diff --git a/.gitignore b/.gitignore
index 3159f7f..823af82 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 *.kdev4
+build
diff --git a/src/CgStr.hpp b/src/CgStr.hpp
index 19b7cb9..ec31d8f 100644
--- a/src/CgStr.hpp
+++ b/src/CgStr.hpp
@@ -6,22 +6,23 @@
 #include <cassert>
 #include <ostream>
 #include <string>
+#include <utility>
 
 namespace synth {
 
-class CgStr {
+class CgStr final {
 public:
     CgStr(CXString&& s)
-        : m_data(s)
+        : m_data(std::move(s))
     { }
 
-    CgStr(CgStr&& other)
+    CgStr(CgStr&& other) noexcept
         : m_data(std::move(other.m_data))
     {
         other.m_data.data = nullptr;
     }
 
-    CgStr& operator=(CgStr&& other) {
+    CgStr& operator=(CgStr&& other) noexcept {
         destroy();
         m_data = std::move(other.m_data);
         other.m_data.data = nullptr; // HACK Undocumented behavior.
@@ -29,7 +30,7 @@ class CgStr {
         return *this;
     }
 
-    ~CgStr() {
+    ~CgStr() noexcept {
         destroy();
     }
 
diff --git a/src/FileIdSupport.hpp b/src/FileIdSupport.hpp
index d0dd52f..26bcce8 100644
--- a/src/FileIdSupport.hpp
+++ b/src/FileIdSupport.hpp
@@ -3,6 +3,8 @@
 
 #include <clang-c/Index.h>
 #include <algorithm>
+#include <iterator>
+#include <functional>
 
 namespace std {
     template <>
@@ -30,7 +32,8 @@ namespace std {
             return std::equal(
                 std::begin(lhs.data),
                 std::end(lhs.data),
-                std::begin(rhs.data));
+                std::begin(rhs.data),
+                std::end(rhs.data));
         }
     };
 }
diff --git a/src/MultiTuProcessor.hpp b/src/MultiTuProcessor.hpp
index 47ebd23..9801e4e 100644
--- a/src/MultiTuProcessor.hpp
+++ b/src/MultiTuProcessor.hpp
@@ -1,7 +1,7 @@
 #ifndef SYNTH_MULTI_TU_PROCESSOR_HPP_INCLUDED
 #define SYNTH_MULTI_TU_PROCESSOR_HPP_INCLUDED
 
-#include "fileidsupport.hpp"
+#include "FileIdSupport.hpp"
 #include "output.hpp"
 
 #include <boost/filesystem/path.hpp>
@@ -84,7 +84,7 @@ class MultiTuProcessor {
     // Common prefix of all keys in m_dirs
     fs::path m_rootInDir;
 
-    std::mutex m_mut;
+    mutable std::mutex m_mut;
 };
 
 } // namespace synth
diff --git a/src/annotate.cpp b/src/annotate.cpp
index 091d0a4..9d7fe07 100644
--- a/src/annotate.cpp
+++ b/src/annotate.cpp
@@ -3,7 +3,7 @@
 #include "CgStr.hpp"
 #include "MultiTuProcessor.hpp"
 #include "cgWrappers.hpp"
-#include "fileIdSupport.hpp"
+#include "FileIdSupport.hpp"
 #include "highlight.hpp"
 #include "output.hpp"
 #include "xref.hpp"
diff --git a/src/cgWrappers.hpp b/src/cgWrappers.hpp
index 9e99eda..387c566 100644
--- a/src/cgWrappers.hpp
+++ b/src/cgWrappers.hpp
@@ -12,15 +12,15 @@
 
 namespace synth {
 
-class CgTokensHandle {
+class CgTokensHandle final {
 public:
     CgTokensHandle(CXToken* data, unsigned ntokens, CXTranslationUnit tu_)
         : m_data(data), m_ntokens(ntokens), m_tu(tu_)
     {}
 
-    ~CgTokensHandle() { destroy(); }
+    ~CgTokensHandle() noexcept { destroy(); }
 
-    CgTokensHandle(CgTokensHandle&& other)
+    CgTokensHandle(CgTokensHandle&& other) noexcept
         : m_data(other.m_data)
         , m_ntokens(other.m_ntokens)
         , m_tu(other.m_tu)
@@ -28,7 +28,7 @@ class CgTokensHandle {
         other.release();
     }
 
-    CgTokensHandle& operator= (CgTokensHandle&& other)
+    CgTokensHandle& operator= (CgTokensHandle&& other) noexcept
     {
         destroy();
         m_data = other.m_data;
@@ -40,7 +40,7 @@ class CgTokensHandle {
 
     CXTranslationUnit tu() const { return m_tu; }
     unsigned size() const { return m_ntokens; }
-    CXToken* tokens() { return m_data; }
+    CXToken* tokens() const { return m_data; }
 
 private:
     void destroy()
diff --git a/src/cmdline.cpp b/src/cmdline.cpp
index 70039fc..80c4677 100644
--- a/src/cmdline.cpp
+++ b/src/cmdline.cpp
@@ -3,6 +3,7 @@
 #include <cstring>
 #include <stdexcept>
 #include <thread>
+#include <utility>
 
 using namespace synth;
 
@@ -77,7 +78,7 @@ CmdLineArgs CmdLineArgs::parse(int argc, char const* const* argv)
         throw std::runtime_error("Superfluous commandline arguments.");
 
     if (r.nThreads == 0)
-        r.nThreads = std::thread::hardware_concurrency();
+        r.nThreads = std::max(std::thread::hardware_concurrency(), 1u);
     for (auto& dir : r.inOutDirs) {
         if (!dir.second)
             dir.second = ".";
diff --git a/src/highlight.cpp b/src/highlight.cpp
index eb7c0c2..7c7ac6e 100644
--- a/src/highlight.cpp
+++ b/src/highlight.cpp
@@ -10,7 +10,7 @@
 using namespace synth;
 
 
-unsigned const kMaxRefRecursion = 16;
+static unsigned const kMaxRefRecursion = 16;
 
 static bool isTypeKind(CXCursorKind k)
 {