Using C++ and ctypes together: a vast conspiracy? ;)

[Sebastian Wiesner]

<Nick Craig-Wood – Mittwoch, 3. Juni 2009 00:29>

> Diez B. Roggisch <deets at nospam.web.de> wrote:
>>  Joseph Garvin schrieb:
>> > So I was curious whether it's possible to use the ctypes module with
>> > C++ and if so how difficult it is. I figure in principal it's possible
>> > if ctypes knows about each compiler's name mangling scheme. So I
>> > searched for "ctypes c++" on Google.
> [snip]
>> > More seriously -- how difficult is it to use ctypes instead of saying,
>> > boost::python, and why isn't this in a FAQ somewhere? ;)
>> 
>>  Because it's much more needed than name-mangling. Name mangling is
>>  (amongst other things) one thing to prevent
>>  C++-inter-compiler-interoperability which results from differing C++
>>  ABIs.
>> 
>>  I'm not an expert on this, but AFAIK no common ABI exists, especially
>>  not amongst VC++ & G++. Which means that to work for C++, ctypes would
>>  need to know about the internals of both compilers, potentially in
>>  several versions, and possibly without prior notice to changes.
> 
> Probably depends on how far you want to dig into C++.  I'm sure it
> will work fine for simple function calls, passing classes as anonymous
> pointers etc.  If you want to dig into virtual classes with multiple
> bases or the STL then you are probably into the territory you
> describe.

Name mangeling starts with namespaces, and namespaces are a thing often seen 
in well-designed C++-libraries.  So even a simple C++-function call could 
become rather difficult to do using ctypes ...

> That said I've used C++ with ctypes loads of times, but I always wrap
> the exported stuff in extern "C" { } blocks.

No wonder, you have never actually used C++ with C types.  An extern "C" 
clause tells the compiler to generate C functions (more precisely, functions 
that conform to the C ABI conventions), so effectively you're calling into 
C, not into C++.

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