From:	"John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: GCC c-program execution problem
Date:	Tue, 01 Jul 1997 20:11:21 +0000
Organization:	Two pounds of chaos and a pinch of salt
Lines:	41
Message-ID:	<33B96469.3133@cs.com>
References:	<33B8D043 DOT 6211 AT ship DOT samsung DOT co DOT kr>
Reply-To:	fighteer AT cs DOT com
NNTP-Posting-Host:	ppp107.cs.com
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

H. J. Son wrote:
> 
> And compiling my program which already tested by another compiler,
> 
> without errors, but frequently refuse to execute
> 
> by printing to screen unusual message as follows:

What is your program trying to do?  The most common causes of
segmentation violations when running DJGPP programs are the following:

- NULL pointer dereference (only when running in DOS with cwsdpmi)
- Attempting to directly access memory-mapped devices in conventional
memory, such as the text-mode or graphics-mode video memory.

If your problem is the former, you have buggy code and need to fix it. 
Try using the '-Wall' switch when compiling to catch common mistakes.

If your problem is the latter, then you need to get the DJGPP Frequently
Asked Questions list (v2/faq210b.zip from SimTel) and read chapters 10
and 18, which document how to access conventional memory from protected
mode programs.

If your problem is not listed here, please break your source code down
to the smallest fragment necessary to generate the error, and post that
fragment along with 1) a 'symified' copy of the crash traceback, 2) the
exact command line you use to compile, and 3) the exact output of gcc if
you got any warnings when compiling with '-Wall'.  See chapter 6 of the
FAQ for information on capturing the output of DJGPP programs.

Thanks.

-- 
John M. Aldrich, aka Fighteer I <fighteer AT cs DOT com>

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