From 0c7bce0ac184c057bacad9c8e615ce82923835fd Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Mon, 9 May 2022 09:53:27 -0400 Subject: c++: constexpr init of union sub-aggr w/ base [PR105491] Here ever since r10-7313-gb599bf9d6d1e18, reduced_constant_expression_p in C++11/14 is rejecting the marked sub-aggregate initializer (of type S) W w = {.D.2445={.s={.D.2387={.m=0}, .b=0}}}; ^ ultimately because said initializer has CONSTRUCTOR_NO_CLEARING set, hence the function must verify that all fields of S are initialized. And before C++17 it doesn't expect to see base class fields (since next_initializable_field skips over them), so the presence thereof causes r_c_e_p to return false. The reason r10-7313-gb599bf9d6d1e18 causes this is because in that commit we began using CONSTRUCTOR_NO_CLEARING to precisely track whether we're in middle of activating a union member. This ends up affecting clear_no_implicit_zero, which recurses into sub-aggregate initializers only if the outer initializer has CONSTRUCTOR_NO_CLEARING set. After that commit, the outer union initializer above no longer has the flag set at this point and so clear_no_implicit_zero no longer recurses into the marked inner initializer. But arguably r_c_e_p should be able to accept the marked initializer regardless of whether CONSTRUCTOR_NO_CLEARING is set. The primary bug therefore seems to be that r_c_e_p relies on next_initializable_field which skips over base class fields in C++11/14. To fix this, this patch introduces a new helper function next_subobject_field which is like next_initializable_field except that it never skips base class fields, and makes r_c_e_p use it. This patch then renames next_initializable_field to next_aggregate_field (and makes it skip over vptr fields again). PR c++/105491 gcc/cp/ChangeLog: * call.cc (field_in_pset): Adjust after next_initializable_field renaming. (build_aggr_conv): Likewise. (convert_like_internal): Likewise. (type_has_extended_temps): Likewise. * class.cc (default_init_uninitialized_part): Likewise. (finish_struct): Likewise. * constexpr.cc (cx_check_missing_mem_inits): Likewise. (reduced_constant_expression_p): Use next_subobject_field instead. * cp-gimplify.cc (get_source_location_impl_type): Adjust after next_initializable_field renaming. (fold_builtin_source_location): Likewise. * cp-tree.h (next_initializable_field): Rename to ... (next_aggregate_field): ... this. (next_subobject_field): Declare. * decl.cc (next_aggregate_field): Renamed from ... (next_initializable_field): ... this. Skip over vptr fields again. (next_subobject_field): Define. (reshape_init_class): Adjust after next_initializable_field renaming. * init.cc (build_value_init_noctor): Likewise. (emit_mem_initializers): Likewise. * lambda.cc (build_capture_proxy): Likewise. * method.cc (build_comparison_op): Likewise. * pt.cc (maybe_aggr_guide): Likewise. * tree.cc (structural_type_p): Likewise. * typeck2.cc (split_nonconstant_init_1): Likewise. (digest_init_r): Likewise. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/constexpr-union7.C: New test. * g++.dg/cpp0x/constexpr-union7a.C: New test. * g++.dg/cpp2a/constinit17.C: New test. --- gcc/cp/constexpr.cc | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'gcc/cp/constexpr.cc') diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index 6c204ab..e560d84 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -784,7 +784,7 @@ cx_check_missing_mem_inits (tree ctype, tree body, bool complain) if (TREE_CODE (ctype) == UNION_TYPE) { - if (nelts == 0 && next_initializable_field (field)) + if (nelts == 0 && next_aggregate_field (field)) { if (complain) error ("% constructor for union %qT must " @@ -3053,7 +3053,7 @@ reduced_constant_expression_p (tree t) field = NULL_TREE; } else - field = next_initializable_field (TYPE_FIELDS (TREE_TYPE (t))); + field = next_subobject_field (TYPE_FIELDS (TREE_TYPE (t))); } else field = NULL_TREE; @@ -3065,15 +3065,15 @@ reduced_constant_expression_p (tree t) return false; /* Empty class field may or may not have an initializer. */ for (; field && e.index != field; - field = next_initializable_field (DECL_CHAIN (field))) + field = next_subobject_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)); + field = next_subobject_field (DECL_CHAIN (field)); } /* There could be a non-empty field at the end. */ - for (; field; field = next_initializable_field (DECL_CHAIN (field))) + for (; field; field = next_subobject_field (DECL_CHAIN (field))) if (!is_really_empty_class (TREE_TYPE (field), /*ignore_vptr*/false)) return false; ok: -- cgit v1.1