Re: [Qemu-devel] [Qemu-trivial] [PATCH] os-win32.c : fix memory leak

[Stefan Weil <sw@weilnetz.de>]

Am 24.11.2011 11:27, schrieb Stefan Hajnoczi:
> 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.
>    

MS claims that putenv is a POSIX function, so I also expected
that free / f_free is not allowed.

I now wrote a short test which indicates that g_free would work:
getenv returns a pointer which is completely different from
the one passed to putenv.

Nevertheless, there is a better solution using _putenv_s.
I'll send a patch.

Regards,
Stefan Weil