commit 4e4684ca6a79b22fe91acaa81af2d4a00d6e1345
author Jason Merrill <jason@redhat.com> Wed Jun 04 13:31:02 2025 -0400
committer Jason Merrill <jason@redhat.com> Mon Jun 09 09:22:07 2025 -0400
tree 7f6253a47f2102426724d80563ae73d71517d850
parent d96603a48d338a92b78628016d00cbf11576621e

c++: constexpr prvalues vs genericize [PR120502]

Here constexpr evaluation was getting confused by the result of
split_nonconstant_init, which leaves an INIT_EXPR from an empty CONSTRUCTOR
to be followed by member initialization.  As a result
CONSTRUCTOR_NO_CLEARING was set for the time_zone, and
cxx_eval_store_expression didn't set it again for the initial clobber in the
basic_string constructor, so when cxx_fold_indirect_ref wants to check
whether the anonymous union active member had type non_trivial_if, we see
that we don't currently have a value for the anonymous union, try to add
one, and fail.

So let's do constexpr evaluation before split_nonconstant_init.

	PR c++/120502

gcc/cp/ChangeLog:

	* cp-gimplify.cc (cp_fold_r) [TARGET_EXPR]: Do constexpr evaluation
	before genericize.
	* constexpr.cc (cxx_eval_store_expression): Add comment.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/constexpr-prvalue2.C: New test.