I am trying to get std::vector<std::size_t> to work with SWIG. I need to provide a python interface for a C ++ library. std::vector primitive types and objects work fine, but there is a problem with std::size_t .
I provide MCVE on github here .
Main problem
The main problem is that std::size_t not recognized, and std::vector<std::size_t> considered as std::vector< int,std::allocator< int > > * . When I try to specify a pattern, 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
Minimal example
C ++ class example
The following class is enough to show the functions I need. std::vector<int> included to display 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
Various interface attempts
a_swig_vec_std_size.i
%module a_swig_vec_std_size %{ #include "class_vec_std_size.hpp" %} %include "class_vec_std_size.hpp"
Exit
[ 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 main naive approach. Pointers are not useful in python, and there are memory leak messages that we cannot provide to users of the interface.
b_swig_vec_std_size.i
%module b_swig_vec_std_size %{ #include "class_vec_std_size.hpp" %} %include "std_vector.i" %include "class_vec_std_size.hpp"
Exit
[ 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 these pointers are not useful for client code in python, and there are memory leak error messages.
c_swig_vec_std_size.i
This interface uses the correct %template directives, such as 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"
Exit
[ 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 std::vector<int> works correctly, but SWIG %template(VecSize) std::vector<size_t>; (without std:: does not do the job.
Some online digging
I found several posts that offer some tips.
Feeling like this. I found a 2006 post with the same problem.
std :: vector :: size_type, wrapped as a non-integer pointer , had some useful information, but the problem is not quite the same.
I found this primitives.i from magnum.fe project, but thought about desire and imported primitives.i does 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 with no luck.
hand painted std_size_t.i
%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 has been imported to 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 it.
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
Makefile
PYTHON=/public/users/paul/dev/software/Python-2.7.11 all: abcd 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
Software versions
python version: Python 2.7.11 g++ version: g++ (GCC) 4.4.7 swig version: SWIG Version 1.3.40
Using the new version of swig (swig-3.0.10) gives me the same result.
Summary
I suspect the answer may be near the d interface, but so far I have been out of luck. There may be a problem with how std::size_t is implemented differently depending on the architecture instead of a fixed size. In any case, I would expect SWIG to be able to handle this. Am I missing something? I would like to find a solution that does not involve making changes to the C ++ library (for example, encapsulating std :: size_t in a struct or using int ).
An attempt to solve the Jena monk
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 %{