[sage-devel] Help with simple C++/Cython Example

Hi,

I was trying to get the C++ cython example described in the docs (http://docs.cython.org/src/userguide/wrapping_CPlusPlus.html) to build in Sage 4.8, but I'm getting some errors I don't understand.  I created a separate development branch called "sage-c_extensions", added extension lines 

    Extension('sage.quadratic_forms.rectangle',

              sources = ['sage/quadratic_forms/rectangle/rectangle.pyx',

                         'sage/quadratic_forms/rectangle/Rectangle.cpp'],

              language = "c++"),

in the file sage-c_extensions/sage/module_list.py, copied the Rectangle.h and Rectangle.cpp files from the tutorial into a new folder sage-c_extensions/sage/quadratic_forms/rectangle/, and created a rectangle.pyx file in that folder with contents

cdef extern from "Rectangle.h" namespace "shapes":

    cdef cppclass Rectangle:

        Rectangle(int, int, int, int)

        int x0, y0, x1, y1

        int getLength()

        int getHeight()

        int getArea()

        void move(int, int)

cdef class PyRectangle:

    cdef Rectangle *thisptr      # hold a C++ instance which we're wrapping

    def __cinit__(self, int x0, int y0, int x1, int y1):

        self.thisptr = new Rectangle(x0, y0, x1, y1)

    def __dealloc__(self):

        del self.thisptr

    def getLength(self):

        return self.thisptr.getLength()

    def getHeight(self):

        return self.thisptr.getHeight()

    def getArea(self):

        return self.thisptr.getArea()

    def move(self, dx, dy):

        self.thisptr.move(dx, dy)

When I run "./sage -br c_extensions" I get the error message 

Updating Cython code....

Building modified file sage/quadratic_forms/rectangle/rectangle.pyx.

Executing 1 command (using 1 thread)

python `which cython` --cplus --old-style-globals --disable-function-redefinition --embed-positions --directive cdivision=True,autotestdict=False,fast_getattr=True -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/devel/sage-c_extensions -o sage/quadratic_forms/rectangle/rectangle.cpp sage/quadratic_forms/rectangle/rectangle.pyx

sage/quadratic_forms/rectangle/rectangle.pyx --> /Users/jonhanke/Dropbox/SAGE/sage-4.8/local/lib/python2.6/site-packages//sage/quadratic_forms/rectangle/rectangle.pyx

Time to execute 1 command: 16.2038929462 seconds

Finished compiling Cython code (time = 31.5890960693 seconds)

running install

running build

running build_py

running build_ext

building 'sage.quadratic_forms.rectangle' extension

Executing 1 command (using 1 thread)

gcc -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/include -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/include/csage -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/devel/sage/sage/ext -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/include/python2.6 -c sage/quadratic_forms/rectangle/rectangle.cpp -o build/temp.macosx-10.6-i386-2.6/sage/quadratic_forms/rectangle/rectangle.o -w

cc1plus: warning: command line option "-Wstrict-prototypes" is valid for C/ObjC but not for C++

gcc -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/include -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/include/csage -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/devel/sage/sage/ext -I/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/include/python2.6 -c sage/quadratic_forms/rectangle/Rectangle.cpp -o build/temp.macosx-10.6-i386-2.6/sage/quadratic_forms/rectangle/Rectangle.o -w

cc1plus: warning: command line option "-Wstrict-prototypes" is valid for C/ObjC but not for C++

g++ -L/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/lib -bundle -undefined dynamic_lookup build/temp.macosx-10.6-i386-2.6/sage/quadratic_forms/rectangle/rectangle.o build/temp.macosx-10.6-i386-2.6/sage/quadratic_forms/rectangle/Rectangle.o -L/Users/jonhanke/Dropbox/SAGE/sage-4.8/local/lib -lcsage -lstdc++ -lntl -o build/lib.macosx-10.6-i386-2.6/sage/quadratic_forms/rectangle.so

ld: duplicate symbol _initrectangle in build/temp.macosx-10.6-i386-2.6/sage/quadratic_forms/rectangle/Rectangle.o and build/temp.macosx-10.6-i386-2.6/sage/quadratic_forms/rectangle/rectangle.o

collect2: ld returned 1 exit status

error: command 'g++' failed with exit status 1

sage: There was an error installing modified sage library code.

Any comments are appreciated.  Also, it seems that Cython converts the Rectangle.cpp file to a "cythoned" file rectangle.cpp, deleting the original file in the process.  Is this normal/ok?

Thanks,

-Jon

 =)

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