I'm trying to get std::vector<std::size_t>
to work with SWIG. I need to provide a python interface to a c++ library. std::vector
s of primitive types and objects are working fine but there is a problem with std::size_t
.
I provide a MCVE on github here.
Basically the problem is that std::size_t
is not recognized and std::vector<std::size_t>
is treated as std::vector< int,std::allocator< int > > *
. When I try to specify the template, I get the following.
Using %template(VecSize) std::vector<std::size_t>;
gives:
swig -c++ -python c_swig_vec_std_size.i
:0: Warning(490): Fragment 'SWIG_AsVal_std_size_t' not found.
:0: Warning(490): Fragment 'SWIG_From_std_size_t' not found.
g++ -fpic -c c_swig_vec_std_size_wrap.cxx -I/public/users/paul/dev/software/Python-2.7.11/Include -I/public/users/paul/dev/software/Python-2.7.11
c_swig_vec_std_size_wrap.cxx: In static member function ‘static int swig::traits_asval<long unsigned int>::asval(PyObject*, swig::traits_asval::value_type*)’:
c_swig_vec_std_size_wrap.cxx:4289: error: ‘SWIG_AsVal_std_size_t’ was not declared in this scope
c_swig_vec_std_size_wrap.cxx: In static member function ‘static PyObject* swig::traits_from<long unsigned int>::from(const swig::traits_from::value_type&)’:
c_swig_vec_std_size_wrap.cxx:4295: error: ‘SWIG_From_std_size_t’ was not declared in this scope
make: *** [c] Error 1
The following class is enough to show the functionality that I need. The std::vector<int>
is included to show the intended behavior.
class_vec_std_size.hpp
#ifndef STD_SIZE_VEC
#define STD_SIZE_VEC
#include <vector>
class StdSizeVec{
public:
StdSizeVec(){
_myVec = std::vector<std::size_t>();
_myVec.push_back(1);
_myVec.push_back(2);
_myInts = std::vector<int>();
_myInts.push_back(1);
_myInts.push_back(2);
}
~StdSizeVec(){
_myVec.clear();
}
inline std::vector<std::size_t> getValues(){
return _myVec;
}
inline std::vector<int> getInts(){
return _myInts;
}
private:
std::vector<std::size_t> _myVec;
std::vector<int> _myInts;
};
#endif
%module a_swig_vec_std_size
%{
#include "class_vec_std_size.hpp"
%}
%include "class_vec_std_size.hpp"
Output
[paul@login-0-0 stack_swig]$ python
Python 2.7.11 (default, May 7 2016, 23:37:19)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-16)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from a_swig_vec_std_size import StdSizeVec
>>> ssv = StdSizeVec()
>>> vals = ssv.getValues()
>>> vals
<Swig Object of type 'std::vector< std::size_t > *' at 0x2ad7047be330>
>>> ints = ssv.getInts()
>>> ints
<Swig Object of type 'std::vector< int > *' at 0x2ad7047be780>
>>> exit()
swig/python detected a memory leak of type 'std::vector< int > *', no destructor found.
swig/python detected a memory leak of type 'std::vector< std::size_t > *', no destructor found.
[paul@login-0-0 stack_swig]$
This is the basic naive approach. The pointers are not useful in python and there are memory leak messages that we can not expose to the users of the interface.
%module b_swig_vec_std_size
%{
#include "class_vec_std_size.hpp"
%}
%include "std_vector.i"
%include "class_vec_std_size.hpp"
Output
[paul@login-0-0 stack_swig]$ python
Python 2.7.11 (default, May 7 2016, 23:37:19)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-16)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from b_swig_vec_std_size import StdSizeVec
>>> ssv = StdSizeVec()
>>> vals = ssv.getValues()
>>> vals
<Swig Object of type 'std::vector< std::size_t,std::allocator< std::size_t > > *' at 0x2aee17458330>
>>> ints = ssv.getInts()
>>> ints
<Swig Object of type 'std::vector< int,std::allocator< int > > *' at 0x2aee17458930>
>>> exit()
swig/python detected a memory leak of type 'std::vector< int,std::allocator< int > > *', no destructor found.
swig/python detected a memory leak of type 'std::vector< std::size_t,std::allocator< std::size_t > > *', no destructor found.
Using the correct "std_vector.i", SWIG knows more about the vector and allocators but still these pointers are not useful to client code in python and there are memory leak error messages.
This interface uses the correct %template
directives like this answer. Here SWIG does not understand std::size_t
as a template argument.
%module c_swig_vec_std_size
%{
#include "class_vec_std_size.hpp"
%}
%include "std_vector.i"
%template(VecInt) std::vector<int>;
// Does not compile
//%template(VecSize) std::vector<std::size_t>;
//
// Gives the following errors
//swig -c++ -python c_swig_vec_std_size.i
// :0: Warning(490): Fragment 'SWIG_AsVal_std_size_t' not found.
// :0: Warning(490): Fragment 'SWIG_From_std_size_t' not found.
