diff --git a/include/yaml-cpp/emitter.h b/include/yaml-cpp/emitter.h
index 1d4edf4da..4f07b0d8f 100644
--- a/include/yaml-cpp/emitter.h
+++ b/include/yaml-cpp/emitter.h
@@ -50,7 +50,7 @@ class YAML_CPP_API Emitter {
 
   // state checking
   bool good() const;
-  const std::string GetLastError() const;
+  std::string GetLastError() const;
 
   // global setters
   bool SetOutputCharset(EMITTER_MANIP value);
@@ -136,7 +136,6 @@ class YAML_CPP_API Emitter {
 
   const char* ComputeFullBoolName(bool b) const;
   const char* ComputeNullName() const;
-  bool CanEmitNewline() const;
 
  private:
   std::unique_ptr<EmitterState> m_pState;
diff --git a/src/emitter.cpp b/src/emitter.cpp
index b69f24bb7..9c7316c79 100644
--- a/src/emitter.cpp
+++ b/src/emitter.cpp
@@ -25,9 +25,7 @@ std::size_t Emitter::size() const { return m_stream.pos(); }
 // state checking
 bool Emitter::good() const { return m_pState->good(); }
 
-const std::string Emitter::GetLastError() const {
-  return m_pState->GetLastError();
-}
+std::string Emitter::GetLastError() const { return m_pState->GetLastError(); }
 
 // global setters
 bool Emitter::SetOutputCharset(EMITTER_MANIP value) {
@@ -281,8 +279,6 @@ void Emitter::EmitNewline() {
   m_pState->SetNonContent();
 }
 
-bool Emitter::CanEmitNewline() const { return true; }
-
 // Put the stream in a state so we can simply write the next node
 // E.g., if we're in a sequence, write the "- "
 void Emitter::PrepareNode(EmitterNodeType::value child) {
diff --git a/src/scanner.cpp b/src/scanner.cpp
index a0abd3b61..f71e72964 100644
--- a/src/scanner.cpp
+++ b/src/scanner.cpp
@@ -7,6 +7,19 @@
 #include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
 
 namespace YAML {
+namespace {
+// IsWhitespaceToBeEaten
+// . We can eat whitespace if it's a space or tab
+// . Note: originally tabs in block context couldn't be eaten
+//         "where a simple key could be allowed
+//         (i.e., not at the beginning of a line, or following '-', '?', or
+// ':')"
+//   I think this is wrong, since tabs can be non-content whitespace; it's just
+//   that they can't contribute to indentation, so once you've seen a tab in a
+//   line, you can't start a simple key
+bool IsWhitespaceToBeEaten(char ch) { return (ch == ' ') || (ch == '\t'); }
+}  // namespace
+
 Scanner::Scanner(std::istream& in)
     : INPUT(in),
       m_tokens{},
@@ -254,27 +267,6 @@ void Scanner::ScanToNextToken() {
 ///////////////////////////////////////////////////////////////////////
 // Misc. helpers
 
-// IsWhitespaceToBeEaten
-// . We can eat whitespace if it's a space or tab
-// . Note: originally tabs in block context couldn't be eaten
-//         "where a simple key could be allowed
-//         (i.e., not at the beginning of a line, or following '-', '?', or
-// ':')"
-//   I think this is wrong, since tabs can be non-content whitespace; it's just
-//   that they can't contribute to indentation, so once you've seen a tab in a
-//   line, you can't start a simple key
-bool Scanner::IsWhitespaceToBeEaten(char ch) {
-  if (ch == ' ') {
-    return true;
-  }
-
-  if (ch == '\t') {
-    return true;
-  }
-
-  return false;
-}
-
 const RegEx& Scanner::GetValueRegex() const {
   if (InBlockContext()) {
     return Exp::Value();
@@ -312,7 +304,7 @@ Token* Scanner::PushToken(Token::TYPE type) {
   return &m_tokens.back();
 }
 
