Re: [pygccxml-development] gil_guard_t example ?

[Roman Y. <rom...@gm...>]

On Tue, Aug 19, 2008 at 4:19 PM, Damien Fagnou
<dam...@mo...> wrote:
> Looking at the result that was what it looked it does
> but in one use of it in pyopensg there is those comments that miss lead me
> ...
>
> def unlocked_native():
>  '''
>  Returns a function transform creator for native functions and methods that
>  do not hold the GIL while they execute.
>  '''
>
> this use a derived class from FT.transformer_t
> with :
>  def required_headers(self):
>     return [ pyplusplus.code_repository.gil_guard.file_name ]
>
>  def __configureSealed(self, controller):
>     # Create a guard for the GIL before the actual fucntion call is made.
>     # This is an exception-safe approach to managing the GIL.
>     controller.add_pre_call_code(
>        'pyplusplus::threading::gil_guard_t guard(true);'
>     )
> .....

https://realityforge.vrsource.org/trac/pyopensg/changeset/505

I took a look on the code. May be I am missing something, but the
effect achieved is the opposite one.
Here is a link to Python documentation: http://docs.python.org/api/threads.html

> so could I use the transformer to write a little wrapper that would do what
> I need ?

May be you not. RAII (
http://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization )
is a popular design pattern,
so Py++ makes developers life easier. Take a look on

http://www.language-binding.net/pyplusplus/documentation/apidocs/pyplusplus.decl_wrappers.calldef_wrapper.member_function_t-class.html

add_override_precall_code
add_default_precall_code

methods.

> static boost::python::object applyTo_0fec81cf95d5ecaac2dd1187f0efac01( ...
> .... )
> {
>   ::Muggins::MugginPtr result;
>   {
>       /// a object that wrapper the GIL unlocking
>       scoped_releaseGIL();
>      /// my functiontion call
>       result = inst.applyTo(target);
>   }
>   return bp::object( result );
> }

The last statement invokes Python, so it has to lock GIL.

You can use gil_guard_t and its "ensure" and "release" functions.

> or some things like that ?

More or less.

I don't have a clear example, so cant give you good advice.
May be, after all you will have to create custom transformation - in
this case, don't forget to contribute it :-)

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/