// g++ -fpic -c c_swig_vec_std_size_wrap.cxx -I/public/users/paul/dev/software/Python-2.7.11/Include -I/public/users/paul/dev/software/Python-2.7.11
// c_swig_vec_std_size_wrap.cxx: In static member function ‘static int swig::traits_asval<long unsigned int>::asval(PyObject*, swig::traits_asval::value_type*)’:
// c_swig_vec_std_size_wrap.cxx:4289: error: ‘SWIG_AsVal_std_size_t’ was not declared in this scope
// c_swig_vec_std_size_wrap.cxx: In static member function ‘static PyObject* swig::traits_from<long unsigned int>::from(const swig::traits_from::value_type&)’:
// c_swig_vec_std_size_wrap.cxx:4295: error: ‘SWIG_From_std_size_t’ was not declared in this scope
// make: *** [c] Error 1
//The following compiles but does not work
%template(VecSize) std::vector<size_t>;
%include "class_vec_std_size.hpp"
Output
[paul@login-0-0 stack_swig]$ python
Python 2.7.11 (default, May 7 2016, 23:37:19)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-16)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from c_swig_vec_std_size import StdSizeVec
>>> ssv = StdSizeVec()
>>> vals = ssv.getValues()
>>> vals
<Swig Object of type 'std::vector< std::size_t,std::allocator< std::size_t > > *' at 0x2b286104bd80>
>>> ints = ssv.getInts()
>>> ints
(1, 2)
>>> exit()
swig/python detected a memory leak of type 'std::vector< std::size_t,std::allocator< std::size_t > > *', no destructor found.
Now the std::vector<int>
is working properly but SWIG's %template(VecSize) std::vector<size_t>;
(without std::
) does not do the job.
I found a few posts which offer some clues.
Feeling like this I found a 2006 post with the same problem
The std::vector::size_type wrapped as a pointer not an integer link had some helpful info but the problem is not exactly the same.
I found this primitives.i from the magnum.fe project, but thinking wishfully and importing primitives.i did not work for me.
After that I tried to implement the SWIG_AsVal_std_size_t
and SWIG_From_std_size_t
similar to their approach, but no luck.
%fragment("SWIG_From_std_size_t", "header", fragment=SWIG_From_frag(std::size_t))
{
SWIGINTERNINLINE PyObject * SWIG_From_std_size_t(std::size_t value)
{
return PyInt_FromSize_t(value);
}
}
%fragment("SWIG_AsVal_std_size_t", "header")
{
SWIGINTERNINLINE bool SWIG_AsVal_std_size_t(PyObject* in, std::size_t& value)
{
// Get integer type
if(PyInt_Check(in)){
long unsigned int long_uint = PyLong_AsLong(in);
value = static_cast<std::size_t>(long_uint);
return true;
}else{
return false;
}
}
}
%fragment(SWIG_From_frag(std::size_t));
%fragment("SWIG_AsVal_std_size_t");
This was imported in d_swig_vec_std_size.i. but it does not compile.
%module d_swig_vec_std_size
%{
#include "class_vec_std_size.hpp"
%}
%include "std_vector.i"
%template(VecInt) std::vector<int>;
%include "std_size_t.i"
%template(VecSize) std::vector<std::size_t>;
%include "class_vec_std_size.hpp"
Here I get this.
swig -c++ -python d_swig_vec_std_size.i
g++ -fpic -c d_swig_vec_std_size_wrap.cxx -I/public/users/paul/dev/software/Python-2.7.11/Include -I/public/users/paul/dev/software/Python-2.7.11
d_swig_vec_std_size_wrap.cxx: In static member function ‘static int swig::traits_asval<long unsigned int>::asval(PyObject*, swig::traits_asval::value_type*)’:
d_swig_vec_std_size_wrap.cxx:4311: error: invalid initialization of reference of type ‘size_t&’ from expression of type ‘swig::traits_asval::value_type*’
d_swig_vec_std_size_wrap.cxx:4288: error: in passing argument 2 of ‘bool SWIG_AsVal_std_size_t(PyObject*, size_t&)’
make: *** [d] Error 1
PYTHON=/public/users/paul/dev/software/Python-2.7.11
all: a b c d
a:
swig -c++ -python a_swig_vec_std_size.i
g++ -fpic -c a_swig_vec_std_size_wrap.cxx -I${PYTHON}/Include -I${PYTHON}
g++ -g -fpic -shared a_swig_vec_std_size_wrap.o -o _a_swig_vec_std_size.so
b:
swig -c++ -python b_swig_vec_std_size.i
g++ -fpic -c b_swig_vec_std_size_wrap.cxx -I${PYTHON}/Include -I${PYTHON}
g++ -g -fpic -shared b_swig_vec_std_size_wrap.o -o _b_swig_vec_std_size.so
c:
swig -c++ -python c_swig_vec_std_size.i
g++ -fpic -c c_swig_vec_std_size_wrap.cxx -I${PYTHON}/Include -I${PYTHON}
g++ -g -fpic -shared c_swig_vec_std_size_wrap.o -o _c_swig_vec_std_size.so
d:
swig -c++ -python d_swig_vec_std_size.i
g++ -fpic -c d_swig_vec_std_size_wrap.cxx -I${PYTHON}/Include -I${PYTHON}
g++ -g -fpic -shared d_swig_vec_std_size_wrap.o -o _d_swig_vec_std_size.so
clean: clean_a clean_b clean_c clean_d
clean_a:
rm a_swig_vec_std_size_wrap.cxx a_swig_vec_std_size.py a_swig_vec_std_size_wrap.o _a_swig_vec_std_size.so
clean_b:
rm b_swig_vec_std_size_wrap.cxx b_swig_vec_std_size.py b_swig_vec_std_size_wrap.o _b_swig_vec_std_size.so
clean_c:
rm c_swig_vec_std_size_wrap.cxx c_swig_vec_std_size.py c_swig_vec_std_size_wrap.o _c_swig_vec_std_size.so
clean_d:
rm d_swig_vec_std_size_wrap.cxx d_swig_vec_std_size.py d_swig_vec_std_size_wrap.o _d_swig_vec_std_size.so
python version: Python 2.7.11
g++ version: g++ (GCC) 4.4.7
swig version: SWIG Version 1.3.40
Using a newer swig version (swig-3.0.10) gives the same result for me.
