[ObjC] Error out when using forward-declared protocol in a @protocol

expression

Clang emits invalid protocol metadata when a @protocol expression is used with a
forward-declared protocol. The protocol metadata is missing protocol conformance
list of the protocol since we don't have access to the definition of it in the
compiled translation unit. The linker then might end up picking the invalid
metadata when linking which will lead to incorrect runtime protocol conformance
checks.

This commit makes sure that Clang fails to compile code that uses a @protocol
expression with a forward-declared protocol. This ensures that Clang does not
emit invalid protocol metadata. I added an extra assert in CodeGen to ensure
that this kind of issue won't happen in other places.

rdar://32787811

Differential Revision: https://reviews.llvm.org/D49462

llvm-svn: 340102

15 files changed, 50 insertions, 38 deletions

diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index c0128f56a59..25c12445f71 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -620,7 +620,8 @@ def DeallocInCategory:DiagGroup<"dealloc-in-category">;
 def SelectorTypeMismatch : DiagGroup<"selector-type-mismatch">;
 def Selector : DiagGroup<"selector", [SelectorTypeMismatch]>;
 def Protocol : DiagGroup<"protocol">;
-def AtProtocol : DiagGroup<"at-protocol">;
+// No longer in use, preserve for backwards compatibility.
+def : DiagGroup<"at-protocol">;
 def PropertyAccessDotSyntax: DiagGroup<"property-access-dot-syntax">;
 def PropertyAttr : DiagGroup<"property-attribute-mismatch">;
 def SuperSubClassMismatch : DiagGroup<"super-class-method-mismatch">;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index dc192aafe38..853bc5eddc4 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -867,8 +867,8 @@ def err_protocol_has_circular_dependency : Error<
   "protocol has circular dependency">;
 def err_undeclared_protocol : Error<"cannot find protocol declaration for %0">;
 def warn_undef_protocolref : Warning<"cannot find protocol definition for %0">;
-def warn_atprotocol_protocol : Warning<
-  "@protocol is using a forward protocol declaration of %0">, InGroup<AtProtocol>;
+def err_atprotocol_protocol : Error<
+  "@protocol is using a forward protocol declaration of %0">;
 def warn_readonly_property : Warning<
   "attribute 'readonly' of property %0 restricts attribute "
   "'readwrite' of property inherited from %1">,
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 92e442d3312..2b6d895f93c 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -6838,8 +6838,9 @@ llvm::Constant *CGObjCNonFragileABIMac::GetOrEmitProtocol(
     return Entry;
 
   // Use the protocol definition, if there is one.
-  if (const ObjCProtocolDecl *Def = PD->getDefinition())
-    PD = Def;
+  assert(PD->hasDefinition() &&
+         "emitting protocol metadata without definition");
+  PD = PD->getDefinition();
 
   auto methodLists = ProtocolMethodLists::get(PD);
 
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 1259d25629b..73e717f605f 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -8095,16 +8095,6 @@ Sema::CheckSingleAssignmentConstraints(QualType LHSType, ExprResult &CallerRHS,
     if (RHS.isInvalid())
       return Incompatible;
   }
-
-  Expr *PRE = RHS.get()->IgnoreParenCasts();
-  if (Diagnose && isa<ObjCProtocolExpr>(PRE)) {
-    ObjCProtocolDecl *PDecl = cast<ObjCProtocolExpr>(PRE)->getProtocol();
-    if (PDecl && !PDecl->hasDefinition()) {
-      Diag(PRE->getExprLoc(), diag::warn_atprotocol_protocol) << PDecl;
-      Diag(PDecl->getLocation(), diag::note_entity_declared_at) << PDecl;
-    }
-  }
-
   CastKind Kind;
   Sema::AssignConvertType result =
     CheckAssignmentConstraints(LHSType, RHS, Kind, ConvertRHS);
diff --git a/clang/lib/Sema/SemaExprObjC.cpp b/clang/lib/Sema/SemaExprObjC.cpp
index bbbe343db0a..13a009090f9 100644
--- a/clang/lib/Sema/SemaExprObjC.cpp
+++ b/clang/lib/Sema/SemaExprObjC.cpp
@@ -1227,8 +1227,12 @@ ExprResult Sema::ParseObjCProtocolExpression(IdentifierInfo *ProtocolId,
     Diag(ProtoLoc, diag::err_undeclared_protocol) << ProtocolId;
     return true;
   }
-  if (PDecl->hasDefinition())
+  if (!PDecl->hasDefinition()) {
+    Diag(ProtoLoc, diag::err_atprotocol_protocol) << PDecl;
+    Diag(PDecl->getLocation(), diag::note_entity_declared_at) << PDecl;
+  } else {
     PDecl = PDecl->getDefinition();
+  }
 
