diff --git a/Lib/distutils/sysconfig.py b/Lib/distutils/sysconfig.py
index e86cb23..dac3035 100644
--- a/Lib/distutils/sysconfig.py
+++ b/Lib/distutils/sysconfig.py
@@ -162,7 +162,7 @@
             "I don't know where Python installs its library "
             "on platform '%s'" % os.name)
 
-_USE_CLANG = None
+
 
 def customize_compiler(compiler):
     """Do any platform-specific customization of a CCompiler instance.
@@ -177,36 +177,7 @@
 
         newcc = None
         if 'CC' in os.environ:
-            newcc = os.environ['CC']
-        elif sys.platform == 'darwin' and cc == 'gcc-4.2':
-            # Issue #13590:
-            #       Since Apple removed gcc-4.2 in Xcode 4.2, we can no
-            #       longer assume it is available for extension module builds.
-            #       If Python was built with gcc-4.2, check first to see if
-            #       it is available on this system; if not, try to use clang
-            #       instead unless the caller explicitly set CC.
-            global _USE_CLANG
-            if _USE_CLANG is None:
-                from distutils import log
-                from subprocess import Popen, PIPE
-                p = Popen("! type gcc-4.2 && type clang && exit 2",
-                                shell=True, stdout=PIPE, stderr=PIPE)
-                p.wait()
-                if p.returncode == 2:
-                    _USE_CLANG = True
-                    log.warn("gcc-4.2 not found, using clang instead")
-                else:
-                    _USE_CLANG = False
-            if _USE_CLANG:
-                newcc = 'clang'
-        if newcc:
-            # On OS X, if CC is overridden, use that as the default
-            #       command for LDSHARED as well
-            if (sys.platform == 'darwin'
-                    and 'LDSHARED' not in os.environ
-                    and ldshared.startswith(cc)):
-                ldshared = newcc + ldshared[len(cc):]
-            cc = newcc
+            cc = os.environ['CC']
         if 'CXX' in os.environ:
             cxx = os.environ['CXX']
         if 'LDSHARED' in os.environ:
@@ -522,6 +493,29 @@
     _config_vars = g
 
 
+def _read_output(commandstring):
+    """
+    Returns os.popen(commandstring, "r").read(), but
+    without actually using os.popen because that
+    function is not usable during python bootstrap
+    """
+    # NOTE: tempfile is also not useable during
+    # bootstrap
+    import contextlib
+    try:
+        import tempfile
+        fp = tempfile.NamedTemporaryFile()
+    except ImportError:
+        fp = open("/tmp/distutils.%s"%(
+            os.getpid(),), "w+b")
+
+    with contextlib.closing(fp) as fp:
+        cmd = "%s >'%s'"%(commandstring, fp.name)
+        os.system(cmd)
+        data = fp.read()
+
+    return data.decode('utf-8')
+
 def get_config_vars(*args):
     """With no arguments, return a dictionary of all configuration
     variables relevant for the current platform.  Generally this includes
@@ -561,9 +555,70 @@
                 _config_vars['srcdir'] = os.path.normpath(srcdir)
 
         if sys.platform == 'darwin':
+            from distutils.spawn import find_executable
+
             kernel_version = os.uname()[2] # Kernel version (8.4.3)
             major_version = int(kernel_version.split('.')[0])
 
+            # Issue #13590:
+            #    The OSX location for the compiler varies between OSX
+            #    (or rather Xcode) releases.  With older releases (up-to 10.5)
+            #    the compiler is in /usr/bin, with newer releases the compiler
+            #    can only be found inside Xcode.app if the "Command Line Tools"
+            #    are not installed.
+            #
+            #    Futhermore, the compiler that can be used varies between
+            #    Xcode releases. Upto Xcode 4 it was possible to use 'gcc-4.2'
+            #    as the compiler, after that 'clang' should be used because
+            #    gcc-4.2 is either not present, or a copy of 'llvm-gcc' that
+            #    miscompiles Python.
+
+            # skip checks if the compiler was overriden with a CC env variable
+            if 'CC' not in os.environ:
+                cc = oldcc = _config_vars['CC']
+                if not find_executable(cc):
+                    # Compiler is not found on the shell search PATH.
+                    # Now search for clang, first on PATH (if the Command LIne
+                    # Tools have been installed in / or if the user has provided
+                    # another location via CC).  If not found, try using xcrun
+                    # to find an uninstalled clang (within a selected Xcode).
+
+                    # NOTE: Cannot use subprocess here because of bootstrap
+                    # issues when building Python itself (and os.popen is
+                    # implemented on top of subprocess and is therefore not
+                    # usable as well)
+
+                    data = (find_executable('clang') or
+                            _read_output(
+                                "/usr/bin/xcrun -find clang 2>/dev/null").strip())
+                    if not data:
+                        raise DistutilsPlatformError(
+                               "Cannot locate working compiler")
+
+                    _config_vars['CC'] = cc = data
+                    _config_vars['CXX'] = cc + '++'
+
+                elif os.path.basename(cc).startswith('gcc'):
+                    # Compiler is GCC, check if it is LLVM-GCC
+                    data = _read_output("'%s' --version 2>/dev/null"
+                                         % (cc.replace("'", "'\"'\"'"),))
+                    if 'llvm-gcc' in data:
+                        # Found LLVM-GCC, fall back to clang
+                        data = (find_executable('clang') or
+                                _read_output(
+                                    "/usr/bin/xcrun -find clang 2>/dev/null").strip())
+                        if find_executable(data):
+                            _config_vars['CC'] = cc = data
+                            _config_vars['CXX'] = cc + '++'
+
+                if (cc != oldcc
+                        and 'LDSHARED' in _config_vars
+                        and 'LDSHARED' not in os.environ):
+                    # modify LDSHARED if we modified CC
+                    ldshared = _config_vars['LDSHARED']
+                    if ldshared.startswith(oldcc):
+                        _config_vars['LDSHARED'] = cc + ldshared[len(oldcc):]
+
             if major_version < 8:
                 # On Mac OS X before 10.4, check if -arch and -isysroot
                 # are in CFLAGS or LDFLAGS and remove them if they are.
@@ -579,19 +634,45 @@
                     _config_vars[key] = flags
 
