Python 3.7 configuration issue

Robin Becker robin at
Wed Jul 4 06:11:48 EDT 2018

On 04/07/2018 05:59, dieter wrote:
> "libffi" contains the so called "foreign function interface"
> (an interface that allows code written in one language to call
> code written in another language). Likely, "ctypes" depends
> on it.
> Since some time, "ctypes" is part of Python's standard library.
> It is likely, that the Python test suite contains tests verifying
> that it could be build successfully.
> Your observations seem to indicate that "ctypes" contains its
> own "foreign function interface" specification and that this
> specification does not fit to the libraries available on your
> system. The "with-system-ffi" likely tells the Python generation
> process to use the system "foreign function interface" rather
> than its own.
I don't disagree with the above. I think the issue is that the configure process did not say anything about this. If ctypes is 
required and cannot be built then ./configure ...... should probably tell me; if that's not possible then the make step should do 
so and fail to complete. Failing at make install seems a bit late.

I have to admit that I no longer understand how python builds its extensions; there used to be a step where you configured 
Modules/Setup*, but that seems no longer required.

Any how as an experiment it seems that if I do have the libffi-dev package installed then the with-system-ffi flag is not required 
and the make install does work. It might be that make silently allows extension builds to fail even if they are 'required' and 
that later causes an error in the install phase.
Robin Becker

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