Oh!
char* is not a C++ string, and there's no built-in converter for that. I note that you're casting away the const-ness of v.c_str() above; that's very bad juju. If you make char* into char const* everywhere, your example should work. Alternatively, you can also register a custom from_python converter for char*... but I recommend against it.
yeah, I just wrote up the simple test like that because I was lazy and didn't think it would make a difference. the same problem occurs with const char* new source code: =================================================== #define BOOST_PYTHON_STATIC_LIB #include <boost/python.hpp> using namespace boost::python; struct X { std::string v; X(const std::string& s) : v(s) {} operator char const*() const { return v.c_str(); } }; void test_x(X& x) { char const* x_string = x; printf("test_x: %s\n", x_string); } void test_string(char const* s) { printf("test_string: %s\n", s); } BOOST_PYTHON_MODULE(test_string) { class_<X>("X", init<const std::string&>()); def("test_x", test_x); def("test_string", test_string); implicitly_convertible<X, char const*>(); } ===================================================
import test_string x = test_string.X("foo") test_string.test_string(x) Traceback (most recent call last): File "<stdin>", line 1, in ? Boost.Python.ArgumentError: Python argument types in test_string.test_string(X) did not match C++ signature: test_string(char const *)