[boost.python] def_readwrite need a default docstring

[qiaozhiqiang@…]

the default docstring defined by def_readwrite is null, can boost.python add the type name of my_s::a as the default docstring? like the function's "C++ signature" docstring.

struct my_s
{
        int a;
};

void export_module
{
      class_<my_s >  s_class("my_s", init<  >());
      s_class.def_readwrite("a", &my_s::a);// __doc__ is empty, can boost.python add the type name of my_s::a as the default docstring? like the function's "C++ signature" docstring.
}

// I do this like this:
// get type name of data member of class 
template<typename T, typename C>
char const* MemberTypeName(T C::*)
{
        char const* name = typeid(T).name();
        return name;
}

// boost::python def_readwrite no docstring
// read write property
#define DEF_READWRITE(n, p) \
        def_readwrite((n), (p), std::string("read write property, type is ") + MemberTypeName(p)).c_str())



void export_module
{
      class_<my_s >  s_class("my_s", init<  >());
      s_class.DEF_READWRITE("a", &my_s::a);// replace all auto genarated def_readwrite to DEF_READWRITE.
}

[Dave Abrahams]

Fix formatting mess.