CMake PythonLibs: Incorrect detection from within python virtual environment about boolector

[mpreiner]

Thanks for bringing this up! I had similar issues with the cmake build for CVC4. I'll look up what I did back then to fix the issue and will also fix it for Boolector. I think that I went with option 1.

[mpreiner]

Ok I checked, option 1 is indeed already the case (FindPythonExtensions.cmake first calls PythonInterp and then PythonLibs). In CVC4 I explicitly checked that Python libs are the same version as the interpreter (https://github.com/CVC4/CVC4/blob/master/src/bindings/python/CMakeLists.txt#L6).

I've commited a fix on branch cmake-improvements (https://github.com/Boolector/boolector/tree/cmake-improvements). Can you check if this fixes your problem?

[marcogario]

In general, that is a good fix. For Travis CI this still does not work for two reasons:

1. python 3.7: The libpython is actually under /opt, and this does not seem to be in the search path of cmake. I am unsure how specific this is to Travis, and therefore I am currently working around it by copying the libpython in a location that is in the cmake search path (i.e., within the virtual environment).
2. python 2.7: The difference is in the release version, and this patch does not account for that:

-- Found PythonInterp: /home/travis/virtualenv/python2.7.15/bin/python (found version "2.7.15") 
-- Found PythonLibs: /usr/lib/x86_64-linux-gnu/libpython2.7.so (found suitable version "2.7.12", minimum required is "2.7")

I am now trying to copy the libpython within the virtualenv, to avoid this problem also for python 2.7. I will let you know if this works.

[mpreiner]

The release version is now also checked (pushed to master).

[mpreiner]

However, this now breaks the mac OS build, since the release version can't be found:

-- Found PythonInterp: /usr/local/bin/python (found version "2.7.15") 
CMake Error at /usr/local/Cellar/cmake/3.11.4/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:137 (message):
  Could NOT find PythonLibs: Found unsuitable version "2.7.10", but required
  is at least "2.7.15" (found /usr/lib/libpython2.7.dylib)

[mpreiner]

It works with Python3 on Travis osx. Seems to be a Python 2.7 configuration issue on Travis osx. @marcogario let me know if this issue is now resolved for you.

[marcogario]

We resolved (well, @mikand did) this in pysmt/pysmt#514 (see [1]) to patch the call to cmake and be explicit about the versions of python that we need.

The cases in which is needed seem to be very few, and mainly when there are multiple versions of python installed with minor mismatches. It might not be valuable to have a fix in boolector for this. In my opinion, this can be closed.

1. https://github.com/pysmt/pysmt/pull/514/files#diff-f1ce7e387e59207202a494f0e81c3d5cR60

[mikand]

@marcogario I agree that a complicated machinery to search python is unnecessary, but it would be useful to expose in the configure script a parameter to force (and possibly override) the cmake configuration. My patch practically rewrites the configure script to pass the correct python directory to cmake, and allowing this override directly as a parameter could be useful.

[marcogario]

This has been fixed in 4c578d4.
It is now possible to define CMAKE_OPTS prior to calling configure.sh to set additional flags in CMake. pySMT now uses this instead of hot-patching the configure.sh (See pysmt/pysmt#577.)