Fix whitespace handling in empty macro arguments

When a function-like macro definition ends with one of the macro's
parameters, and the argument is empty, any whitespace before the
parameter name in the macro definition needs to be preserved. Promoting
the existing NextTokGetsSpace to a preserved bit-field and checking it
at the end of the macro expansion allows it to be moved to the first
token following the macro expansion result.

Patch by Harald van Dijk!

llvm-svn: 200786

1 files changed, 13 insertions, 18 deletions

diff --git a/clang/lib/Lex/TokenLexer.cpp b/clang/lib/Lex/TokenLexer.cpp
index d41af3f41a9..2f29f7c9c8c 100644
--- a/clang/lib/Lex/TokenLexer.cpp
+++ b/clang/lib/Lex/TokenLexer.cpp
@@ -37,6 +37,7 @@ void TokenLexer::Init(Token &Tok, SourceLocation ELEnd, MacroInfo *MI,
   ExpandLocEnd = ELEnd;
   AtStartOfLine = Tok.isAtStartOfLine();
   HasLeadingSpace = Tok.hasLeadingSpace();
+  NextTokGetsSpace = false;
   Tokens = &*Macro->tokens_begin();
   OwnsTokens = false;
   DisableMacroExpansion = false;
@@ -95,6 +96,7 @@ void TokenLexer::Init(const Token *TokArray, unsigned NumToks,
   ExpandLocStart = ExpandLocEnd = SourceLocation();
   AtStartOfLine = false;
   HasLeadingSpace = false;
+  NextTokGetsSpace = false;
   MacroExpansionStart = SourceLocation();
 
   // Set HasLeadingSpace/AtStartOfLine so that the first token will be
@@ -119,13 +121,10 @@ void TokenLexer::destroy() {
   if (ActualArgs) ActualArgs->destroy(PP);
 }
 
-/// Remove comma ahead of __VA_ARGS__, if present, according to compiler dialect
-/// settings.  Returns true if the comma is removed.
-static bool MaybeRemoveCommaBeforeVaArgs(SmallVectorImpl<Token> &ResultToks,
-                                         bool &NextTokGetsSpace,
-                                         bool HasPasteOperator,
-                                         MacroInfo *Macro, unsigned MacroArgNo,
-                                         Preprocessor &PP) {
+bool TokenLexer::MaybeRemoveCommaBeforeVaArgs(SmallVectorImpl<Token> &ResultToks,
+                                              bool HasPasteOperator,
+                                              MacroInfo *Macro, unsigned MacroArgNo,
+                                              Preprocessor &PP) {
   // Is the macro argument __VA_ARGS__?
   if (!Macro->isVariadic() || MacroArgNo != Macro->getNumArgs()-1)
     return false;
@@ -179,11 +178,6 @@ void TokenLexer::ExpandFunctionArguments() {
   // we install the newly expanded sequence as the new 'Tokens' list.
   bool MadeChange = false;
 
-  // NextTokGetsSpace - When this is true, the next token appended to the
-  // output list will get a leading space, regardless of whether it had one to
-  // begin with or not.  This is used for placemarker support.
-  bool NextTokGetsSpace = false;
-
   for (unsigned i = 0, e = NumTokens; i != e; ++i) {
     // If we found the stringify operator, get the argument stringified.  The
     // preprocessor already verified that the following token is a macro name
@@ -256,7 +250,7 @@ void TokenLexer::ExpandFunctionArguments() {
     // In Microsoft mode, remove the comma before __VA_ARGS__ to ensure there
     // are no trailing commas if __VA_ARGS__ is empty.
     if (!PasteBefore && ActualArgs->isVarargsElidedUse() &&
-        MaybeRemoveCommaBeforeVaArgs(ResultToks, NextTokGetsSpace,
+        MaybeRemoveCommaBeforeVaArgs(ResultToks,
                                      /*HasPasteOperator=*/false,
                                      Macro, ArgNo, PP))
       continue;
@@ -311,9 +305,10 @@ void TokenLexer::ExpandFunctionArguments() {
                                              NextTokGetsSpace);
         NextTokGetsSpace = false;
       } else {
-        // If this is an empty argument, and if there was whitespace before the
-        // formal token, make sure the next token gets whitespace before it.
-        NextTokGetsSpace = CurTok.hasLeadingSpace();
+        // If this is an empty argument, if there was whitespace before the
+        // formal token, and this is not the first token in the macro
+        // definition, make sure the next token gets whitespace before it.
+        NextTokGetsSpace |= i != 0 && CurTok.hasLeadingSpace();
       }
       continue;
     }
@@ -396,7 +391,7 @@ void TokenLexer::ExpandFunctionArguments() {
     // the ## was a comma, remove the comma.  This is a GCC extension which is
     // disabled when using -std=c99.
     if (ActualArgs->isVarargsElidedUse())
-      MaybeRemoveCommaBeforeVaArgs(ResultToks, NextTokGetsSpace,
+      MaybeRemoveCommaBeforeVaArgs(ResultToks,
                                    /*HasPasteOperator=*/true,
                                    Macro, ArgNo, PP);
 
@@ -428,7 +423,7 @@ bool TokenLexer::Lex(Token &Tok) {
 
     Tok.startToken();
     Tok.setFlagValue(Token::StartOfLine , AtStartOfLine);
-    Tok.setFlagValue(Token::LeadingSpace, HasLeadingSpace);
+    Tok.setFlagValue(Token::LeadingSpace, HasLeadingSpace || NextTokGetsSpace);
     if (CurToken == 0)
       Tok.setFlag(Token::LeadingEmptyMacro);
     return PP.HandleEndOfTokenLexer(Tok);