Re: [PATCH] KVM: selftests: Guard execinfo.h inclusion for non-glibc builds

[Shuah Khan <skhan@linuxfoundation.org>]

On 3/25/26 12:47, Hisam Mehboob wrote:
> On 3/25/26 23:03, Shuah Khan wrote:
>> On 3/24/26 12:02, Shuah Khan wrote:
>>> On 3/18/26 18:08, Hisam Mehboob wrote:
>>>> The backtrace() function and execinfo.h are GNU extensions available
>>>> in glibc but not in non-glibc C libraries such as musl. Building KVM
>>>> selftests with musl-gcc fails with:
>>>>
>>>>    lib/assert.c:9:10: fatal error: execinfo.h: No such file or directory
>>>>
>>>> Guard the inclusion of execinfo.h under #ifdef __GLIBC__, and wrap
>>>> all backtrace() usage under the same guard with a fallback message
>>>> for non-glibc builds indicating that stack traces are not available.
>>>>
>>>> Unlike the approach of adding a weak stub for backtrace(), this
>>>> explicitly handles the non-glibc case rather than silently providing
>>>> an empty implementation.
>>>>
>>>> Link: https://lore.kernel.org/kvm/20250829142556.72577-7- aqibaf@amazon.com/
>>>>
>>>> Suggested-by: Aqib Faruqui <aqibaf@amazon.com>
>>>> Signed-off-by: Hisam Mehboob <hisamshar@gmail.com>
>>>> ---
>>>>   tools/testing/selftests/kvm/lib/assert.c | 7 +++++++
>>>>   1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/tools/testing/selftests/kvm/lib/assert.c b/tools/ testing/selftests/kvm/lib/assert.c
>>>> index b49690658c60..3442b80c37c1 100644
>>>> --- a/tools/testing/selftests/kvm/lib/assert.c
>>>> +++ b/tools/testing/selftests/kvm/lib/assert.c
>>>> @@ -6,7 +6,9 @@
>>>>    */
>>>>   #include "test_util.h"
>>>> +#ifdef __GLIBC__
>>>>   #include <execinfo.h>
>>>> +#endif
>>> > Is __GLIBC__ defined in musl-gcc? Looks like that is the case with the
>>> error?
>>
>> If __GLIBC__ isn't there you shouldn't see this error because the include
>> is in - this error doesn't make sense if __GLIBC__ isn't defined. What
>> am I missing?
>>
> 
> To clarify the compiler error you mentioned: the error log in the commit message shows the failure that occurs before this patch is applied. Because musl-gcc doesn't define __GLIBC__, the original unconditional <execinfo.h> inclusion causes the build to fail. The #ifdef in my patch was intended to fix that exact failure.
> 
>> +#ifdef __GLIBC__
>>   #include <execinfo.h>
>> +#endif
>>
>> Also check tools/testing/selftests/bpf/test_progs.c - I think backtrace()
>> stub needs be defined only for the !__GLIBC__ case
>>
> 
> Looking at how bpf/test_progs.c handles it, I agree the weak stub approach is much cleaner. I will implement it so that it still prints an explicit warning message when a trace is unavailable.
> 
> If you are okay with this, I will move forward with a v2 patch.
> 

Ultimately kvm maintainers make the call - send v2 patch

thanks,
-- Shuah