Re: [xml] side effects of thread-enabling libxml2

[Daniel Veillard <veillard redhat com>]

On Sun, May 04, 2003 at 06:05:21PM +0200, Stéphane Bidoul wrote:
> Daniel Veillard wrote:
> > Basically what you're asking for is the possibility to set up
> > the global variable default used to initialize the values inherited
> > from new threads, and that would be sufficient, right ? I doubt you
> > actually want to change the global variable dynamically in the 
> > various threads running at a given point in time.
> >  Seems to me that making the affectation in the "main thread" is one
> > way to do this. The other option is to generate xmlSetGlobalXXX()
> > funtions, which should be realtively easy to do within globals.c
> >
> >  
> The concept of "main thread" is unclear to me (running being mod_python 
> and apache,
> I don't control thread creation). Is the main thread the one that loads 
> the library,
> or the first one calling into libxml? [the patch I proposed to for win32 
> threads
> assume it's the thread loading the library]

  It's the thread which initialized the library, right ...

> And currently, per-thread globals don't inherit the values set in the 
> main thread.

  Hum, right... maybe that should be changed, see
     xmlInitializeGlobalState()
The problem then is that xmlInitializeGlobalState() should take
a lock if it's peeking in the main thread global variables I think.
     
> What do you think of a flag controlling the use of per-thread globals at 
> run-time?
> It could be something like xmlSet/GetPerThreadGlobalsEnabled();
> And entries in global.c could read like
>
> #undef    xmlGenericError
> xmlGenericErrorFunc *
> __xmlGenericError(void) {
>     if (!perThreadGlobalsEnabled || IS_MAIN_THREAD)
>     return (&xmlGenericError);
>     else
>     return (&xmlGetGlobalState()->xmlGenericError);
> }

  Sounds too heavy. I would prefer something per-variable, though
I understand that from your point of view it would garantee the same
behaviour at minimal costs. I'm not strongly sided, if other users of
the thread features could voice their concern/preferences this would
help ...

Daniel

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