I suspect the answer may be along the lines of interface d somewhere, but I have had no luck so far. There could be a problem with how std::size_t
is implemented differently depending on the architecture instead of having a fixed size. In any case, I would expect SWIG to be able to handle it. Am I missing something? I would like to find a solution that does not involve making changes to the C++ library (such as encapsulating std::size_t in a struct
or using int
instead).
namespace std {
%template(VecSize) vector<size_t>;
}
I get this:
[paul@login-0-0 stack_swig]$ make clean
rm a_swig_vec_std_size_wrap.cxx a_swig_vec_std_size.py a_swig_vec_std_size_wrap.o _a_swig_vec_std_size.so
rm b_swig_vec_std_size_wrap.cxx b_swig_vec_std_size.py b_swig_vec_std_size_wrap.o _b_swig_vec_std_size.so
rm c_swig_vec_std_size_wrap.cxx c_swig_vec_std_size.py c_swig_vec_std_size_wrap.o _c_swig_vec_std_size.so
rm d_swig_vec_std_size_wrap.cxx d_swig_vec_std_size.py d_swig_vec_std_size_wrap.o _d_swig_vec_std_size.so
[paul@login-0-0 stack_swig]$ make
swig -c++ -python a_swig_vec_std_size.i
g++ -fpic -c a_swig_vec_std_size_wrap.cxx -I/public/users/paul/dev/software/Python-2.7.11/Include -I/public/users/paul/dev/software/Python-2.7.11
g++ -g -fpic -shared a_swig_vec_std_size_wrap.o -o _a_swig_vec_std_size.so
swig -c++ -python b_swig_vec_std_size.i
g++ -fpic -c b_swig_vec_std_size_wrap.cxx -I/public/users/paul/dev/software/Python-2.7.11/Include -I/public/users/paul/dev/software/Python-2.7.11
g++ -g -fpic -shared b_swig_vec_std_size_wrap.o -o _b_swig_vec_std_size.so
swig -c++ -python c_swig_vec_std_size.i
g++ -fpic -c c_swig_vec_std_size_wrap.cxx -I/public/users/paul/dev/software/Python-2.7.11/Include -I/public/users/paul/dev/software/Python-2.7.11
g++ -g -fpic -shared c_swig_vec_std_size_wrap.o -o _c_swig_vec_std_size.so
swig -c++ -python -I/public/users/paul/dev/software/swig-3.0.10 d_swig_vec_std_size.i
g++ -fpic -c d_swig_vec_std_size_wrap.cxx -I/public/users/paul/dev/software/Python-2.7.11/Include -I/public/users/paul/dev/software/Python-2.7.11
g++ -g -fpic -shared d_swig_vec_std_size_wrap.o -o _d_swig_vec_std_size.so
[paul@login-0-0 stack_swig]$ python
Python 2.7.11 (default, May 7 2016, 23:37:19)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-16)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from d_swig_vec_std_size import StdSizeVec
>>> ssv = StdSizeVec()
>>> vals = ssv.getValues()
>>> vals
<Swig Object of type 'std::vector< std::size_t,std::allocator< std::size_t > > *' at 0x2aba7dd8bd80>
>>> ints - ssv.getInts()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'ints' is not defined
>>> ints = ssv.getInts()
>>> ints
(1, 2)
>>> exit()
swig/python detected a memory leak of type 'std::vector< std::size_t,std::allocator< std::size_t > > *', no destructor found.
[paul@login-0-0 stack_swig]$ cat d_swig_vec_std_size.i
%module d_swig_vec_std_size
%{
#include "class_vec_std_size.hpp"
%}
%include "std_vector.i"
%template(VecInt) std::vector<int>;
%include "std_size_t.i"
namespace std {
%template(VecSize) vector<size_t>;
}
%include "class_vec_std_size.hpp"
Try defining size_t for swig as shown here - http://www.swig.org/Doc1.3/SWIG.html#SWIG_nn20
%inline %{
typedef long unsigned int size_t;
%}
namespace std {
%template(VecSize) vector<size_t>;
}
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