c++: C++26 returning reference to temporary

P2748R5 makes it ill-formed to return a reference to temporary in C++26;
implementing this is a simple matter of changing the existing warning to a
permerror.

For most of the tests I just changed dg-warning to dg-message to accept
both; I test the specific diagnostic type in Wreturn-local-addr-5.C.

gcc/cp/ChangeLog:

	* typeck.cc (maybe_warn_about_returning_address_of_local):
	Permerror in C++26.

gcc/testsuite/ChangeLog:

	* g++.dg/conversion/pr16333.C: Change dg-warning to dg-message.
	* g++.dg/cpp0x/constexpr-48324.C
	* g++.dg/other/pr94326.C
	* g++.dg/warn/Wreturn-local-addr-2.C
	* g++.old-deja/g++.jason/warning8.C: Likewise.
	* g++.dg/cpp1y/auto-fn6.C: Check that others don't complain.
	* g++.dg/warn/Wreturn-local-addr-5.C: Expect error in C++26.

0 files changed, 0 insertions, 0 deletions