scons: Use python-config instead of distutils

This patch changes how we determine the Python-related compiler and
linker flags. The previous approach used the internal LINKFORSHARED
which is not intended as part of the external API
(http://bugs.python.org/issue3588) and causes failures on recent OSX
installations.

Instead of using distutils we now rely on python-config and scons
ParseConfig. For backwards compatibility we also parse out the
includes and libs although this could safely be dropped. The drawback
of this patch is that Python 2.5 is now required, but hopefully that
is an acceptable compromise as any system with gcc 4.4 most likely
will have Python >= 2.5.

SConstruct

@@ -1,5 +1,17 @@
 # -*- mode:python -*-
 
+# Copyright (c) 2013 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright (c) 2011 Advanced Micro Devices, Inc.
 # Copyright (c) 2009 The Hewlett-Packard Development Company
 # Copyright (c) 2004-2005 The Regents of The University of Michigan
@@ -81,16 +93,15 @@ For more details, see:
 """
     raise
 
-# We ensure the python version early because we have stuff that
+# We ensure the python version early because because python-config
-# requires python 2.4
+# requires python 2.5
 try:
-    EnsurePythonVersion(2, 4)
+    EnsurePythonVersion(2, 5)
 except SystemExit, e:
     print """
 You can use a non-default installation of the Python interpreter by
-either (1) rearranging your PATH so that scons finds the non-default
+rearranging your PATH so that scons finds the non-default 'python' and
-'python' first or (2) explicitly invoking an alternative interpreter
+'python-config' first.
-on the scons script.
 
 For more details, see:
     http://gem5.org/wiki/index.php/Using_a_non-default_Python_installation
@@ -827,55 +838,35 @@ if not conf:
 
     conf = NullConf(main)
 
-# Find Python include and library directories for embedding the
-# interpreter.  For consistency, we will use the same Python
-# installation used to run scons (and thus this script).  If you want
-# to link in an alternate version, see above for instructions on how
-# to invoke scons with a different copy of the Python interpreter.
-from distutils import sysconfig
-
-py_getvar = sysconfig.get_config_var
-
-py_debug = getattr(sys, 'pydebug', False)
-py_version = 'python' + py_getvar('VERSION') + (py_debug and "_d" or "")
-
-py_general_include = sysconfig.get_python_inc()
-py_platform_include = sysconfig.get_python_inc(plat_specific=True)
-py_includes = [ py_general_include ]
-if py_platform_include != py_general_include:
-    py_includes.append(py_platform_include)
-
-py_lib_path = [ py_getvar('LIBDIR') ]
-# add the prefix/lib/pythonX.Y/config dir, but only if there is no
-# shared library in prefix/lib/.
-if not py_getvar('Py_ENABLE_SHARED'):
-    py_lib_path.append(py_getvar('LIBPL'))
-    # Python requires the flags in LINKFORSHARED to be added the
-    # linker flags when linking with a statically with Python. Failing
-    # to do so can lead to errors from the Python's dynamic module
-    # loader at start up.
-    main.Append(LINKFLAGS=[py_getvar('LINKFORSHARED').split()])
-
-py_libs = []
-for lib in py_getvar('LIBS').split() + py_getvar('SYSLIBS').split():
-    if not lib.startswith('-l'):
-        # Python requires some special flags to link (e.g. -framework
-        # common on OS X systems), assume appending preserves order
-        main.Append(LINKFLAGS=[lib])
-    else:
-        lib = lib[2:]
-        if lib not in py_libs:
-            py_libs.append(lib)
-py_libs.append(py_version)
-
-main.Append(CPPPATH=py_includes)
-main.Append(LIBPATH=py_lib_path)
-
 # Cache build files in the supplied directory.
 if main['M5_BUILD_CACHE']:
     print 'Using build cache located at', main['M5_BUILD_CACHE']
     CacheDir(main['M5_BUILD_CACHE'])
 
+# Find Python include and library directories for embedding the
+# interpreter. We rely on python-config to resolve the appropriate
+# includes and linker flags. ParseConfig does not seem to understand
+# the more exotic linker flags such as -Xlinker and -export-dynamic so
+# we add them explicitly below. If you want to link in an alternate
+# version of python, see above for instructions on how to invoke
+# scons with the appropriate PATH set.
+py_includes = readCommand(['python-config', '--includes'],
+                          exception='').split()
+# Strip the -I from the include folders before adding them to the
+# CPPPATH
+main.Append(CPPPATH=map(lambda inc: inc[2:], py_includes))
+
+# Read the linker flags and split them into libraries and other link
+# flags. The libraries are added later through the call the CheckLib.
+py_ld_flags = readCommand(['python-config', '--ldflags'], exception='').split()
+py_libs = []
+for lib in py_ld_flags:
+     if not lib.startswith('-l'):
+         main.Append(LINKFLAGS=[lib])
+     else:
+         lib = lib[2:]
+         if lib not in py_libs:
+             py_libs.append(lib)
 
 # verify that this stuff works
 if not conf.CheckHeader('Python.h', '<>'):