   QualType Ty = Context.getObjCProtoType();
   if (Ty.isNull())
diff --git a/clang/test/CodeGenObjC/forward-declare-protocol-gnu.m b/clang/test/CodeGenObjC/forward-declare-protocol-gnu.m
index b57a4a48d4a..3731fb078ee 100644
--- a/clang/test/CodeGenObjC/forward-declare-protocol-gnu.m
+++ b/clang/test/CodeGenObjC/forward-declare-protocol-gnu.m
@@ -3,9 +3,11 @@
 // Regression test: check that we don't crash when referencing a forward-declared protocol.
 @protocol P;
 
-Protocol *getProtocol(void)
-{
-	        return @protocol(P);
-}
+@interface I <P>
+@end
+
+@implementation I
+
+@end
 
 // CHECK: @.objc_protocol
diff --git a/clang/test/CodeGenObjC/forward-protocol-metadata-symbols.m b/clang/test/CodeGenObjC/forward-protocol-metadata-symbols.m
index 16d33ec15d8..76afc9c6c76 100644
--- a/clang/test/CodeGenObjC/forward-protocol-metadata-symbols.m
+++ b/clang/test/CodeGenObjC/forward-protocol-metadata-symbols.m
@@ -3,7 +3,7 @@
 
 @interface NSObject @end
 
-@protocol P0;
+@protocol P0 @end
 
 @interface A : NSObject <P0>
 +(Class) getClass;
@@ -19,8 +19,8 @@ int main() {
 }
 
 // CHECK: @"\01l_OBJC_PROTOCOL_$_P0" = weak hidden global
-// CHECK: @"\01l_OBJC_CLASS_PROTOCOLS_$_A" = private global
 // CHECK: @"\01l_OBJC_LABEL_PROTOCOL_$_P0" = weak hidden global
+// CHECK: @"\01l_OBJC_CLASS_PROTOCOLS_$_A" = private global
 // CHECK: @"\01l_OBJC_PROTOCOL_REFERENCE_$_P0" = weak hidden global
 
 // CHECK: llvm.used = appending global [3 x i8*]
@@ -33,7 +33,7 @@ int main() {
 // CHECK-SAME: OBJC_METH_VAR_NAME_
 // CHECK-SAME: OBJC_METH_VAR_TYPE_
 // CHECK-SAME: "\01l_OBJC_$_CLASS_METHODS_A"
-// CHECK-SAME: "\01l_OBJC_CLASS_PROTOCOLS_$_A"
 // CHECK-SAME: OBJC_CLASS_NAME_.1
+// CHECK-SAME: "\01l_OBJC_CLASS_PROTOCOLS_$_A"
 // CHECK-SAME: "OBJC_LABEL_CLASS_$"
 // CHECK-SAME: section "llvm.metadata"
diff --git a/clang/test/CodeGenObjC/hidden-visibility.m b/clang/test/CodeGenObjC/hidden-visibility.m
index cb23ca18f81..03290c29bbd 100644
--- a/clang/test/CodeGenObjC/hidden-visibility.m
+++ b/clang/test/CodeGenObjC/hidden-visibility.m
@@ -16,7 +16,7 @@
 @end
 
 
-@protocol Prot0;
+@protocol Prot0 @end
 
 id f0() {
   return @protocol(Prot0);
diff --git a/clang/test/CodeGenObjC/link-errors.m b/clang/test/CodeGenObjC/link-errors.m
index f2d9ddba883..44797d9e8d1 100644
--- a/clang/test/CodeGenObjC/link-errors.m
+++ b/clang/test/CodeGenObjC/link-errors.m
@@ -10,7 +10,7 @@
 -(id) init;
 @end
 
-@protocol P;
+@protocol P @end
 
 @interface A : Root
 @end
diff --git a/clang/test/CodeGenObjC/protocol-comdat.m b/clang/test/CodeGenObjC/protocol-comdat.m
index a19ba8cf35d..ddf8e5a77d4 100644
--- a/clang/test/CodeGenObjC/protocol-comdat.m
+++ b/clang/test/CodeGenObjC/protocol-comdat.m
@@ -4,8 +4,8 @@
 - (void) method;
 @end
 
-@protocol Q;
-@protocol R;
+@protocol Q @end
+@protocol R @end
 
 @interface I<P>
 @end
diff --git a/clang/test/CodeGenObjC/protocols-lazy.m b/clang/test/CodeGenObjC/protocols-lazy.m
index fba7454b954..a2dfc106d64 100644
--- a/clang/test/CodeGenObjC/protocols-lazy.m
+++ b/clang/test/CodeGenObjC/protocols-lazy.m
@@ -18,7 +18,10 @@ void f0() { id x = @protocol(P2); }
 // RUN: grep OBJC_PROTOCOL_P3 %t | count 3
 // RUN: not grep OBJC_PROTOCOL_INSTANCE_METHODS_P3 %t
 @protocol P3;
-void f1() { id x = @protocol(P3); }
+@interface UserP3<P3>
+@end
+@implementation UserP3
+@end
 
