From: "jansb000" <jansb000 AT wxs DOT nl>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Need help with very nasty bug
Date: Tue, 24 Jul 2001 17:53:40 +0200
Organization: Planet Internet
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

> Actually, much can be deduced without more info. All he changed was
> the object layout and the program broke. Ergo, its behavior has a
> dependency on object layout, which is bad. Most probably, this came
> from one of three causes:
>
> * A bug involving uninitialized memory or pointer wildness; the
>   program happened to always work before the spr was added perhaps
>   because a padding zero was there before, or another field.

Unlikely since I reshuffeled (is this English ?) the attributes with exactly
the same result.

> * The code was unwisely depending on fields of the object being at
>   certain hardcoded offsets in bytes, rather than using offsetof.

No. I never use or depend on hardcoded offsets.

> * The code was unwisely writing out and reading the objects
>   byte-by-byte to and from binary files, and so the object format
>   changed when the spr field was added, making the program choke on
>   earlier versions' files.

Bingo!, Indeed my testprogram reads a binary file (containing this class)
written with an older (unmodified) version of the program.

Thanx for the tips!