diff --git a/llvm/include/llvm/Support/raw_ostream.h b/llvm/include/llvm/Support/raw_ostream.h
index 0debc5da7a68..705f1790b1d3 100644
--- a/llvm/include/llvm/Support/raw_ostream.h
+++ b/llvm/include/llvm/Support/raw_ostream.h
@@ -64,7 +64,7 @@ private:
   /// this buffer.
   char *OutBufStart, *OutBufEnd, *OutBufCur;
 
-  enum BufferKind {
+  enum class BufferKind {
     Unbuffered = 0,
     InternalBuffer,
     ExternalBuffer
@@ -97,7 +97,8 @@ public:
   static const Colors RESET = Colors::RESET;
 
   explicit raw_ostream(bool unbuffered = false)
-      : BufferMode(unbuffered ? Unbuffered : InternalBuffer) {
+      : BufferMode(unbuffered ? BufferKind::Unbuffered
+                              : BufferKind::InternalBuffer) {
     // Start out ready to flush.
     OutBufStart = OutBufEnd = OutBufCur = nullptr;
   }
@@ -121,13 +122,13 @@ public:
   /// Set the stream to be buffered, using the specified buffer size.
   void SetBufferSize(size_t Size) {
     flush();
-    SetBufferAndMode(new char[Size], Size, InternalBuffer);
+    SetBufferAndMode(new char[Size], Size, BufferKind::InternalBuffer);
   }
 
   size_t GetBufferSize() const {
     // If we're supposed to be buffered but haven't actually gotten around
     // to allocating the buffer yet, return the value that would be used.
-    if (BufferMode != Unbuffered && OutBufStart == nullptr)
+    if (BufferMode != BufferKind::Unbuffered && OutBufStart == nullptr)
       return preferred_buffer_size();
 
     // Otherwise just return the size of the allocated buffer.
@@ -139,7 +140,7 @@ public:
   /// when the stream is being set to unbuffered.
   void SetUnbuffered() {
     flush();
-    SetBufferAndMode(nullptr, 0, Unbuffered);
+    SetBufferAndMode(nullptr, 0, BufferKind::Unbuffered);
   }
 
   size_t GetNumBytesInBuffer() const {
@@ -325,7 +326,7 @@ protected:
   /// use only by subclasses which can arrange for the output to go directly
   /// into the desired output buffer, instead of being copied on each flush.
   void SetBuffer(char *BufferStart, size_t Size) {
-    SetBufferAndMode(BufferStart, Size, ExternalBuffer);
+    SetBufferAndMode(BufferStart, Size, BufferKind::ExternalBuffer);
   }
 
   /// Return an efficient buffer size for the underlying output mechanism.
@@ -384,7 +385,7 @@ public:
 class raw_fd_ostream : public raw_pwrite_stream {
   int FD;
   bool ShouldClose;
-  bool SupportsSeeking;
+  bool SupportsSeeking = false;
   bool ColorEnabled = true;
 
 #ifdef _WIN32
@@ -395,7 +396,7 @@ class raw_fd_ostream : public raw_pwrite_stream {
 
   std::error_code EC;
 
-  uint64_t pos;
+  uint64_t pos = 0;
 
   /// See raw_ostream::write_impl.
   void write_impl(const char *Ptr, size_t Size) override;
diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
index b9989371f5ea..4bb315f824af 100644
--- a/llvm/lib/Support/raw_ostream.cpp
+++ b/llvm/lib/Support/raw_ostream.cpp
@@ -82,7 +82,7 @@ raw_ostream::~raw_ostream() {
   assert(OutBufCur == OutBufStart &&
          "raw_ostream destructor called with non-empty buffer!");
 
-  if (BufferMode == InternalBuffer)
+  if (BufferMode == BufferKind::InternalBuffer)
     delete [] OutBufStart;
 }
 
@@ -102,14 +102,14 @@ void raw_ostream::SetBuffered() {
 
 void raw_ostream::SetBufferAndMode(char *BufferStart, size_t Size,
                                    BufferKind Mode) {
-  assert(((Mode == Unbuffered && !BufferStart && Size == 0) ||
-          (Mode != Unbuffered && BufferStart && Size != 0)) &&
+  assert(((Mode == BufferKind::Unbuffered && !BufferStart && Size == 0) ||
+          (Mode != BufferKind::Unbuffered && BufferStart && Size != 0)) &&
          "stream must be unbuffered or have at least one byte");
   // Make sure the current buffer is free of content (we can't flush here; the
   // child buffer management logic will be in write_impl).
   assert(GetNumBytesInBuffer() == 0 && "Current buffer is non-empty!");
 
-  if (BufferMode == InternalBuffer)
+  if (BufferMode == BufferKind::InternalBuffer)
     delete [] OutBufStart;
   OutBufStart = BufferStart;
   OutBufEnd = OutBufStart+Size;
@@ -223,7 +223,7 @@ raw_ostream &raw_ostream::write(unsigned char C) {
   // Group exceptional cases into a single branch.
   if (LLVM_UNLIKELY(OutBufCur >= OutBufEnd)) {
     if (LLVM_UNLIKELY(!OutBufStart)) {
-      if (BufferMode == Unbuffered) {
+      if (BufferMode == BufferKind::Unbuffered) {
         write_impl(reinterpret_cast<char*>(&C), 1);
         return *this;
       }
@@ -243,7 +243,7 @@ raw_ostream &raw_ostream::write(const char *Ptr, size_t Size) {
   // Group exceptional cases into a single branch.
   if (LLVM_UNLIKELY(size_t(OutBufEnd - OutBufCur) < Size)) {
     if (LLVM_UNLIKELY(!OutBufStart)) {
-      if (BufferMode == Unbuffered) {
+      if (BufferMode == BufferKind::Unbuffered) {
         write_impl(Ptr, Size);
         return *this;
       }