Re: memset_explicit: Fix compilation error on some OpenSolaris derivatives

[Collin Funk]

Hi Bruno,

On 4/19/24 3:12 PM, Bruno Haible wrote:
> The reason is that on this system, the function 'memset_s' exists in libc,
> but is only declared (in /usr/include/iso/string_iso.h) if __EXT1_VISIBLE
> is set. __EXT1_VISIBLE is defined by <sys/feature_tests.h> if
> __STDC_WANT_LIB_EXT1__ is defined to non-zero at that point.
> gnulib's lib/memset_explicit.c defines __STDC_WANT_LIB_EXT1__, but it comes
> too late, because <config.h> has already included <stdalign.h>, <stddef.h>,
> <stdbool.h>, or <assert.h>. <stdbool.h> and <assert.h> include
> <sys/feature_tests.h>.

In GNU inetutils I see the following warnings in multiple places:

In file included from telnetd.h:19,
                 from pty.c:21:
../config.h:2783:9: warning: "__STDC_WANT_LIB_EXT1__" redefined
 2783 | #define __STDC_WANT_LIB_EXT1__ 1
      |         ^~~~~~~~~~~~~~~~~~~~~~
In file included from ./telnetd.h:19,
                 from term.c:21:
../config.h:2783:9: warning: "__STDC_WANT_LIB_EXT1__" redefined
 2783 | #define __STDC_WANT_LIB_EXT1__ 1
      |         ^~~~~~~~~~~~~~~~~~~~~~

In pty.c we have:

    #include <config.h>
    #include "telnetd.h"

in telnetd.h:

     #include <config.h>
     #include <sys/types.h>
     /* Many more system headers (or gnulib versions). */

I'm a bit confused as to why I only see warnings for this macro from
gcc. Should this be wrapped in an #ifndef like the ones in
AC_USE_SYSTEM_EXTENSIONS?

Collin