diff --git a/debuggerd/test/BacktraceMock.h b/debuggerd/test/BacktraceMock.h
index f75534e..6104f7e 100644
--- a/debuggerd/test/BacktraceMock.h
+++ b/debuggerd/test/BacktraceMock.h
@@ -41,7 +41,7 @@
 
 class BacktraceMock : public Backtrace {
  public:
-  BacktraceMock(BacktraceMapMock* map) : Backtrace(0, 0, map) {
+  explicit BacktraceMock(BacktraceMapMock* map) : Backtrace(0, 0, map) {
     if (map_ == nullptr) {
       abort();
     }
diff --git a/fastboot/socket.h b/fastboot/socket.h
index de543db..7eaa0ab 100644
--- a/fastboot/socket.h
+++ b/fastboot/socket.h
@@ -104,7 +104,7 @@
 
   protected:
     // Protected constructor to force factory function use.
-    Socket(cutils_socket_t sock);
+    explicit Socket(cutils_socket_t sock);
 
     // Blocks up to |timeout_ms| until a read is possible on |sock_|, and sets |receive_timed_out_|
     // as appropriate to help distinguish between normal timeouts and fatal errors. Returns true if
diff --git a/init/action.h b/init/action.h
index 6dee2d0..0bae9f0 100644
--- a/init/action.h
+++ b/init/action.h
@@ -44,7 +44,7 @@
 
 class Action {
 public:
-    Action(bool oneshot = false);
+    explicit Action(bool oneshot = false);
 
     bool AddCommand(const std::vector<std::string>& args,
                     const std::string& filename, int line, std::string* err);
diff --git a/init/parser/tokenizer.h b/init/parser/tokenizer.h
index 8312a08..ade8f73 100644
--- a/init/parser/tokenizer.h
+++ b/init/parser/tokenizer.h
@@ -36,7 +36,7 @@
 // a TOK_NEWLINE will not be generated for that line.
 class Tokenizer {
  public:
-  Tokenizer(const std::string& data);
+  explicit Tokenizer(const std::string& data);
   ~Tokenizer();
 
   enum TokenType { TOK_START, TOK_END, TOK_NEWLINE, TOK_TEXT };
diff --git a/libbacktrace/UnwindMap.h b/libbacktrace/UnwindMap.h
index f85b54a..d5bec06 100644
--- a/libbacktrace/UnwindMap.h
+++ b/libbacktrace/UnwindMap.h
@@ -29,7 +29,7 @@
 
 class UnwindMap : public BacktraceMap {
 public:
-  UnwindMap(pid_t pid);
+  explicit UnwindMap(pid_t pid);
 
   unw_map_cursor_t* GetMapCursor() { return &map_cursor_; }
 
@@ -39,7 +39,7 @@
 
 class UnwindMapRemote : public UnwindMap {
 public:
-  UnwindMapRemote(pid_t pid);
+  explicit UnwindMapRemote(pid_t pid);
   virtual ~UnwindMapRemote();
 
   bool Build() override;
diff --git a/liblog/tests/benchmark.h b/liblog/tests/benchmark.h
index 57b3748..e9280f6 100644
--- a/liblog/tests/benchmark.h
+++ b/liblog/tests/benchmark.h
@@ -38,7 +38,7 @@
   Benchmark(const char* name, void (*fn)(int)) : name_(strdup(name)), fn_(fn) {
     BenchmarkRegister(this);
   }
-  Benchmark(const char* name) : name_(strdup(name)), fn_(NULL) {}
+  explicit Benchmark(const char* name) : name_(strdup(name)), fn_(NULL) {}
 
   virtual ~Benchmark() {
     free(name_);
diff --git a/libmemunreachable/Allocator.h b/libmemunreachable/Allocator.h
index a8f579e..5390739 100644
--- a/libmemunreachable/Allocator.h
+++ b/libmemunreachable/Allocator.h
@@ -109,13 +109,13 @@
   }
 
   // Construct an STLAllocator on top of a Heap
-  STLAllocator(const Heap& heap) :
+  STLAllocator(const Heap& heap) :  // NOLINT, implicit
       heap_(heap) {
   }
 
