Force f2py to discover libgfortran path

f2py_libgfortran_hack.py

# the folloing gfortran hacks are to work around a treacherous bug when
# using anaconda + f2py (numpy) + a local gfortran on MacOS / Linux...
# in short, anaconda ships its own libgfortran to make numpy / scipy
# work, but this will conflict with some gfortran compilers...
# AND numpy assumes that `gfortran -print-libgcc-file-name` will give the
# path to libgfortran (it practice it doesn't on Debian / MacPorts)... SO
# we let numpy discover the path to libgfortran using
# `gfortran -print-file-name=libgfortran.so` (or dylib) because that will
# give us the correct link path, and fortran code that we compile with f2py
# will be correctly linked to the lib supplied by OUR compiler
if sys.platform[:5] == 'linux' or sys.platform == 'darwin':
    from numpy.distutils.fcompiler import gnu as _gnu
    from numpy.distutils import fcompiler as _fcompiler

    def _get_libgfortran_dir(compiler_args):
        if sys.platform[:5] == 'linux':
            libgfortran_name = 'libgfortran.so'
        elif sys.platform == 'darwin':
            libgfortran_name = 'libgfortran.dylib'
        else:
            libgfortran_name = None

        libgfortran_dir = None
        if libgfortran_name:
            find_lib_arg = ['-print-file-name={0}'.format(libgfortran_name)]
            status, output = exec_command(compiler_args + find_lib_arg,
                                          use_tee=0)
            if not status:
                libgfortran_dir = os.path.dirname(output)
        return libgfortran_dir

    class GnuFCompilerHack(_gnu.GnuFCompiler):
        def get_library_dirs(self):
            try:
                opt = super(GnuFCompilerHack, self).get_library_dirs()
            except TypeError:
                # old distutils use old-style classes
                opt = _gnu.GnuFCompiler.get_library_dirs(self)
            if sys.platform[:5] == 'linux' or sys.platform == 'darwin':
                libgfortran_dir = _get_libgfortran_dir(self.compiler_f77)
                if libgfortran_dir:
                    opt.append(libgfortran_dir)
            return opt

    class Gnu95FCompilerHack(_gnu.Gnu95FCompiler):
        def get_library_dirs(self):
            try:
                opt = super(Gnu95FCompilerHack, self).get_library_dirs()
            except TypeError:
                # old distutils use old-style classes
                opt = _gnu.Gnu95FCompiler.get_library_dirs(self)
            if sys.platform[:5] == 'linux' or sys.platform == 'darwin':
                libgfortran_dir = _get_libgfortran_dir(self.compiler_f77)
                if libgfortran_dir:
                    opt.append(libgfortran_dir)
                return opt

    _fcompiler.load_all_fcompiler_classes()
    _fcompiler.fcompiler_class['gnu'] = ('gnu', GnuFCompilerHack,
                                         'GNU Fortran 77 compile Hack')
    _fcompiler.fcompiler_class['gnu95'] = ('gnu', Gnu95FCompilerHack,
                                           'GNU Fortran 95 compile Hack')