[Distutils] Question re extension modules.

[M.-A. Lemburg]

Titus Brown wrote:
> Hi again,
> 
> I'm developing a C++ library & associated extension module within the
> same directory.  My setup.py contains this line:
> 
> parser_mod = Extension("paircomp._paircomp_parser",
>                        ["c++-ext/_paircomp_parser.cc",],
>                        include_dirs=['../lib',],
>                        library_dirs=['../lib',],
>                        libraries=['paircomp', 'stdc++'])
> 
> One of the important libraries that I need to include is -lpaircomp,
> in '../lib/libpaircomp.a'.
> 
> Currently when I change libpaircomp.a (by, for example, making some
> internal change to the C++ library that's not reflected in the API)
> my Python extensions do not get recompiled by 'python setup.py build'.
> (This is run automatically by the Makefile.)

distutils doesn't do dependency tracking like make.

> So at the moment I either have to use Makefile trickery or just do an
> 'rm -fr build' to force recompilation of the extension when the library
> is changed.
> 
> Is there a canonical way to tell distutils that 'this extension depends
> on this file, so force rebuild if the file changes'?

No.

> One obvious possibility would be to simple compare last-changed dates
> on all of the libraries with last-changed dates on the .so file
> produced by setup.py.

distutils is a tool for packaging code, not a replacement
for development tools like make. You normally only run
distutils setup.py scripts after you've completed developing
your code.

make is a much better tool for dependency checking, so the
"right" way to handle the dependency problem is to add
proper targets to the Makefile.

-- 
Marc-Andre Lemburg
eGenix.com

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