[CMake] Temp workaround for FindPythonLibs on Win7 64-bit

[Jeremy Carter]

Hi,

It has been established that the FindPythonLibs module fails to find
64-bit Python on Win7 64-bit, due to the fact that CMake can't read
the 64-bit portion of the Windows Registry (and that's where the
module looks to find Python). See:
http://www.cmake.org/Bug/view.php?id=11303 .

I made a temporary fix that requires the Python libs folder to be in
the Windows Path. It hasn't been tested on platforms other than
Windows 7 64-bit, so I'm sorry if it breaks things, and it's the first
time I've posted on this list and also the first time I've patched
anything, anyway, here's the patch I'm using until there's an official
CMake fix:

# ---------- begin patch ----------

--- C:\Program Files (x86)\CMake
2.8\share\cmake-2.8\Modules\FindPythonLibs.cmake    2013-05-15
13:46:30 -0400
+++ FindPythonLibs.cmake    2013-05-31 12:50:10 -0400
@@ -31,6 +31,13 @@
 #=============================================================================
 # (To distribute this file outside of CMake, substitute the full
 #  License text for the above reference.)
+#=============================================================================
+# This is a modified version of FindPythonLibs.cmake, hacked to support
+# finding Python 64-bit on Windows 7 64-bit. It requires the Python libs
+# directory to be in the Windows Path, since CMake is unable to read the
+# 64-bit Windows Registry.
+#
+# Modified by Jeremy Carter (jeremy [at] jeremycarter [dot] ca) on 2013-05-31.

 include(${CMAKE_CURRENT_LIST_DIR}/CMakeFindFrameworks.cmake)
 # Search for the python framework on Apple.
@@ -81,6 +88,11 @@

 foreach(_CURRENT_VERSION ${_Python_VERSIONS})
   string(REPLACE "." "" _CURRENT_VERSION_NO_DOTS ${_CURRENT_VERSION})
+
+  # Registry lookup doesn't work on Windows 7 64-bit with 64-bit Python.
+  # Find Python in Windows Path instead.
+  set(WINDOWS_PATH $ENV{Path})
+
   if(WIN32)
     find_library(PYTHON_DEBUG_LIBRARY
       NAMES python${_CURRENT_VERSION_NO_DOTS}_d python
@@ -89,6 +101,7 @@
       [HKEY_CURRENT_USER\\SOFTWARE\\Python\\PythonCore\\${_CURRENT_VERSION}\\InstallPath]/libs/Debug
       [HKEY_LOCAL_MACHINE\\SOFTWARE\\Python\\PythonCore\\${_CURRENT_VERSION}\\InstallPath]/libs
       [HKEY_CURRENT_USER\\SOFTWARE\\Python\\PythonCore\\${_CURRENT_VERSION}\\InstallPath]/libs
+      ${WINDOWS_PATH} # Not tested. Added to look in Windows Path.
       )
   endif()

@@ -102,6 +115,7 @@
     PATHS
       [HKEY_LOCAL_MACHINE\\SOFTWARE\\Python\\PythonCore\\${_CURRENT_VERSION}\\InstallPath]/libs
       [HKEY_CURRENT_USER\\SOFTWARE\\Python\\PythonCore\\${_CURRENT_VERSION}\\InstallPath]/libs
+      ${WINDOWS_PATH} # Added to look in Windows Path.
     # Avoid finding the .dll in the PATH.  We want the .lib.
     NO_SYSTEM_ENVIRONMENT_PATH
   )
@@ -129,12 +143,16 @@
     endforeach()
   endif()

+  # Added this because find_path() wasn't finding Python include dir
from $ENV{Path} for some reason.
+  get_filename_component(WINDOWS_PYTHON_LIB_PATH ${PYTHON_LIBRARY} PATH)
+
   find_path(PYTHON_INCLUDE_DIR
     NAMES Python.h
     PATHS
       ${PYTHON_FRAMEWORK_INCLUDES}
       [HKEY_LOCAL_MACHINE\\SOFTWARE\\Python\\PythonCore\\${_CURRENT_VERSION}\\InstallPath]/include
       [HKEY_CURRENT_USER\\SOFTWARE\\Python\\PythonCore\\${_CURRENT_VERSION}\\InstallPath]/include
+      ${WINDOWS_PYTHON_LIB_PATH}/../include # The Python include
directory is probably here.
     PATH_SUFFIXES
       python${_CURRENT_VERSION}mu
       python${_CURRENT_VERSION}m

# ---------- end patch ----------

This might work in the short term, but CMake should probably be fixed
so that this hack isn't necessary. I'm also open to suggestions on how
this could be done better.

Regards,
Jeremy Carter