   // Rebind an STLAllocator from an another STLAllocator
   template<typename U>
-  STLAllocator(const STLAllocator<U>& other) :
+  STLAllocator(const STLAllocator<U>& other) :  // NOLINT, implicit
       heap_(other.heap_) {
   }
 
@@ -155,12 +155,12 @@
  public:
   ~Allocator() {}
 
-  Allocator(const Heap& other) :
+  Allocator(const Heap& other) : // NOLINT, implicit
       STLAllocator<T>(other) {
   }
 
   template<typename U>
-  Allocator(const STLAllocator<U>& other) :
+  Allocator(const STLAllocator<U>& other) :  // NOLINT, implicit
       STLAllocator<T>(other) {
   }
 
diff --git a/libmemunreachable/HeapWalker.h b/libmemunreachable/HeapWalker.h
index 3c1b513..b25696f 100644
--- a/libmemunreachable/HeapWalker.h
+++ b/libmemunreachable/HeapWalker.h
@@ -48,7 +48,7 @@
 
 class HeapWalker {
  public:
-  HeapWalker(Allocator<HeapWalker> allocator) : allocator_(allocator),
+  explicit HeapWalker(Allocator<HeapWalker> allocator) : allocator_(allocator),
     allocations_(allocator), allocation_bytes_(0),
 	roots_(allocator), root_vals_(allocator),
 	segv_handler_(allocator), walking_ptr_(0) {
diff --git a/libmemunreachable/LeakFolding.h b/libmemunreachable/LeakFolding.h
index 732d3f2..9c6a525 100644
--- a/libmemunreachable/LeakFolding.h
+++ b/libmemunreachable/LeakFolding.h
@@ -54,7 +54,7 @@
     bool dominator;
     SCCInfo* accumulator;
 
-    SCCInfo(Allocator<SCCInfo> allocator) : node(this, allocator),
+    explicit SCCInfo(Allocator<SCCInfo> allocator) : node(this, allocator),
         count(0), size(0), cuumulative_count(0), cuumulative_size(0),
         dominator(false), accumulator(nullptr) {}
    private:
diff --git a/libmemunreachable/LinkedList.h b/libmemunreachable/LinkedList.h
index 3e44035..132842d 100644
--- a/libmemunreachable/LinkedList.h
+++ b/libmemunreachable/LinkedList.h
@@ -21,7 +21,7 @@
 class LinkedList {
 public:
     LinkedList() : next_(this), prev_(this), data_() {}
-    LinkedList(T data) : LinkedList() {
+    explicit LinkedList(T data) : LinkedList() {
         data_ = data;
     }
     ~LinkedList() {}
diff --git a/libmemunreachable/PtracerThread.h b/libmemunreachable/PtracerThread.h
index 4d6ca9a..f88b599 100644
--- a/libmemunreachable/PtracerThread.h
+++ b/libmemunreachable/PtracerThread.h
@@ -32,7 +32,7 @@
 // the parent.
 class PtracerThread {
  public:
-  PtracerThread(const std::function<int()>& func);
+  explicit PtracerThread(const std::function<int()>& func);
   ~PtracerThread();
   bool Start();
   int Join();
diff --git a/libmemunreachable/ScopedDisableMalloc.h b/libmemunreachable/ScopedDisableMalloc.h
index 4f96376..758d317 100644
--- a/libmemunreachable/ScopedDisableMalloc.h
+++ b/libmemunreachable/ScopedDisableMalloc.h
@@ -74,7 +74,7 @@
 
 class ScopedDisableMallocTimeout {
  public:
-  ScopedDisableMallocTimeout(std::chrono::milliseconds timeout = std::chrono::milliseconds(2000)) :
+  explicit ScopedDisableMallocTimeout(std::chrono::milliseconds timeout = std::chrono::milliseconds(2000)) :
     timeout_(timeout), timed_out_(false), disable_malloc_() {
     Disable();
   }
diff --git a/libmemunreachable/ScopedSignalHandler.h b/libmemunreachable/ScopedSignalHandler.h
index e006d43..1fd9d4d 100644
--- a/libmemunreachable/ScopedSignalHandler.h
+++ b/libmemunreachable/ScopedSignalHandler.h
@@ -30,7 +30,7 @@
  public:
   using Fn = std::function<void(ScopedSignalHandler&, int, siginfo_t*, void*)>;
 