             else:
+                # Different Xcode releases support different sets for '-arch'
+                # flags. In particular, Xcode 4.x no longer supports the
+                # PPC architectures.
+                #
+                # This code automatically removes '-arch ppc' and '-arch ppc64'
+                # when these are not supported. That makes it possible to
+                # build extensions on OSX 10.7 and later with the prebuilt
+                # 32-bit installer on the python.org website.
+                flags = _config_vars['CFLAGS']
+                if re.search('-arch\s+ppc', flags) is not None:
+                    # NOTE: Cannot use subprocess here because of bootstrap
+                    # issues when building Python itself
+                    status = os.system("'%s' -arch ppc -x c /dev/null 2>/dev/null"%(
+                        _config_vars['CC'].replace("'", "'\"'\"'"),))
+
+                    if status != 0:
+                        # Compiler doesn't support PPC, remove the related
+                        # '-arch' flags.
+                        for key in ('LDFLAGS', 'BASECFLAGS',
+                            # a number of derived variables. These need to be
+                            # patched up as well.
+                            'CFLAGS', 'PY_CFLAGS', 'BLDSHARED', 'LDSHARED'):
+
+                            flags = _config_vars[key]
+                            flags = re.sub('-arch\s+ppc\w*\s', ' ', flags)
+                            _config_vars[key] = flags
+
 
                 # Allow the user to override the architecture flags using
                 # an environment variable.
                 # NOTE: This name was introduced by Apple in OSX 10.5 and
                 # is used by several scripting languages distributed with
                 # that OS release.
-
                 if 'ARCHFLAGS' in os.environ:
                     arch = os.environ['ARCHFLAGS']
                     for key in ('LDFLAGS', 'BASECFLAGS',
                         # a number of derived variables. These need to be
                         # patched up as well.
-                        'CFLAGS', 'PY_CFLAGS', 'BLDSHARED'):
+                        'CFLAGS', 'PY_CFLAGS', 'BLDSHARED', 'LDSHARED'):
 
                         flags = _config_vars[key]
                         flags = re.sub('-arch\s+\w+\s', ' ', flags)
diff --git a/Lib/distutils/unixccompiler.py b/Lib/distutils/unixccompiler.py
index c70a3cc..5d45faa 100644
--- a/Lib/distutils/unixccompiler.py
+++ b/Lib/distutils/unixccompiler.py
@@ -83,9 +83,8 @@
         except ValueError:
             pass
 
-    # Check if the SDK that is used during compilation actually exists,
-    # the universal build requires the usage of a universal SDK and not all
-    # users have that installed by default.
+    # Check if the SDK that is used during compilation actually exists.
+    # If not, revert to using the installed headers and hope for the best.
     sysroot = None
     if '-isysroot' in cc_args:
         idx = cc_args.index('-isysroot')
@@ -97,7 +96,21 @@
     if sysroot and not os.path.isdir(sysroot):
         log.warn("Compiling with an SDK that doesn't seem to exist: %s",
                 sysroot)
-        log.warn("Please check your Xcode installation")
+        log.warn("Attempting to compile without the SDK")
+        while True:
+            try:
+                index = cc_args.index('-isysroot')
+                # Strip this argument and the next one:
+                del cc_args[index:index+2]
+            except ValueError:
+                break
+        while True:
+            try:
+                index = compiler_so.index('-isysroot')
+                # Strip this argument and the next one:
+                del compiler_so[index:index+2]
+            except ValueError:
+                break
 
     return compiler_so
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 9b7d00a..031550e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -234,6 +234,21 @@
 Build
 -----
 
