diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index bccd7ff..5ee8dfa 100644
--- a/.waf-tools/default-compiler-flags.py
+++ b/.waf-tools/default-compiler-flags.py
@@ -1,64 +1,67 @@
 # -*- Mode: python; py-indent-offset: 4; indent-tabs-mode: nil; coding: utf-8; -*-
 
-from waflib import Logs, Configure, Utils
+from waflib import Configure, Logs, Utils
 
 def options(opt):
-    opt.add_option('--debug', '--with-debug', action='store_true', default=False, dest='debug',
-                   help='''Compile in debugging mode with minimal optimizations (-O0 or -Og)''')
+    opt.add_option('--debug', '--with-debug', action='store_true', default=False,
+                   help='Compile in debugging mode with minimal optimizations (-O0 or -Og)')
 
 def configure(conf):
     conf.start_msg('Checking C++ compiler version')
 
-    cxx = conf.env['CXX_NAME'] # CXX_NAME is the generic name of the compiler
-    ccver = tuple(int(i) for i in conf.env['CC_VERSION'])
+    cxx = conf.env.CXX_NAME # generic name of the compiler
+    ccver = tuple(int(i) for i in conf.env.CC_VERSION)
+    ccverstr = '.'.join(conf.env.CC_VERSION)
     errmsg = ''
     warnmsg = ''
     if cxx == 'gcc':
-        if ccver < (4, 8, 2):
+        if ccver < (5, 3, 0):
             errmsg = ('The version of gcc you are using is too old.\n'
-                      'The minimum supported gcc version is 4.8.2.')
-        flags = GccFlags()
+                      'The minimum supported gcc version is 5.3.0.')
+        conf.flags = GccFlags()
     elif cxx == 'clang':
-        if ccver < (3, 4, 0):
+        if ccver < (3, 5, 0):
             errmsg = ('The version of clang you are using is too old.\n'
-                      'The minimum supported clang version is 3.4.0.')
-        flags = ClangFlags()
+                      'The minimum supported clang version is 3.5.0.')
+        conf.flags = ClangFlags()
     else:
         warnmsg = 'Note: %s compiler is unsupported' % cxx
-        flags = CompilerFlags()
+        conf.flags = CompilerFlags()
 
     if errmsg:
-        conf.end_msg('.'.join(conf.env['CC_VERSION']), color='RED')
+        conf.end_msg(ccverstr, color='RED')
         conf.fatal(errmsg)
     elif warnmsg:
-        conf.end_msg('.'.join(conf.env['CC_VERSION']), color='YELLOW')
+        conf.end_msg(ccverstr, color='YELLOW')
         Logs.warn(warnmsg)
     else:
-        conf.end_msg('.'.join(conf.env['CC_VERSION']))
+        conf.end_msg(ccverstr)
 
-    areCustomCxxflagsPresent = (len(conf.env.CXXFLAGS) > 0)
+    conf.areCustomCxxflagsPresent = (len(conf.env.CXXFLAGS) > 0)
 
-    # General flags are always applied (e.g., selecting C++11 mode)
-    generalFlags = flags.getGeneralFlags(conf)
+    # General flags are always applied (e.g., selecting C++ language standard)
+    generalFlags = conf.flags.getGeneralFlags(conf)
     conf.add_supported_cxxflags(generalFlags['CXXFLAGS'])
     conf.add_supported_linkflags(generalFlags['LINKFLAGS'])
     conf.env.DEFINES += generalFlags['DEFINES']
 
+@Configure.conf
+def check_compiler_flags(conf):
     # Debug or optimized CXXFLAGS and LINKFLAGS are applied only if the
     # corresponding environment variables are not set.
     # DEFINES are always applied.
     if conf.options.debug:
-        extraFlags = flags.getDebugFlags(conf)
-        if areCustomCxxflagsPresent:
+        extraFlags = conf.flags.getDebugFlags(conf)
+        if conf.areCustomCxxflagsPresent:
             missingFlags = [x for x in extraFlags['CXXFLAGS'] if x not in conf.env.CXXFLAGS]
-            if len(missingFlags) > 0:
-                Logs.warn("Selected debug mode, but CXXFLAGS is set to a custom value '%s'"
-                          % " ".join(conf.env.CXXFLAGS))
-                Logs.warn("Default flags '%s' are not activated" % " ".join(missingFlags))
+            if missingFlags:
+                Logs.warn('Selected debug mode, but CXXFLAGS is set to a custom value "%s"'
+                          % ' '.join(conf.env.CXXFLAGS))
+                Logs.warn('Default flags "%s" will not be used' % ' '.join(missingFlags))
     else:
-        extraFlags = flags.getOptimizedFlags(conf)
+        extraFlags = conf.flags.getOptimizedFlags(conf)
 
