python - Cython ImportError: ./h_f.so: undefined symbol: _ZN9haystack27featureD1Ev caused by Operation only allowed in c++ error from new feature() -

i have read relevant posts on site whole day. seems general error caused different reasons. still post question here. comments appreciated!!!

i trying wrap c++ code 1 h_feature.h , 1 h_feature.cpp file 1 h_f.pyx file. below h_f.pyx file:

from libcpp cimport bool cdef extern "h_feature.h" namespace "h2":      cdef cppclass feature:         feature() except +         feature(char* modeldir, bool) except +         bool load_feature_extractor(char* modeldir, bool)       cdef cppclass image:     # struct in .h file, write class in pyx file here         pass   cdef class pyimage:     cdef image* image  cdef class pyfeature:     cdef feature* c_feature     def __cinit__(self, bytes modeldir, bint usegpu = 0):         self.c_feature = new feature(modeldir, usegpu)     def pyload_feature_extractor(self, bytes modeldir, bint usegpu = 0):         return self.c_feature.load_feature_extractor(modeldir, usegpu)     def __dealloc__(self):         del self.c_feature 

below setup.py:

    distutils.core import setup, extension     cython.build import cythonize      compile_args = ['-g', '-std=c++11']     setup(ext_modules = cythonize(extension(        "h_f",                                # extension name        sources=["h_f.pyx", "h_feature.cpp"], # cython source ,        extra_compile_args=compile_args,                       language="c++",                        # generate , compile c++ code   ))) 

below warning during compile:

    x86_64-linux-gnu-gcc -pthread -fno-strict-aliasing -dndebug -g -     fwrapv -o2 -wall -wstrict-prototypes -fpic -i/usr/include/python2.7      -c h_feature.cpp -o build/temp.linux-x86_64-2.7/h_feature.o     cc1plus: warning: command line option '-wstrict-prototypes'      valid c/objc not c++ [enabled default]     in file included /usr/include/python2.7/python.h:121:0,              h_feature.cpp:21:     hashtag2.cpp: in function 'pyobject* newarrayobject(pytypeobject*,      py_ssize_t, arraydescr*)':     /usr/include/python2.7/pyerrors.h:220:74: warning: deprecated      conversion string constant 'char*' [-wwrite-strings]     #define pyerr_badinternalcall() _pyerr_badinternalcall(__file__, __line__)                                                                       ^     h_feature.cpp:959:9: note: in expansion of macro      'pyerr_badinternalcall'      pyerr_badinternalcall();      ^     x86_64-linux-gnu-gcc -pthread -fno-strict-aliasing -dndebug -g -     fwrapv -o2 -wall -wstrict-prototypes -fpic -i/usr/include/python2.7      -c h_feature.cpp -o build/temp.linux-x86_64-     2.7/h_feature.o     cc1plus: warning: command line option '-wstrict-prototypes'      valid c/objc not c++ [enabled default]     in file included /usr/include/python2.7/python.h:121:0,              h_feature.cpp:21:     h_feature.cpp: in function 'pyobject*      newarrayobject(pytypeobject*, py_ssize_t, arraydescr*)':     /usr/include/python2.7/pyerrors.h:220:74: warning: deprecated      conversion string constant 'char*' [-wwrite-strings]     #define pyerr_badinternalcall() _pyerr_badinternalcall(__file__, __line__)                                                                       ^     h_feature.cpp:959:9: note: in expansion of macro      'pyerr_badinternalcall'      pyerr_badinternalcall();      ^     c++ -pthread -shared -wl,-o1 -wl,-bsymbolic-functions -wl,-     bsymbolic-functions -wl,-z,relro -fno-strict-aliasing -dndebug -g -     fwrapv -o2 -wall -wstrict-prototypes -d_fortify_source=2 -g -     fstack-protector --param=ssp-buffer-size=4 -wformat -werror=format-     security build/temp.linux-x86_64-2.7/hashtag2.o build/temp.linux-     x86_64-2.7/haystack2_feature.o -o      /root/h_feature/project/src/feature_wrapper/h_feature.so 

based on comment, add c_feature.h below:

namespace h2 {      typedef unsigned char pixel_type;       struct image;     class feature_impl;      class dllexport feature     {     public:      feature();     feature(const char* modeldir, bool usegpu = false);                    ~feature();      /*-------------------------------------------------------     method load feature extractor     input: modeldir           model directory (...model/)    */     bool load_feature_extractor(const char* modeldir, bool usegpu = false);    }     struct image {           image() { }           image(const image& i) : width(i.width), height(i.height), bytes_per_row(i.bytes_per_row), pixels(i.pixels) { }           image(pixel_type* p, int w, int h, int bpr) : width(w), height(h), bytes_per_row(bpr), pixels(p) { }            int width,height,bytes_per_row;           pixel_type* pixels;     };     } 

h_feature.cpp below:

namespace h2 {      typedef std::mutex mutex;      // use lock primitive acquire given mutex object's lifetime.      // mutex released when object destroyed, typically when goes    // out of scope.    class lock {       public:           lock(mutex& _m) : m(_m) { m.lock(); }           ~lock() { m.unlock(); }        private:           mutex& m;            // don't allow copying or null constructor           lock();                         // unimplemented           lock(const lock&);              // unimplemented           lock& operator=(const lock&);   // unimplemented     };      // now, use heavyweight mutex prevent concurrency issues in api.     // is, api calls must acquire mutex , hold entire call.    static mutex threadmutex;     class feature_impl   {     // base class feature. threadmutex used in class. ommitted implementation of class.    }     feature::feature() : fi(new feature_impl)   {      }     feature::feature(const char* modeldir, bool usegpu) : fi(new feature_impl)   {       fi->load_feat_extractor(modeldir, usegpu);   }    feature::~feature()   {     if(fi != null)  delete fi;   }    bool feature::load_feature_extractor(const char* modeldir, bool usegpu)   {       return fi->load_feat_extractor(std::string(modeldir), usegpu);   }     }; // namespace h2