+- Issue #13590: Improve support for OS X Xcode 4:
+    * Try to avoid building Python or extension modules with problematic
+      llvm-gcc compiler.
+    * Since Xcode 4 removes ppc support, extension module builds now
+      check for ppc compiler support and automatically remove ppc and
+      ppc64 archs when not available.
+    * Since Xcode 4 no longer install SDKs in default locations,
+      extension module builds now revert to using installed headers
+      and libs if the SDK used to build the interpreter is not
+      available.
+    * Update ./configure to use better defaults for universal builds;
+      in particular, --enable-universalsdk=yes uses the Xcode default
+      SDK and --with-universal-archs now defaults to "intel" if ppc
+      not available.
+
 - Issue #14225: Fix Unicode support for curses (#12567) on OS X
 
 - Issue #14928: Fix importlib bootstrap issues by using a custom executable
diff --git a/configure b/configure
index d09d740..c13aae0 100755
--- a/configure
+++ b/configure
@@ -1,13 +1,11 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.68 for python 3.3.
+# Generated by GNU Autoconf 2.69 for python 3.3.
 #
 # Report bugs to <http://bugs.python.org/>.
 #
 #
-# Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
-# 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software
-# Foundation, Inc.
+# Copyright (C) 1992-1996, 1998-2012 Free Software Foundation, Inc.
 #
 #
 # This configure script is free software; the Free Software Foundation
@@ -136,6 +134,31 @@
 # CDPATH.
 (unset CDPATH) >/dev/null 2>&1 && unset CDPATH
 
+# Use a proper internal environment variable to ensure we don't fall
+  # into an infinite loop, continuously re-executing ourselves.
+  if test x"${_as_can_reexec}" != xno && test "x$CONFIG_SHELL" != x; then
+    _as_can_reexec=no; export _as_can_reexec;
+    # We cannot yet assume a decent shell, so we have to provide a
+# neutralization value for shells without unset; and this also
+# works around shells that cannot unset nonexistent variables.
+# Preserve -v and -x to the replacement shell.
+BASH_ENV=/dev/null
+ENV=/dev/null
+(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
+case $- in # ((((
+  *v*x* | *x*v* ) as_opts=-vx ;;
+  *v* ) as_opts=-v ;;
+  *x* ) as_opts=-x ;;
+  * ) as_opts= ;;
+esac
+exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
+# Admittedly, this is quite paranoid, since all the known shells bail
+# out after a failed `exec'.
+$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
+as_fn_exit 255
+  fi
+  # We don't want this to propagate to other subprocesses.
+          { _as_can_reexec=; unset _as_can_reexec;}
 if test "x$CONFIG_SHELL" = x; then
   as_bourne_compatible="if test -n \"\${ZSH_VERSION+set}\" && (emulate sh) >/dev/null 2>&1; then :
   emulate sh
@@ -169,7 +192,8 @@
 else
   exitcode=1; echo positional parameters were not saved.
 fi
-test x\$exitcode = x0 || exit 1"
+test x\$exitcode = x0 || exit 1
+test -x / || exit 1"
   as_suggested="  as_lineno_1=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_1a=\$LINENO
   as_lineno_2=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_2a=\$LINENO
   eval 'test \"x\$as_lineno_1'\$as_run'\" != \"x\$as_lineno_2'\$as_run'\" &&
@@ -214,21 +238,25 @@
 
 
       if test "x$CONFIG_SHELL" != x; then :
-  # We cannot yet assume a decent shell, so we have to provide a
-	# neutralization value for shells without unset; and this also
-	# works around shells that cannot unset nonexistent variables.
-	# Preserve -v and -x to the replacement shell.
-	BASH_ENV=/dev/null
-	ENV=/dev/null
-	(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
-	export CONFIG_SHELL
-	case $- in # ((((
-	  *v*x* | *x*v* ) as_opts=-vx ;;
-	  *v* ) as_opts=-v ;;
-	  *x* ) as_opts=-x ;;
-	  * ) as_opts= ;;
-	esac
-	exec "$CONFIG_SHELL" $as_opts "$as_myself" ${1+"$@"}
+  export CONFIG_SHELL
+             # We cannot yet assume a decent shell, so we have to provide a
+# neutralization value for shells without unset; and this also
+# works around shells that cannot unset nonexistent variables.
+# Preserve -v and -x to the replacement shell.
+BASH_ENV=/dev/null
+ENV=/dev/null
+(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
+case $- in # ((((
+  *v*x* | *x*v* ) as_opts=-vx ;;
+  *v* ) as_opts=-v ;;
+  *x* ) as_opts=-x ;;
+  * ) as_opts= ;;
+esac
+exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
+# Admittedly, this is quite paranoid, since all the known shells bail
+# out after a failed `exec'.
+$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
+exit 255
 fi
 
     if test x$as_have_required = xno; then :
@@ -331,6 +359,14 @@
 
 
 } # as_fn_mkdir_p
+
+# as_fn_executable_p FILE
+# -----------------------
+# Test if FILE is an executable regular file.
+as_fn_executable_p ()
+{
+  test -f "$1" && test -x "$1"
+} # as_fn_executable_p
 # as_fn_append VAR VALUE
 # ----------------------
 # Append the text in VALUE to the end of the definition contained in VAR. Take
@@ -452,6 +488,10 @@
   chmod +x "$as_me.lineno" ||
     { $as_echo "$as_me: error: cannot create $as_me.lineno; rerun with a POSIX shell" >&2; as_fn_exit 1; }
 
