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Date:      Sat, 22 May 2004 11:52:19 -0700
From:      Tim Kientzle <kientzle@freebsd.org>
To:        Cole <cole@opteqint.net>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: Memory Leak
Message-ID:  <40AFA163.4020109@freebsd.org>
In-Reply-To: <000701c4402b$a54e73d0$4206000a@stalker>
References:  <000701c4402b$a54e73d0$4206000a@stalker>

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Cole wrote:
> Hey
> 
> I just wanted to know what programs any of you have used to track down a
> memory leak in your programs?
> Also wondering if there is maybe a good tutorial on the subject under
> FreeBSD or even linux if possible.
> 
> Im running FreeBSD 4.9 so just looking for something try to help me track it
> down.
> 
> Unless there is someone willing to help me with this since ive never really
> had to do anything like this, else i can easily read something, just kinda
> need to know a good memory tracing program or something of the sorts.

I've had pretty good luck with dmalloc from ports.

Just add
   #include <dmalloc.h>
to the *END* of your includes and link against
the dmalloc library.  The tracing is controlled
by environment variables; you can use the 'dmalloc'
program to help set those.  The one problem I've had
is that dmalloc.h redefines some standard functions,
which can cause gcc to complain.  I've locally
modified some of the standard system headers to
not define malloc/free/strdup/calloc/realloc/etc
if DMALLOC is defined.  It's a hack, but it works.

dmalloc also gives good statistics about malloc
usage.  I've used it to identify over-use of
malloc in bsdtar, with some concrete performance
improvements.  (For example, by switching from
heap-allocated buffers to stack-allocated buffers
or by re-using buffers to avoid repeated
malloc/free calls.)

The FreeBSD standard malloc also has some nice debugging
features.  I've found that switching between dmalloc
and the libc malloc helps a lot, as each catches
different sorts of problems.

Tim Kientzle



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