cmake python detection gets confused if multiple python versions are installed

[Marcus von Appen]

>Submitter-Id:	current-users
>Originator:	Marcus von Appen
>Organization:	
>Confidential:	no 
>Synopsis:	cmake python detection gets confused if multiple python versions are installed
>Severity:	non-critical
>Priority:	medium
>Category:	ports
>Class:		sw-bug
>Release:	FreeBSD 9.0-STABLE amd64
>Environment:
System: FreeBSD medusa.sysfault.org 9.0-STABLE FreeBSD 9.0-STABLE #0: Mon May 14 15:08:44 CEST 2012 root at medusa.sysfault.org:/usr/obj/usr/src/sys/MEDUSA amd64


	
>Description:
        If multiple Python versions are installed, cmake's
        find_host_package(PythonInterp) and
        find_host_package(PythonLibs) statements may return different
        Python versions, causing cmake to try to detect and link
        against the wrong Python default version

>How-To-Repeat:

        Install lang/python27, lang/python31, lang/python
        Try to configure and build graphics/py-opencv:

        [...]
root at medusa:/usr/ports/graphics/py-opencv # make configure
===>  License BSD accepted by the user
===>  Extracting for py27-opencv-2.3.1_3
=> SHA256 Checksum OK for OpenCV-2.3.1a.tar.bz2.
===>  Patching for py27-opencv-2.3.1_3
===>  Applying extra patch /usr/ports/graphics/py-opencv/../opencv/files/extra-patch-opencv-python
===>  Applying FreeBSD patches for py27-opencv-2.3.1_3
===>   py27-opencv-2.3.1_3 depends on file: /usr/local/lib/python2.7/site-packages/numpy/core/numeric.py - found
===>   py27-opencv-2.3.1_3 depends on file: /usr/local/bin/python2.7 - found
===>   py27-opencv-2.3.1_3 depends on executable: pkg-config - found
===>   py27-opencv-2.3.1_3 depends on file: /usr/local/bin/cmake - found
===>   py27-opencv-2.3.1_3 depends on shared library: opencv_legacy.2 - found
===>  Configuring for py27-opencv-2.3.1_3
[...]
-- Looking for pthread.h - found
-- Found PythonInterp: /usr/local/bin/python (found version "2.7.3")
-- Found PythonLibs: /usr/local/lib/libpython3.1.so (found version "3.1.5")
--     Use NumPy headers from: /usr/local/lib/python2.7/site-packages/numpy/core/include
--     Found Sphinx 1.1.2: /usr/local/bin/sphinx-build
-- Parsing 'cvconfig.h.cmake'


>Fix:
        I'm not entirely sure, if that should be fixed in the related
        cmake files

        /usr/local/share/cmake/Modules/FindPythonInterp.cmake
        /usr/local/share/cmake/Modules/FindPythonLibs.cmake

        by adjusting the search/find order or go into the relevant Mk
        files. Below is a patch for bsd.python.mk, which explicitly sets
        the Python version to be used in bsd.python.mk, based on the
        detected PYTHON_VER.

Index: Mk/bsd.python.mk
===================================================================
RCS file: /home/pcvs/ports/Mk/bsd.python.mk,v
retrieving revision 1.143
diff -u -r1.143 bsd.python.mk
--- Mk/bsd.python.mk	11 Apr 2012 12:52:16 -0000	1.143
+++ Mk/bsd.python.mk	20 May 2012 08:31:02 -0000
@@ -674,6 +674,11 @@

 .endif # defined(USE_TWISTED)

+.if defined(USE_CMAKE)
+CMAKE_ARGS+=	-DPythonLibs_FIND_VERSION:STRING="${PYTHON_VER}" \
+		-DPythonInterp_FIND_VERSIN:STRING="${PYTHON_VER}"
+.endif
+
 # XXX Hm, should I export some of the variables above to *_ENV?

 .endif		# !defined(_POSTMKINCLUDED) &&
 !defined(Python_Pre_Include)