+  # If we had to re-execute with $CONFIG_SHELL, we're ensured to have
+  # already done that, so ensure we don't try to do so again and fall
+  # in an infinite loop.  This has already happened in practice.
+  _as_can_reexec=no; export _as_can_reexec
   # Don't try to exec as it changes $[0], causing all sort of problems
   # (the dirname of $[0] is not the place where we might find the
   # original and so on.  Autoconf is especially sensitive to this).
@@ -486,16 +526,16 @@
     # ... but there are two gotchas:
     # 1) On MSYS, both `ln -s file dir' and `ln file dir' fail.
     # 2) DJGPP < 2.04 has no symlinks; `ln -s' creates a wrapper executable.
-    # In both cases, we have to default to `cp -p'.
+    # In both cases, we have to default to `cp -pR'.
     ln -s conf$$.file conf$$.dir 2>/dev/null && test ! -f conf$$.exe ||
-      as_ln_s='cp -p'
+      as_ln_s='cp -pR'
   elif ln conf$$.file conf$$ 2>/dev/null; then
     as_ln_s=ln
   else
-    as_ln_s='cp -p'
+    as_ln_s='cp -pR'
   fi
 else
-  as_ln_s='cp -p'
+  as_ln_s='cp -pR'
 fi
 rm -f conf$$ conf$$.exe conf$$.dir/conf$$.file conf$$.file
 rmdir conf$$.dir 2>/dev/null
@@ -507,28 +547,8 @@
   as_mkdir_p=false
 fi
 
-if test -x / >/dev/null 2>&1; then
-  as_test_x='test -x'
-else
-  if ls -dL / >/dev/null 2>&1; then
-    as_ls_L_option=L
-  else
-    as_ls_L_option=
-  fi
-  as_test_x='
-    eval sh -c '\''
-      if test -d "$1"; then
-	test -d "$1/.";
-      else
-	case $1 in #(
-	-*)set "./$1";;
-	esac;
-	case `ls -ld'$as_ls_L_option' "$1" 2>/dev/null` in #((
-	???[sx]*):;;*)false;;esac;fi
-    '\'' sh
-  '
-fi
-as_executable_p=$as_test_x
+as_test_x='test -x'
+as_executable_p=as_fn_executable_p
 
 # Sed expression to map a string onto a valid CPP name.
 as_tr_cpp="eval sed 'y%*$as_cr_letters%P$as_cr_LETTERS%;s%[^_$as_cr_alnum]%_%g'"
@@ -1243,8 +1263,6 @@
 if test "x$host_alias" != x; then
   if test "x$build_alias" = x; then
     cross_compiling=maybe
-    $as_echo "$as_me: WARNING: if you wanted to set the --build type, don't use --host.
-    If a cross compiler is detected then cross compile mode will be used" >&2
   elif test "x$build_alias" != "x$host_alias"; then
     cross_compiling=yes
   fi
@@ -1404,7 +1422,7 @@
   --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)
   --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]
   --enable-universalsdk[=SDKDIR]
-                          Build against Mac OS X 10.4u SDK (ppc/i386)
+                          Build fat binary against Mac OS X SDK
   --enable-framework[=INSTALLDIR]
                           Build (MacOSX|Darwin) framework
   --enable-shared         disable/enable building shared python library
@@ -1534,9 +1552,9 @@
 if $ac_init_version; then
   cat <<\_ACEOF
 python configure 3.3
-generated by GNU Autoconf 2.68
+generated by GNU Autoconf 2.69
 
