scons: Bump the compiler version to gcc 4.6 and clang 3.0

This patch bumps the supported version of gcc from 4.4 to 4.6, and
clang from 2.9 to 3.0. This enables, amongst other things, range-based
for loops, lambda expressions, etc. The STL implementation shipping
with 4.6 also has a full functional implementation of unique_ptr and
shared_ptr.

2 files changed, 26 insertions, 34 deletions

diff --git a/SConstruct b/SConstruct
index f20492a0b..6a44f3a94 100755
--- a/SConstruct
+++ b/SConstruct
@@ -568,52 +568,46 @@ else:
     Exit(1)
 
 if main['GCC']:
-    # Check for a supported version of gcc, >= 4.4 is needed for c++0x
-    # support. See http://gcc.gnu.org/projects/cxx0x.html for details
+    # Check for a supported version of gcc. >= 4.6 is chosen for its
+    # level of c++11 support. See
+    # http://gcc.gnu.org/projects/cxx0x.html for details. 4.6 is also
+    # the first version with proper LTO support.
     gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
-    if compareVersions(gcc_version, "4.4") < 0:
-        print 'Error: gcc version 4.4 or newer required.'
+    if compareVersions(gcc_version, "4.6") < 0:
+        print 'Error: gcc version 4.6 or newer required.'
         print '       Installed version:', gcc_version
         Exit(1)
 
     main['GCC_VERSION'] = gcc_version
 
-    # Check for versions with bugs
-    if not compareVersions(gcc_version, '4.4.1') or \
-       not compareVersions(gcc_version, '4.4.2'):
-        print 'Info: Tree vectorizer in GCC 4.4.1 & 4.4.2 is buggy, disabling.'
-        main.Append(CCFLAGS=['-fno-tree-vectorize'])
-
-    # LTO support is only really working properly from 4.6 and beyond
-    if compareVersions(gcc_version, '4.6') >= 0:
-        # Add the appropriate Link-Time Optimization (LTO) flags
-        # unless LTO is explicitly turned off. Note that these flags
-        # are only used by the fast target.
-        if not GetOption('no_lto'):
-            # Pass the LTO flag when compiling to produce GIMPLE
-            # output, we merely create the flags here and only append
-            # them later/
-            main['LTO_CCFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
-
-            # Use the same amount of jobs for LTO as we are running
-            # scons with, we hardcode the use of the linker plugin
-            # which requires either gold or GNU ld >= 2.21
-            main['LTO_LDFLAGS'] = ['-flto=%d' % GetOption('num_jobs'),
-                                   '-fuse-linker-plugin']
+    # Add the appropriate Link-Time Optimization (LTO) flags
+    # unless LTO is explicitly turned off. Note that these flags
+    # are only used by the fast target.
+    if not GetOption('no_lto'):
+        # Pass the LTO flag when compiling to produce GIMPLE
+        # output, we merely create the flags here and only append
+        # them later/
+        main['LTO_CCFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
+
+        # Use the same amount of jobs for LTO as we are running
+        # scons with, we hardcode the use of the linker plugin
+        # which requires either gold or GNU ld >= 2.21
+        main['LTO_LDFLAGS'] = ['-flto=%d' % GetOption('num_jobs'),
+                               '-fuse-linker-plugin']
 
     main.Append(TCMALLOC_CCFLAGS=['-fno-builtin-malloc', '-fno-builtin-calloc',
                                   '-fno-builtin-realloc', '-fno-builtin-free'])
 
 elif main['CLANG']:
-    # Check for a supported version of clang, >= 2.9 is needed to
-    # support similar features as gcc 4.4. See
+    # Check for a supported version of clang, >= 3.0 is needed to
+    # support similar features as gcc 4.6. See
     # http://clang.llvm.org/cxx_status.html for details
     clang_version_re = re.compile(".* version (\d+\.\d+)")
     clang_version_match = clang_version_re.search(CXX_version)
     if (clang_version_match):
         clang_version = clang_version_match.groups()[0]
-        if compareVersions(clang_version, "2.9") < 0:
-            print 'Error: clang version 2.9 or newer required.'
+        if compareVersions(clang_version, "3.0") < 0:
+            print 'Error: clang version 3.0 or newer required.'
             print '       Installed version:', clang_version
             Exit(1)
     else:
diff --git a/src/SConscript b/src/SConscript
index 287c388ba..f5b082819 100755
--- a/src/SConscript
+++ b/src/SConscript
@@ -925,10 +925,8 @@ def makeEnv(env, label, objsfx, strip = False, **kwargs):
         # warnings about uninitialized variables and missing field
         # initializers.
         swig_env.Append(CCFLAGS=['-Wno-uninitialized',
-                                 '-Wno-missing-field-initializers'])
-
-        if compareVersions(env['GCC_VERSION'], '4.6') >= 0:
-            swig_env.Append(CCFLAGS='-Wno-unused-but-set-variable')
+                                 '-Wno-missing-field-initializers',
+                                 '-Wno-unused-but-set-variable'])
 
         # If gcc supports it, also warn for deletion of derived
         # classes with non-virtual desctructors. For gcc >= 4.7 we