A tricky macro

This is a discussion on A tricky macro within the C Programming forums, part of the General Programming Boards category; Ok itz atleast tricky to me! I want to write a macro which will do something like #define PRINTF(x) printf ...

  1. #1
    Unregistered
    Guest

    Angry A tricky macro

    Ok itz atleast tricky to me!

    I want to write a macro which will do something
    like

    #define PRINTF(x) printf x

    :
    somewhere in code
    :
    PRINTF(("This is a zero %d\n", 0));
    :
    :

    Works fine until now.

    Now I need to make it something like

    #define PRINTFX(x) \
    fnCall(someparam, x)

    Cant get this to work! Please note that x denotes variable number of parameters like printf.

    The intended use is like
    PRINTFX("One", "This is one %d\n", 1);
    PRINTFX("Two", "Nothing);

    Can add any number of paranthesis to the parameters.

    Thanks for any help, nope this is not a brain teaser, it would be cool if I could make this work ... else the good old way, multiple functions with variable number of parameters to a function.

  2. #2
    Just because ygfperson's Avatar
    Join Date
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    2,493
    i don't think it's possible with #defines. printf is a weird function, though. it doesn't use multiple prototypes.
    http://www.purdue.edu/PUCC/Short-Cou...s/p_00930.html
    this should help answer questions

    Edit: i read your post again and realized you knew this already. i don't think it's possible with #define. can't overload a define, nor can you just put it all in parenthesis without causing problems.
    Last edited by ygfperson; 02-12-2002 at 04:09 PM.

  3. #3
    and the hat of wrongness Salem's Avatar
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    This might work for you, but you still have to use the (()) trick for all the additional parameters

    Code:
    #include <stdio.h>
    #include <stdarg.h>
    
    #define PRINTFX(x,y) \
        fnCall( x, magic y ) 
    
    void fnCall ( char *x, char *y ) {
      printf( "%s %s\n", x, y );
    }
    char *magic ( const char *fmt, ... ) {
      static char buff[BUFSIZ]; // must be static
      va_list   ap;
      va_start ( ap, fmt );
      vsprintf ( buff, fmt, ap );
      va_end ( ap );
      return buff;
    }
    
    int main ( ) {
      PRINTFX( "One", ("This is one %d\n",1) ); 
      PRINTFX( "Two", ("Nothing") ); 
      return 0;
    }

  4. #4
    Unregistered
    Guest

    Thumbs up

    Thanks! That worked. Sorry I was tardy in getting back to the list.

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