From:	Antti =?iso-8859-1?Q?Koskip=E4=E4?= <antti DOT koskipaa AT nic DOT fi>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: #PF, #PF, #PF... Aargh, HELP!!!
Date:	Wed, 03 Nov 1999 18:46:24 +0200
Organization:	NIC Tietoverkot Oy / NIC Data Networks Ltd.
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Whoops, I knew I forgot something... Here's the traceback:

Exiting due to signal SIGSEGV
Page fault at eip=0000163e, error=0006
eax=00000000 ebx=00259040 ecx=00000000 edx=00000003 esi=00000054
edi=00214d68
ebp=00254d40 esp=00254d38 cs=00a7 ds=00af es=00af fs=008f gs=00bf
ss=00af
Call frame traceback EIPs:
  0x0000163e   _main+34, line 47 of main.c
  0x00017dd7   ___crt1_startup+115

c:\djgpp\bin\commdoom>symify -o tracebak.dmp cdoom.exe

The instruction at 0x163e is a NOP.

Antti Koskipää wrote:
> 
> I came across an interesting bug in my program.
> 
> Piece of code from the main program:
> 
> init ();
> playmidi (23);
> init_graphics ();
> 
> This executes always in the beginning. The game loads itself
> succesfully,
> generates all tables, etc.
> All is fine until it hits the address 0x163e. Page Fault.
> 
> I first run symify to check where it crashes. Ok. playmidi(23). I always
> check
> with fsdb what kind of instruction in at the address. It was a CALL.
> Then I comment out the call (in the C code) and try again. Now it
> crashes
> when it calls init_graphics. Again re-check. Again the CALL instruction,
> and at the same address 0x163e. (of course it is, since the previous
> call is out
> of the way) So this is not a problem with a corrupted function or
> function
> address. Next, I insert a few inline NOPs before init_graphics to be
> placed
> at the address 0x163e. Compile. Run. THE NOP CAUSES A PAGE FAULT!?
> What the h***???
> 
> HELP! I'm frustrated!
> 
> This program worked a long time ago... The only thing that is changed
> is my binutils... it's 2.9.1. It did work with 2.8.1... In the
> beginning...
> At a later time, it didn't anymore. I'm using PGCC 1.0.1 and no
> optimizations
> nor special flags. OS: MS-DOS 7.10.
> I tried under both CWSDPMI and CWSDPR0, no success. Under W95, no
> success.
> 
> I have used djgpp for years now, and I've never seen such things happen.
> 
> --
> - Antti

-- 
- Antti

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