Don't require nullability on 'va_list'.

[jordan_rose]

Summary

There are many non-portable typedefs, but va_list is one that nobody ever thinks of as a pointer or an array. (When's the last time you saw someone check for a NULL va_list?) Make an exception for this one special type.

(Is this the best way to do this?)

Part of rdar://problem/25846421. Depends on D26226 and D25850.

[jordan_rose]

Depends on D26108 too (for the tests to apply cleanly).

[doug.gregor]

I don't see a better way to do this. Nice meta programming hack.

[jordan_rose]

Committed in rL286522, with a fix-up to make the check for va_lists more conservative in rL286531.

[jordan_rose]

One more fix-up in rL286542. Hopefully the last one.

lib/Sema/SemaType.cpp

       if (auto *attr = inferPointerNullability(
                          pointerKind, D.getDeclSpec().getTypeSpecTypeLoc(),
                          D.getMutableDeclSpec().getAttributes().getListRef())) {
         T = Context.getAttributedType(
               AttributedType::getNullabilityAttrKind(*inferNullability), T, T);
         attr->setUsedAsTypeAttr();
       }
     }
+
+    auto isVaList = [&S](QualType T) -> bool {
+      auto *typedefTy = T->getAs<TypedefType>();
+      if (!typedefTy)
+        return false;
+      TypedefDecl *vaListTypedef = S.Context.getBuiltinVaListDecl();
+      do {
+        if (typedefTy->getDecl() == vaListTypedef)
+          return true;
+        typedefTy = typedefTy->desugar()->getAs<TypedefType>();
+      } while (typedefTy);
+      return false;
+    };
+
     if (complainAboutMissingNullability == CAMN_Yes &&
-        T->isArrayType() && !T->getNullability(S.Context) &&
+        T->isArrayType() && !T->getNullability(S.Context) && !isVaList(T) &&
         D.isPrototypeContext() &&
         !hasOuterPointerLikeChunk(D, D.getNumTypeObjects())) {
       checkNullabilityConsistency(S, SimplePointerKind::Array,
                                   D.getDeclSpec().getTypeSpecTypeLoc());
     }
   }
 
   // Walk the DeclTypeInfo, building the recursive type as we go.

test/SemaObjCXX/Inputs/nullability-consistency-arrays.h

+#include <stdarg.h>
+
 void firstThingInTheFileThatNeedsNullabilityIsAnArray(int ints[]);
 #if ARRAYS_CHECKED
 // expected-warning@-2 {{array parameter is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)}}
 #endif
 
 int *secondThingInTheFileThatNeedsNullabilityIsAPointer;
 #if !ARRAYS_CHECKED
 // expected-warning@-2 {{pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)}}
void testArraysOK(
     int ints[_Nonnull],
     void *ptrs[_Nonnull], // expected-warning {{pointer is missing a nullability type specifier}}
     void **nestedPtrs[_Nonnull]); // expected-warning 2 {{pointer is missing a nullability type specifier}}
 void testAllOK(
     int ints[_Nonnull],
     void * _Nullable ptrs[_Nonnull],
     void * _Nullable * _Nullable nestedPtrs[_Nonnull]);
 
+void testVAList(va_list ok); // no warning
+
+#if __cplusplus
+// Carefully construct a test case such that if a platform's va_list is an array
+// or pointer type, it gets tested, but otherwise it does not.
+template<class T, class F>
+struct pointer_like_or { typedef F type; };
+template<class T, class F>
+struct pointer_like_or<T*, F> { typedef T *type; };
+template<class T, class F>
+struct pointer_like_or<T* const, F> { typedef T * const type; };
+template<class T, class F>
+struct pointer_like_or<T[], F> { typedef T type[]; };
+template<class T, class F, unsigned size>
+struct pointer_like_or<T[size], F> { typedef T type[size]; };
+
+void testVAListWithNullability(
+  pointer_like_or<va_list, void*>::type _Nonnull x); // no errors
+#endif
+
 void nestedArrays(int x[5][1]) {}
 #if ARRAYS_CHECKED
 // expected-warning@-2 {{array parameter is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified)}}
 #endif
 void nestedArraysOK(int x[_Nonnull 5][1]) {}
 
 #if !__cplusplus
 void staticOK(int x[static 5][1]){}