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c++: TARGET_EXPR_ELIDING_P and std::move [PR107267]

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With -ffold-simple-inlines, we turn calls to std::move into the static_cast
equivalent.  In this testcase, this exposes the FindResult temporary to copy
elision which is not specified by the standard, through an optimization in
gimplify_modify_expr_rhs.  Since the type is not TREE_ADDRESSABLE, this is
not detectable by the user, so we just need to soften the assert.

	PR c++/107267

gcc/cp/ChangeLog:

	* cp-gimplify.cc (cp_gimplify_init_expr): Allow unexpected elision
	of trivial types.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/move2.C: New test.
This commit is contained in:
Jason Merrill 2023-01-23 17:14:11 -05:00
parent 51767f3187
commit 4cbc71691e
2 changed files with 18 additions and 1 deletions
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5
gcc/cp/cp-gimplify.cc
View file

@ -250,7 +250,10 @@ cp_gimplify_init_expr (tree *expr_p)
if (TREE_CODE (from) == TARGET_EXPR)
if (tree init = TARGET_EXPR_INITIAL (from))
{
gcc_checking_assert (TARGET_EXPR_ELIDING_P (from));
/* Make sure that we expected to elide this temporary. But also allow
gimplify_modify_expr_rhs to elide temporaries of trivial type. */
gcc_checking_assert (TARGET_EXPR_ELIDING_P (from)
|| !TREE_ADDRESSABLE (TREE_TYPE (from)));
if (target_expr_needs_replace (from))
{
/* If this was changed by cp_genericize_target_expr, we need to

14
gcc/testsuite/g++.dg/cpp0x/move2.C Normal file
View file

@ -0,0 +1,14 @@
// PR c++/107267
// { dg-do compile { target c++11 } }
// { dg-additional-options -ffold-simple-inlines }
namespace std {
template<typename _Tp> _Tp &&move(_Tp &&);
}
struct FindResult {
FindResult();
int result;
};
FindResult pop_ret = std::move(FindResult());