Re: Errors compiling BPF programs from Linux selftests/bpf with GCC

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2025-01-03 at 01:16 +0100, Jose E. Marchesi wrote:

[...]

> Yes, in the GCC BPF backend we are using
> 
>   use_gcc_stdint=provide
> 
> which makes GCC to provide the version of stdint.h that assumes
> freestanding ("baremetal") mode.  If we changed it to use
> 
>   use_gcc_stdint=wrap
> 
> then it would install a stdint.h that does somethins similar to what
> clang does, at least in hosts providing C99 headers (note the lack of
> __has_include_next):
> 
>   #ifndef _GCC_WRAP_STDINT_H
>   #if __STDC_HOSTED__
>   # if defined __cplusplus && __cplusplus >= 201103L
>   #  undef __STDC_LIMIT_MACROS
>   #  define __STDC_LIMIT_MACROS
>   #  undef __STDC_CONSTANT_MACROS
>   #  define __STDC_CONSTANT_MACROS
>   # endif
>   #pragma GCC diagnostic push
>   #pragma GCC diagnostic ignored "-Wpedantic" // include_next
>   # include_next <stdint.h>
>   #pragma GCC diagnostic pop
>   #else
>   # include "stdint-gcc.h"
>   #endif
>   #define _GCC_WRAP_STDINT_H
>   #endif
> 
> We could switch to "wrap" to align with clang, but in that case it would
> be up to the user to provide a "host" stdint.h that contains sensible
> definitions for BPF.  The kernel selftests, for example, would need to
> do so to avoid including /usr/include/stdint.h that more likely than not
> will provide incorrect definitions for int64_t and friends...

Would it be possible to push a branch that uses '=wrap' thing somewhere?
So that it could be further tested to see if there are more issues with selftests.