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

[Stefan Weil]

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