python , Boost and straight (but complex) C code

O

Osiris

I have these pieces of C-code (NOT C++ !!) I want to call from Python.
I found Boost.
I have MS Visual Studio 2005 with C++.

is this the idea:
I write the following C source file:
============================
#include <iostream>
#include <stdafx.h>

namespace { // Avoid cluttering the global namespace.

int my_int; /* a global integer: or outside namespace ? */
double calc ( double f)
{
my_int = (int) (f/2);
printf( "Half of %f is %d\n", f, my_int );
return f/2;
}

}

#include <boost/python.hpp>
using namespace boost::python;

BOOST_PYTHON_MODULE( half )
{
def("calc", calc );
}

================================

Which I put in a VC project and compile into a .DLL
This DLL I put somewhere on my disk, where Python 2.4 can find it.
then I write the following Python source:
=====================
from half import *
calc(34655.0)

et voila ?

Can I acces my_int too, this way ?
 
O

Osiris

I get, from Visual C++, these linker errors, 8 in total, trying to
build the above C++ source:

C_test.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) void __cdecl
boost::python::detail::init_module(char const *,void
(__cdecl*)(void))"
(__imp_?init_module@detail@python@boost@@YAXPBDP6AXXZ@Z) referenced in
function _inithalf

C_test.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) void __cdecl
boost::python::detail::scope_setattr_doc(char const *,class
boost::python::api::eek:bject const &,char const *)"
(__imp_?scope_setattr_doc@detail@python@boost@@YAXPBDABVobject@api@23@0@Z)
referenced in function "void __cdecl boost::python::def<int
(__cdecl*)(float)>(char const *,int (__cdecl*)(float))"
(??$def@P6AHM@Z@python@boost@@YAXPBDP6AHM@Z@Z)

C_test.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) class boost::python::api::eek:bject __cdecl
boost::python::eek:bjects::function_object(struct
boost::python::eek:bjects::py_function const &)"
(__imp_?function_object@objects@python@boost@@YA?AVobject@api@23@ABUpy_function@123@@Z)
referenced in function "class boost::python::api::eek:bject __cdecl
boost::python::detail::make_function_aux<int (__cdecl*)(float),struct
boost::python::default_call_policies,struct
boost::mpl::vector2<int,float> >(int (__cdecl*)(float),struct
boost::python::default_call_policies const &,struct
boost::mpl::vector2<int,float> const &)"
(??$make_function_aux@P6AHM@ZUdefault_call_policies@python@boost@@U?$vector2@HM@mpl@3@@detail@python@boost@@YA?AVobject@api@12@P6AHM@ZABUdefault_call_policies@12@ABU?$vector2@HM@mpl@2@@Z)
C_test.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) public: __thiscall
boost::python::eek:bjects::py_function_impl_base::py_function_impl_base(void)"
(__imp_??0py_function_impl_base@objects@python@boost@@QAE@XZ)
referenced in function "public: __thiscall
boost::python::eek:bjects::caller_py_function_impl<struct
boost::python::detail::caller<int (__cdecl*)(float),struct
boost::python::default_call_policies,struct
boost::mpl::vector2<int,float> > >::caller_py_function_impl<struct
boost::python::detail::caller<int (__cdecl*)(float),struct
boost::python::default_call_policies,struct
boost::mpl::vector2<int,float> > >(struct
boost::python::detail::caller<int (__cdecl*)(float),struct
boost::python::default_call_policies,struct
boost::mpl::vector2<int,float> > const &)"
(??0?$caller_py_function_impl@U?$caller@P6AHM@ZUdefault_call_policies@python@boost@@U?$vector2@HM@mpl@3@@detail@python@boost@@@objects@python@boost@@QAE@ABU?$caller@P6AHM@ZUdefault_call_policies@python@boost@@U?$vector2@HM@mpl@3@@detail@23@@Z)
C_test.obj : error LNK2001: unresolved external symbol "public:
virtual unsigned int __thiscall
boost::python::eek:bjects::py_function_impl_base::max_arity(void)const "
(?max_arity@py_function_impl_base@objects@python@boost@@UBEIXZ)
C_test.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) public: virtual __thiscall
boost::python::eek:bjects::py_function_impl_base::~py_function_impl_base(void)"
(__imp_??1py_function_impl_base@objects@python@boost@@UAE@XZ)
referenced in function "public: virtual __thiscall
boost::python::eek:bjects::caller_py_function_impl<struct
boost::python::detail::caller<int (__cdecl*)(float),struct
boost::python::default_call_policies,struct
boost::mpl::vector2<int,float> > >::~caller_py_function_impl<struct
boost::python::detail::caller<int (__cdecl*)(float),struct
boost::python::default_call_policies,struct
boost::mpl::vector2<int,float> > >(void)"
(??1?$caller_py_function_impl@U?$caller@P6AHM@ZUdefault_call_policies@python@boost@@U?$vector2@HM@mpl@3@@detail@python@boost@@@objects@python@boost@@UAE@XZ)
C_test.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) struct
boost::python::converter::rvalue_from_python_stage1_data __cdecl
boost::python::converter::rvalue_from_python_stage1(struct _object
*,struct boost::python::converter::registration const &)"
(__imp_?rvalue_from_python_stage1@converter@python@boost@@YA?AUrvalue_from_python_stage1_data@123@PAU_object@@ABUregistration@123@@Z)
referenced in function "public: __thiscall
boost::python::converter::arg_rvalue_from_python<float>::arg_rvalue_from_python<float>(struct
_object *)"
(??0?$arg_rvalue_from_python@M@converter@python@boost@@QAE@PAU_object@@@Z)
C_test.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) struct boost::python::converter::registration
const & __cdecl boost::python::converter::registry::lookup(struct
boost::python::type_info)"
(__imp_?lookup@registry@converter@python@boost@@YAABUregistration@234@Utype_info@34@@Z)
referenced in function "struct boost::python::converter::registration
const & __cdecl
boost::python::converter::detail::registry_lookup<float const volatile
(float const volatile & (__cdecl*)(void))"
Click to expand...
(??$registry_lookup@$$CDM@detail@converter@python@boost@@YAABUregistration@123@P6AADMXZ@Z)
C:\Documents and Settings\Erik\My Documents\Visual Studio
2005\Projects\C_test\Debug\C_test.dll : fatal error LNK1120: 8
unresolved externals
 
