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Date:	Tue, 25 Jul 2000 12:27:37 +0200
From:	Corinna Vinschen <vinschen AT cygnus DOT com>
Reply-To:	cygwin <cygwin AT sources DOT redhat DOT com>
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To:	Andrej Borsenkow <Andrej DOT Borsenkow AT mow DOT siemens DOT ru>
CC:	Cygwin AT Sourceware DOT Cygnus DOT Com
Subject:	Re: memory leak in setenv()?
References:	<001201bff612$88df19f0$21c9ca95 AT mow DOT siemens DOT ru>

Andrej Borsenkow wrote:
> 
> If existing value is longer than new, old value is simply overwritten.
> But if old value is shorter, new memory chunk is allocated via malloc(),
> but old one is never freed. Initially all environment strings are
> allocated using strdup() in environ_init(), so who is responsible for
> freeing unused memory in this case?

Nobody in case of setenv() and unsetenv(). It's a known problem
of the environment implementation that freeing environment
variables is not easy. The library can't decide if a string is
currently in use by the application.

As another example take a look into the implementation of
setenv/unsetenv in glibc. It does never free environment strings
by itself so each call to setenv(NAME, VAL, 1) creates a new
memory leak unless it is a known string value once given to
setenv. In that case, glibc tries to recycle strings to use
memory more efficient.

Corinna

-- 
Corinna Vinschen
Cygwin Developer
Cygnus Solutions, a Red Hat company

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