTSTAR_EXPR: + case MEM_REF: + case BINARY_LEFT_FOLD_EXPR: + case BINARY_RIGHT_FOLD_EXPR: + binary: + for (i = 0; i < 2; ++i) + if (!RECUR (TREE_OPERAND (t, i), want_rval)) + return false; + return true; + + case VEC_PERM_EXPR: + for (i = 0; i < 3; ++i) + if (!RECUR (TREE_OPERAND (t, i), true)) + return false; + return true; + + case COND_EXPR: + if (COND_EXPR_IS_VEC_DELETE (t) && cxx_dialect < cxx20) + { + if (flags & tf_error) + error_at (loc, "%<delete[]%> is not a constant expression"); + return false; + } + /* Fall through. */ + case IF_STMT: + case VEC_COND_EXPR: + /* If the condition is a known constant, we know which of the legs we + care about; otherwise we only require that the condition and + either of the legs be potentially constant. */ + tmp = TREE_OPERAND (t, 0); + if (!RECUR (tmp, rval)) + return false; + if (!processing_template_decl) + tmp = cxx_eval_outermost_constant_expr (tmp, true); + /* potential_constant_expression* isn't told if it is called for + manifestly_const_eval or not, so for consteval if always + process both branches as if the condition is not a known + constant. */ + if (TREE_CODE (t) != IF_STMT || !IF_STMT_CONSTEVAL_P (t)) + { + if (integer_zerop (tmp)) + return RECUR (TREE_OPERAND (t, 2), want_rval); + else if (TREE_CODE (tmp) == INTEGER_CST) + return RECUR (TREE_OPERAND (t, 1), want_rval); + } + tmp = *jump_target; + for (i = 1; i < 3; ++i) + { + tree this_jump_target = tmp; + if (potential_constant_expression_1 (TREE_OPERAND (t, i), + want_rval, strict, now, + tf_none, &this_jump_target)) + { + if (returns (&this_jump_target)) + *jump_target = this_jump_target; + else if (!returns (jump_target)) + { + if (breaks (&this_jump_target) + || continues (&this_jump_target)) + *jump_target = this_jump_target; + if (i == 1) + { + /* If the then branch is potentially constant, but + does not return, check if the else branch + couldn't return, break or continue. */ + hash_set<tree> pset; + check_for_return_continue_data data = { &pset, NULL_TREE, + NULL_TREE }; + if (tree ret_expr + = cp_walk_tree (&TREE_OPERAND (t, 2), + check_for_return_continue, &data, + &pset)) + *jump_target = ret_expr; + else if (*jump_target == NULL_TREE) + { + if (data.continue_stmt) + *jump_target = data.continue_stmt; + else if (data.break_stmt) + *jump_target = data.break_stmt; + } + } + } + return true; + } + } + if (flags & tf_error) + error_at (loc, "expression %qE is not a constant expression", t); + return false; + + case VEC_INIT_EXPR: + if (VEC_INIT_EXPR_IS_CONSTEXPR (t)) + return true; + if (flags & tf_error) + { + error_at (loc, "non-constant array initialization"); + diagnose_non_constexpr_vec_init (t); + } + return false; + + case TYPE_DECL: + case TAG_DEFN: + /* We can see these in statement-expressions. */ + return true; + + case CLEANUP_STMT: + if (!RECUR (CLEANUP_BODY (t), any)) + return false; + if (!CLEANUP_EH_ONLY (t) && !RECUR (CLEANUP_EXPR (t), any)) + return false; + return true; + + case EMPTY_CLASS_EXPR: + return true; + + case GOTO_EXPR: + { + tree *target = &TREE_OPERAND (t, 0); + /* Gotos representing break and continue are OK. */ + if (breaks (target) || continues (target)) + { + *jump_target = *target; + return true; + } + if (flags & tf_error) + error_at (loc, "%<goto%> is not a constant expression"); + return false; + } + + case LABEL_EXPR: + t = LABEL_EXPR_LABEL (t); + if (DECL_ARTIFICIAL (t) || cxx_dialect >= cxx23) + return true; + else if (flags & tf_error) + error_at (loc, "label definition in %<constexpr%> function only " + "available with %<-std=c++2b%> or %<-std=gnu++2b%>"); + return false; + + case ANNOTATE_EXPR: + return RECUR (TREE_OPERAND (t, 0), rval); + + case BIT_CAST_EXPR: + return RECUR (TREE_OPERAND (t, 0), rval); + + /* Coroutine await, yield and return expressions are not. */ + case CO_AWAIT_EXPR: + case CO_YIELD_EXPR: + case CO_RETURN_EXPR: + return false; + + case NONTYPE_ARGUMENT_PACK: + { + tree args = ARGUMENT_PACK_ARGS (t); + int len = TREE_VEC_LENGTH (args); + for (int i = 0; i < len; ++i) + if (!RECUR (TREE_VEC_ELT (args, i), any)) + return false; + return true; + } + + default: + if (objc_non_constant_expr_p (t)) + return false; + + sorry ("unexpected AST of kind %s", get_tree_code_name (TREE_CODE (t))); + gcc_unreachable (); + return false; + } +#undef RECUR +} + +bool +potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, + tsubst_flags_t flags) +{ + if (flags & tf_error) + { + /* Check potentiality quietly first, as that could be performed more + efficiently in some cases (currently only for TRUTH_*_EXPR). If + that fails, replay the check noisily to give errors. */ + flags &= ~tf_error; + if (potential_constant_expression_1 (t, want_rval, strict, now, flags)) + return true; + flags |= tf_error; + } + + tree target = NULL_TREE; + return potential_constant_expression_1 (t, want_rval, strict, now, + flags, &target); +} + +/* The main entry point to the above. */ + +bool +potential_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, false, true, false, tf_none); +} + +/* As above, but require a constant rvalue. */ + +bool +potential_rvalue_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, true, true, false, tf_none); +} + +/* Like above, but complain about non-constant expressions. */ + +bool +require_potential_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, false, true, false, + tf_warning_or_error); +} + +/* Cross product of the above. */ + +bool +require_potential_rvalue_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, true, true, false, + tf_warning_or_error); +} + +/* Like above, but don't consider PARM_DECL a potential_constant_expression. */ + +bool +require_rvalue_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, true, true, true, + tf_warning_or_error); +} + +/* Like potential_constant_expression, but don't consider possible constexpr + substitution of the current function. That is, PARM_DECL qualifies under + potential_constant_expression, but not here. + + This is basically what you can check when any actual constant values might + be value-dependent. */ + +bool +is_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, false, true, true, tf_none); +} + +/* As above, but expect an rvalue. */ + +bool +is_rvalue_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, true, true, true, tf_none); +} + +/* Like above, but complain about non-constant expressions. */ + +bool +require_constant_expression (tree t) +{ + return potential_constant_expression_1 (t, false, true, true, + tf_warning_or_error); +} + +/* Like is_constant_expression, but allow const variables that are not allowed + under constexpr rules. */ + +bool +is_static_init_expression (tree t) +{ + return potential_constant_expression_1 (t, false, false, true, tf_none); +} + +/* Returns true if T is a potential constant expression that is not + instantiation-dependent, and therefore a candidate for constant folding even + in a template. */ + +bool +is_nondependent_constant_expression (tree t) +{ + return (!type_unknown_p (t) + && is_constant_expression (t) + && !instantiation_dependent_expression_p (t)); +} + +/* Returns true if T is a potential static initializer expression that is not + instantiation-dependent. */ + +bool +is_nondependent_static_init_expression (tree t) +{ + return (!type_unknown_p (t) + && is_static_init_expression (t) + && !instantiation_dependent_expression_p (t)); +} + +/* True iff FN is an implicitly constexpr function. */ + +bool +decl_implicit_constexpr_p (tree fn) +{ + if (!(flag_implicit_constexpr + && TREE_CODE (fn) == FUNCTION_DECL + && DECL_DECLARED_CONSTEXPR_P (fn))) + return false; + + if (DECL_CLONED_FUNCTION_P (fn)) + fn = DECL_CLONED_FUNCTION (fn); + + return (DECL_LANG_SPECIFIC (fn) + && DECL_LANG_SPECIFIC (fn)->u.fn.implicit_constexpr); +} + +/* Finalize constexpr processing after parsing. */ + +void +fini_constexpr (void) +{ + /* The contexpr call and fundef copies tables are no longer needed. */ + constexpr_call_table = NULL; + fundef_copies_table = NULL; +} + +#include "gt-cp-constexpr.h" |