[Cython] [Fwd: [cython-users] Conditional compilation of Cython code / preprocessor / external conditions]

[Yury V. Zaytsev]

Hi,

After a bit more research, I found two options that I initially
overlooked:

1) (Apparently undocumented) provisions to provide external attributes
in cython_compile_time_env

2) Generation of the PXI file from the external build system

I don't like (2) very much, so I've got an idea to extend (1) with the
ability to pass -D options to cython compiler, like:

    cython -DHAVE_LIBFOO=1

Will any such pull request be accepted?

-- 
Sincerely yours,
Yury V. Zaytsev


-------- Forwarded Message --------
From: Yury V. Zaytsev <yury at shurup.com>
Reply-to: cython-users at googlegroups.com
To: cython-users at googlegroups.com
Subject: [cython-users] Conditional compilation of Cython code /
preprocessor / external conditions
Date: Mon, 22 Jul 2013 16:17:58 +0200

Hi folks,

Is it possible to conditionally compile Cython code depending on some
externally defined value? 

>From reading the documentation, I've got an impression that presently
Cython doesn't have any kind of preprocessor, and I hope that I'm just
missing something here:

http://docs.cython.org/src/userguide/language_basics.html

My use case is as follows:

The application that I'm wrapping links against a number of libraries,
and some might be unavailable at compile time, so the corresponding
parts of the Cython code shouldn't be compiled either.

During the build, a preprocessor constant is defined, such as
HAVE_LIBFOO that I can get by including config.h or pass via the
autotools build system to the external tools. However, I can't figure
out how to use that from Cython...

So far, I was able to come up with an idea of replicating the API of the
missing libraries with dummies on the C++ level, such that the Cython
code compiles either way.

Or else, I can make a poor man's preprocessor based on sed and just
strip parts marked for conditional compilation from the PYX files.

Both solutions look really disgusting and unmaintainable. I would
greatly appreciate better ideas! To me it sounds like a rather common
problem, so somebody must have come up with a solution already...

Thanks,

-- 
Sincerely yours,
Yury V. Zaytsev



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