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

[Hisam Mehboob <hisamshar@gmail.com>]

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.