improve fprintf declaration and warning

[Bruno Haible]

The override in stdio.in.h of fprintf, printf, vfprintf, vprintf introduced
on 2008-09-26 was suboptimal. Now that we use _GL_WARN_ON_USE, since 2010-01-20,
it can be improved. I'm applying this:


2010-02-20  Bruno Haible  <address@hidden>

        Improve *printf warning condition.
        * lib/stdio.in.h (fprintf, printf, vfprintf, vprintf): Emit warning
        also if GNULIB_POSIXCHECK is defined, the *-posix module is not used,
        and the function is overridden due to SIGPIPE emulation.

*** lib/stdio.in.h.orig Sun Feb 21 00:56:35 2010
--- lib/stdio.in.h      Sun Feb 21 00:52:35 2010
***************
*** 133,152 ****
                   "use gnulib module fopen for portability");
  #endif
  
! #if @GNULIB_FPRINTF_POSIX@
! # if @REPLACE_FPRINTF@
  #  define fprintf rpl_fprintf
  extern int fprintf (FILE *fp, const char *format, ...)
         __attribute__ ((__format__ (__printf__, 2, 3)))
         _GL_ARG_NONNULL ((1, 2));
  # endif
! #elif @GNULIB_FPRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@
! # define fprintf rpl_fprintf
! extern int fprintf (FILE *fp, const char *format, ...)
!        __attribute__ ((__format__ (__printf__, 2, 3)))
!        _GL_ARG_NONNULL ((1, 2));
! #elif defined GNULIB_POSIXCHECK
! # undef fprintf
  /* Assume fprintf is always declared.  */
  _GL_WARN_ON_USE (fprintf, "fprintf is not always POSIX compliant - "
                   "use gnulib module fprintf-posix for portable "
--- 133,152 ----
                   "use gnulib module fopen for portability");
  #endif
  
! #if @GNULIB_FPRINTF_POSIX@ || @GNULIB_FPRINTF@
! # if (@GNULIB_FPRINTF_POSIX@ && @REPLACE_FPRINTF@) \
!      || (@GNULIB_FPRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@)
  #  define fprintf rpl_fprintf
+ #  define GNULIB_overrides_fprintf 1
  extern int fprintf (FILE *fp, const char *format, ...)
         __attribute__ ((__format__ (__printf__, 2, 3)))
         _GL_ARG_NONNULL ((1, 2));
  # endif
! #endif
! #if address@hidden@ && defined GNULIB_POSIXCHECK
! # if !GNULIB_overrides_fprintf
! #  undef fprintf
! # endif
  /* Assume fprintf is always declared.  */
  _GL_WARN_ON_USE (fprintf, "fprintf is not always POSIX compliant - "
                   "use gnulib module fprintf-posix for portable "
***************
*** 439,458 ****
  # endif
  #endif
  
! #if @GNULIB_PRINTF_POSIX@
! # if @REPLACE_PRINTF@
  /* Don't break __attribute__((format(printf,M,N))).  */
  #  define printf __printf__
  extern int printf (const char *format, ...)
         __attribute__ ((__format__ (__printf__, 1, 2))) _GL_ARG_NONNULL ((1));
  # endif
! #elif @GNULIB_PRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@
! /* Don't break __attribute__((format(printf,M,N))).  */
! # define printf __printf__
! extern int printf (const char *format, ...)
!        __attribute__ ((__format__ (__printf__, 1, 2))) _GL_ARG_NONNULL ((1));
! #elif defined GNULIB_POSIXCHECK
! # undef printf
  /* Assume printf is always declared.  */
  _GL_WARN_ON_USE (printf, "printf is not always POSIX compliant - "
                   "use gnulib module printf-posix for portable "
--- 439,458 ----
  # endif
  #endif
  
! #if @GNULIB_PRINTF_POSIX@ || @GNULIB_PRINTF@
! # if (@GNULIB_PRINTF_POSIX@ && @REPLACE_PRINTF@) \
!      || (@GNULIB_PRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@)
  /* Don't break __attribute__((format(printf,M,N))).  */
  #  define printf __printf__
+ #  define GNULIB_overrides_printf 1
  extern int printf (const char *format, ...)
         __attribute__ ((__format__ (__printf__, 1, 2))) _GL_ARG_NONNULL ((1));
  # endif
! #endif
! #if address@hidden@ && defined GNULIB_POSIXCHECK
! # if !GNULIB_overrides_printf
! #  undef printf
! # endif
  /* Assume printf is always declared.  */
  _GL_WARN_ON_USE (printf, "printf is not always POSIX compliant - "
                   "use gnulib module printf-posix for portable "
***************
*** 595,632 ****
  # endif
  #endif
  