-  ScopedSignalHandler(Allocator<Fn> allocator) : allocator_(allocator), signal_(-1) {}
+  explicit ScopedSignalHandler(Allocator<Fn> allocator) : allocator_(allocator), signal_(-1) {}
   ~ScopedSignalHandler() {
     reset();
   }
diff --git a/libmemunreachable/Semaphore.h b/libmemunreachable/Semaphore.h
index 45e8c81..6bcf4ea 100644
--- a/libmemunreachable/Semaphore.h
+++ b/libmemunreachable/Semaphore.h
@@ -24,7 +24,7 @@
 
 class Semaphore {
  public:
-  Semaphore(int count = 0) : count_(count) {}
+  explicit Semaphore(int count = 0) : count_(count) {}
   ~Semaphore() = default;
 
   void Wait(std::chrono::milliseconds ms) {
diff --git a/libmemunreachable/Tarjan.h b/libmemunreachable/Tarjan.h
index d7ecdb9..dcd139a 100644
--- a/libmemunreachable/Tarjan.h
+++ b/libmemunreachable/Tarjan.h
@@ -62,7 +62,7 @@
 template<class T>
 class TarjanAlgorithm {
  public:
-  TarjanAlgorithm(Allocator<void> allocator) : index_(0),
+  explicit TarjanAlgorithm(Allocator<void> allocator) : index_(0),
     stack_(allocator), components_(allocator) {}
 
   void Execute(Graph<T>& graph, SCCList<T>& out);
diff --git a/libmemunreachable/tests/MemUnreachable_test.cpp b/libmemunreachable/tests/MemUnreachable_test.cpp
index 0747b12..2ae3db8 100644
--- a/libmemunreachable/tests/MemUnreachable_test.cpp
+++ b/libmemunreachable/tests/MemUnreachable_test.cpp
@@ -27,7 +27,7 @@
 
 class HiddenPointer {
  public:
-  HiddenPointer(size_t size = 256) {
+  explicit HiddenPointer(size_t size = 256) {
     Set(malloc(size));
   }
   ~HiddenPointer() {
diff --git a/libpixelflinger/codeflinger/ARMAssembler.h b/libpixelflinger/codeflinger/ARMAssembler.h
index 7178c65..76acf7e 100644
--- a/libpixelflinger/codeflinger/ARMAssembler.h
+++ b/libpixelflinger/codeflinger/ARMAssembler.h
@@ -35,7 +35,7 @@
 class ARMAssembler : public ARMAssemblerInterface
 {
 public:
-                ARMAssembler(const sp<Assembly>& assembly);
+    explicit    ARMAssembler(const sp<Assembly>& assembly);
     virtual     ~ARMAssembler();
 
     uint32_t*   base() const;
diff --git a/libpixelflinger/codeflinger/ARMAssemblerProxy.h b/libpixelflinger/codeflinger/ARMAssemblerProxy.h
index b852794..10d0390 100644
--- a/libpixelflinger/codeflinger/ARMAssemblerProxy.h
+++ b/libpixelflinger/codeflinger/ARMAssemblerProxy.h
@@ -34,7 +34,7 @@
     // ARMAssemblerProxy take ownership of the target
 
                 ARMAssemblerProxy();
-                ARMAssemblerProxy(ARMAssemblerInterface* target);
+    explicit    ARMAssemblerProxy(ARMAssemblerInterface* target);
     virtual     ~ARMAssemblerProxy();
 
     void setTarget(ARMAssemblerInterface* target);
diff --git a/libpixelflinger/codeflinger/Arm64Assembler.h b/libpixelflinger/codeflinger/Arm64Assembler.h
index c9be116..527c757 100644
--- a/libpixelflinger/codeflinger/Arm64Assembler.h
+++ b/libpixelflinger/codeflinger/Arm64Assembler.h
@@ -47,8 +47,8 @@
 class ArmToArm64Assembler : public ARMAssemblerInterface
 {
 public:
-                ArmToArm64Assembler(const sp<Assembly>& assembly);
-                ArmToArm64Assembler(void *base);
+    explicit    ArmToArm64Assembler(const sp<Assembly>& assembly);
+    explicit    ArmToArm64Assembler(void *base);
     virtual     ~ArmToArm64Assembler();
 
