https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108219
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-12 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:73e86b6766cc92aa8c18cc987bf95929c4ea0672 commit r12-9492-g73e86b6766cc92aa8c18cc987bf95929c4ea0672 Author: Patrick Palka <ppa...@redhat.com> Date: Wed Mar 1 14:09:37 2023 -0500 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 <ja...@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)
