c++: clobber object on placement new [PR121068]HEADtrunkmaster

My r16-2432 patch addressed the original testcase involving an array of
scalars, but not this additional testcase involving an array of classes.

This patch addresses the issue more thoroughly, by having placement new
first clobber the new object, and improving cxx_eval_store_expression to
implement initial clobbers as well.

My earlier attempt to do this clobbered the array as a whole, which broke
construct_at after the resolution of LWG3436 due to trying to create a
multidimensional array over the top of a single-dimensional array.  To
side-step that issue, this patch instead clobbers the individual elements of
an array, taking advantage of the earlier change to let that activate the
array member of a union.

	PR c++/121068

gcc/cp/ChangeLog:

	* constexpr.cc (cxx_eval_store_expression): Handle clobbers.
	(potential_constant_expression_1): Handle clobbers more.
	* decl.cc (build_clobber_this): Use INIT_EXPR for initial clobber.
	* init.cc (build_new_1): Clobber on placement new.
	(build_vec_init): Don't clean up after clobber.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp26/constexpr-new5.C: New test.

0 files changed, 0 insertions, 0 deletions