Message-ID: <35103FD5.A9F59A26@mail.ucsm.edu.pe>
Date: Wed, 18 Mar 1998 16:42:49 -0500
From: rpinnell AT characato DOT ucsm DOT edu DOT pe
Reply-To: rpinnell AT characato DOT ucsm DOT edu DOT pe
MIME-Version: 1.0
To: djgpp AT delorie DOT com
Subject: Pointers and DJGPP
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Hi I have been trying to teach myself C for the last few months or so
and have been using DJGPP.  I seem to be having a lot of problems
whenever I use pointers with DJGPP.  Take the following example a simple
strcat.

#include <stdio.h>

void mstrcat(char *s,char *t);

int main()
{
char ms1[]="Hello";
char ms2[]=" World";
mstrcat(ms1,ms2);
printf("After mstrcat ms1 = %s\n",ms1);
return 0;
}

void mstrcat(char *s,char *t)
{
   while(*s++ != '\0')
      ;
   s--;
   while((*s++ = *t++) != '\0')
      ;
}
The program compiles fine and does what I want it to when it runs but
exits with the following error message.
Exiting due to signal SIGSEGV
General Protection Fault at eip=000015dd
eax=00000000 ebx=0004e100 ecx=00000000 edx=00000024 esi=00000054
edi=0000c4c0
ebp=6e6e6950 esp=0004c498 program=C:\WORK\A.EXE
cs: sel=00af  base=8327b000  limit=0005ffff
ds: sel=00b7  base=8327b000  limit=0005ffff
es: sel=00b7  base=8327b000  limit=0005ffff
fs: sel=0087  base=00009930  limit=0000ffff
gs: sel=00c7  base=00000000  limit=ffffffff
ss: sel=00b7  base=8327b000  limit=0005ffff

Call frame traceback EIPs:
  0x000015dd
Which is all Greek to me!  It isnīt just this simple program that I have
problems with I seem to get similar error messages whenever I pass
pointers to a function.  The same things work ok if I just use arrays
rather than pointers.  Any advice would be aprreciated.  My apologies if
this is the wrong place to ask this question  but it seems to me it is
more a DGJPP/DOS question that a general C one.
Richard Pinnell
Arequipa Peru