diff --git a/gfx/layers/d3d9/CompositorD3D9.cpp b/gfx/layers/d3d9/CompositorD3D9.cpp
index c8b1515a5307..be92764754ce 100644
--- a/gfx/layers/d3d9/CompositorD3D9.cpp
+++ b/gfx/layers/d3d9/CompositorD3D9.cpp
@@ -489,7 +489,6 @@ CompositorD3D9::SetMask(const EffectChain &aEffectChain, uint32_t aMaskTexture)
 
   TextureSourceD3D9 *source = maskEffect->mMaskTexture->AsSourceD3D9();
 
-  MOZ_ASSERT(aMaskTexture >= 0);
   device()->SetTexture(aMaskTexture, source->GetD3D9Texture());
 
   const gfx::Matrix4x4& maskTransform = maskEffect->mMaskTransform;
diff --git a/hal/windows/WindowsGamepad.cpp b/hal/windows/WindowsGamepad.cpp
index a1266c97a37e..3419971d0906 100644
--- a/hal/windows/WindowsGamepad.cpp
+++ b/hal/windows/WindowsGamepad.cpp
@@ -50,6 +50,8 @@ const uint32_t kDevicesChangedStableDelay = 200;
 // poll it periodically. 50ms is arbitrarily chosen.
 const uint32_t kXInputPollInterval = 50;
 
+const UINT kRawInputError = (UINT)-1;
+
 #ifndef XUSER_MAX_COUNT
 #define XUSER_MAX_COUNT 4
 #endif
@@ -178,7 +180,7 @@ bool
 GetPreparsedData(HANDLE handle, nsTArray<uint8_t>& data)
 {
   UINT size;
-  if (GetRawInputDeviceInfo(handle, RIDI_PREPARSEDDATA, nullptr, &size) < 0) {
+  if (GetRawInputDeviceInfo(handle, RIDI_PREPARSEDDATA, nullptr, &size) == kRawInputError) {
     return false;
   }
   data.SetLength(size);
@@ -418,13 +420,13 @@ WindowsGamepadService::ScanForRawInputDevices()
 
   UINT numDevices;
   if (GetRawInputDeviceList(nullptr, &numDevices, sizeof(RAWINPUTDEVICELIST))
-      == -1) {
+      == kRawInputError) {
     return;
   }
   nsTArray<RAWINPUTDEVICELIST> devices(numDevices);
   devices.SetLength(numDevices);
   if (GetRawInputDeviceList(devices.Elements(), &numDevices,
-                            sizeof(RAWINPUTDEVICELIST)) == -1) {
+                            sizeof(RAWINPUTDEVICELIST)) == kRawInputError) {
     return;
   }
 
@@ -631,7 +633,7 @@ WindowsGamepadService::GetRawGamepad(HANDLE handle)
 
   RID_DEVICE_INFO rdi = {};
   UINT size = rdi.cbSize = sizeof(RID_DEVICE_INFO);
-  if (GetRawInputDeviceInfo(handle, RIDI_DEVICEINFO, &rdi, &size) < 0) {
+  if (GetRawInputDeviceInfo(handle, RIDI_DEVICEINFO, &rdi, &size) == kRawInputError) {
     return false;
   }
   // Ensure that this is a device we care about
@@ -642,14 +644,13 @@ WindowsGamepadService::GetRawGamepad(HANDLE handle)
   Gamepad gamepad = {};
 
   // Device name is a mostly-opaque string.
-  if (GetRawInputDeviceInfo(handle, RIDI_DEVICENAME, nullptr, &size) < 0) {
+  if (GetRawInputDeviceInfo(handle, RIDI_DEVICENAME, nullptr, &size) == kRawInputError) {
     return false;
   }
 
   nsTArray<wchar_t> devname(size);
   devname.SetLength(size);
-  if (GetRawInputDeviceInfo(handle, RIDI_DEVICENAME, devname.Elements(), &size)
-      <= 0) {
+  if (GetRawInputDeviceInfo(handle, RIDI_DEVICENAME, devname.Elements(), &size) == kRawInputError) {
     return false;
   }
 
