From: Nate Eldredge <neldredge AT hmc DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: 1. Win98 2. bug?
Date: Mon, 13 Sep 1999 13:12:43 -0700
Organization: Harvey Mudd College
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To: djgpp AT delorie DOT com
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Mikko Lehtonen wrote:
> 
>         Hello!
> 
> I have two things:
> 
> 1.
> I code in win98 dosbox quite happily, without problems etc. but then I
> tried in clean win98 dos.. (dos7?) without the gui loaded, and a problem
> raised!
>         first it told me that there's no dpmi. ah okey, I forgot this, I
> put cwsdpmi in the dir.. the machines hangs.. and with little more poking,
> I find that every time I trie to use cwsdpmi, my machine hangs! (no, not
> in win98 dosBOX when it says protected mode not accesible, which is
> because of win98's dpmi service ?)
> has microsoft done a another stupid mistake or have I missed something?
> 
> 2.
> 
> I have this program that moves couple of cool lights around on the screen,
> and then I pondered, that a background could be cool.. so I wrote a fast
> opentga routine which wasn't completely ripped, but it was some..
>         the strangest thing happened when playing around with this code!
> fclose(fp); doesn't work, it crashes the program, free(backg); doesn't
> work, crashes the program, and if I have neither of them, it crashes in
> the end anyways.
> 
> small peezes of code:
> (its in vesa2 btw.)
> 
> unsigned int *backg;
> unsigned int *loadtga(char *filename, int size) {
>   unsigned char r,g,b;
>   int i=0;
>   FILE *fd;
>   unsigned int *p;
>   fd=fopen(filename,"rb");
>   printf("%d\n",fd);
>   fflush(stdout);
>   if(!fd) { printf("couldn't open file %s!\n",filename); exit(0); }
>   fseek(fd,18,SEEK_SET);
>   p=calloc(size,sizeof(int));
>   if(!p) { printf("calloc failed in loadtga!\n"); exit(0); }
>   while(!feof(fd) || i<size) {

If the file has more than `size' triples, you'll overrun the p array
here.  This could easily cause crashes in free and the like (fclose
calls free internally).  You probably want

while (!feof(fd) && i<size)

>     b=fgetc(fd);
>     g=fgetc(fd);
>     r=fgetc(fd);
>     p[i++]=(r<<16)+(g<<8)+b;
>   }
>   printf("%d\n",fd);
>   fflush(stdout);
>   fclose(fd);
>   return p;
> }
> 
> int main(...) {
> 
>   backg=loadtga("backgrnd.tga",640*480);
> 
>   while(!kbhit()) {
>     ...
>   }
> 
>   free(backg);
> 
> }
> 
> What is wrong??
> 
> ps.
> please try to answer as email atleast! I don't read this newgroup that
> often!
> 
> - Scorpion - scorpion AT sgic DOT fi - www.sgic.fi/~scorpion -
> -------------------------------------------------------
> Experience is something what you can't get until just
> after you need it.
> -------------------------------------------------------

-- 

Nate Eldredge
neldredge AT hmc DOT edu