https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94205
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:49a86fce1a879a206fb4b27f097910005d968fda commit r10-7557-g49a86fce1a879a206fb4b27f097910005d968fda Author: Patrick Palka <ppa...@redhat.com> Date: Thu Apr 2 16:03:18 2020 -0400 c++: Refrain from using replace_placeholders in constexpr evaluation [PR94205] This removes the use of replace_placeholders in cxx_eval_constant_expression (which is causing the new test lambda-this6.C to ICE due to replace_placeholders mutating the shared TARGET_EXPR_INITIAL tree which then trips up the gimplifier). In its place, this patch adds a 'parent' field to constexpr_ctx which is used to store a pointer to an outer constexpr_ctx that refers to another object under construction. With this new field, we can beef up lookup_placeholder to resolve PLACEHOLDER_EXPRs which refer to former objects under construction, which fixes PR94205 without needing to do replace_placeholders. Also we can now respect the CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag when resolving PLACEHOLDER_EXPRs, and doing so fixes the constexpr analogue of PR79937. gcc/cp/ChangeLog: PR c++/94205 PR c++/79937 * constexpr.c (struct constexpr_ctx): New field 'parent'. (cxx_eval_bare_aggregate): Propagate CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag from the original constructor to the reduced constructor. (lookup_placeholder): Prefer to return the outermost matching object by recursively calling lookup_placeholder on the 'parent' context, but don't cross CONSTRUCTOR_PLACEHOLDER_BOUNDARY constructors. (cxx_eval_constant_expression): Link the 'ctx' context to the 'new_ctx' context via 'new_ctx.parent' when being expanded without an explicit target. Don't call replace_placeholders. (cxx_eval_outermost_constant_expr): Initialize 'ctx.parent' to NULL. gcc/testsuite/ChangeLog: PR c++/94205 PR c++/79937 * g++.dg/cpp1y/pr79937-5.C: New test. * g++.dg/cpp1z/lambda-this6.C: New test.