S

Sebastian 'lunar' Wiesner

Osiris said:
I have these pieces of C-code (NOT C++ !!) I want to call from Python.
I found Boost.
I have MS Visual Studio 2005 with C++.

is this the idea:
I write the following C source file:
============================
#include <iostream>
Click to expand...

iostream is a C++ header file...
#include <stdafx.h>

namespace { // Avoid cluttering the global namespace.
Click to expand...

C doesn't know about namespaces. They are a C++ thing, too.
int my_int; /* a global integer: or outside namespace ? */
double calc ( double f)
{
my_int = (int) (f/2);
printf( "Half of %f is %d\n", f, my_int );
Click to expand...

You include a C++ IO header, but use traditional C IO functions here.
Either you use C++ streams here, or you replace <iostream> with
return f/2;
}

}

#include <boost/python.hpp>
using namespace boost::python;

BOOST_PYTHON_MODULE( half )
{
def("calc", calc );
}

================================

Which I put in a VC project and compile into a .DLL
This DLL I put somewhere on my disk, where Python 2.4 can find it.
then I write the following Python source:
=====================
from half import *
calc(34655.0)

et voila ?

Can I acces my_int too, this way ?
Click to expand...

May be... Didn't you try it?
It may also be, that you have to create a PyObject first...
 
E

Erik Max Francis

Osiris said:
I have these pieces of C-code (NOT C++ !!) I want to call from Python.
I found Boost.
I have MS Visual Studio 2005 with C++.

is this the idea:
I write the following C source file:
============================
#include <iostream>
#include <stdafx.h>

namespace { // Avoid cluttering the global namespace.
Click to expand...

iostream and namespaces are both most definitely C++ features, not C.
 
R

Roman Yakovenko

Visual C++ build log at:

http://213.10.133.192/BuildLog.htm
Click to expand...

It is better to ask Boost.Python related questions on it mailing list:
http://mail.python.org/mailman/listinfo/c++-sig/

You should add to the link line boost_python.lib, thus you will eliminate
"unresolved reference symbol" errors. If you did not build Boost.Python
next page( http://boost.org/libs/python/doc/building.html ) contains pretty
good explanation how to do this.

http://boost.org/libs/python/doc/v2/scope.html - here you will find example how
to expose my_int variable to Python. my_int has type int, so C++ code will not
see changes to the variable that are done from Python. You will have to write
set_my_int( x ) function to achieve this.

