From: Endlisnis <s257m AT unb DOT ca>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: ? array[n] or array[n+1] ?
Date: Wed, 12 May 1999 17:36:21 -0400
Organization: BrunNet
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Ya'qub wrote:

> Greetings,
>     With all due respect, this explanation does not seem very convincing.
> Surely, the compiler *should* complain when you do such a thing as
> overrunning an array. I hoped that the compiler would help such a poor
> programmer as myself in catching such bugs which I suppose could cause quite
> a lot of headache to locate. Can anybody else confirm that gcc makes such
> assumptions that we know what we are doing and let us carry on regardless.
> Also, out of curiosity, if you do overrun an array and the program has
> compiled without any warning or error, is there anything that can be said
> about its execution? i.e. do we know what is going to happen when the
> program tries to access an element from the array beyond its length. Thanks

Outcome #1:  If you access some protected memory (on a machine that supports it,
like with DJGPP or Win32) that is outside one of the 2K banks assigned to you,
there will be a GPF and your program will nicely terminate.
Outcome #2:  If you access some of your memory that is associated with some
other variable or code, your program may run perfectly, or may suffer some
strage effects.
Outcome #3:  Something terrible might happen.  Worst case scenario (never known
anyone it has happened to, but it's possible): overwriting some buffered portion
of a hard-drive or memory mapped io could desroy data or hardware.

--
     (\/) Endlisnis (\/)
          s257m AT unb DOT ca
          Endlisnis AT HotMail DOT com
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