From:	"Michael Beck" <beck AT dresearch DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: HELP! SIGSEGV Page Fault
Date:	Mon, 28 Dec 1998 10:54:34 +0100
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leonj AT geocities DOT com wrote in message <7677mg$ri0$1 AT nnrp1 DOT dejanews DOT com>...
>Im having a problem that's ticking me off.
>I picked up a tutorial for Allegro from:

[...]

>
>Shutting down Allegro
>Exiting due to signal SIGSEGV
>Page fault at eip=00012996, error=0004
>eax=00000000 ebx=00000000 ecx=00000100 edx=000003c9 esi=0f580000
edi=00042270


Looks like a NULL pointer access. Look at the eax, ebx registers.

>
>set_pallette((RGB*)data[TUT_GAMEPAL].dat);
>
add a check for NULL pointer before calling set_palette, for instance:

#inlcude <assert.h>

...

assert(((RGB*)data[TUT_GAMEPAL].dat != NULL);
set_pallette((RGB*)data[TUT_GAMEPAL].dat);

Now, if your program stops with an 'assertion failed' message, check while
this is NULL.

Hope that helps,
--
Michael Beck,                   email: beck AT dresearch DOT de

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