Fix a crash on the testcase in PR9981 / rdar://9486765.

llvm-svn: 133003

clang/lib/Lex/TokenLexer.cpp

@@ -487,9 +487,10 @@ bool TokenLexer::PasteTokens(Token &Tok) {
           // Explicitly convert the token location to have proper instantiation
           // information so that the user knows where it came from.
           SourceManager &SM = PP.getSourceManager();
-          SourceLocation Loc =
-            SM.createInstantiationLoc(PasteOpLoc, InstantiateLocStart,
-                                      InstantiateLocEnd, 2);
+          SourceLocation Loc = PasteOpLoc;
+          if (InstantiateLocStart.isValid())
+            Loc = SM.createInstantiationLoc(Loc, InstantiateLocStart,
+                                            InstantiateLocEnd, 2);
           // If we're in microsoft extensions mode, downgrade this from a hard
           // error to a warning that defaults to an error.  This allows
           // disabling it.

clang/test/Preprocessor/macro_paste_bad.c

@@ -33,3 +33,9 @@ XX     // expected-error {{attempt to use a poisoned identifier}}
 int VA;   // expected-warning {{__VA_ARGS__ can only appear in the expansion of a C99 variadic macro}}
 
 
+// PR9981
+#define M1(A) A
+#define M2(X) 
+M1(M2(##))   // expected-error {{pasting formed '()', an invalid preprocessing token}}
+
+