-Copyright (C) 2010 Free Software Foundation, Inc.
+Copyright (C) 2012 Free Software Foundation, Inc.
 This configure script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it.
 _ACEOF
@@ -1612,7 +1630,7 @@
 	 test ! -s conftest.err
        } && test -s conftest$ac_exeext && {
 	 test "$cross_compiling" = yes ||
-	 $as_test_x conftest$ac_exeext
+	 test -x conftest$ac_exeext
        }; then :
   ac_retval=0
 else
@@ -1910,7 +1928,8 @@
 main ()
 {
 static int test_array [1 - 2 * !((($ac_type) -1 >> ($2 / 2 - 1)) >> ($2 / 2 - 1) == 3)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -1964,7 +1983,8 @@
 main ()
 {
 static int test_array [1 - 2 * !(0 < ($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1))];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -1980,7 +2000,8 @@
 {
 static int test_array [1 - 2 * !(($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1)
 		 < ($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 2))];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2030,7 +2051,8 @@
 main ()
 {
 static int test_array [1 - 2 * !(($2) >= 0)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2046,7 +2068,8 @@
 main ()
 {
 static int test_array [1 - 2 * !(($2) <= $ac_mid)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2072,7 +2095,8 @@
 main ()
 {
 static int test_array [1 - 2 * !(($2) < 0)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2088,7 +2112,8 @@
 main ()
 {
 static int test_array [1 - 2 * !(($2) >= $ac_mid)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2122,7 +2147,8 @@
 main ()
 {
 static int test_array [1 - 2 * !(($2) <= $ac_mid)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2365,7 +2391,7 @@
 running configure, to aid debugging if configure makes a mistake.
 
 It was created by python $as_me 3.3, which was
-generated by GNU Autoconf 2.68.  Invocation command line was
+generated by GNU Autoconf 2.69.  Invocation command line was
 
   $ $0 $@
 
@@ -2735,7 +2761,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_HAS_HG="found"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -2944,10 +2970,16 @@
   enableval=$enable_universalsdk;
 	case $enableval in
 	yes)
-		enableval=/Developer/SDKs/MacOSX10.4u.sdk
-		if test ! -d "${enableval}"
+		# Locate the best usable SDK, see Mac/README.txt for more
+		# information
+		enableval="`/usr/bin/xcodebuild -version -sdk macosx Path 2>/dev/null`"
+		if test -z "${enableval}"
 		then
-			enableval=/
+			enableval=/Developer/SDKs/MacOSX10.4u.sdk
+			if test ! -d "${enableval}"
+			then
+				enableval=/
+			fi
 		fi
 		;;
 	esac
@@ -2985,7 +3017,20 @@
 
 
 
+# For backward compatibility reasons we prefer to select '32-bit' if available,
+# otherwise use 'intel'
 UNIVERSAL_ARCHS="32-bit"
+if test "`uname -s`" = "Darwin"
+then
+	if test -n "${UNIVERSALSDK}"
+	then
+		if test -z "`/usr/bin/file "${UNIVERSALSDK}/usr/lib/libSystem.dylib" | grep ppc`"
+		then
+			UNIVERSAL_ARCHS="intel"
+		fi
+	fi
+fi
+
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-universal-archs" >&5
 $as_echo_n "checking for --with-universal-archs... " >&6; }
@@ -2999,8 +3044,8 @@
 
 else
 
- 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: 32-bit" >&5
-$as_echo "32-bit" >&6; }
+ 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: ${UNIVERSAL_ARCHS}" >&5
+$as_echo "${UNIVERSAL_ARCHS}" >&6; }
 
 fi
 
@@ -3377,6 +3422,66 @@
 if test -z "$CFLAGS"; then
         CFLAGS=
 fi
+
+if test "$ac_sys_system" = "Darwin"
+then
+	# Compiler selection on MacOSX is more complicated than
+	# AC_PROG_CC can handle, see Mac/README.txt for more
+	# information
+	if test -z "${CC}"
+	then
+		found_gcc=
+		found_clang=
+		as_save_IFS=$IFS; IFS=:
+		for as_dir in $PATH
+		do
+			IFS=$as_save_IFS
+			if test -x $as_dir/gcc; then
+				if test -z "${found_gcc}"; then
+					found_gcc=$as_dir/gcc
+				fi
+			fi
+			if test -x $as_dir/clang; then
+				if test -z "${found_clang}"; then
+					found_clang=$as_dir/clang
+				fi
+			fi
+		done
+		IFS=$as_save_IFS
+
+		if test -n "$found_gcc" -a -n "$found_clang"
+		then
+			if test -n "`"$found_gcc" --version | grep llvm-gcc`"
+			then
+				{ $as_echo "$as_me:${as_lineno-$LINENO}: Detected llvm-gcc, falling back to clang" >&5
+$as_echo "$as_me: Detected llvm-gcc, falling back to clang" >&6;}
+				CC="$found_clang"
+				CXX="$found_clang++"
+			fi
+
+
+		elif test -z "$found_gcc" -a -n "$found_clang"
+		then
+			{ $as_echo "$as_me:${as_lineno-$LINENO}: No GCC found, use CLANG" >&5
+$as_echo "$as_me: No GCC found, use CLANG" >&6;}
+			CC="$found_clang"
+			CXX="$found_clang++"
+
+		elif test -z "$found_gcc" -a -z "$found_clang"
+		then
+			found_clang=`/usr/bin/xcrun -find clang 2>/dev/null`
+			if test -n "${found_clang}"
+			then
+				{ $as_echo "$as_me:${as_lineno-$LINENO}: Using clang from Xcode.app" >&5
+$as_echo "$as_me: Using clang from Xcode.app" >&6;}
+				CC="${found_clang}"
+				CXX="`/usr/bin/xcrun -find clang++`"
+
+			# else: use default behaviour
+			fi
+		fi
+	fi
+fi
 ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
 ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
@@ -3399,7 +3504,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CC="${ac_tool_prefix}gcc"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3439,7 +3544,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_ac_ct_CC="gcc"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3492,7 +3597,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CC="${ac_tool_prefix}cc"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3533,7 +3638,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     if test "$as_dir/$ac_word$ac_exec_ext" = "/usr/ucb/cc"; then
        ac_prog_rejected=yes
        continue
@@ -3591,7 +3696,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CC="$ac_tool_prefix$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3635,7 +3740,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_ac_ct_CC="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -4081,8 +4186,7 @@
 /* end confdefs.h.  */
 #include <stdarg.h>
 #include <stdio.h>
-#include <sys/types.h>
-#include <sys/stat.h>
+struct stat;
 /* Most of the following tests are stolen from RCS 5.7's src/conf.sh.  */
 struct buf { int x; };
 FILE * (*rcsopen) (struct buf *, struct stat *, int);
@@ -4221,7 +4325,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_CXX="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -4262,7 +4366,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_CXX="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -4285,6 +4389,47 @@
 fi
 
