Re: Including config.h emits warnings from -Wundef

[Tim Rühsen]

Awesome, thank you Bruno !

Tested and your patch fixes the issue(s) for me.

Tim

On 8/3/23 18:11, Bruno Haible wrote:
> On Donnerstag, 3. August 2023 17:52:29 CEST Tim Rühsen wrote:
> > Hi,
> >
> > I just updated gnulib and recognized these warnings with every '#include
> > <config.h>'. Before the update there were no warnings.
> >
> > ../config.h:3317:34: warning: "__cplusplus" is not defined, evaluates to
> > 0 [-Wundef]
> >    3317 | #if !defined HAVE_C_ALIGNASOF && __cplusplus < 201103 &&
> > !defined alignof
> >         |                                  ^~~~~~~~~~~
> > ../config.h:3318:6: warning: "HAVE_STDALIGN_H" is not defined, evaluates
> > to 0 [-Wundef]
> >    3318 | # if HAVE_STDALIGN_H
> >         |      ^~~~~~~~~~~~~~~
> > ../config.h:3415:7: warning: "HAVE_STDALIGN_H" is not defined, evaluates
> > to 0 [-Wundef]
> >    3415 | # if !HAVE_STDALIGN_H
> >         |       ^~~~~~~~~~~~~~~
> > ../config.h:3424:6: warning: "_GL_STDALIGN_NEEDS_STDDEF" is not defined,
> > evaluates to 0 [-Wundef]
> >    3424 | # if _GL_STDALIGN_NEEDS_STDDEF
> >         |      ^~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Disabling -Wundef for the whole project is not my preferred solution =).
> > Using a #pragma around the #include is ugly and tedious (too many files
> > to change).
>
> Using a #pragma include config.h would also be ugly.
>
> > Can this be fixed in gnulib ?
>
> Done:
>
>
> 2023-08-03  Bruno Haible  <bruno@clisp.org>
>
>         alignasof, stdalign: Avoid some -Wundef warnings from config.h.
>         Reported by Tim Rühsen <tim.ruehsen@gmx.de> in
>         <https://lists.gnu.org/archive/html/bug-gnulib/2023-08/msg00012.html>.
>         * m4/stdalign.m4 (gl_ALIGNASOF): Test whether __cplusplus is defined
>         before evaluating it. Assume HAVE_STDALIGN_H, _GL_STDALIGN_NEEDS_STDDEF
>         are never defined to 0.
>
> diff --git a/m4/stdalign.m4 b/m4/stdalign.m4
> index 1a236d66d2..6a39ffe756 100644
> --- a/m4/stdalign.m4
> +++ b/m4/stdalign.m4
> @@ -68,8 +68,10 @@ AC_DEFUN([gl_ALIGNASOF]
>     dnl The "zz" puts this toward config.h's end, to avoid potential
>     dnl collisions with other definitions.
>     AH_VERBATIM([zzalignas],
> -[#if !defined HAVE_C_ALIGNASOF && __cplusplus < 201103 && !defined alignof
> -# if HAVE_STDALIGN_H
> +[#if !defined HAVE_C_ALIGNASOF \
> +    && !(defined __cplusplus && 201103 <= __cplusplus) \
> +    && !defined alignof
> +# if defined HAVE_STDALIGN_H
>   #  include <stdalign.h>
>   # endif
>   
> @@ -166,7 +168,7 @@ AC_DEFUN([gl_ALIGNASOF]
>   #   define _Alignas(a) __declspec (align (a))
>   #  endif
>   # endif
> -# if !HAVE_STDALIGN_H
> +# if !defined HAVE_STDALIGN_H
>   #  if ((defined _Alignas \
>           && !(defined __cplusplus \
>                && (201103 <= __cplusplus || defined _MSC_VER))) \
> @@ -175,7 +177,7 @@ AC_DEFUN([gl_ALIGNASOF]
>   #  endif
>   # endif
>   
> -# if _GL_STDALIGN_NEEDS_STDDEF
> +# if defined _GL_STDALIGN_NEEDS_STDDEF
>   #  include <stddef.h>
>   # endif
>   #endif])

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