[MSVC Compat] Accept elided commas in macro function arguments

Summary:
This fixes PR25875.  When the trailing comma in a macro argument list is
elided, we need to treat it similarly to the case where a variadic macro
misses one actual argument.

Reviewers: rnk, rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D15670

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@258530 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 1 deletions

diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 18348df0a3..11b4a0b3d8 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -723,6 +723,7 @@ MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(Token &MacroName,
   // heap allocations in the common case.
   SmallVector<Token, 64> ArgTokens;
   bool ContainsCodeCompletionTok = false;
+  bool FoundElidedComma = false;
 
   SourceLocation TooManyArgsLoc;
 
@@ -765,6 +766,10 @@ MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(Token &MacroName,
         // If we found the ) token, the macro arg list is done.
         if (NumParens-- == 0) {
           MacroEnd = Tok.getLocation();
+          if (!ArgTokens.empty() &&
+              ArgTokens.back().commaAfterElided()) {
+            FoundElidedComma = true;
+          }
           break;
         }
       } else if (Tok.is(tok::l_paren)) {
@@ -909,7 +914,7 @@ MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(Token &MacroName,
       // then we have an empty "()" argument empty list.  This is fine, even if
       // the macro expects one argument (the argument is just empty).
       isVarargsElided = MI->isVariadic();
-    } else if (MI->isVariadic() &&
+    } else if ((FoundElidedComma || MI->isVariadic()) &&
                (NumActuals+1 == MinArgsExpected ||  // A(x, ...) -> A(X)
                 (NumActuals == 0 && MinArgsExpected == 2))) {// A(x,...) -> A()
       // Varargs where the named vararg parameter is missing: OK as extension.