[PATCH v2] ginclude: Add comments to <stdalign.h> and <stdbool.h> about deprecated macros

[Jason Merrill]

On 9/29/26 7:19 AM, Jonathan Wakely wrote:
> On Fri, 25 Sept 2026 at 18:18, Jason Merrill wrote:
>> While we're touching the comments, how about mentioning the C23 changes
>> as well?
> 
> Good idea. Like so?

OK.
> -- >8 --
> 
> The <stdalign.h> macros were removed from C23 and C++26 but this patch
> just tweaks the comment, without actually removing them. Doing so would
> technically be a breaking change, but it's not expected that these
> macros are widely used.
> 
> gcc/ChangeLog:
> 
> 	* ginclude/stdalign.h (__alignas_is_defined, __alignof_is_defined):
> 	Note that the macros were removed in C23 and C++26.
> 	* ginclude/stdbool.h (__bool_true_false_are_defined): Note that
> 	the macro is obsolescent since C23 and deprecated since C++23.
> ---
>   gcc/ginclude/stdalign.h | 3 ++-
>   gcc/ginclude/stdbool.h  | 2 ++
>   2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/gcc/ginclude/stdalign.h b/gcc/ginclude/stdalign.h
> index a68cb28059ce..fdf016ef3bfe 100644
> --- a/gcc/ginclude/stdalign.h
> +++ b/gcc/ginclude/stdalign.h
> @@ -33,7 +33,8 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>   #define alignof _Alignof
>   #endif
>   
> -/* These are defined for C++, but deprecated in C++23.  */
> +/* Added in C99, removed in C23.
> +   Also defined in C++ since C++11, deprecated in C++23 and gone in C++26.  */
>   #define __alignas_is_defined 1
>   #define __alignof_is_defined 1
>   
> diff --git a/gcc/ginclude/stdbool.h b/gcc/ginclude/stdbool.h
> index 9070a1876233..a45bd9b7712b 100644
> --- a/gcc/ginclude/stdbool.h
> +++ b/gcc/ginclude/stdbool.h
> @@ -46,6 +46,8 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>   #endif /* __cplusplus */
>   
>   /* Signal that all the definitions are present.  */
> +/* Added in C99, made obsolescent in C23.
> +   Also defined in C++ since C++11, but deprecated in C++23.  */
>   #define __bool_true_false_are_defined	1
>   
>   #endif	/* stdbool.h */