  ;;
+        clang|*/clang)     # Extract the first word of "clang++", so it can be a program name with args.
+set dummy clang++; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_CXX+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $CXX in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_CXX="$CXX" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in notfound
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_CXX="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  test -z "$ac_cv_path_CXX" && ac_cv_path_CXX="clang++"
+  ;;
+esac
+fi
+CXX=$ac_cv_path_CXX
+if test -n "$CXX"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CXX" >&5
+$as_echo "$CXX" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+ ;;
         esac
 	if test "$CXX" = "notfound"
 	then
@@ -4311,7 +4456,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CXX="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -4542,7 +4687,7 @@
     for ac_prog in grep ggrep; do
     for ac_exec_ext in '' $ac_executable_extensions; do
       ac_path_GREP="$as_dir/$ac_prog$ac_exec_ext"
-      { test -f "$ac_path_GREP" && $as_test_x "$ac_path_GREP"; } || continue
+      as_fn_executable_p "$ac_path_GREP" || continue
 # Check for GNU ac_path_GREP and select it if it is found.
   # Check for GNU $ac_path_GREP
 case `"$ac_path_GREP" --version 2>&1` in
@@ -4608,7 +4753,7 @@
     for ac_prog in egrep; do
     for ac_exec_ext in '' $ac_executable_extensions; do
       ac_path_EGREP="$as_dir/$ac_prog$ac_exec_ext"
-      { test -f "$ac_path_EGREP" && $as_test_x "$ac_path_EGREP"; } || continue
+      as_fn_executable_p "$ac_path_EGREP" || continue
 # Check for GNU ac_path_EGREP and select it if it is found.
   # Check for GNU $ac_path_EGREP
 case `"$ac_path_EGREP" --version 2>&1` in
@@ -4815,8 +4960,8 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
-#	  define __EXTENSIONS__ 1
-	  $ac_includes_default
+#         define __EXTENSIONS__ 1
+          $ac_includes_default
 int
 main ()
 {
@@ -5210,7 +5355,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_RANLIB="${ac_tool_prefix}ranlib"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5250,7 +5395,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_ac_ct_RANLIB="ranlib"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5304,7 +5449,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_AR="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5355,7 +5500,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_HAS_PYTHON="found"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5428,7 +5573,7 @@
     # by default.
     for ac_prog in ginstall scoinst install; do
       for ac_exec_ext in '' $ac_executable_extensions; do
-	if { test -f "$as_dir/$ac_prog$ac_exec_ext" && $as_test_x "$as_dir/$ac_prog$ac_exec_ext"; }; then
+	if as_fn_executable_p "$as_dir/$ac_prog$ac_exec_ext"; then
 	  if test $ac_prog = install &&
 	    grep dspmsg "$as_dir/$ac_prog$ac_exec_ext" >/dev/null 2>&1; then
 	    # AIX install.  It has an incompatible calling convention.
@@ -5497,7 +5642,7 @@
   test -z "$as_dir" && as_dir=.
     for ac_prog in mkdir gmkdir; do
 	 for ac_exec_ext in '' $ac_executable_extensions; do
-	   { test -f "$as_dir/$ac_prog$ac_exec_ext" && $as_test_x "$as_dir/$ac_prog$ac_exec_ext"; } || continue
+	   as_fn_executable_p "$as_dir/$ac_prog$ac_exec_ext" || continue
 	   case `"$as_dir/$ac_prog$ac_exec_ext" --version 2>&1` in #(
 	     'mkdir (GNU coreutils) '* | \
 	     'mkdir (coreutils) '* | \
@@ -8387,7 +8532,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -8430,7 +8575,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_ac_pt_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -10032,7 +10177,7 @@
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_TRUE="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -11469,7 +11614,8 @@
 main ()
 {
 static int test_array [1 - 2 * !(((char) -1) < 0)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -11500,11 +11646,11 @@
 int
 main ()
 {
-/* FIXME: Include the comments suggested by Paul. */
+
 #ifndef __cplusplus
-  /* Ultrix mips cc rejects this.  */
+  /* Ultrix mips cc rejects this sort of thing.  */
   typedef int charset[2];
-  const charset cs;
+  const charset cs = { 0, 0 };
   /* SunOS 4.1.1 cc rejects this.  */
   char const *const *pcpcc;
   char **ppc;
@@ -11521,8 +11667,9 @@
   ++pcpcc;
   ppc = (char**) pcpcc;
   pcpcc = (char const *const *) ppc;
-  { /* SCO 3.2v4 cc rejects this.  */
-    char *t;
+  { /* SCO 3.2v4 cc rejects this sort of thing.  */
+    char tx;
+    char *t = &tx;
     char const *s = 0 ? (char *) 0 : (char const *) 0;
 
