scons: Bump compiler requirement to gcc >= 4.7 and clang >= 3.1

This patch updates the compiler minimum requirement to gcc 4.7 and
clang 3.1, thus allowing:

1. Explicit virtual overrides (no need for M5_ATTR_OVERRIDE)
2. Non-static data member initializers
3. Template aliases
4. Delegating constructors

This patch also enables a transition from --std=c++0x to --std=c++11.

2 files changed, 14 insertions, 26 deletions

diff --git a/SConstruct b/SConstruct
index 981cd0da9..9ad589661 100755
--- a/SConstruct
+++ b/SConstruct
@@ -556,9 +556,8 @@ if main['GCC'] or main['CLANG']:
     # Enable -Wall and then disable the few warnings that we
     # consistently violate
     main.Append(CCFLAGS=['-Wall', '-Wno-sign-compare', '-Wundef'])
-    # We always compile using C++11, but only gcc >= 4.7 and clang 3.1
-    # actually use that name, so we stick with c++0x
-    main.Append(CXXFLAGS=['-std=c++0x'])
+    # We always compile using C++11
+    main.Append(CXXFLAGS=['-std=c++11'])
     # Add selected sanity checks from -Wextra
     main.Append(CXXFLAGS=['-Wmissing-field-initializers',
                           '-Woverloaded-virtual'])
@@ -582,13 +581,12 @@ else:
     Exit(1)
 
 if main['GCC']:
-    # Check for a supported version of gcc. >= 4.6 is chosen for its
+    # Check for a supported version of gcc. >= 4.7 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.
+    # http://gcc.gnu.org/projects/cxx0x.html for details.
     gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
-    if compareVersions(gcc_version, "4.6") < 0:
-        print 'Error: gcc version 4.6 or newer required.'
+    if compareVersions(gcc_version, "4.7") < 0:
+        print 'Error: gcc version 4.7 or newer required.'
         print '       Installed version:', gcc_version
         Exit(1)
 
@@ -642,15 +640,15 @@ if main['GCC']:
                                   '-fno-builtin-realloc', '-fno-builtin-free'])
 
 elif main['CLANG']:
-    # Check for a supported version of clang, >= 3.0 is needed to
-    # support similar features as gcc 4.6. See
+    # Check for a supported version of clang, >= 3.1 is needed to
+    # support similar features as gcc 4.7. 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, "3.0") < 0:
-            print 'Error: clang version 3.0 or newer required.'
+        if compareVersions(clang_version, "3.1") < 0:
+            print 'Error: clang version 3.1 or newer required.'
             print '       Installed version:', clang_version
             Exit(1)
     else:
diff --git a/src/SConscript b/src/SConscript
index a479464a1..95c8f002f 100755
--- a/src/SConscript
+++ b/src/SConscript
@@ -1015,7 +1015,8 @@ def makeEnv(env, label, objsfx, strip = False, **kwargs):
 
     # Add additional warnings here that should not be applied to
     # the SWIG generated code
-    new_env.Append(CXXFLAGS='-Wmissing-declarations')
+    new_env.Append(CXXFLAGS=['-Wmissing-declarations',
+                             '-Wdelete-non-virtual-dtor'])
 
     if env['GCC']:
         # Depending on the SWIG version, we also need to supress
@@ -1023,15 +1024,8 @@ def makeEnv(env, label, objsfx, strip = False, **kwargs):
         # initializers.
         swig_env.Append(CCFLAGS=['-Wno-uninitialized',
                                  '-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
-        # also have to disable warnings about the SWIG code having
-        # potentially uninitialized variables.
-        if compareVersions(env['GCC_VERSION'], '4.7') >= 0:
-            new_env.Append(CXXFLAGS='-Wdelete-non-virtual-dtor')
-            swig_env.Append(CCFLAGS='-Wno-maybe-uninitialized')
+                                 '-Wno-unused-but-set-variable',
+                                 '-Wno-maybe-uninitialized'])
 
         # Only gcc >= 4.9 supports UBSan, so check both the version
         # and the command-line option before adding the compiler and
@@ -1042,10 +1036,6 @@ def makeEnv(env, label, objsfx, strip = False, **kwargs):
             new_env.Append(LINKFLAGS='-fsanitize=undefined')
 
     if env['CLANG']:
-        # Always enable the warning for deletion of derived classes
-        # with non-virtual destructors
-        new_env.Append(CXXFLAGS=['-Wdelete-non-virtual-dtor'])
-
         swig_env.Append(CCFLAGS=[
                 # Some versions of SWIG can return uninitialized values
                 '-Wno-sometimes-uninitialized',