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Date: Thu, 24 Nov 2011 10:27:12 +0000
From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [Qemu-trivial] [PATCH] os-win32.c : fix memory leak
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To: Mark <wudx05@gmail.com>
Cc: qemu-trivial@nongnu.org, Zhi Hui Li <zhihuili@linux.vnet.ibm.com>, qemu-devel@nongnu.org, stefanha@linux.vnet.ibm.com

On Thu, Nov 24, 2011 at 05:15:30PM +0800, Mark wrote:
> If you free the string, it will cause the environment variable unavailable.
>  More details please see the following text extracted from manual of
> "putenv":
> 
>        The  libc4  and  libc5  and  glibc 2.1.2 versions conform to SUSv2:
> the pointer string given to putenv() is used.  In particular, this
>        string becomes part of the environment; changing it later will
> change the environment.  (Thus, it is an error is to call putenv() with
>        an automatic variable as the argument, then return from the calling
> function while string is still part of the environment.)  However,
>        glibc 2.0-2.1.1 differs: a copy of the string is used.  On the one
> hand this causes a memory leak, and on the other hand  it  violates
>        SUSv2.  This has been fixed in glibc 2.1.2.

I don't think this matters since os-win32.c is only built for mingw,
which uses the Microsoft C runtime and not glibc.

However, there is no documentation for putenv(3) on MSDN because the
function has been deprecated :(.  So I think the safest thing to do is
to assume this will leak memory but we are not allowed to free the
string.

Either you could investigate the new _putenv(3) and test the Windows
build to make sure it works.  Or you could send a patch that adds a
comment explaining why there is a memory leak here.

Stefan