     *t++ = 0;
@@ -11538,10 +11685,10 @@
     iptr p = 0;
     ++p;
   }
-  { /* AIX XL C 1.02.0.0 rejects this saying
+  { /* AIX XL C 1.02.0.0 rejects this sort of thing, saying
        "k.c", line 2.27: 1506-025 (S) Operand must be a modifiable lvalue. */
-    struct s { int j; const int *ap[3]; };
-    struct s *b; b->j = 5;
+    struct s { int j; const int *ap[3]; } bx;
+    struct s *b = &bx; b->j = 5;
   }
   { /* ULTRIX-32 V3.1 (Rev 9) vcc rejects this */
     const int foo = 10;
@@ -14830,16 +14977,16 @@
     # ... but there are two gotchas:
     # 1) On MSYS, both `ln -s file dir' and `ln file dir' fail.
     # 2) DJGPP < 2.04 has no symlinks; `ln -s' creates a wrapper executable.
-    # In both cases, we have to default to `cp -p'.
+    # In both cases, we have to default to `cp -pR'.
     ln -s conf$$.file conf$$.dir 2>/dev/null && test ! -f conf$$.exe ||
-      as_ln_s='cp -p'
+      as_ln_s='cp -pR'
   elif ln conf$$.file conf$$ 2>/dev/null; then
     as_ln_s=ln
   else
-    as_ln_s='cp -p'
+    as_ln_s='cp -pR'
   fi
 else
-  as_ln_s='cp -p'
+  as_ln_s='cp -pR'
 fi
 rm -f conf$$ conf$$.exe conf$$.dir/conf$$.file conf$$.file
 rmdir conf$$.dir 2>/dev/null
@@ -14899,28 +15046,16 @@
   as_mkdir_p=false
 fi
 
-if test -x / >/dev/null 2>&1; then
-  as_test_x='test -x'
-else
-  if ls -dL / >/dev/null 2>&1; then
-    as_ls_L_option=L
-  else
-    as_ls_L_option=
-  fi
-  as_test_x='
-    eval sh -c '\''
-      if test -d "$1"; then
-	test -d "$1/.";
-      else
-	case $1 in #(
-	-*)set "./$1";;
-	esac;
-	case `ls -ld'$as_ls_L_option' "$1" 2>/dev/null` in #((
-	???[sx]*):;;*)false;;esac;fi
-    '\'' sh
-  '
-fi
-as_executable_p=$as_test_x
+
+# as_fn_executable_p FILE
+# -----------------------
+# Test if FILE is an executable regular file.
+as_fn_executable_p ()
+{
+  test -f "$1" && test -x "$1"
+} # as_fn_executable_p
+as_test_x='test -x'
+as_executable_p=as_fn_executable_p
 
 # Sed expression to map a string onto a valid CPP name.
 as_tr_cpp="eval sed 'y%*$as_cr_letters%P$as_cr_LETTERS%;s%[^_$as_cr_alnum]%_%g'"
@@ -14942,7 +15077,7 @@
 # values after options handling.
 ac_log="
 This file was extended by python $as_me 3.3, which was
-generated by GNU Autoconf 2.68.  Invocation command line was
+generated by GNU Autoconf 2.69.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
   CONFIG_HEADERS  = $CONFIG_HEADERS
@@ -15004,10 +15139,10 @@
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
 python config.status 3.3
-configured by $0, generated by GNU Autoconf 2.68,
+configured by $0, generated by GNU Autoconf 2.69,
   with options \\"\$ac_cs_config\\"
 
-Copyright (C) 2010 Free Software Foundation, Inc.
+Copyright (C) 2012 Free Software Foundation, Inc.
 This config.status script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it."
 
