Re: [pygccxml-development] Status of code inserters

[Matthias B. <ba...@ir...>]

Allen Bierbaum wrote:
> Matthias:
> 
> What is the status of the code inserter's?  Do you have any py++ addons 
> that I can try out yet?

I was just about to post a message on this subject....

Well, I don't have a readily available addon yet, but I think the 
general way to proceed is more or less clear. Right now, it's like I 
have all the individual pieces spread out before me but I'm not sure how 
to assemble them...

The result from my earlier wiki entry was that there are up to two 
functions involved:

1) the wrapper function that gets called from Python and that makes a 
call "down to" C++ where the actual work is done

2) the virtual function that gets called from C++ and that may make a 
call to Python

So for the general case, an arg policy must be prepared to deal with 
both functions and there must be an API that allows it to do so. This 
led to some updates which I have already entered into the wiki here: 
https://realityforge.vrsource.org/view/PyppApi/CodeInserter#Arg_policy_interface
Basically, there are now two sets of methods to create pre-call and 
post-call code, one for the wrapper function and one for the virtual 
function.

In the previous version I have proposed a class WrapperManager (or 
wrapper_manager_t) that represents the code creator for the wrapper 
function, i.e. that created the complete C++ source code. I have changed 
this and made this class only a helper class for creating C++ functions. 
Now it basically provides text substitution services which could be used 
by the existing Py++ code creators. Those code creators still create the 
rough layout of the code and insert special variables at appropriate 
places that will get substituted by the wrapper manager.  These 
variables represent individual parts of the C++ function. I have 
documented the class in the wiki over here: 
https://realityforge.vrsource.org/view/PyppApi/Wrapper_manager

This wrapper manager object is also the object that the individual 
methods of the arg policies (sometimes I also call them "code blocks" in 
the wiki) receive as input ("wm") and which they have to use to modify 
either the wrapper function or the virtual function.

I have already implemented most parts of the mentioned classes (wrapper 
manager, code manager, policy base class). Now I could add it to 
pypp_api but it could only make use of the "wrapper function" part and 
not the virtual functions. So if everyone (in particular Roman) agrees 
with this approach, I would rather try to update the Py++ code creators 
so that they use the text substitution service from above. But that's 
where I'm a bit lost because I'm not familiar with the implementation 
and all the dependencies involved.

So before I continue with this I'd rather like to know if Roman agrees 
to the general approach. The things that I'd like to do next are:

- Add the "wrapper manager" class to Py++. It's more or less a 
stand-alone module that I would stick into its own directory inside 
"pyplusplus".

- Add a new decoration attribute to the decl_wrappers that stores the 
"arg policy" objects.

- Update the Py++ calldef code creators so that they use the arg 
policies via the above text substitution mechanism.


Additionally, I'd like to introduce the "thread_safe" decoration 
attribute. This involves the same code as above so I think it safes time 
if it is done at the same time. This option should be implemented right 
in the Py++ code creators and not via the "arg policy" mechanism because 
it affects code on a lower level than what the arg policies are doing.


- Matthias -