-    if not areCustomCxxflagsPresent:
+    if not conf.areCustomCxxflagsPresent:
         conf.add_supported_cxxflags(extraFlags['CXXFLAGS'])
         conf.add_supported_linkflags(extraFlags['LINKFLAGS'])
 
@@ -75,9 +78,10 @@
     self.start_msg('Checking supported CXXFLAGS')
 
     supportedFlags = []
-    for flag in cxxflags:
-        if self.check_cxx(cxxflags=['-Werror', flag], mandatory=False):
-            supportedFlags += [flag]
+    for flags in cxxflags:
+        flags = Utils.to_list(flags)
+        if self.check_cxx(cxxflags=['-Werror'] + flags, mandatory=False):
+            supportedFlags += flags
 
     self.end_msg(' '.join(supportedFlags))
     self.env.prepend_value('CXXFLAGS', supportedFlags)
@@ -93,15 +97,19 @@
     self.start_msg('Checking supported LINKFLAGS')
 
     supportedFlags = []
-    for flag in linkflags:
-        if self.check_cxx(linkflags=['-Werror', flag], mandatory=False):
-            supportedFlags += [flag]
+    for flags in linkflags:
+        flags = Utils.to_list(flags)
+        if self.check_cxx(linkflags=['-Werror'] + flags, mandatory=False):
+            supportedFlags += flags
 
     self.end_msg(' '.join(supportedFlags))
     self.env.prepend_value('LINKFLAGS', supportedFlags)
 
 
 class CompilerFlags(object):
+    def getCompilerVersion(self, conf):
+        return tuple(int(i) for i in conf.env.CC_VERSION)
+
     def getGeneralFlags(self, conf):
         """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are always needed"""
         return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': []}
@@ -120,7 +128,7 @@
     """
     def getGeneralFlags(self, conf):
         flags = super(GccBasicFlags, self).getGeneralFlags(conf)
-        flags['CXXFLAGS'] += ['-std=c++11']
+        flags['CXXFLAGS'] += ['-std=c++14']
         return flags
 
     def getDebugFlags(self, conf):
@@ -132,6 +140,7 @@
                               '-Wall',
                               '-Wextra',
                               '-Werror',
+                              '-Wnon-virtual-dtor',
                               '-Wno-error=deprecated-declarations', # Bug #3795
                               '-Wno-error=maybe-uninitialized', # Bug #1615
                               '-Wno-unused-parameter',
@@ -146,6 +155,7 @@
                               '-pedantic',
                               '-Wall',
                               '-Wextra',
+                              '-Wnon-virtual-dtor',
                               '-Wno-unused-parameter',
                               ]
         flags['LINKFLAGS'] += ['-fuse-ld=gold', '-Wl,-O1']
@@ -154,15 +164,23 @@
 class GccFlags(GccBasicFlags):
     def getDebugFlags(self, conf):
         flags = super(GccFlags, self).getDebugFlags(conf)
-        flags['CXXFLAGS'] += ['-fdiagnostics-color'] # gcc >= 4.9
+        flags['CXXFLAGS'] += ['-fdiagnostics-color']
         return flags
 
     def getOptimizedFlags(self, conf):
         flags = super(GccFlags, self).getOptimizedFlags(conf)
-        flags['CXXFLAGS'] += ['-fdiagnostics-color'] # gcc >= 4.9
+        flags['CXXFLAGS'] += ['-fdiagnostics-color']
         return flags
 
 class ClangFlags(GccBasicFlags):
+    def getGeneralFlags(self, conf):
+        flags = super(ClangFlags, self).getGeneralFlags(conf)
+        if Utils.unversioned_sys_platform() == 'darwin' and self.getCompilerVersion(conf) >= (9, 0, 0):
+            # Bug #4296
+            flags['CXXFLAGS'] += [['-isystem', '/usr/local/include'], # for Homebrew
+                                  ['-isystem', '/opt/local/include']] # for MacPorts
+        return flags
+
     def getDebugFlags(self, conf):
         flags = super(ClangFlags, self).getDebugFlags(conf)
         flags['CXXFLAGS'] += ['-fcolor-diagnostics']