[PATCH][OBVIOUS] Fix ifunc detection.

[Jeff Law]

On 03/02/2018 09:38 AM, Thomas Schwinge wrote:
> Hi!
> 
> On Fri, 26 Jan 2018 16:24:48 +0100, Martin Liška <mliska@suse.cz> wrote:
>> This fixes detection of ifunc target capability.
>> I'm going to install the patch.
> 
> You could also just have approved the patch I had sent two months before:
> <http://mid.mail-archive.com/87fu9aiemr.fsf@euler.schwinge.homeip.net>.
> ;-)
> 
> One remark:
> 
>> --- a/gcc/testsuite/lib/target-supports.exp
>> +++ b/gcc/testsuite/lib/target-supports.exp
>> @@ -449,7 +449,7 @@ proc check_ifunc_available { } {
>>  	extern "C" {
>>  	#endif
>>  	typedef void F (void);
>> -	F* g (void) {}
>> +	F* g (void) { return 0; }
>>  	void f () __attribute__ ((ifunc ("g")));
>>  	#ifdef __cplusplus
>>  	}
> 
> Is it OK to "return 0" from this ifunc handler, or might some analysis in
> GCC trip over that (at some later point)?  In my patch, I returned the
> address of an "extern" function.
ISTM the question is whether or not ifuncs are ever allowed to return
NULL.  Maybe ping the glibc folks since that's where the extension started?

jeff