Suppressing "ISO C99 requires rest arguments to be used"

Consider the following two macros:

#define PNORM( v, s, ... )  { \
  if( VERBOSITY_CHECK( v ) ) { \
    if( ( errno = pthread_mutex_lock(&server.output_mutex) ) ) { \
      PERROR_LOCKFREE( normal, "\tpthread_mutex_lock failed on output_mutex.\r\n" ) ; \
    } \
    fprintf( stdout, s, ## __VA_ARGS__ ) ; \
    fflush( stdout ) ; \
    if( ( errno = pthread_mutex_unlock(&server.output_mutex) ) ) { \
      PERROR_LOCKFREE( normal, "\tpthread_mutex_unlock failed on output_mutex.\r\n" ) ; \
    } \
  } \
}

#define PERROR_LOCKFREE( v, s, ... ) { \
  if( VERBOSITY_CHECK( v ) ) { \
    PERRNO ;\
    fprintf( stderr, s, ## __VA_ARGS__ ) ; \
    fflush( stderr ) ; \
  } \
}

Now consider an example use of these:

PNORM( verbose, "\tSomeText [%d]开发者_Go百科 More [%p]\r\n", 0, ptr ) ;

When compiled with the -pedantic option and -std=c99 I get this error many times:

mycode.c:410:112: warning: ISO C99 requires rest arguments to be used

The complier is right in complaining about this but is there a simple way I can suppress this warning since I don't care about it?

Combine the s argument with the variadic arguments so that you always have at least one argument as part of the ellipsis. This also allows you to avoid using the ,## extension of GCC:

#define PNORM( v, ... )  { \
  if( VERBOSITY_CHECK( v ) ) { \
    if( ( errno = pthread_mutex_lock(&server.output_mutex) ) ) { \
      PERROR_LOCKFREE( normal, "\tpthread_mutex_lock failed on output_mutex.\r\n" ) ; \
    } \
    fprintf( stdout, __VA_ARGS__ ) ; \
    fflush( stdout ) ; \
    if( ( errno = pthread_mutex_unlock(&server.output_mutex) ) ) { \
      PERROR_LOCKFREE( normal, "\tpthread_mutex_unlock failed on output_mutex.\r\n" ) ; \
    } \
  } \
}

#define PERROR_LOCKFREE( v, ... ) { \
  if( VERBOSITY_CHECK( v ) ) { \
    PERRNO ;\
    fprintf( stderr, __VA_ARGS__ ) ; \
    fflush( stderr ) ; \
  } \
}

The ## token in combination with __VA_ARGS__ is a gcc extension that's not part of ISO C99. That's why you're getting the warning.

You can disable warnings just around your macros, or disable the specific warning entirely with pragma Warnings in GCC. You could also not use -pedantic, since it is, well, pedantic.

Depends on what is simple for you. In P99 there are P99 conditionals that would allow you doing something like

#define USER_MACRO(...) P99_IF_DEC_LE(P99_NARG(__VA_ARGS__),2)(USER_MACRO2(__VA_ARGS__))(USER_MACRO3(__VA_ARGS__))

So with that there is no need for the ,## extension of gcc.