If you are new to Boost.Python try to use Py++ - the code generator for
the library. The Py++ GUI( http://tinyurl.com/ycwvwo ) will help you
to start\learn Boost.Python.
 
O

Osiris

iostream and namespaces are both most definitely C++ features, not C.
Click to expand...

yes, but C can be compiled with a C++ compiler, One can put C code in
C++ source.... Boost should not complain... should it ?
Boost text is all about C++.. so... C should not be a problem...
 
E

Erik Max Francis

Osiris said:
yes, but C can be compiled with a C++ compiler, One can put C code in
C++ source.... Boost should not complain... should it ?
Boost text is all about C++.. so... C should not be a problem...
Click to expand...

That you're dealing with a `boost` namespace below clearly indicates
that you're dealing with C++ code throughout, not C, contrary to what
you had claimed. C and C++ are not the same language.
 
C

Christophe Cavalaria

Osiris said:
yes, but C can be compiled with a C++ compiler, One can put C code in
C++ source.... Boost should not complain... should it ?
Boost text is all about C++.. so... C should not be a problem...
Click to expand...

Not all C code can be compiled by a C++ compiler. And anyway, this is
definitively NOT C code.
 
O

Osiris

Not all C code can be compiled by a C++ compiler. And anyway, this is
definitively NOT C code.
Click to expand...

ok ok,
but the examples of the application of boost only show how to do C++.
So I followed those examples and try to embed my C code in the
framework of the examples...
Which seems not to be without merit, because my example here compiles
ok, but the linking into a DLL goes wrong, looking at the log.
I told VC where the boost libs are, and still....
 
O

Osiris

It is better to ask Boost.Python related questions on it mailing list:
http://mail.python.org/mailman/listinfo/c++-sig/

You should add to the link line boost_python.lib, thus you will eliminate
"unresolved reference symbol" errors. If you did not build Boost.Python
next page( http://boost.org/libs/python/doc/building.html ) contains pretty
good explanation how to do this.
Click to expand...

That explanation I find confusing:
"To build boost_python, use Boost.Build...": Where is boost.build and
what is it ?
in my D:\boost\libs\python\build there is no boost.build...

in D:\boost there is a build-boost.jam file.... Is that it ?

I have a D:\boost\libs\python\build\bin-stage\boost_python.dll (204kB
size) and a D:\boost\libs\python\build\bin-stage\boost_build.lib (163
KB)
I made them with Visual Studio...


I made a bjam, it is in C:\

In D:\boost\libs\python\build there are a bin_stage and a
VisualStudio folder , the files
jamfile
jamfile.v2
python_v1.zip

Is it so, that I can build the boost_python.dll and lib, either with
bjam OR with VisualStudio C++ ?

Why are all those other folders there in d:\boost ? people,
regression, tools, status etc ?

What do I do with d:\boost\boost ? a lot of headers there...

what are all these folders in d:\boost\libs\ ?

In short: it's all rather confusing....

I think it must be like this:

To use my C/C++ code with Python, add some stuff in the C/C++ source
and compile it into a DLL, that must be combined with some boost-DLL
to make it accessible to Python 2.4.
Therefore I need a boost DLL from boost.org, and some headerfiles that
belong to the boost DLL.
(where are those boost header files )

As you see, a lot of obfuscation....
MAybe I see too many bears on the road...
 
R

Roman Yakovenko

In short: it's all rather confusing....

I think it must be like this:

To use my C/C++ code with Python, add some stuff in the C/C++ source
and compile it into a DLL, that must be combined with some boost-DLL
to make it accessible to Python 2.4.
Therefore I need a boost DLL from boost.org, and some headerfiles that
belong to the boost DLL.
(where are those boost header files )

As you see, a lot of obfuscation....
MAybe I see too many bears on the road...
Click to expand...

Boost project is an open source, consider to contribute your
experience, knowledge
and time to make it better.

You can download pre-built binaries for Windows platform from here:
http://www.boost-consulting.com/download.html
 

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