[C++-sig] Passing std::wstring to Python callback

[Bogdan Cristea]

Hi

I am using boost python for providing python bindings for a C++ library. I am using Python 2.7. My library needs to call callbacks that are defined in Python. There callbacks can take a string parameter. C++ side I am always using std::wstring. Everything works on as long as std::wstring contains only ASCII chars, but once I get something like “é” my application crashes. This issue seems to be related to the way I pass std::wstring to Python callbacks: as long as I make sure that the passed string has only ASCII chars it is ok. My problem is how do I pass unicode strings to Python.

thanks
Bogdan

[Giuseppe Corbelli]

Post by Bogdan Cristea
Hi
I am using boost python for providing python bindings for a C++ library. I am
using Python 2.7. My library needs to call callbacks that are defined in
Python. There callbacks can take a string parameter. C++ side I am always
using std::wstring. Everything works on as long as std::wstring contains only
ASCII chars, but once I get something like “é” my application crashes. This
as long as I make sure that the passed string has only ASCII chars it is ok.
My problem is how do I pass unicode strings to Python.

Late reply, I know...
Have a look at boost/python/converter/builtin_converters.hpp

You should find something like
#if defined(Py_USING_UNICODE) && !defined(BOOST_NO_STD_WSTRING)
BOOST_PYTHON_TO_PYTHON_BY_VALUE(std::wstring,
::PyUnicode_FromWideChar(x.data(),implicit_cast<ssize_t>(x.size())),
&PyUnicode_Type)
# endif

PyUnicode_FromWideChar returns NULL on failure, so a SEGV may as well be expected.

AFAIK an UTF16 encoding should be OK.