[PATCH bpf] tools/headers: Regenerate stddef.h to fix BPF selftests

[PATCH bpf] tools/headers: Regenerate stddef.h to fix BPF selftests

[Paul Chaignon]

With commit dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv
with __counted_by"), two selftests, test_tag and crypto_sanity, now
indirectly rely on the __counted_by macro. On systems with commit
dacbfc167808 in the installed UAPI headers, the selftests build fails
with:

  In file included from tools/testing/selftests/bpf/prog_tests/crypto_sanity.c:7:
  /usr/include/linux/if_alg.h:45:22: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘__counted_by’
     45 |         __u8    iv[] __counted_by(ivlen);
        |                      ^~~~~~~~~~~~

This patch fixes it by regenerating stddef.h in tools/include using the
instructions from commit a778f5d46b62 ("tools/headers: Pull in stddef.h
to uapi to fix BPF selftests build in CI").

Fixes: dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv with __counted_by")
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
---
I'm a bit unsure if this should go to bpf or bpf-next, but it currently
applies cleanly to both.

 tools/include/uapi/linux/stddef.h | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/tools/include/uapi/linux/stddef.h b/tools/include/uapi/linux/stddef.h
index c53cde425406..457498259494 100644
--- a/tools/include/uapi/linux/stddef.h
+++ b/tools/include/uapi/linux/stddef.h
@@ -3,7 +3,6 @@
 #define _LINUX_STDDEF_H
 
 
-
 #ifndef __always_inline
 #define __always_inline __inline__
 #endif
@@ -36,6 +35,11 @@
 		struct __struct_group_tag(TAG) { MEMBERS } ATTRS NAME; \
 	} ATTRS
 
+#ifdef __cplusplus
+/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
+#define __DECLARE_FLEX_ARRAY(T, member)	\
+	T member[0]
+#else
 /**
  * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
  *
@@ -52,3 +56,23 @@
 		TYPE NAME[]; \
 	}
 #endif
+
+#ifndef __counted_by
+#define __counted_by(m)
+#endif
+
+#ifndef __counted_by_le
+#define __counted_by_le(m)
+#endif
+
+#ifndef __counted_by_be
+#define __counted_by_be(m)
+#endif
+
+#ifndef __counted_by_ptr
+#define __counted_by_ptr(m)
+#endif
+
+#define __kernel_nonstring
+
+#endif /* _LINUX_STDDEF_H */
-- 
2.43.0

Re: [PATCH bpf] tools/headers: Regenerate stddef.h to fix BPF selftests

[Alan Maguire]

On 02/05/2026 11:12, Paul Chaignon wrote:
> With commit dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv
> with __counted_by"), two selftests, test_tag and crypto_sanity, now
> indirectly rely on the __counted_by macro. On systems with commit
> dacbfc167808 in the installed UAPI headers, the selftests build fails
> with:
> 
>   In file included from tools/testing/selftests/bpf/prog_tests/crypto_sanity.c:7:
>   /usr/include/linux/if_alg.h:45:22: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘__counted_by’
>      45 |         __u8    iv[] __counted_by(ivlen);
>         |                      ^~~~~~~~~~~~
> 
> This patch fixes it by regenerating stddef.h in tools/include using the
> instructions from commit a778f5d46b62 ("tools/headers: Pull in stddef.h
> to uapi to fix BPF selftests build in CI").
> 
> Fixes: dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv with __counted_by")
> Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>

Thanks for the fix!

Reviewed-by: Alan Maguire <alan.maguire@oracle.com>

> ---
> I'm a bit unsure if this should go to bpf or bpf-next, but it currently
> applies cleanly to both.
> 
>  tools/include/uapi/linux/stddef.h | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/include/uapi/linux/stddef.h b/tools/include/uapi/linux/stddef.h
> index c53cde425406..457498259494 100644
> --- a/tools/include/uapi/linux/stddef.h
> +++ b/tools/include/uapi/linux/stddef.h
> @@ -3,7 +3,6 @@
>  #define _LINUX_STDDEF_H
>  
>  
> -
>  #ifndef __always_inline
>  #define __always_inline __inline__
>  #endif
> @@ -36,6 +35,11 @@
>  		struct __struct_group_tag(TAG) { MEMBERS } ATTRS NAME; \
>  	} ATTRS
>  
> +#ifdef __cplusplus
> +/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
> +#define __DECLARE_FLEX_ARRAY(T, member)	\
> +	T member[0]
> +#else
>  /**
>   * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
>   *
> @@ -52,3 +56,23 @@
>  		TYPE NAME[]; \
>  	}
>  #endif
> +
> +#ifndef __counted_by
> +#define __counted_by(m)
> +#endif
> +
> +#ifndef __counted_by_le
> +#define __counted_by_le(m)
> +#endif
> +
> +#ifndef __counted_by_be
> +#define __counted_by_be(m)
> +#endif
> +
> +#ifndef __counted_by_ptr
> +#define __counted_by_ptr(m)
> +#endif
> +
> +#define __kernel_nonstring
> +
> +#endif /* _LINUX_STDDEF_H */

