* ubsan.c (ubsan_source_location): Don't crash on
	unknown locations.
	(ubsan_pass): Ignore clobber stmts.

	* sanitizer.def (BUILT_IN_UBSAN_HANDLE_MISSING_RETURN): New built-in.
	* opts.c (common_handle_option): Add -fsanitize=return.
	* flag-types.h (enum sanitize_code): Add SANITIZE_RETURN and
	or it into SANITIZE_UNDEFINED.
c-family/
	* c-ubsan.h (ubsan_instrument_return): New prototype.
	* c-ubsan.c (ubsan_instrument_return): New function.
cp/
	* cp-gimplify.c: Include target.h and c-family/c-ubsan.h.
	(cp_ubsan_maybe_instrument_return): New function.
	(cp_genericize): Call it if -fsanitize=return.
testsuite/
	* g++.dg/ubsan/return-1.C: New test.
	* g++.dg/ubsan/return-2.C: New test.

From-SVN: r205283