     uint32_t*   base() const;
diff --git a/libpixelflinger/codeflinger/CodeCache.h b/libpixelflinger/codeflinger/CodeCache.h
index 0fb6fd5..c0e0684 100644
--- a/libpixelflinger/codeflinger/CodeCache.h
+++ b/libpixelflinger/codeflinger/CodeCache.h
@@ -42,7 +42,7 @@
 class AssemblyKey : public AssemblyKeyBase
 {
 public:
-    AssemblyKey(const T& rhs) : mKey(rhs) { }
+    explicit AssemblyKey(const T& rhs) : mKey(rhs) { }
     virtual int compare_type(const AssemblyKeyBase& key) const {
         const T& rhs = static_cast<const AssemblyKey&>(key).mKey;
         return android::compare_type(mKey, rhs);
@@ -56,7 +56,7 @@
 class Assembly
 {
 public:
-                Assembly(size_t size);
+    explicit    Assembly(size_t size);
     virtual     ~Assembly();
 
     ssize_t     size() const;
@@ -80,13 +80,13 @@
 {
 public:
 // pretty simple cache API...
-                CodeCache(size_t size);
-                ~CodeCache();
-    
-            sp<Assembly>        lookup(const AssemblyKeyBase& key) const;
+    explicit            CodeCache(size_t size);
+                        ~CodeCache();
 
-            int                 cache(  const AssemblyKeyBase& key,
-                                        const sp<Assembly>& assembly);
+    sp<Assembly>        lookup(const AssemblyKeyBase& key) const;
+
+    int                 cache(const AssemblyKeyBase& key,
+                              const sp<Assembly>& assembly);
 
 private:
     // nothing to see here...
@@ -105,7 +105,7 @@
         const AssemblyKeyBase* mKey;
     public:
         key_t() { };
-        key_t(const AssemblyKeyBase& k) : mKey(&k)  { }
+        explicit key_t(const AssemblyKeyBase& k) : mKey(&k)  { }
     };
 
     mutable pthread_mutex_t             mLock;
diff --git a/libpixelflinger/codeflinger/GGLAssembler.h b/libpixelflinger/codeflinger/GGLAssembler.h
index ecc242a..47dbf3a 100644
--- a/libpixelflinger/codeflinger/GGLAssembler.h
+++ b/libpixelflinger/codeflinger/GGLAssembler.h
@@ -49,7 +49,7 @@
 public:
     class RegisterFile;
     
-                    RegisterAllocator(int arch);
+                    RegisterAllocator(int arch);  // NOLINT, implicit
     RegisterFile&   registerFile();
     int             reserveReg(int reg);
     int             obtainReg();
@@ -59,7 +59,7 @@
     class RegisterFile
     {
     public:
-                            RegisterFile(int arch);
+                            RegisterFile(int arch);  // NOLINT, implicit
                             RegisterFile(const RegisterFile& rhs, int arch);
                             ~RegisterFile();
 
@@ -101,7 +101,7 @@
     class Scratch
     {
     public:
-            Scratch(RegisterFile& regFile)
+            explicit Scratch(RegisterFile& regFile)
                 : mRegFile(regFile), mScratch(0) { 
             }
             ~Scratch() {
@@ -177,8 +177,8 @@
 {
 public:
 
-                    GGLAssembler(ARMAssemblerInterface* target);
-        virtual     ~GGLAssembler();
+    explicit    GGLAssembler(ARMAssemblerInterface* target);
+    virtual     ~GGLAssembler();
 
