From: "Edmund Horner" <ejrh AT paradise DOT net DOT nz>
Newsgroups: comp.os.msdos.djgpp
References: <8qi4hm$ism$1 AT nnrp1 DOT deja DOT com>
Subject: Re: GPF caused by string functions...
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Date: Sun, 24 Sep 2000 01:31:22 +1200
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

No offense, but I think you should rewrite the function...

Otherwise, I believe your GPF will be occuring in the first strcat() line.
That's because you don't ensure that buf is a valid string!

To fix it, stick this just after the memset():

buf[j] = 0;

Try that.  (You may have further problems, I haven't checked.)

Edmund.


<raynee AT my-deja DOT com> wrote in message news:8qi4hm$ism$1 AT nnrp1 DOT deja DOT com...
> I am trying to get some string functions to work as part of the
> interface for my program. I am using ScreenPutString to write to the
> screen and my code appears to work when I call my centrestring()
> function once it works okay. A second call, however, causes a General
> Protection fault no matter how I specify my parameters. The code that I
> am using is:
>
> /* Include standard DJGPP libraries */
> #include <pc.h>
> #include <conio.h>
> #include <string.h>
>
> /*  putstring ( str, fg, bg, col, row )
>     Calls the DJGPP function ScreenPutString from libc.a */
> int putstring ( char *str, int fg, int bg, int col, int row ) {
>     ScreenPutString(str, (bg<<4) | fg, col, row);
> }
>
> /*  centrestring ( str, fg, bg, row, col, width )
>     Writes the specified string to the screen, centring it as it does */
> int centrestring ( char *str, int fg, int bg, int col, int row, int
> width ) {
>     char buf[81], spacer[81];
>     int i,j,k;
>     i = strlen(str);
>     j = (width - i) / 2;
>     memset(buf,' ',--j);
>     strcat(buf,str);
>     memset(spacer,' ',(width-i-j));
>     strcat(buf,spacer);
>     buf[width] = 0;
>     putstring(buf,fg,bg,col,row);
> }
>
> /*  main
>     Tests the code */
> int main ( void ) {
>     centrestring("Just one line is okay",WHITE,BLUE,0,0,80);
>     centrestring("This should work.",WHITE,BLUE,0,1,80);
> }
>
> If anyone has any ideas as to why this doesn't work I would appreciate
> any feedback.
>
> Regards,
>
> Ed
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.