Instrument function exit with __builtin_unreachable in C++

Instrument function exit with __builtin_unreachable in C++

2017-11-06  Martin Liska  <mliska@suse.cz>

	PR middle-end/82404
	* c-opts.c (c_common_post_options): Set -Wreturn-type for C++
	FE.
	* c.opt: Set default value of warn_return_type.
2017-11-06  Martin Liska  <mliska@suse.cz>

	PR middle-end/82404
	* constexpr.c (cxx_eval_builtin_function_call): Handle
	__builtin_unreachable call.
	(get_function_named_in_call): Declare function earlier.
	(constexpr_fn_retval): Skip __builtin_unreachable.
	* cp-gimplify.c (cp_ubsan_maybe_instrument_return): Rename to
	...
	(cp_maybe_instrument_return): ... this.
	(cp_genericize): Call the function unconditionally.
2017-11-06  Martin Liska  <mliska@suse.cz>

	PR middle-end/82404
	* options.c (gfc_post_options): Set default value of
	-Wreturn-type to false.

From-SVN: r254437