Date:	Sun, 15 Jun 1997 16:57:34 -0400 (EDT)
From:	Michael Phelps <morphine AT hops DOT cs DOT jhu DOT edu>
To:	Jawed Karim <jawed AT tc DOT umn DOT edu>
cc:	djgpp AT delorie DOT com
Subject:	Re: DJGPP MEM BUG?
In-Reply-To:	<33A36EAE.17D4@tc.umn.edu>
Message-ID:	<Pine.GSO.3.95.970615165152.18642B-100000@hops.cs.jhu.edu>
MIME-Version:	1.0

On Sat, 14 Jun 1997, Jawed Karim wrote:

> I really need the following code to work. Under Linux, this works
> PERFECTLY. Under DJGPP I get SIGSEVs every single time. See for
> yourself:
> 
> Exiting due to signal SIGSEGV
> Stack Fault at eip=00001559
> eax=00000000 ebx=0004c100 ecx=00000000 edx=0000033e esi=00000054
> edi=0000a2d4
> ebp=0004a2a8 esp=fffcaaa8 program=D:\JAW3D\A.EXE
> cs: sel=00a7  base=82e4e000  limit=0005ffff
> ds: sel=00af  base=82e4e000  limit=0005ffff
> es: sel=00af  base=82e4e000  limit=0005ffff
> fs: sel=0087  base=0000cfc0  limit=0000ffff
> gs: sel=00bf  base=00000000  limit=ffffffff
> ss: sel=00af  base=82e4e000  limit=0005ffff
> ---------
> It doesnt crash with [255][32] but it does with [255][64]. In any case,
> even with 128 it SHOULD NOT. It's not that much memory, and under linux
> gcc it works. Any ideas? Please email me directly...
> 

When you declare an automatic variable, the space for it is allocated on
the stack (256K by default).  So, if the variables require more space then
that, you need to either stubedit the executable file to increase the
default stack space, or dynamically allocate it, as I have done to your
program below.

> -- 
> #include <stdio.h>
#include <stdlib.h>
> 
> typedef struct {
>         int r, g, b;
>         int closest_fit;
> } Table;
> 
> main()
> {
>       /*  Table thingy[255][128]; */
	Table **thingy;
	int	x;

	thingy = (Table **)malloc(255 * sizeof(Table *));
	if (thingy == NULL)
	{
		fprintf(stderr, "Unable to allocate sufficient
memory.\n");
		exit(1);
	}

	for (x = 0; x < 255; x++)
	{
		thingy[x] = (Table *)malloc(128 * sizeof(Table));
		if (thingy[x] == NULL)
		{
			fprintf(stderr, "Insufficient memory.\n");
			exit(1);
		}
	}

	/* now you can use thingy the way you wanted to */

	return 0; /* main returns an int */
> }
> ---

> Jawed Karim
> jawed AT tc DOT umn DOT edu
> http://umn.edu/~jawed
> 


						---Michael Phelps
						   morphine AT cs DOT jhu DOT edu


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                   Morphine

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