From: Robert Hoehne <Robert DOT Hoehne AT Mathematik DOT TU-Chemnitz DOT DE>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: ctor ?
Date: Thu, 10 Jul 1997 11:44:16 +0200
Organization: TU Chemnitz-Zwickau
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Message-ID: <33C4AEF0.3FE9@Mathematik.TU-Chemnitz.DE>
References: <199707100209 DOT AA214490589 AT typhoon DOT rose DOT hp DOT com>
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To: djgpp AT delorie DOT com
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Andrew Crabtree wrote:
> 
> 
>  Could someone explain how the .ctor section works for DJGPP
>  and if it actually works OK?

I know how it works and that it works but (sorry) I cannot explain
it here in short words.

>  it can't get it to (or tell if it is) work properly.
> 
>  If I compile the following code

Your example and the ctor topic have nothing to do with each
other.

>  As C the compiler complains that it is using a non-constant initializer.
Exact, and when I remember correct (I have not POSIX or ANSI documents)
this is not allowed at all!

>  First I'm not sure if this is right.  I believe (2nd hand reference),
>  that this works with linux gcc.  I wouldn't normally code something that

You are wrong. Here some output from a linux machine:

rho AT pandora-508 $ cat test.c
#include <stdio.h>
 int f()
 {
 return 5;
 }
 int x = f();
 main()
 {
 printf("x = %d\n",x);
 return 0;
 }
rho AT pandora-509 $ gcc -v -c test.c
Reading specs from /usr/lib/gcc-lib/i386-linux/2.7.2.1/specs
gcc version 2.7.2.1
 /usr/lib/gcc-lib/i386-linux/2.7.2.1/cpp -lang-c -v -undef -D__GNUC__=2
-D__GNUC_MINOR__=7 -D__ELF__ -Dunix -Di386 -Dlinux -D__ELF__ -D__unix__
-D__i386__ -D__linux__ -D__unix -D__i386 -D__linux -Asystem(unix)
-Asystem(posix) -Acpu(i386) -Amachine(i386) test.c /tmp/cca31189.i
GNU CPP version 2.7.2.1 (i386 Linux/ELF)
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/i386-linux/include
 /usr/lib/gcc-lib/i386-linux/2.7.2.1/include
 /usr/include
End of search list.
 /usr/lib/gcc-lib/i386-linux/2.7.2.1/cc1 /tmp/cca31189.i -quiet
-dumpbase test.c -version -o /tmp/cca31189.s
GNU C version 2.7.2.1 (i386 Linux/ELF) compiled by GNU C version
2.7.2.1.
test.c:7: initializer element is not constant
rho AT pandora-510 $ 




The solution for you problem should be the following:

#include <stdio.h>

int f()
{
 return 5;
}

int x;

static void _init_my_variables() __attribute__((__constructor__));

static void _init_my_variables()
{
  x = f();
}

main()
{
  printf("x = %d\n",x);
  return 0;
}

-- 
*****************************************************************
* Robert Hoehne, Fakultaet fuer Mathematik, TU-Chemnitz-Zwickau *
* Post:    Am Berg 3, D-09573 Dittmannsdorf                     *
* e-Mail:  Robert DOT Hoehne AT Mathematik DOT TU-Chemnitz DOT DE              *
* WWW:     http://www.tu-chemnitz.de/~rho                       *
*****************************************************************