ufc needs Python 2, but Python 3 may be found (with fix)

[Nico Schlömer]

Hi,

I tried to compile ufc on another machine today and got the error messages

============================== *snip* ==============================
[...]
[ 50%] Building CXX object CMakeFiles/_ufc.dir/src/ufc/ufcPYTHON_wrap.cxx.o
/usr/bin/c++ -D_ufc_EXPORTS -O3 -DNDEBUG -fPIC -I/homes/numerik/nschloe/Work/FEniCS/src/ufc/src/ufc -I/usr/include/python3.2mu -o CMakeFiles/_ufc.dir/src/ufc/ufcPYTHON_wrap.cxx.o -c /homes/numerik/nschloe/Work/FEniCS/src/ufc/dorsal_build_dir/src/ufc/ufcPYTHON_wrap.cxx
/homes/numerik/nschloe/Work/FEniCS/src/ufc/dorsal_build_dir/src/ufc/ufcPYTHON_wrap.cxx: In function ‘bool Py_convert_uint(PyObject*, std::size_t&)’:
/homes/numerik/nschloe/Work/FEniCS/src/ufc/dorsal_build_dir/src/ufc/ufcPYTHON_wrap.cxx:3288:46: error: ‘PyInt_AS_LONG’ was not declared in this scope
/homes/numerik/nschloe/Work/FEniCS/src/ufc/dorsal_build_dir/src/ufc/ufcPYTHON_wrap.cxx:3290:54: error: ‘PyInt_AS_LONG’ was not declared in this scope
============================== *snap* ==============================

This is because CMake spit out the Python3.2 include folder which doesn't have those symbols.
To make sure that Python 2 is found, add

set(PythonInterp_FIND_VERSION 2)

right before

find_package(PythonInterp QUIET)

in ufc's main CMakeLists.txt.

--Nico

[Nico Schlömer (nschloe)]

Also, if UFC_ENABLE_PYTHON, one requires PythonLibs. You may want to replace

# Find Python library corresponding to Python interpreter
find_package(PythonLibs ${PYTHON_VERSION_STRING} EXACT QUIET)

by

# Find Python library corresponding to Python interpreter
if (UFC_ENABLE_PYTHON)
  find_package(PythonLibs ${PYTHON_VERSION_STRING} EXACT QUIET REQUIRED)
else()
  find_package(PythonLibs ${PYTHON_VERSION_STRING} EXACT QUIET)
endif()

[Nico Schlömer (nschloe)]

Moreover, because of bug http://public.kitware.com/Bug/view.php?id=13216, UFC needs CMake 2.8.9 to work correctly. This should probably be reflected by cmake_minimum_required().