Re: git: 28cecfe27964 - main - libc: Restrict ATOMIC_VAR_INIT for C23 conformance

On 6/19/26 17:24, Warner Losh wrote:
> The branch main has been updated by imp:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=28cecfe27964fdb67497800f5dcd5d3e1033727f
> 
> commit 28cecfe27964fdb67497800f5dcd5d3e1033727f
> Author:     Faraz Vahedi <kfv@kfv.io>
> AuthorDate: 2026-05-01 14:34:44 +0000
> Commit:     Warner Losh <imp@FreeBSD.org>
> CommitDate: 2026-06-20 00:23:28 +0000
> 
>     libc: Restrict ATOMIC_VAR_INIT for C23 conformance
>     
>     Omit `ATOMIC_VAR_INIT` when targeting C23, where it has been removed.
>     Retain it for earlier C standards and for C++ (as it still remains in
>     C++23, albeit marked as deprecated since C17 and C++20.)
>     
>     Also separate `atomic_init` definitions from `ATOMIC_VAR_INIT` to
>     avoid coupling with a deprecated initialisation mechanism.
>     
>     No functional change intended for `atomic_init`; this is purely a
>     conformance and cleanup adjustment.
>     
>     Signed-off-by: Faraz Vahedi <kfv@kfv.io>
>     Reviewed by: imp
>     Pull Request: https://github.com/freebsd/freebsd-src/pull/2185
> ---
>  sys/sys/stdatomic.h | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/sys/sys/stdatomic.h b/sys/sys/stdatomic.h
> index c3f9b217519c..2d565ce991be 100644
> --- a/sys/sys/stdatomic.h
> +++ b/sys/sys/stdatomic.h
> @@ -86,11 +86,17 @@
>   * 7.17.2 Initialization.
>   */
>  
> +#if __ISO_C_VISIBLE < 2023 || defined(__cplusplus)
>  #if defined(__CLANG_ATOMICS)
>  #define	ATOMIC_VAR_INIT(value)		(value)
> -#define	atomic_init(obj, value)		__c11_atomic_init(obj, value)
>  #else
>  #define	ATOMIC_VAR_INIT(value)		{ .__val = (value) }
> +#endif
> +#endif
> +
> +#if defined(__CLANG_ATOMICS)
> +#define	atomic_init(obj, value)		__c11_atomic_init(obj, value)
> +#else
>  #define	atomic_init(obj, value)		((void)((obj)->__val = (value)))
>  #endif
>  
> 
> 

I expect that the problem reports for port package build failures are
tied to src/sys/sys/_visible.h :

. . .
#elif defined(_C23_SOURCE)      /* Localism to specify strict C23 env. */
#define __POSIX_VISIBLE         0
#define __XSI_VISIBLE           0
#define __BSD_VISIBLE           0
#define __ISO_C_VISIBLE         2023
#define __EXT1_VISIBLE          0
#else                           /* Default environment: show everything. */
#define __POSIX_VISIBLE         202405
#define __XSI_VISIBLE           800
#define __BSD_VISIBLE           1
#define __ISO_C_VISIBLE         2023
#define __EXT1_VISIBLE          1
#endif
#endif /* _POSIX_C_SOURCE */


The "show everything" note is  wrong now, as C23 removes at least
ATOMIC_VAR_INIT . A real "show everything" would require more logic,
such as still keeping ATOMIC_VAR_INIT for __BSD_VISIBLE also being 1 or
some such (may be inventing a new configuration macro for, say,
__ISO_C_BUT_WITHOUT_SOME_REMOVALS).

-- 
===
Mark Millard
marklmi at yahoo.com