Re: strdup falsely detected when CFLAGS contains -ansi on MSYS/MinGW (gcc)

[Chris Pickett]

Chris Pickett wrote:
> Hi,
>
> When -ansi is passed to GCC, strdup becomes unavailable on MSYS/MinGW, 
> but autoconf still detects the existence of strdup.  The mingw string.h 
> is in /mingw/include/string.h, and includes some funny stuff with 
> #ifndef __STRICT_ANSI__ and later #ifndef _NO_OLDNAMES.  The former gets 
> defined by GCC with -ansi, the latter I couldn't see where it gets 
> defined if at all.

Ok, I can do better than that.  string.h looks like this:

#ifndef __STRICT_ANSI__
...
_CRTIMP char* __cdecl __MINGW_NOTHROW   _strdup (const char*) 
__MINGW_ATTRIB_MALLOC;
...
#ifndef _NO_OLDNAMES
...
_CRTIMP char* __cdecl __MINGW_NOTHROW   strdup (const char*) 
__MINGW_ATTRIB_MALLOC;
...
#endif /* _NO_OLDNAMES */
#endif  /* Not __STRICT_ANSI__ */

So it seems like the configure test for strdup isn't using CFLAGS when 
it invokes the compiler but in this case it needs to so that 
__STRICT_ANSI__ is defined and strdup is unavailable.

Maybe there's a way to force this and I missed it?  Or should I just:

#undef __STRICT_ANSI__
#include <string.h>
#define __STRICT_ANSI__

Thanks,
Chris

> Chris
>
> mkdir src
> cat >configure.ac <<\END
> AC_INIT(a,1)
> AM_INIT_AUTOMAKE(foreign)
> AC_CONFIG_FILES(Makefile src/Makefile)
> AC_PROG_CC
> AC_PROG_LIBTOOL
> AC_REPLACE_FUNCS([strdup])
> AC_CONFIG_HEADERS([config.h])
> AC_OUTPUT
> END
> cat >Makefile.am <<\END
> SUBDIRS = src
> END
> cat >src/Makefile.am <<\END
> libcheck_la_LIBADD = @LTLIBOBJS@
> lib_LTLIBRARIES = libcheck.la
> END
> cat >src/libcheck.c <<\END
> #if HAVE_CONFIG_H
> #include "config.h"
> #endif
>
> #include <string.h>
>
> #if !HAVE_STRDUP
> char *strdup (const char *str);
> #endif /* !HAVE_STRDUP */
>
> void use_strdup (void)
> {
>   strdup (NULL);
> }
> END
> cat >src/strdup.c <<\END
> char *
> strdup (const char *str)
> {
>   /* obviously this is broken */
>   return NULL;
> }
> END
>
> autoreconf -vif # all is fine, src/strdup.c is there
>
> CFLAGS="-Wall -ansi" ./configure # says yes for strdup (incorrectly)
>
> make # libcheck.c:13: warning: implicit declaration of function `strdup'
>
> make clean
>
> CFLAGS="-Wall" ./configure # says yes for strdup (correctly)
>
> make # libcheck.c:13: warning: null argument where non-null required 
> (arg 1)