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  <br...@clisp.org>

        alignasof, stdalign: Avoid some -Wundef warnings from config.h.
        Reported by Tim Rühsen <tim.rueh...@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

  #   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 defined _GL_STDALIGN_NEEDS_STDDEF
  #  include <stddef.h>
  # endif
  #endif])

@@ -166,7 +168,7 @@ AC_DEFUN([gl_ALIGNASOF] -# if _GL_STDALIGN_NEEDS_STDDEF

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