Fix a nasty corner case that Neil noticed in PR1900, where we would

incorrectly apply the multiple include optimization to files with 
guards like:

#if !defined(x) MACRO

where MACRO could expand to different things in different contexts.
Thanks Neil!

llvm-svn: 45716

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/Lex/Preprocessor.cpp b/clang/Lex/Preprocessor.cpp
index baabd8ee00b..accccc4fbcd 100644
--- a/clang/Lex/Preprocessor.cpp
+++ b/clang/Lex/Preprocessor.cpp
@@ -784,6 +784,10 @@ bool Preprocessor::isNextPPTokenLParen() {
 /// expanded as a macro, handle it and return the next token as 'Identifier'.
 bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier, 
                                                  MacroInfo *MI) {
+  // If this is a macro exapnsion in the "#if !defined(x)" line for the file,
+  // then the macro could expand to different things in other contexts, we need
+  // to disable the optimization in this case.
+  if (CurLexer) CurLexer->MIOpt.ExpandedMacro();
   
   // If this is a builtin macro, like __LINE__ or _Pragma, handle it specially.
   if (MI->isBuiltinMacro()) {