A small issue with _GNU_SOURCE

[Corinna Vinschen]

On Feb 25 16:04, Jon TURNEY wrote:
> On 24/02/2015 13:28, Corinna Vinschen wrote:
> >On Feb 24 12:46, Jon TURNEY wrote:
> >>	* libc/include/sys/cdefs.h (_GNU_SOURCE): Move check so it has an
> >>	effect when _XOPEN_SOURCE is also defined.
> >
> >Looks good, with a single nit:
> 
> >>+/* Deal with _GNU_SOURCE, which implies everything and the kitchen sink */
> >>+#ifdef _GNU_SOURCE
> >
> >Before defining _XOPEN_SOURCE this should undef _XOPEN_SOURCE to avoid
> >potential compiler warnings about a redefined macro.  With this change,
> >please apply.
> 
> Done.
> 
> But even now, I'm not sure this is quite right.
> 
> $ cat test.c
> 
> #include <string.h>
> 
> int main()
> {
>  strdup("test");
>  return ffsll(0);
> }
> 
> $ gcc test.c -Wall -ansi
> test.c: In function ‘main’:
> test.c:7:2: warning: implicit declaration of function ‘ffsll’
> 
> I think this should also warn about no prototype for strdup(), because that
> shouldn't be in scope due to __STRICT_ANSI__, which cdefs.h doesn't even
> consider...

That's how it is in Glibc, but AFAICS, not on the BSDs.  For instance,
OpenBSD defines this as:

  #ifdef _POSIX_C_SOURCE
  # if (_POSIX_C_SOURCE - 0 >= 200809)
  #  define __POSIX_VISIBLE       200809
  #  define __ISO_C_VISIBLE       1999
  [...etc...]

  #if defined(_ANSI_SOURCE) && !defined(__POSIX_VISIBLE) && \
      !defined(__XPG_VISIBLE)
  # define __POSIX_VISIBLE        0
  # define __XPG_VISIBLE          0
  # define __ISO_C_VISIBLE        1990
  #endif

So __POSIX_VISIBLE and __XPG_VISIBLE override strict ANSI, isn't it?
Can somebody with access to a BSD system test this, perhaps?


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat
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