@@ -667,7 +668,7 @@ WindowsGamepadService::GetRawGamepad(HANDLE handle)
   size = sizeof(name);
   nsTArray<char> gamepad_name;
   HANDLE hid_handle = CreateFile(devname.Elements(), GENERIC_READ | GENERIC_WRITE,
-    FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, NULL, NULL);
+    FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL);
   if (hid_handle) {
     if (mHID.mHidD_GetProductString(hid_handle, &name, size)) {
       int bytes = WideCharToMultiByte(CP_UTF8, 0, name, -1, nullptr, 0, nullptr,
@@ -786,7 +787,7 @@ WindowsGamepadService::HandleRawInput(HRAWINPUT handle)
   nsTArray<uint8_t> data(size);
   data.SetLength(size);
   if (GetRawInputData(handle, RID_INPUT, data.Elements(), &size,
-                      sizeof(RAWINPUTHEADER)) < 0) {
+                      sizeof(RAWINPUTHEADER)) == kRawInputError) {
     return false;
   }
   PRAWINPUT raw = reinterpret_cast<PRAWINPUT>(data.Elements());
diff --git a/ipc/chromium/src/base/waitable_event_win.cc b/ipc/chromium/src/base/waitable_event_win.cc
index ac85c5c80d64..21ee0a900140 100644
--- a/ipc/chromium/src/base/waitable_event_win.cc
+++ b/ipc/chromium/src/base/waitable_event_win.cc
@@ -86,7 +86,7 @@ size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
       WaitForMultipleObjects(count, handles,
                              FALSE,      // don't wait for all the objects
                              INFINITE);  // no timeout
-  if (result < WAIT_OBJECT_0 || result >= WAIT_OBJECT_0 + count) {
+  if (result >= WAIT_OBJECT_0 + count) {
     NOTREACHED() << "WaitForMultipleObjects failed: " << GetLastError();
     return 0;
   }
diff --git a/widget/windows/KeyboardLayout.cpp b/widget/windows/KeyboardLayout.cpp
index e248235b9c7c..162e4beffc15 100644
--- a/widget/windows/KeyboardLayout.cpp
+++ b/widget/windows/KeyboardLayout.cpp
@@ -606,7 +606,7 @@ UniCharsAndModifiers
 VirtualKey::GetNativeUniChars(ShiftState aShiftState) const
 {
 #ifdef DEBUG
-  if (aShiftState < 0 || aShiftState >= ArrayLength(mShiftStates)) {
+  if (aShiftState >= ArrayLength(mShiftStates)) {
     nsPrintfCString warning("Shift state is out of range: "
                             "aShiftState=%d, ArrayLength(mShiftState)=%d",
                             aShiftState, ArrayLength(mShiftStates));
@@ -2259,8 +2259,8 @@ KeyboardLayout::LoadLayout(HKL aLayout)
     static const UINT kMapType =
       IsVistaOrLater() ? MAPVK_VSC_TO_VK_EX : MAPVK_VSC_TO_VK;
     PR_LOG(sKeyboardLayoutLogger, PR_LOG_DEBUG,
-           ("Logging virtual keycode values for scancode (0x%08X)...",
-            reinterpret_cast<const uint32_t>(mKeyboardLayout)));
+           ("Logging virtual keycode values for scancode (0x%p)...",
+            mKeyboardLayout));
     for (uint32_t i = 0; i < ArrayLength(kExtendedScanCode); i++) {
       for (uint32_t j = 1; j <= 0xFF; j++) {
         UINT scanCode = kExtendedScanCode[i] + j;
diff --git a/widget/windows/WindowHook.cpp b/widget/windows/WindowHook.cpp
index 2c3a533f34bf..8e87a3a55efa 100644
--- a/widget/windows/WindowHook.cpp
+++ b/widget/windows/WindowHook.cpp
@@ -94,7 +94,7 @@ WindowHook::DeleteIfEmpty(MessageData *data) {
 
   MessageDataArray::index_type idx;
   idx = data - mMessageData.Elements();
-  NS_ASSERTION(idx >= 0 && idx < mMessageData.Length(), "Attempted to delete MessageData that doesn't belong to this array!");
+  NS_ASSERTION(idx < mMessageData.Length(), "Attempted to delete MessageData that doesn't belong to this array!");
   mMessageData.RemoveElementAt(idx);
 }
 
diff --git a/widget/windows/nsDragService.cpp b/widget/windows/nsDragService.cpp
index 4d9016d612b8..96c7c1c7a20d 100644
--- a/widget/windows/nsDragService.cpp
+++ b/widget/windows/nsDragService.cpp
@@ -424,7 +424,7 @@ nsDragService::GetData(nsITransferable * aTransferable, uint32_t anItem)
     // multiple items, use |anItem| as an index into our collection
     nsDataObjCollection * dataObjCol = GetDataObjCollection(mDataObject);
     uint32_t cnt = dataObjCol->GetNumDataObjects();
-    if (anItem >= 0 && anItem < cnt) {
+    if (anItem < cnt) {
       IDataObject * dataObj = dataObjCol->GetDataObjectAt(anItem);
       dataFound = nsClipboard::GetDataFromDataObject(dataObj, 0, nullptr,
                                                      aTransferable);