[Distutils] C++, swig, and distutils

[Vishnu Bob]

Hi,

I have a two comments about the usability of C++, swig, and distutils. 
I'm using python 2.4.2.

Comment 1:

First, build_ext.py:525 tests the list "swig_opts".  If the string
"-c++" is in the swig_opts list, build_ext.py will build the wrapper
with a ".cpp" extension instead of the default ".c"

        if self.swig_cpp or ('-c++' in self.swig_opts):
            target_ext = '.cpp'
        else:
            target_ext = '.c'

However, "swig_cpp" is a command level option, and it's impossible to
set via the Extension() arguments.  This gets a little weird, because of
build_ext.py:550:

        # Do not override commandline arguments
        if not self.swig_opts:
            for o in extension.swig_opts:
                swig_cmd.append(o)

This is below the "-c++" string test described above.  So, if you
specify "-c++" like this:

        Extension( 'package.module', ['src/module.i'],
swig_opts=['-c++'], language='c++' )

build_ext.py will include "-c++" into the swig command, but the output
file will /still/ have a ".c" extension.  In order to workaround this
without specifying a command line argument or building a setup.cfg file,
you have to specify an "options" keyword argument in the call to setup():

        options={'build_ext':{'swig_opts':'-c++'}}

Comment 2:

In spite of workaround described above, build_ext.py:464 compiles the
swig generated ".cpp" wrapper with "gcc".  Luckily, gcc sees the ".cpp"
extension and switches to g++, but that's totally sloppy.

I've tried to coax distutils to use its C++ swig strategies with three
different variables, and it's still assuming C.

thanks,
-g