fix PR3880, fixing a comma swallowing bug handling macros that only take

... arguments.

llvm-svn: 67706

clang/lib/Lex/PPMacroExpansion.cpp

@@ -403,6 +403,12 @@ MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(Token &MacroName,
     Tok.setLocation(EndLoc);
     Tok.setLength(0);
     ArgTokens.push_back(Tok);
+  } else if (NumActuals == 1 && ArgTokens.size() == 1) {
+    // If there is exactly one argument, and that argument is just an EOF token,
+    // then we have an empty "()" argument empty list.  This is fine, even if
+    // the macro expects one argument (the argument is just empty).  However, if
+    // the macro expects "...", then we need to know that it was elided.
+    isVarargsElided = MinArgsExpected == 1 && MI->isVariadic();
   }
   
   return MacroArgs::create(MI, &ArgTokens[0], ArgTokens.size(),isVarargsElided);

clang/test/Preprocessor/macro_fn_comma_swallow.c

@@ -14,3 +14,8 @@ X2()
 X3(foo)
 
 
+
+// RUN: clang-cc %s -E | grep 'AA BB'
+// PR3880
+#define X4(...)  AA , ## __VA_ARGS__ BB
+X4()