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author | Patrick Palka <ppalka@redhat.com> | 2023-03-01 14:09:37 -0500 |
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committer | Patrick Palka <ppalka@redhat.com> | 2023-04-28 15:47:54 -0400 |
commit | 73e86b6766cc92aa8c18cc987bf95929c4ea0672 (patch) | |
tree | df6d789ed524b9a4f4c16b418d286201f4f53f1e | |
parent | dbdcc2017689805a8118c8c959e07817f025f83a (diff) | |
download | gcc-73e86b6766cc92aa8c18cc987bf95929c4ea0672.zip gcc-73e86b6766cc92aa8c18cc987bf95929c4ea0672.tar.gz gcc-73e86b6766cc92aa8c18cc987bf95929c4ea0672.tar.bz2 |
c++: unevaluated array new-expr size constantness [PR108219]
Here we're mishandling the unevaluated array new-expressions due to a
supposed non-constant array size ever since r12-5253-g4df7f8c79835d569
made us no longer perform constant evaluation of non-manifestly-constant
expressions within unevaluated contexts. This shouldn't make a difference
here since the array sizes are constant literals, except they're expressed
as NON_LVALUE_EXPR location wrappers around INTEGER_CST, wrappers which
used to get stripped as part of constant evaluation and now no longer do.
Moreover it means build_vec_init can't constant fold the MINUS_EXPR
'maxindex' passed from build_new_1 when in an unevaluated context (since
it tries reducing it via maybe_constant_value called with mce_unknown).
This patch fixes these issues by making maybe_constant_value (and
fold_non_dependent_expr) try folding an unevaluated non-manifestly-constant
operand via fold(), as long as it simplifies to a simple constant, rather
than doing no simplification at all. This covers e.g. simple arithmetic
and casts including stripping of location wrappers around INTEGER_CST.
In passing, this patch also fixes maybe_constant_value to avoid constant
evaluating an unevaluated operand when called with mce_false, by adjusting
the early exit test appropriately.
Co-authored-by: Jason Merrill <jason@redhat.com>
PR c++/108219
PR c++/108218
gcc/cp/ChangeLog:
* constexpr.cc (fold_to_constant): Define.
(maybe_constant_value): Move up early exit test for unevaluated
operands. Try reducing an unevaluated operand to a constant via
fold_to_constant.
(fold_non_dependent_expr_template): Add early exit test for
CONSTANT_CLASS_P nodes. Try reducing an unevaluated operand
to a constant via fold_to_constant.
* cp-tree.h (fold_to_constant): Declare.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/new6.C: New test.
* g++.dg/cpp2a/concepts-new1.C: New test.
(cherry picked from commit 096f034a8f5df41f610e62c1592fb90a3f551cd5)
-rw-r--r-- | gcc/cp/constexpr.cc | 25 | ||||
-rw-r--r-- | gcc/cp/cp-tree.h | 1 | ||||
-rw-r--r-- | gcc/testsuite/g++.dg/cpp0x/new6.C | 13 | ||||
-rw-r--r-- | gcc/testsuite/g++.dg/cpp2a/concepts-new1.C | 13 |
4 files changed, 49 insertions, 3 deletions
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index b4e2898..46b2b02 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -8144,6 +8144,19 @@ fold_simple (tree t) return t; } +/* Try folding the expression T to a simple constant. + Returns that constant, otherwise returns T. */ + +tree +fold_to_constant (tree t) +{ + tree r = fold (t); + if (CONSTANT_CLASS_P (r) && !TREE_OVERFLOW (r)) + return r; + else + 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. @@ -8188,9 +8201,10 @@ maybe_constant_value (tree t, tree decl, bool manifestly_const_eval) return r; } - /* Don't evaluate an unevaluated operand. */ + /* Don't constant evaluate an unevaluated non-manifestly-constant operand, + but at least try folding it to a simple constant. */ if (cp_unevaluated_operand) - return t; + return fold_to_constant (t); uid_sensitive_constexpr_evaluation_checker c; r = cxx_eval_outermost_constant_expr (t, true, true, false, false, decl); @@ -8254,9 +8268,14 @@ fold_non_dependent_expr_template (tree t, tsubst_flags_t complain, } return t; } + else if (CONSTANT_CLASS_P (t)) + /* No evaluation needed. */ + return t; + /* Don't constant evaluate an unevaluated non-manifestly-constant operand, + but at least try folding it to a simple constant. */ if (cp_unevaluated_operand && !manifestly_const_eval) - return t; + return fold_to_constant (t); tree r = cxx_eval_outermost_constant_expr (t, true, true, manifestly_const_eval, diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index 8228a7b..64b3196 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -8438,6 +8438,7 @@ extern tree fold_non_dependent_init (tree, tsubst_flags_t = tf_warning_or_error, bool = false, tree = NULL_TREE); extern tree fold_simple (tree); +extern tree fold_to_constant (tree); extern bool reduced_constant_expression_p (tree); extern bool is_instantiation_of_constexpr (tree); extern bool var_in_constexpr_fn (tree); diff --git a/gcc/testsuite/g++.dg/cpp0x/new6.C b/gcc/testsuite/g++.dg/cpp0x/new6.C new file mode 100644 index 0000000..d8f1144 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/new6.C @@ -0,0 +1,13 @@ +// PR c++/108218 +// { dg-do compile { target c++11 } } + +template<class T> +void f() { + decltype(new int[-1]) p; // { dg-error "negative" } + decltype(new int[0-1]) q; // { dg-error "negative" } + decltype(new int[1*-1]) r; // { dg-error "negative" } +} + +decltype(new int[-1]) p; // { dg-error "negative" } +decltype(new int[0-1]) q; // { dg-error "negative" } +decltype(new int[1*-1]) r; // { dg-error "negative" } diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-new1.C b/gcc/testsuite/g++.dg/cpp2a/concepts-new1.C new file mode 100644 index 0000000..6200720 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-new1.C @@ -0,0 +1,13 @@ +// PR c++/108219 +// { dg-do compile { target c++20 } } + +template<class T> +concept C = requires { new T[1]{{ 42 }}; }; + +template<class T> +concept D = requires { new T[2][1]{{{ 42 }}, {{ 42 }}}; }; + +struct A { A(int); }; + +static_assert(C<A>); +static_assert(D<A>); |