Date: Fri, 10 May 96 09:34:03 +0200
From: wank AT ftth DOT uebemc DOT siemens DOT de (Rainer Wank)
Message-Id: <9605100734.AA19401@malta>
To: djgpp AT delorie DOT com
Subject: vararg the second
Cc: wank AT ftth DOT uebemc DOT siemens DOT de

Hi folks,

thank you for your answers, but there are still a few
questions concerning my little test program:


1.) You wrote, ELI ZARETSKII, that what i have done is forbidden in ANSI C.
    What parts of my code are not ANSI conform ?
    Why does the djgpp compiler does not warn me, even if have
    used switches like -pedantic -ansi -Wall and so on ?
    Where can i read that the parts of the code you will mention
    are not ANSI conform ?

2.) S. Kagels' explanation (processors X86, little endian, ...) why my
    little program does not work as i expected seems to be plausible.
    Your suggestion to pass an unsigned int instead of an unsigned char
    after the predefined arguments fails.  :-(
    Here is my modified test program and the output on stdout:

     #include <stdarg.h>
     #include <stdio.h>

     unsigned int fg;

     void abc(int anzahl, char abc, ...)
     {
      va_list ap;
      va_start(ap, abc);
      fg = va_arg(ap, unsigned int);
      printf("\n\rErster variabler Parameter: %d", fg);
      va_end(ap);
     }

     void main(void)
     {
      abc((int) 10, (char) 10, (unsigned int) 51);
     }

    
     D:\GNU_V2>a

     Erster variabler Parameter: 1422080
    ---------------------------------------------

    decimal: 1422080   hexadecimal: 15B300
    decimal:      51   hexadecimal:     33

    Even the passed parameter 51 decimal does not appear in the
    printed value.

    We also have the gcc on our SUN and so i tried both programs
    (the first and the modified) on the SUN. The first program 
    fails but the second works on the SUN.


    After that i have tried a third program with djgpp gcc. I have
    changed the second parameter (unsigned char) into an unsigned int
    and it works :-)

    #include <stdarg.h>
    #include <stdio.h>

    unsigned int fg;

    void abc(int anzahl, unsigned int abc, ...)
    {
     va_list ap;
     va_start(ap, abc);
     fg = va_arg(ap, unsigned int);
     printf("\n\rErster variabler Parameter: %d", fg);
     va_end(ap);
    }

    void main(void)
    {
     abc((int) 10, (unsigned int) 10, (unsigned int) 51);
    }

    D:\GNU_V2>a

    Erster variabler Parameter: 51
    ---------------------------------------------

    Isn't it possible that the success of my third program has to do
    with the address of the passed arguments on the stack ?


 Thanx a lot and have a nice weekend !

 Wank Rainer
 e-mail: wank AT ftth DOT uebemc DOT siemens DOT de