[C++-sig] No automatic upcasting with std::shared_ptr in function calls?
Hello,
I have a sample hierarchy of polymorphic classes (A from which B inherits).
One of them (A1, B1) is managed with boost::shared_ptr, the other one
(A2, B2) via std::shared_ptr (I defined the get_pointer template for
std::shared_ptr).
When I call f1(boost::shared_ptr) with an object B1 from python,
it is correctly upcast to the pointer to its base class and the c++
function is called. When I call f2(std::shared_ptr) with B2 argument
from python, no upcasting takes place and I get Boost.Python.Argument
error.
The code is here:
foo.cpp:
#include
/// make boost::python understand std::shared_ptr
#include
namespace boost {
template T* get_pointer(std::shared_ptr p){ return p.get(); }
}
// define a hierarchy
struct A1{ virtual ~A1(){} };
struct B1: public A1{ virtual ~B1(){} };
void f1(boost::shared_ptr ptr){ std::cerr<<"f1()"< ptr){ std::cerr<<"f2()"<
using namespace boost::python;
BOOST_PYTHON_MODULE(foo){
class_>("A1");
class_,bases>("B1");
def("f1",f1);
class_>("A2");
class_,bases>("B2");
def("f2",f2);
}
compiling with (under Linux):
g++ -std=c++0x foo.cpp -o foo.so -fPIC -shared -lboost_python
`pkg-config python --libs --cflags`
Running
PYTHONPATH=. python -c "import foo; foo.f1(foo.B1()); foo.f2(foo.B2());"
I obtain:
f1()
Traceback (most recent call last):
File "", line 1, in
Boost.Python.ArgumentError: Python argument types in
foo.f2(B2)
did not match C++ signature:
f2(std::shared_ptr)
Where is the problem?
Cheers, Vaclav
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[C++-sig] Re : Re : boost::python: C++/Python function overload issue
Thank you very much. I knew the link already but it made me read my code again and realize that I forgot to reflect the overloaded functions with boost::python. Christophe Jean-Joseph De : JS Unkn0wn À : christophe jean-joseph ; Development of Python/C++ integration Envoyé le : Jeudi 19 avril 2012 1h21 Objet : Re: [C++-sig] Re : boost::python: C++/Python function overload issue Does this ( http://www.boost.org/doc/libs/1_49_0/libs/python/doc/tutorial/doc/html/python/exposing.html ) answer your question? specifically "Class Virtual Functions". On Wed, Apr 18, 2012 at 11:55 PM, christophe jean-joseph wrote: > >Hi, > > >here is my problem. > > >Let say have a C++ A class and a Ader class in Python, derived from A (through >boost::python). >I have a list of functions f_i in Ader overloading the equivalent functions >with same name in A. >The main is written in Python and call a method g of a C++ class B passing and >argument of type Ader (it's written as A type under C++, but I don't have any >type issue there). >Let say B::g call a function f_1, calling f_2, calling f_3. The error occur at >f_3 as I could identify it uses A::f_3 instead of Ader::f_3. >By going down, I could confirm that, from f_1 to f_3, all the 3 called >functions are the A version. >So my question is, how can I fix this issue so that the B::g function uses >Ader functions (meanning Python functions) and not A functions? >On a side, this is a C++/Python version of a code working fine when fully >written in C++. > >Christophe Jean-Joseph > >___ >Cplusplus-sig mailing list >Cplusplus-sig@python.org >http://mail.python.org/mailman/listinfo/cplusplus-sig >___ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
[C++-sig] boost python writing converters for list to std::vector
Hi,
using
http://misspent.wordpress.com/2009/09/27/how-to-write-boost-python-converters/,
I tried to write a converter for list to std::vector (In the example, T will
be double).
The code (see converter.cxx) I wrote is still in early stage of
development (no check) but compiles fine on ubuntu oneiric with boost
python 1.46. I used it to create an std module. However, a simple test
(see test.py) does not work as exepted.
Did I misunderstood something or does boost have a special treatment for
the list object which bypasses converters ?
Thanks for any help,
Sincerly,
Helfer THomas
#include
#include
#include
#include
#include
template
struct Vector_to_python_list
{
static PyObject* convert(std::vector const& v)
{
using namespace std;
using namespace boost::python;
using boost::python::list;
list l;
typename vector::const_iterator p;
for(p=v.begin();p!=v.end();++p){
l.append(object(*p));
}
return incref(l.ptr());
}
};
template
struct Vector_from_python_list
{
Vector_from_python_list()
{
using namespace boost::python;
using namespace boost::python::converter;
registry::push_back(&Vector_from_python_list::convertible,
&Vector_from_python_list::construct,
type_id >());
}
// Determine if obj_ptr can be converted in a std::vector
static void* convertible(PyObject* obj_ptr)
{
if (!PyList_Check(obj_ptr)){
return 0;
}
return obj_ptr;
}
// Convert obj_ptr into a std::vector
static void construct(
PyObject* obj_ptr,
boost::python::converter::rvalue_from_python_stage1_data* data)
{
using namespace boost::python;
// Extract the character data from the python string
// const char* value = PyString_AsString(obj_ptr);
list l(handle<>(borrowed(obj_ptr)));
// // Verify that obj_ptr is a string (should be ensured by convertible())
// assert(value);
// Grab pointer to memory into which to construct the new std::vector
void* storage = (
(boost::python::converter::rvalue_from_python_storage >*)
data)->storage.bytes;
// in-place construct the new std::vector using the character data
// extraced from the python object
std::vector& v = *(new (storage) std::vector());
// populate the vector from list contains !!!
int le = len(l);
v.resize(le);
for(int i = 0;i!=le;++i){
v[i] = extract(l[i]);
}
// Stash the memory chunk pointer for later use by boost.python
data->convertible = storage;
}
};
void initializeConverters()
{
}
void
print(std::vector&v)
{
using namespace std;
copy(v.begin(),v.end(),
ostream_iterator(cout," "));
cout << endl;
}
BOOST_PYTHON_MODULE(std)
{
using namespace boost::python;
using namespace boost::python;
// register the to-python converter
to_python_converter<
std::vector,
Vector_to_python_list >();
// register the from-python converter
Vector_from_python_list();
def("display",print);
}
import std
std.display([3.,12.])
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