Re: [PATCH bpf] tools/headers: Regenerate stddef.h to fix BPF selftests

[Ihor Solodrai]

On 5/2/26 11:12 AM, Paul Chaignon wrote:
> With commit dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv
> with __counted_by"), two selftests, test_tag and crypto_sanity, now
> indirectly rely on the __counted_by macro. On systems with commit
> dacbfc167808 in the installed UAPI headers, the selftests build fails
> with:
> 
>   In file included from tools/testing/selftests/bpf/prog_tests/crypto_sanity.c:7:
>   /usr/include/linux/if_alg.h:45:22: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘__counted_by’
>      45 |         __u8    iv[] __counted_by(ivlen);
>         |                      ^~~~~~~~~~~~
> 
> This patch fixes it by regenerating stddef.h in tools/include using the
> instructions from commit a778f5d46b62 ("tools/headers: Pull in stddef.h
> to uapi to fix BPF selftests build in CI").
> 
> Fixes: dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv with __counted_by")
> Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>

Hi Paul, thank you for fixing this. You beat me to it :)

Can confirm the patch fixes selftests/bpf build on BPF CI:
https://github.com/kernel-patches/vmtest/actions/runs/25255756746/job/74054783017

Tested-by: Ihor Solodrai <ihor.solodrai@linux.dev>

> ---
> I'm a bit unsure if this should go to bpf or bpf-next, but it currently
> applies cleanly to both.

I think this should go through bpf tree, it's a clean fix.

> 
>  tools/include/uapi/linux/stddef.h | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/include/uapi/linux/stddef.h b/tools/include/uapi/linux/stddef.h
> index c53cde425406..457498259494 100644
> --- a/tools/include/uapi/linux/stddef.h
> +++ b/tools/include/uapi/linux/stddef.h
> @@ -3,7 +3,6 @@
>  #define _LINUX_STDDEF_H
>  
>  
> -
>  #ifndef __always_inline
>  #define __always_inline __inline__
>  #endif
> @@ -36,6 +35,11 @@
>  		struct __struct_group_tag(TAG) { MEMBERS } ATTRS NAME; \
>  	} ATTRS
>  
> +#ifdef __cplusplus
> +/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
> +#define __DECLARE_FLEX_ARRAY(T, member)	\
> +	T member[0]
> +#else
>  /**
>   * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
>   *
> @@ -52,3 +56,23 @@
>  		TYPE NAME[]; \
>  	}
>  #endif
> +
> +#ifndef __counted_by
> +#define __counted_by(m)
> +#endif
> +
> +#ifndef __counted_by_le
> +#define __counted_by_le(m)
> +#endif
> +
> +#ifndef __counted_by_be
> +#define __counted_by_be(m)
> +#endif
> +
> +#ifndef __counted_by_ptr
> +#define __counted_by_ptr(m)
> +#endif
> +
> +#define __kernel_nonstring
> +
> +#endif /* _LINUX_STDDEF_H */

Re: [PATCH bpf] tools/headers: Regenerate stddef.h to fix BPF selftests

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Sat, 2 May 2026 12:12:40 +0200 you wrote:
> With commit dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv
> with __counted_by"), two selftests, test_tag and crypto_sanity, now
> indirectly rely on the __counted_by macro. On systems with commit
> dacbfc167808 in the installed UAPI headers, the selftests build fails
> with:
> 
>   In file included from tools/testing/selftests/bpf/prog_tests/crypto_sanity.c:7:
>   /usr/include/linux/if_alg.h:45:22: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘__counted_by’
>      45 |         __u8    iv[] __counted_by(ivlen);
>         |                      ^~~~~~~~~~~~
> 
> [...]

Here is the summary with links:
  - [bpf] tools/headers: Regenerate stddef.h to fix BPF selftests
    https://git.kernel.org/bpf/bpf/c/0c7ae130698e

You are awesome, thank you!
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