[C++-sig] function with >15 args yields get_signature error

[troy d. straszheim]

Eilif Mueller wrote:
> Hi,
> 
> Wrapping a function f with 16 arguments:
> 
> int f(int x1, int x2, int x3, int x4, int x5,
>       int x6, int x7, int x8, int x9, int x10,
>       int x11, int x12, int x13, int x14, int x15,
>       int x16) {
> 
>   return x1;
> 
> }
> 
> BOOST_PYTHON_MODULE(test)
> {
> 
>   def("f",f);
> 
> }
> 
> 
> yields
> 
> /usr/include/boost/python/make_function.hpp: In function ‘boost::python::api::object boost::python::make_function(F) [with F = int (*)(int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int)]’:
> /usr/include/boost/python/def.hpp:82:   instantiated from ‘boost::python::api::object boost::python::detail::make_function1(T, ...) [with T = int (*)(int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int)]’
> /usr/include/boost/python/def.hpp:91:   instantiated from ‘void boost::python::def(const char*, Fn) [with Fn = int (*)(int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int)]’
> test_module.cpp:20:   instantiated from here
> /usr/include/boost/python/make_function.hpp:104: error: no matching function for call to ‘get_signature(int (*&)(int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int))’
> make: *** [stream.o] Error 1
> 
> 
> whereas all is fine if that last arg "int x16" is removed.  All of gcc-4.2, gcc-4.3 and gcc-4.4 seem to exhibit the same behaviour.  Same effect for libboost-python1.38-dev on Ubuntu karmic and libboost-python1.35-dev on Ubuntu jaunty.
> 
> I need that 16th arg and more ... about 32 args, I think.
> 
> Thanks for any help you can offer.
> 

This came up recently.  You're going to have various problems (not all 
boost.python problems) getting arity that large.  The workaround is to 
introduce an intermediate function that takes a boost::python::tuple
and forward to the zillion-arguments one, example here:
 
http://gitorious.org/~straszheim/boost/straszheim/blobs/python/libs/python/test/zillion_arguments_workaround.cpp

-t