Don't reallocate MetaLexer on the heap for every line. Its a waste of time for 24 bytes that will be needed for every line anyway. Remove bufferEnd field as it was entirely unused.

lib/MetaProcessor/MetaLexer.cpp

@@ -43,6 +43,11 @@ namespace cling {
     : bufferStart(line.data()), curPos(line.data())
   { }
 
+  void MetaLexer::reset(llvm::StringRef line) {
+    bufferStart = line.data();
+    curPos = line.data();
+  }
+
   void MetaLexer::Lex(Token& Tok) {
     Tok.startToken(curPos);
     char C = *curPos++;

lib/MetaProcessor/MetaLexer.h

@@ -82,10 +82,8 @@ namespace cling {
     const char* bufferStart;
     const char* curPos;
   public:
-    MetaLexer(const char* bufStart)
-      : bufferStart(bufStart), curPos(bufStart)
-    { }
     MetaLexer(llvm::StringRef input);
+    void reset(llvm::StringRef Line);
 
     void Lex(Token& Tok);
     void LexAnyString(Token& Tok);

lib/MetaProcessor/MetaParser.cpp

@@ -23,8 +23,7 @@
 
 namespace cling {
 
-  MetaParser::MetaParser(MetaSema* Actions) {
-    m_Lexer.reset(0);
+  MetaParser::MetaParser(MetaSema* Actions) : m_Lexer("") {
     m_Actions.reset(Actions);
     const InvocationOptions& Opts = Actions->getInterpreter().getOptions();
     MetaLexer metaSymbolLexer(Opts.MetaString);
@@ -38,7 +37,7 @@ namespace cling {
   }
 
   void MetaParser::enterNewInputLine(llvm::StringRef Line) {
-    m_Lexer.reset(new MetaLexer(Line));
+    m_Lexer.reset(Line);
     m_TokenCache.clear();
   }
 
@@ -86,7 +85,7 @@ namespace cling {
 
     for (unsigned C = N+1 - m_TokenCache.size(); C > 0; --C) {
       m_TokenCache.push_back(Token());
-      m_Lexer->Lex(m_TokenCache.back());
+      m_Lexer.Lex(m_TokenCache.back());
     }
     return m_TokenCache.back();
   }

lib/MetaProcessor/MetaParser.h

@@ -63,7 +63,7 @@ namespace cling {
   //
   class MetaParser {
   private:
-    std::unique_ptr<MetaLexer> m_Lexer;
+    MetaLexer m_Lexer;
     std::unique_ptr<MetaSema> m_Actions;
     llvm::SmallVector<Token, 2> m_TokenCache;
     llvm::SmallVector<Token, 4> m_MetaSymbolCache;