diff --git a/.waf-tools/compiler-features.py b/.waf-tools/compiler-features.py
index 8389025..cf41970 100644
--- a/.waf-tools/compiler-features.py
+++ b/.waf-tools/compiler-features.py
@@ -73,7 +73,7 @@
 STD_TO_STRING = '''
 #include <string>
 int
-main(int argc, char** argv)
+main()
 {
   std::string s = std::to_string(0);
   s = std::to_string(0l);
@@ -85,7 +85,6 @@
   s = std::to_string(0.0);
   s = std::to_string(0.0l);
   s.clear();
-  return 0;
 }
 '''
 
@@ -107,7 +106,6 @@
   v.insert(it, 2);
   it = v.cend() - 1;
   v.erase(it);
-  return 0;
 }
 '''
 
diff --git a/.waf-tools/cryptopp.py b/.waf-tools/cryptopp.py
index bf49c04..a005123 100644
--- a/.waf-tools/cryptopp.py
+++ b/.waf-tools/cryptopp.py
@@ -40,7 +40,6 @@
   StringSource(buffer, true, new HashFilter(hash, new FileSink(std::cout)));
   StringSource(reinterpret_cast<const uint8_t*>(buffer.c_str()), buffer.size(),
                true, new HashFilter(hash, new FileSink(std::cout)));
-  return 0;
 }
 '''
 
diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index f82fe10..9f15fcc 100644
--- a/.waf-tools/default-compiler-flags.py
+++ b/.waf-tools/default-compiler-flags.py
@@ -40,7 +40,7 @@
 
     if not areCustomCxxflagsPresent:
         conf.add_supported_cxxflags(extraFlags['CXXFLAGS'])
-        conf.add_supported_cxxflags(extraFlags['LINKFLAGS'])
+        conf.add_supported_linkflags(extraFlags['LINKFLAGS'])
 
     conf.env.DEFINES += extraFlags['DEFINES']
 
@@ -83,15 +83,15 @@
 
 class CompilerFlags(object):
     def getGeneralFlags(self, conf):
-        """Get dict {'CXXFLAGS':[...], LINKFLAGS:[...], DEFINES:[...]} that are always needed"""
+        """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are always needed"""
         return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': []}
 
     def getDebugFlags(self, conf):
-        """Get tuple {CXXFLAGS, LINKFLAGS, DEFINES} that are needed in debug mode"""
+        """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are needed only in debug mode"""
         return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': ['_DEBUG']}
 
     def getOptimizedFlags(self, conf):
-        """Get tuple {CXXFLAGS, LINKFLAGS, DEFINES} that are needed in optimized mode"""
+        """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are needed only in optimized mode"""
         return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': ['NDEBUG']}
 
 class GccBasicFlags(CompilerFlags):
@@ -100,21 +100,25 @@
     """
     def getDebugFlags(self, conf):
         flags = super(GccBasicFlags, self).getDebugFlags(conf)
-        flags['CXXFLAGS'] += ['-pedantic',
-                              '-Wall',
-                              '-O0',
+        flags['CXXFLAGS'] += ['-O0',
                               '-g3',
+                              '-pedantic',
+                              '-Wall',
+                              '-Wextra',
                               '-Werror',
+                              '-Wno-unused-parameter',
                               '-Wno-error=maybe-uninitialized', # Bug #1615
                               ]
         return flags
 
     def getOptimizedFlags(self, conf):
         flags = super(GccBasicFlags, self).getOptimizedFlags(conf)
-        flags['CXXFLAGS'] += ['-pedantic',
-                              '-Wall',
-                              '-O2',
+        flags['CXXFLAGS'] += ['-O2',
                               '-g',
+                              '-pedantic',
+                              '-Wall',
+                              '-Wextra',
+                              '-Wno-unused-parameter',
                               ]
         return flags
 
@@ -136,6 +140,9 @@
 
     def getDebugFlags(self, conf):
         flags = super(GccFlags, self).getDebugFlags(conf)
+        version = tuple(int(i) for i in conf.env['CC_VERSION'])
+        if version < (5, 1, 0):
+            flags['CXXFLAGS'] += ['-Wno-missing-field-initializers']
         flags['CXXFLAGS'] += ['-Og', # gcc >= 4.8
                               '-fdiagnostics-color', # gcc >= 4.9
                               ]
@@ -143,6 +150,9 @@
 
     def getOptimizedFlags(self, conf):
         flags = super(GccFlags, self).getOptimizedFlags(conf)
+        version = tuple(int(i) for i in conf.env['CC_VERSION'])
+        if version < (5, 1, 0):
+            flags['CXXFLAGS'] += ['-Wno-missing-field-initializers']
         flags['CXXFLAGS'] += ['-fdiagnostics-color'] # gcc >= 4.9
         return flags
 
diff --git a/.waf-tools/osx-security.py b/.waf-tools/osx-security.py
index 9bcb3a8..f7f273e 100644
--- a/.waf-tools/osx-security.py
+++ b/.waf-tools/osx-security.py
@@ -10,11 +10,7 @@
 #include <Security/SecRandom.h>
 #include <CoreServices/CoreServices.h>
 #include <Security/SecDigestTransform.h>
-
-int main(int argc, char **argv) {
-    (void)argc; (void)argv;
-    return 0;
-}
+int main() {}
 '''
 
 @conf