From e5fbc6c85d98f91357f6f8bfd19c67e96c4f143f Mon Sep 17 00:00:00 2001
From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Fri, 18 May 2012 19:32:16 +0000
Subject: [PATCH] Lexer::ReadToEndOfLine: Only build the string if it's
 actually used and do so in a less malloc-intensive way.

llvm-svn: 157064
---
 clang/include/clang/Lex/Lexer.h |  2 +-
 clang/lib/Lex/Lexer.cpp         | 15 ++++++++-------
 clang/lib/Lex/PPDirectives.cpp  | 10 ++++------
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/clang/include/clang/Lex/Lexer.h b/clang/include/clang/Lex/Lexer.h
index 4878123d1bb7..e96e1d7cb792 100644
--- a/clang/include/clang/Lex/Lexer.h
+++ b/clang/include/clang/Lex/Lexer.h
@@ -200,7 +200,7 @@ public:
 
   /// ReadToEndOfLine - Read the rest of the current preprocessor line as an
   /// uninterpreted string.  This switches the lexer out of directive mode.
-  std::string ReadToEndOfLine();
+  void ReadToEndOfLine(SmallVectorImpl<char> *Result = 0);
 
 
   /// Diag - Forwarding function for diagnostics.  This translate a source
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 535a852429b5..c6c39144af00 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2286,10 +2286,9 @@ bool Lexer::SkipBlockComment(Token &Result, const char *CurPtr) {
 
 /// ReadToEndOfLine - Read the rest of the current preprocessor line as an
 /// uninterpreted string.  This switches the lexer out of directive mode.
-std::string Lexer::ReadToEndOfLine() {
+void Lexer::ReadToEndOfLine(SmallVectorImpl<char> *Result) {
   assert(ParsingPreprocessorDirective && ParsingFilename == false &&
          "Must be in a preprocessing directive!");
-  std::string Result;
   Token Tmp;
 
   // CurPtr - Cache BufferPtr in an automatic variable.
@@ -2298,7 +2297,8 @@ std::string Lexer::ReadToEndOfLine() {
     char Char = getAndAdvanceChar(CurPtr, Tmp);
     switch (Char) {
     default:
-      Result += Char;
+      if (Result)
+        Result->push_back(Char);
       break;
     case 0:  // Null.
       // Found end of file?
@@ -2306,11 +2306,12 @@ std::string Lexer::ReadToEndOfLine() {
         if (isCodeCompletionPoint(CurPtr-1)) {
           PP->CodeCompleteNaturalLanguage();
           cutOffLexing();
-          return Result;
+          return;
         }
 
         // Nope, normal character, continue.
-        Result += Char;
+        if (Result)
+          Result->push_back(Char);
         break;
       }
       // FALL THROUGH.
@@ -2329,8 +2330,8 @@ std::string Lexer::ReadToEndOfLine() {
       }
       assert(Tmp.is(tok::eod) && "Unexpected token!");
 
-      // Finally, we're done, return the string we found.
-      return Result;
+      // Finally, we're done;
+      return;
     }
   }
 }
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 625a204af995..c6290170892a 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1018,15 +1018,13 @@ void Preprocessor::HandleUserDiagnosticDirective(Token &Tok,
   // tokens.  For example, this is allowed: "#warning `   'foo".  GCC does
   // collapse multiple consequtive white space between tokens, but this isn't
   // specified by the standard.
-  std::string Message = CurLexer->ReadToEndOfLine();
+  SmallString<128> Message;
+  CurLexer->ReadToEndOfLine(&Message);
 
   // Find the first non-whitespace character, so that we can make the
   // diagnostic more succinct.
-  StringRef Msg(Message);
-  size_t i = Msg.find_first_not_of(' ');
-  if (i < Msg.size())
-    Msg = Msg.substr(i);
-  
+  StringRef Msg = Message.str().ltrim(" ");
+
   if (isWarning)
     Diag(Tok, diag::pp_hash_warning) << Msg;
   else