Re: [PATCH] bpf_helpers.h: define bpf_tail_call_static when building with GCC

["Jose E. Marchesi" <jose.marchesi@oracle.com>]

> On 1/23/24 10:59 AM, Jose E. Marchesi wrote:
>> The definition of bpf_tail_call_static in tools/lib/bpf/bpf_helpers.h
>> is guarded by a preprocessor check to assure that clang is recent
>> enough to support it.  This patch updates the guard so the function is
>> compiled when using GCC as well.
>>
>> Tested in bpf-next master.
>> No regressions.
>>
>> Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>
>> Cc: Yonghong Song <yhs@meta.com>
>> Cc: Eduard Zingerman <eddyz87@gmail.com>
>> Cc: david.faust@oracle.com
>> Cc: cupertino.miranda@oracle.com
>> ---
>>   tools/lib/bpf/bpf_helpers.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
>> index 2324cc42b017..3306f50c5081 100644
>> --- a/tools/lib/bpf/bpf_helpers.h
>> +++ b/tools/lib/bpf/bpf_helpers.h
>> @@ -136,7 +136,7 @@
>>   /*
>>    * Helper function to perform a tail call with a constant/immediate map slot.
>>    */
>> -#if __clang_major__ >= 8 && defined(__bpf__)
>> +#if (!defined(__clang__) || __clang_major__ >= 8) && defined(__bpf__)
>
> Do you want to guard with a gcc version as well here or you assume any gcc which supports bpf
> should be okay here?

The second, because GCC versions that do not support
bpf_tail_call_static are not capable of building the selftests for many
other reasons, so there is little point to support them.

>
>>   static __always_inline void
>>   bpf_tail_call_static(void *ctx, const void *map, const __u32 slot)
>>   {