-Token::TYPE Scanner::GetStartTokenFor(IndentMarker::INDENT_TYPE type) const {
+Token::TYPE Scanner::GetStartTokenFor(IndentMarker::INDENT_TYPE type) {
   switch (type) {
     case IndentMarker::SEQ:
       return Token::BLOCK_SEQ_START;
diff --git a/src/scanner.h b/src/scanner.h
index a3bfb662d..e9d5ba06f 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -88,7 +88,7 @@ class Scanner {
   bool InBlockContext() const { return m_flows.empty(); }
   std::size_t GetFlowLevel() const { return m_flows.size(); }
 
-  Token::TYPE GetStartTokenFor(IndentMarker::INDENT_TYPE type) const;
+  static Token::TYPE GetStartTokenFor(IndentMarker::INDENT_TYPE type);
 
   /**
    * Pushes an indentation onto the stack, and enqueues the proper token
@@ -129,8 +129,6 @@ class Scanner {
    */
   void ThrowParserException(const std::string &msg) const;
 
-  bool IsWhitespaceToBeEaten(char ch);
-
   /**
    * Returns the appropriate regex to check if the next token is a value token.
    */
diff --git a/src/scantag.cpp b/src/scantag.cpp
index 176cc5c71..63bc1e537 100644
--- a/src/scantag.cpp
+++ b/src/scantag.cpp
@@ -6,7 +6,7 @@
 #include "yaml-cpp/mark.h"
 
 namespace YAML {
-const std::string ScanVerbatimTag(Stream& INPUT) {
+std::string ScanVerbatimTag(Stream& INPUT) {
   std::string tag;
 
   // eat the start character
@@ -29,7 +29,7 @@ const std::string ScanVerbatimTag(Stream& INPUT) {
   throw ParserException(INPUT.mark(), ErrorMsg::END_OF_VERBATIM_TAG);
 }
 
-const std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle) {
+std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle) {
   std::string tag;
   canBeHandle = true;
   Mark firstNonWordChar;
@@ -62,7 +62,7 @@ const std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle) {
   return tag;
 }
 
-const std::string ScanTagSuffix(Stream& INPUT) {
+std::string ScanTagSuffix(Stream& INPUT) {
   std::string tag;
 
   while (INPUT) {
diff --git a/src/scantag.h b/src/scantag.h
index 522ba5495..9fa1684dc 100644
--- a/src/scantag.h
+++ b/src/scantag.h
@@ -11,9 +11,9 @@
 #include "stream.h"
 
 namespace YAML {
-const std::string ScanVerbatimTag(Stream& INPUT);
-const std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle);
-const std::string ScanTagSuffix(Stream& INPUT);
+std::string ScanVerbatimTag(Stream& INPUT);
+std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle);
+std::string ScanTagSuffix(Stream& INPUT);
 }
 
 #endif  // SCANTAG_H_62B23520_7C8E_11DE_8A39_0800200C9A66
diff --git a/src/singledocparser.cpp b/src/singledocparser.cpp
index c60a2e8b5..ca80bea2c 100644
--- a/src/singledocparser.cpp
+++ b/src/singledocparser.cpp
@@ -99,7 +99,7 @@ void SingleDocParser::HandleNode(EventHandler& eventHandler) {
     tag = (token.type == Token::NON_PLAIN_SCALAR ? "!" : "?");
 
   if (token.type == Token::PLAIN_SCALAR
-      && tag.compare("?") == 0 && IsNullString(token.value.data(), token.value.size())) {
+      && tag == "?" && IsNullString(token.value.data(), token.value.size())) {
     eventHandler.OnNull(mark, anchor);
     m_scanner.pop();
     return;
diff --git a/src/tag.cpp b/src/tag.cpp
index 35a1b4656..9d36317de 100644
--- a/src/tag.cpp
+++ b/src/tag.cpp
@@ -29,7 +29,7 @@ Tag::Tag(const Token& token)
   }
 }
 
-std::string Tag::Translate(const Directives& directives) {
+std::string Tag::Translate(const Directives& directives) const {
   switch (type) {
     case VERBATIM:
       return value;
diff --git a/src/tag.h b/src/tag.h
index c811f3955..efa77f0fb 100644
--- a/src/tag.h
+++ b/src/tag.h
@@ -23,7 +23,7 @@ struct Tag {
   };
 
   Tag(const Token& token);
-  std::string Translate(const Directives& directives);
+  std::string Translate(const Directives& directives) const;
 
   TYPE type;
   std::string handle, value;