[ODRHash] Fix null pointer dereference for ObjC selectors with empty slots.

`Selector::getIdentifierInfoForSlot` returns NULL if a slot has no
corresponding identifier. Add a boolean to the hash and a NULL check.

rdar://problem/51615164

Reviewers: rtrieu

Reviewed By: rtrieu

Subscribers: dexonsmith, cfe-commits, jkorous

Differential Revision: https://reviews.llvm.org/D63789

llvm-svn: 364664

clang/lib/AST/ODRHash.cpp

@@ -71,8 +71,13 @@ void ODRHash::AddDeclarationNameImpl(DeclarationName Name) {
     AddBoolean(S.isKeywordSelector());
     AddBoolean(S.isUnarySelector());
     unsigned NumArgs = S.getNumArgs();
+    ID.AddInteger(NumArgs);
     for (unsigned i = 0; i < NumArgs; ++i) {
-      AddIdentifierInfo(S.getIdentifierInfoForSlot(i));
+      const IdentifierInfo *II = S.getIdentifierInfoForSlot(i);
+      AddBoolean(II);
+      if (II) {
+        AddIdentifierInfo(II);
+      }
     }
     break;
   }

clang/test/Modules/odr_hash.mm

@@ -57,6 +57,14 @@
 @interface Interface3 <T : I1 *>
 @end
 
+@interface EmptySelectorSlot
+- (void)method:(int)arg;
+- (void)method:(int)arg :(int)empty;
+
+- (void)multiple:(int)arg1 args:(int)arg2 :(int)arg3;
+- (void)multiple:(int)arg1 :(int)arg2 args:(int)arg3;
+@end
+
 #endif
 
 #if defined(FIRST)
@@ -289,6 +297,29 @@ Invalid3 i3;
 }  // namespace ObjCTypeParam
 }  // namespace Types
 
+namespace CallMethods {
+#if defined(FIRST)
+void invalid1(EmptySelectorSlot *obj) {
+  [obj method:0];
+}
+void invalid2(EmptySelectorSlot *obj) {
+  [obj multiple:0 args:0 :0];
+}
+#elif defined(SECOND)
+void invalid1(EmptySelectorSlot *obj) {
+  [obj method:0 :0];
+}
+void invalid2(EmptySelectorSlot *obj) {
+  [obj multiple:0 :0 args:0];
+}
+#endif
+// expected-error@second.h:* {{'CallMethods::invalid1' has different definitions in different modules; definition in module 'SecondModule' first difference is function body}}
+// expected-note@first.h:* {{but in 'FirstModule' found a different body}}
+
+// expected-error@second.h:* {{'CallMethods::invalid2' has different definitions in different modules; definition in module 'SecondModule' first difference is function body}}
+// expected-note@first.h:* {{but in 'FirstModule' found a different body}}
+}  // namespace CallMethods
+
 // Keep macros contained to one file.
 #ifdef FIRST
 #undef FIRST