@@ -15097,7 +15232,7 @@
 _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 if \$ac_cs_recheck; then
-  set X '$SHELL' '$0' $ac_configure_args \$ac_configure_extra_args --no-create --no-recursion
+  set X $SHELL '$0' $ac_configure_args \$ac_configure_extra_args --no-create --no-recursion
   shift
   \$as_echo "running CONFIG_SHELL=$SHELL \$*" >&6
   CONFIG_SHELL='$SHELL'
diff --git a/configure.ac b/configure.ac
index f1197b0..a497ac8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -104,14 +104,20 @@
 
 AC_MSG_CHECKING([for --enable-universalsdk])
 AC_ARG_ENABLE(universalsdk,
-	AS_HELP_STRING([--enable-universalsdk@<:@=SDKDIR@:>@], [Build against Mac OS X 10.4u SDK (ppc/i386)]),
+	AS_HELP_STRING([--enable-universalsdk@<:@=SDKDIR@:>@], [Build fat binary against Mac OS X SDK]),
 [
 	case $enableval in
 	yes)
-		enableval=/Developer/SDKs/MacOSX10.4u.sdk
-		if test ! -d "${enableval}"
+		# Locate the best usable SDK, see Mac/README.txt for more
+		# information
+		enableval="`/usr/bin/xcodebuild -version -sdk macosx Path 2>/dev/null`"
+		if test -z "${enableval}"
 		then
-			enableval=/
+			enableval=/Developer/SDKs/MacOSX10.4u.sdk
+			if test ! -d "${enableval}"
+			then
+				enableval=/
+			fi
 		fi
 		;;
 	esac
@@ -143,7 +149,20 @@
 
 AC_SUBST(ARCH_RUN_32BIT)
 
+# For backward compatibility reasons we prefer to select '32-bit' if available,
+# otherwise use 'intel'
 UNIVERSAL_ARCHS="32-bit"
+if test "`uname -s`" = "Darwin"
+then
+	if test -n "${UNIVERSALSDK}"
+	then
+		if test -z "`/usr/bin/file "${UNIVERSALSDK}/usr/lib/libSystem.dylib" | grep ppc`"
+		then
+			UNIVERSAL_ARCHS="intel"
+		fi
+	fi
+fi
+
 AC_SUBST(LIPO_32BIT_FLAGS)
 AC_MSG_CHECKING(for --with-universal-archs)
 AC_ARG_WITH(universal-archs,
@@ -153,7 +172,7 @@
 	UNIVERSAL_ARCHS="$withval"
 ],
 [
- 	AC_MSG_RESULT(32-bit)
+ 	AC_MSG_RESULT(${UNIVERSAL_ARCHS})
 ])
 
 
@@ -501,6 +520,63 @@
 if test -z "$CFLAGS"; then
         CFLAGS=
 fi
+
+if test "$ac_sys_system" = "Darwin"
+then
+	# Compiler selection on MacOSX is more complicated than
+	# AC_PROG_CC can handle, see Mac/README.txt for more
+	# information
+	if test -z "${CC}"
+	then
+		found_gcc=
+		found_clang=
+		as_save_IFS=$IFS; IFS=:
+		for as_dir in $PATH
+		do
+			IFS=$as_save_IFS
+			if test -x $as_dir/gcc; then
+				if test -z "${found_gcc}"; then
+					found_gcc=$as_dir/gcc
+				fi
+			fi
+			if test -x $as_dir/clang; then
+				if test -z "${found_clang}"; then
+					found_clang=$as_dir/clang
+				fi
+			fi
+		done
+		IFS=$as_save_IFS
+
+		if test -n "$found_gcc" -a -n "$found_clang"
+		then
+			if test -n "`"$found_gcc" --version | grep llvm-gcc`"
+			then
+				AC_MSG_NOTICE([Detected llvm-gcc, falling back to clang])
+				CC="$found_clang"
+				CXX="$found_clang++"
+			fi
+
+
+		elif test -z "$found_gcc" -a -n "$found_clang"
+		then
+			AC_MSG_NOTICE([No GCC found, use CLANG])
+			CC="$found_clang"
+			CXX="$found_clang++"
+
+		elif test -z "$found_gcc" -a -z "$found_clang"
+		then
+			found_clang=`/usr/bin/xcrun -find clang 2>/dev/null`
+			if test -n "${found_clang}"
+			then
+				AC_MSG_NOTICE([Using clang from Xcode.app])
+				CC="${found_clang}"
+				CXX="`/usr/bin/xcrun -find clang++`"
+
+			# else: use default behaviour
+			fi
+		fi
+	fi
+fi
 AC_PROG_CC
 
 AC_SUBST(CXX)
@@ -534,6 +610,7 @@
         case "$CC" in
         gcc)    AC_PATH_PROG(CXX, [g++], [g++], [notfound]) ;;
         cc)     AC_PATH_PROG(CXX, [c++], [c++], [notfound]) ;;
+        clang|*/clang)     AC_PATH_PROG(CXX, [clang++], [clang++], [notfound]) ;;
         esac
 	if test "$CXX" = "notfound"
 	then