what's wrong with this macro?

This is a discussion on what's wrong with this macro? within the C Programming forums, part of the General Programming Boards category; Code: #include <stdio.h> #define P( fmt...) printf( ##fmt) #define FP( fmt...) fprintf( stderr, ##fmt) #define PP( fmt...) printf( "Wen%d\n",##fmt) int ...

  1. #1
    Registered User
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    Question what's wrong with this macro?

    Code:
    #include <stdio.h>
    #define P( fmt...)    printf( ##fmt)
    #define FP( fmt...)    fprintf( stderr, ##fmt)
    #define PP( fmt...)    printf( "Wen%d\n",##fmt)
    int main(int argc, char *argv[])
    {
        PP(520);
        FP("Xiao %d\n", 520);
        P("Wener%d",520);/* this not work */
    /*
    test2.c:9:1: error: pasting "(" and ""Wener%d"" does not give a valid preprocessing token
    */
        return 0;
    }

  2. #2
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    sorry i made a mistake

    it should be
    #define P( fmt...) printf( fmt)
    /* it works */

  3. #3
    SAMARAS std10093's Avatar
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    Nice, France
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    If you use this
    Code:
    #define P( fmt...)    fprintf( stdout,##fmt)
    it will be ok

    EDIt - sam is too slow
    Last edited by std10093; 08-06-2012 at 05:14 AM.

  4. #4
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    Apr 2008
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    395
    Why the ##? ## is used to paste parts of a single token, you don't want that, just remove the double ## everywhere in your macros.

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