Using ctypes inside a C application embedding the CPython runtime

Hi,

We have a python server application that will load a shared library (using
ctypes) and make its functions available to a client application on another
host.

Now we're been asked to embedded that application into a larger C
application that also loads the same library (the goal is to let the C
application turn on and off the server as needed). We used the CPython
runtime to embed the python application inside the C application
successfully, using the documentation available here[0].

The problem is that right now we make sure that our python application is
using the same library (in memory) as the C application by passing None as
the name parameter to the CDLL constructor, which means it ultimately calls
dlopen() with Null as it's filename parameter, having the following effect:

If *filename* is NULL, then the returned handle is for the main
       program.  When given to *dlsym*(), this handle causes a search for a
       symbol in the main program, followed by all shared objects loaded at
       program startup, and then all shared objects loaded by *dlopen*() with
       the flag *RTLD_GLOBAL*.

As documented on dlopen's manpage[1], and this is working right now. What
we're worried about is that passing None to the CDLL constructor is not
documented anywhere (at least that I could find), so we're not sure if we
can rely on this functionality (if so, the documentation should probably be
updated and I can help with that if needed) or if there's an alternate
recommended and documented way of achieving the same result.

Thank you very much for your time.


Regards,

[0] https://docs.python.org/3.5/extending/embedding.html
[1] http://man7.org/linux/man-pages/man3/dlopen.3.html

-- 
Jeffrey Esquivel S.

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