     uint32_t*   base() const { return 0; } // XXX
     uint32_t*   pc() const { return 0; } // XXX
@@ -206,7 +206,7 @@
         struct reg_t {
             reg_t() : reg(-1), flags(0) {
             }
-            reg_t(int r, int f=0)
+            reg_t(int r, int f=0)  // NOLINT, implicit
                 : reg(r), flags(f) {
             }
             void setTo(int r, int f=0) {
@@ -219,7 +219,7 @@
         struct integer_t : public reg_t {
             integer_t() : reg_t(), s(0) {
             }
-            integer_t(int r, int sz=32, int f=0)
+            integer_t(int r, int sz=32, int f=0)  // NOLINT, implicit
                 : reg_t(r, f), s(sz) {
             }
             void setTo(int r, int sz=32, int f=0) {
@@ -251,7 +251,7 @@
         struct component_t : public reg_t {
             component_t() : reg_t(), h(0), l(0) {
             }
-            component_t(int r, int f=0)
+            component_t(int r, int f=0)  // NOLINT, implicit
                 : reg_t(r, f), h(0), l(0) {
             }
             component_t(int r, int lo, int hi, int f=0)
diff --git a/libpixelflinger/codeflinger/tinyutils/smartpointer.h b/libpixelflinger/codeflinger/tinyutils/smartpointer.h
index 9d0a16e..23a5f7e 100644
--- a/libpixelflinger/codeflinger/tinyutils/smartpointer.h
+++ b/libpixelflinger/codeflinger/tinyutils/smartpointer.h
@@ -51,10 +51,10 @@
 public:
     inline sp() : m_ptr(0) { }
 
-    sp(T* other);
+    sp(T* other);  // NOLINT, implicit
     sp(const sp<T>& other);
-    template<typename U> sp(U* other);
-    template<typename U> sp(const sp<U>& other);
+    template<typename U> sp(U* other);  // NOLINT, implicit
+    template<typename U> sp(const sp<U>& other);  // NOLINT, implicit
 
     ~sp();
     
diff --git a/libutils/tests/Looper_test.cpp b/libutils/tests/Looper_test.cpp
index 00077e6..bdb1bb7 100644
--- a/libutils/tests/Looper_test.cpp
+++ b/libutils/tests/Looper_test.cpp
@@ -76,7 +76,7 @@
     int fd;
     int events;
 
-    StubCallbackHandler(int nextResult) : nextResult(nextResult),
+    explicit StubCallbackHandler(int nextResult) : nextResult(nextResult),
             callbackCount(0), fd(-1), events(-1) {
     }
 
diff --git a/libutils/tests/StrongPointer_test.cpp b/libutils/tests/StrongPointer_test.cpp
index f46d6d1..323a6f2 100644
--- a/libutils/tests/StrongPointer_test.cpp
+++ b/libutils/tests/StrongPointer_test.cpp
@@ -23,7 +23,7 @@
 
 class Foo : public LightRefBase<Foo> {
 public:
-    Foo(bool* deleted_check) : mDeleted(deleted_check) {
+    explicit Foo(bool* deleted_check) : mDeleted(deleted_check) {
         *mDeleted = false;
     }
 
diff --git a/libutils/tests/TestHelpers.h b/libutils/tests/TestHelpers.h
index d8e985e..6801cd7 100644
--- a/libutils/tests/TestHelpers.h
+++ b/libutils/tests/TestHelpers.h
@@ -60,7 +60,7 @@
     int mDelayMillis;
 
 public:
-    DelayedTask(int delayMillis) : mDelayMillis(delayMillis) { }
+    explicit DelayedTask(int delayMillis) : mDelayMillis(delayMillis) { }
 
 protected:
     virtual ~DelayedTask() { }
diff --git a/logd/FlushCommand.h b/logd/FlushCommand.h
index 9224773..7172d5f 100644
--- a/logd/FlushCommand.h
+++ b/logd/FlushCommand.h
@@ -35,7 +35,7 @@
     uint64_t mTimeout;
 
 public:
-    FlushCommand(LogReader &mReader,
+    explicit FlushCommand(LogReader &mReader,
                  bool nonBlock = false,
                  unsigned long tail = -1,
                  unsigned int logMask = -1,
diff --git a/logd/LogBuffer.h b/logd/LogBuffer.h
index b390a0c..162c189 100644
--- a/logd/LogBuffer.h
+++ b/logd/LogBuffer.h
@@ -103,7 +103,7 @@
 public:
     LastLogTimes &mTimes;
 
