Path: utzoo!utgpu!watmath!iuvax!purdue!haven!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.questions
Subject: Re: Problems with ndbm
Message-ID: <18934@mimsy.UUCP>
Date: 7 Aug 89 18:57:26 GMT
References: <34200002@zaphod> <34200003@zaphod> <18933@mimsy.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 22

In article <18933@mimsy.UUCP> I wrote:
>[someone else's code was probably something like this]:
>		x = dbm_fetch(thedb, thekey);
>		x.dptr[x.dsize] = '\0';
>		printf("%s\n", x.dptr);

and---O fool that I was---did not even notice that this corrupts
the memory buffer returned from dbm_fetch.

You are NOT allowed to scribble on the memory pointed to by
x.dptr!

In this particular case, the result is to clobber the key that
follows the key `thekey' in the ndbm buffer, or, if that is the
last datum, the next byte in the buffer, which is most likely
unused, but could be one byte of a two-byte index.

In any case, the operation is not legal, and while a subsequent
fetch of the same key is likely to work, nothing is guaranteed.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris