Re: [xml] xmlCleanupParser() question / patch

[Daniel Veillard <veillard redhat com>]

On Thu, Jan 14, 2010 at 02:59:50AM +0100, Aron Szabo wrote:
> Hi!
>
> If I use the library in a threaded program and call
> xmlCleanupParser() I can't reinitialize it.
>
> So here's what happens:
>
> 1. xmlCleanupThreads() is called from xmlCleanupParser()
> 2. the global key is deleted by xmlCleanupParser() which was created
> by xmlOnceInit()
>
> So the problem is that if I want to clear the data allocated then I
> can't use the library because it will leak memory (xmlOnceInit will
> not be called). The simplest way to solve this issue is to reset
> once_control.
>
> The other way is to remove xmlCleanupThreads() from the cleanup
> process and let the user/programmer do the dirty work...
>
> Aron Szabo
> Pointless Software

> diff --git a/threads.c b/threads.c
> index 98fd2c2..7f421dd 100644
> --- a/threads.c
> +++ b/threads.c
> @@ -911,8 +911,10 @@ xmlCleanupThreads(void)
>      xmlGenericError(xmlGenericErrorContext, "xmlCleanupThreads()\n");
>  #endif
>  #ifdef HAVE_PTHREAD_H
> -    if ((libxml_is_threaded)  && (pthread_key_delete != NULL))
> +    if ((libxml_is_threaded)  && (pthread_key_delete != NULL)) {
>          pthread_key_delete(globalkey);
> +     once_control = PTHREAD_ONCE_INIT;
> +    }
>  #elif defined(HAVE_WIN32_THREADS) && !defined(HAVE_COMPILER_TLS) && (!defined(LIBXML_STATIC) || 
> defined(LIBXML_STATIC_FOR_DLL))
>      if (globalkey != TLS_OUT_OF_INDEXES) {
>          xmlGlobalStateCleanupHelperParams *p;


  That makes sense. there is a big problem anyway with
xmlCleanupParser() most people seems to think it need to be used after
parsing while it's a library global operation and really should not
be called after parsing but only when the library is not in use anymore.

So overall I'm tempted to change xmlCleanupParser() to become an empty
routine, and rename the real function as xmlCleanupLibrary().
That way the various shared libraries deployed with that bug won't need
to be changed specifically, avoiding crashes when multiple libraries
using libxml2 are used. Then your patch should be applied to the new
xmlCleanupLibrary() function.

  Opinions ?

Daniel


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