! #if @GNULIB_VFPRINTF_POSIX@
! # if @REPLACE_VFPRINTF@
  #  define vfprintf rpl_vfprintf
  extern int vfprintf (FILE *fp, const char *format, va_list args)
         __attribute__ ((__format__ (__printf__, 2, 0)))
         _GL_ARG_NONNULL ((1, 2));
  # endif
! #elif @GNULIB_VFPRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@
! # define vfprintf rpl_vfprintf
! extern int vfprintf (FILE *fp, const char *format, va_list args)
!        __attribute__ ((__format__ (__printf__, 2, 0)))
!        _GL_ARG_NONNULL ((1, 2));
! #elif defined GNULIB_POSIXCHECK
! # undef vfprintf
  /* Assume vfprintf is always declared.  */
  _GL_WARN_ON_USE (vfprintf, "vfprintf is not always POSIX compliant - "
                   "use gnulib module vfprintf-posix for portable "
                        "POSIX compliance");
  #endif
  
! #if @GNULIB_VPRINTF_POSIX@
! # if @REPLACE_VPRINTF@
  #  define vprintf rpl_vprintf
  extern int vprintf (const char *format, va_list args)
         __attribute__ ((__format__ (__printf__, 1, 0))) _GL_ARG_NONNULL ((1));
  # endif
! #elif @GNULIB_VPRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@
! # define vprintf rpl_vprintf
! extern int vprintf (const char *format, va_list args)
!        __attribute__ ((__format__ (__printf__, 1, 0))) _GL_ARG_NONNULL ((1));
! #elif defined GNULIB_POSIXCHECK
! # undef vprintf
  /* Assume vprintf is always declared.  */
  _GL_WARN_ON_USE (vprintf, "vprintf is not always POSIX compliant - "
                   "use gnulib module vprintf-posix for portable "
--- 595,633 ----
  # endif
  #endif
  
! #if @GNULIB_VFPRINTF_POSIX@ || @GNULIB_VFPRINTF@
! # if (@GNULIB_VFPRINTF_POSIX@ && @REPLACE_VFPRINTF@) \
!      || (@GNULIB_VFPRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@)
  #  define vfprintf rpl_vfprintf
+ #  define GNULIB_overrides_vfprintf 1
  extern int vfprintf (FILE *fp, const char *format, va_list args)
         __attribute__ ((__format__ (__printf__, 2, 0)))
         _GL_ARG_NONNULL ((1, 2));
  # endif
! #endif
! #if address@hidden@ && defined GNULIB_POSIXCHECK
! # if !GNULIB_overrides_vfprintf
! #  undef vfprintf
! # endif
  /* Assume vfprintf is always declared.  */
  _GL_WARN_ON_USE (vfprintf, "vfprintf is not always POSIX compliant - "
                   "use gnulib module vfprintf-posix for portable "
                        "POSIX compliance");
  #endif
  
! #if @GNULIB_VPRINTF_POSIX@ || @GNULIB_VPRINTF@
! # if (@GNULIB_VPRINTF_POSIX@ && @REPLACE_VPRINTF@) \
!      || (@GNULIB_VPRINTF@ && @REPLACE_STDIO_WRITE_FUNCS@ && 
@GNULIB_STDIO_H_SIGPIPE@)
  #  define vprintf rpl_vprintf
+ #  define GNULIB_overrides_vprintf 1
  extern int vprintf (const char *format, va_list args)
         __attribute__ ((__format__ (__printf__, 1, 0))) _GL_ARG_NONNULL ((1));
  # endif
! #endif
! #if address@hidden@ && defined GNULIB_POSIXCHECK
! # if !GNULIB_overrides_vprintf
! #  undef vprintf
! # endif
  /* Assume vprintf is always declared.  */
  _GL_WARN_ON_USE (vprintf, "vprintf is not always POSIX compliant - "
                   "use gnulib module vprintf-posix for portable "