Index: clang/lib/Sema/SemaType.cpp
===================================================================
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -4762,7 +4762,7 @@
         break;
       case DeclaratorChunk::Function: {
         const DeclaratorChunk::FunctionTypeInfo &FTI = DeclType.Fun;
-        if (FTI.NumParams == 0)
+        if (FTI.NumParams == 0 && !FTI.isVariadic)
           S.Diag(DeclType.Loc, diag::warn_strict_prototypes)
               << IsBlock
               << FixItHint::CreateInsertion(FTI.getRParenLoc(), "void");
Index: clang/test/Sema/warn-strict-prototypes.c
===================================================================
--- clang/test/Sema/warn-strict-prototypes.c
+++ clang/test/Sema/warn-strict-prototypes.c
@@ -65,3 +65,9 @@
 void __attribute__((cdecl)) foo12(d) // expected-warning {{this old-style function definition is not preceded by a prototype}}
   short d;
 {}
+
+// No warnings for variadic functions. Overloadable attribute is required
+// to avoid err_ellipsis_first_param error.
+// rdar://problem/33251668
+void foo13(...) __attribute__((overloadable));
+void foo13(...) __attribute__((overloadable)) {}