-    LogBuffer(LastLogTimes *times);
+    explicit LogBuffer(LastLogTimes *times);
     void init();
     bool isMonotonic() { return monotonic; }
 
diff --git a/logd/LogCommand.h b/logd/LogCommand.h
index c944478..0adc2a1 100644
--- a/logd/LogCommand.h
+++ b/logd/LogCommand.h
@@ -22,7 +22,7 @@
 
 class LogCommand : public FrameworkCommand {
 public:
-    LogCommand(const char *cmd);
+    explicit LogCommand(const char *cmd);
     virtual ~LogCommand() {}
 };
 
diff --git a/logd/LogReader.h b/logd/LogReader.h
index 98674b8..fdcedf1 100644
--- a/logd/LogReader.h
+++ b/logd/LogReader.h
@@ -27,7 +27,7 @@
     LogBuffer &mLogbuf;
 
 public:
-    LogReader(LogBuffer *logbuf);
+    explicit LogReader(LogBuffer *logbuf);
     void notifyNewLog();
 
     LogBuffer &logbuf(void) const { return mLogbuf; }
diff --git a/metricsd/collectors/cpu_usage_collector.h b/metricsd/collectors/cpu_usage_collector.h
index f81dfcb..9f92cf3 100644
--- a/metricsd/collectors/cpu_usage_collector.h
+++ b/metricsd/collectors/cpu_usage_collector.h
@@ -23,7 +23,7 @@
 
 class CpuUsageCollector {
  public:
-  CpuUsageCollector(MetricsLibraryInterface* metrics_library);
+  explicit CpuUsageCollector(MetricsLibraryInterface* metrics_library);
 
   // Initialize this collector's state.
   void Init();
diff --git a/metricsd/collectors/disk_usage_collector.h b/metricsd/collectors/disk_usage_collector.h
index c1d4546..288b34b 100644
--- a/metricsd/collectors/disk_usage_collector.h
+++ b/metricsd/collectors/disk_usage_collector.h
@@ -23,7 +23,7 @@
 
 class DiskUsageCollector {
  public:
-  DiskUsageCollector(MetricsLibraryInterface* metrics_library);
+  explicit DiskUsageCollector(MetricsLibraryInterface* metrics_library);
 
   // Schedule the next collection.
   void Schedule();
diff --git a/metricsd/uploader/metricsd_service_runner.h b/metricsd/uploader/metricsd_service_runner.h
index f5dad21..b36d4a5 100644
--- a/metricsd/uploader/metricsd_service_runner.h
+++ b/metricsd/uploader/metricsd_service_runner.h
@@ -27,7 +27,7 @@
 
 class MetricsdServiceRunner {
  public:
-  MetricsdServiceRunner(std::shared_ptr<CrashCounters> counters);
+  explicit MetricsdServiceRunner(std::shared_ptr<CrashCounters> counters);
 
   // Start the Metricsd Binder service in a new thread.
   void Start();
diff --git a/trusty/gatekeeper/trusty_gatekeeper.h b/trusty/gatekeeper/trusty_gatekeeper.h
index 82108dc..2becc49 100644
--- a/trusty/gatekeeper/trusty_gatekeeper.h
+++ b/trusty/gatekeeper/trusty_gatekeeper.h
@@ -27,7 +27,7 @@
 class TrustyGateKeeperDevice {
     public:
 
-    TrustyGateKeeperDevice(const hw_module_t* module);
+    explicit TrustyGateKeeperDevice(const hw_module_t* module);
     ~TrustyGateKeeperDevice();
 
     hw_device_t* hw_device();
diff --git a/trusty/keymaster/trusty_keymaster_device.h b/trusty/keymaster/trusty_keymaster_device.h
index cb74386..68cf40c 100644
--- a/trusty/keymaster/trusty_keymaster_device.h
+++ b/trusty/keymaster/trusty_keymaster_device.h
@@ -39,7 +39,7 @@
      * These are the only symbols that will be exported by libtrustykeymaster.  All functionality
      * can be reached via the function pointers in device_.
      */
-    __attribute__((visibility("default"))) TrustyKeymasterDevice(const hw_module_t* module);
+    __attribute__((visibility("default"))) explicit TrustyKeymasterDevice(const hw_module_t* module);
     __attribute__((visibility("default"))) hw_device_t* hw_device();
 
     ~TrustyKeymasterDevice();