// Visual V++ 2005(8.0) sp1, boost 1.34.0
// union not is_class.
// because there is BOOST_STATIC_ASSERT(is_class<T>::value) in make_instance_impl
// can not export union. eg, class_<union my_u>
// can not return_internal_reference<> when T not is_class, eg, return char*, char&, union u&
// how to write return_internal_pointer: char* get();
// how to return_value_policy work: char* get()
// def_readwrite(union): default get() return by value ?
// is_class<T> ? T& : T get() ??
// delete BOOST_STATIC_ASSERT(is_class<T>::value); of make_instance_impl, then compile OK, and work not all OK
boost/python/object/make_instance.hpp
template
struct make_instance_impl
{
typedef objects::instance<Holder> instance_t;
template <class Arg>
static inline PyObject* execute(Arg& x)
{
// must is_class ?? to BOOST_STATIC_ASSERT(is_class<T>::value || is_union<T>::value)??
BOOST_STATIC_ASSERT(is_class<T>::value);
///////////////////////////////
#include
using namespace boost::python;
union my_u
{
int a;
char b;
char& get_ref()
{
return b;
}
char* get_ptr()
{
return *b;
}
}
struct my_s
{
my_u u;
my_u& get_ref()
{
return u;
}
my_u* get_ptr()
{
return &u;
}
};
void my_module()
{
//1. compile ERROR: my_u not is_class, my_u is_union, I modify one line in make_instance.hpp
// BOOST_STATIC_ASSERT(is_class<T>::value) to
//BOOST_STATIC_ASSERT(is_class<T>::value || is_union<T>::value)
// and the def_readwrite a, b work OK.
// and work OK, why not export an union?
class_ u_class("my_u", init< >());
u_class.def_readwrite("a", &my_u::a);
u_class.def_readwrite("b", &my_u::b);
//2. compile ERROR: char not is_class, delete BOOST_STATIC_ASSERT(is_class<T>::value), but run error
u_class.def("get_ref", &my_u::get_ref, return_internal_reference< >());
//3. compile ERROR: char not is_class, delete BOOST_STATIC_ASSERT(is_class<T>::value), but run error, how to return_internal_reference a char? Use def_readwrite？
u_class.def("get_ptr", &my_u::get_ptr, return_internal_reference< >());
//4. compile OK, but run ERROR, I need it return a char
.def("get_value", &my_u::get_ptr,
return_value_policy());
//5. compile ERROR, char* is not a reference, I need but have no copy_non_const_pointer, how to write copy_non_const_pointer?
u_class.def("get_copy", &my_u::get_ptr,
return_value_policy());
class_ s_class("my_s", init< >());
//6. compile OK, buy run ERROR:
// s = my_s()
// s.u.a = 100
// print s.u.a
// but output s.u.a != 100 !!!
// s.u.a = 100 is s.get_u().set_a(100) and get_u() not return u(is_union) by ref ?
s_class.def_readwrite("u", &my_s::u);
// 7. compile ERROR: my_u not is_class, is_union, modify BOOST_STATIC_ASSERT(is_class<T>::value) to
// BOOST_STATIC_ASSERT(is_class<T>::value || is_union<T>::value)
s_class.def("get_ptr", &my_s::get_ptr, return_internal_reference<>());
s_class.def("get_ref", &my_s::get_ref, return_value_policy());//compile ok
}
Best
Regards !
Qiao Zhi Qiang