 // Definition triggered by class reference.
 // RUN: grep OBJC_PROTOCOL_P4 %t | count 3
@@ -31,10 +34,16 @@ void f1() { id x = @protocol(P3); }
 // RUN: grep OBJC_PROTOCOL_P5 %t | count 3
 // RUN: grep OBJC_PROTOCOL_INSTANCE_METHODS_P5 %t | count 3
 @protocol P5;
-void f2() { id x = @protocol(P5); } // This generates a forward
-                                    // reference, which has to be
-                                    // updated on the next line.
-@protocol P5 -im1; @end               
+@interface UserP5<P5> // This generates a forward
+                      // reference, which has to be
+                      // updated on the next line.
+@end
+@protocol P5 -im1; @end
+@implementation UserP5
+
+- im1 { }
+
+@end
 
 // Protocol reference following definition.
 // RUN: grep OBJC_PROTOCOL_P6 %t | count 4
diff --git a/clang/test/CodeGenObjC/protocols.m b/clang/test/CodeGenObjC/protocols.m
index 6dadb11273d..31965e17118 100644
--- a/clang/test/CodeGenObjC/protocols.m
+++ b/clang/test/CodeGenObjC/protocols.m
@@ -7,7 +7,8 @@ void p(const char*, ...);
 -(int) conformsTo: (id) x;
 @end
 
-@protocol P0;
+@protocol P0
+@end
 
 @protocol P1
 +(void) classMethodReq0;
diff --git a/clang/test/PCH/objc_exprs.h b/clang/test/PCH/objc_exprs.h
index 807304c20f8..e4952f5929b 100644
--- a/clang/test/PCH/objc_exprs.h
+++ b/clang/test/PCH/objc_exprs.h
@@ -1,11 +1,13 @@
 
 @protocol foo;
+@protocol foo2
+@end
 @class itf;
 
 // Expressions
 typedef typeof(@"foo" "bar") objc_string;
 typedef typeof(@encode(int)) objc_encode;
-typedef typeof(@protocol(foo)) objc_protocol;
+typedef typeof(@protocol(foo2)) objc_protocol;
 typedef typeof(@selector(noArgs)) objc_selector_noArgs;
 typedef typeof(@selector(oneArg:)) objc_selector_oneArg;
 typedef typeof(@selector(foo:bar:)) objc_selector_twoArg;
diff --git a/clang/test/Parser/objc-cxx-keyword-identifiers.mm b/clang/test/Parser/objc-cxx-keyword-identifiers.mm
index 6791f0d3732..cff38c55437 100644
--- a/clang/test/Parser/objc-cxx-keyword-identifiers.mm
+++ b/clang/test/Parser/objc-cxx-keyword-identifiers.mm
@@ -18,7 +18,9 @@ struct S {
 @protocol new // expected-error {{expected identifier; 'new' is a keyword in Objective-C++}}
 @end
 
-@protocol P2, delete; // expected-error {{expected identifier; 'delete' is a keyword in Objective-C++}}
+@protocol P2;
+@protocol delete // expected-error {{expected identifier; 'delete' is a keyword in Objective-C++}}
+@end
 
 @class Foo, try; // expected-error {{expected identifier; 'try' is a keyword in Objective-C++}}
 
diff --git a/clang/test/SemaObjC/protocol-expr-neg-1.m b/clang/test/SemaObjC/protocol-expr-neg-1.m
index 26cdac70ae8..f659b30046e 100644
--- a/clang/test/SemaObjC/protocol-expr-neg-1.m
+++ b/clang/test/SemaObjC/protocol-expr-neg-1.m
@@ -12,7 +12,7 @@
 int main()
 {
 	Protocol *proto = @protocol(p1);
-        Protocol *fproto = @protocol(fproto); // expected-warning {{@protocol is using a forward protocol declaration of 'fproto'}}
+        Protocol *fproto = @protocol(fproto); // expected-error {{@protocol is using a forward protocol declaration of 'fproto'}}
 	Protocol *pp = @protocol(i); // expected-error {{cannot find protocol declaration for 'i'}}
 	Protocol *p1p = @protocol(cl); // expected-error {{cannot find protocol declaration for 'cl'}}
 }
@@ -26,9 +26,9 @@ int main()
 @end
 
 int doesConform(id foo) {
-  return [foo conformsToProtocol:@protocol(TestProtocol)]; // expected-warning {{@protocol is using a forward protocol declaration of 'TestProtocol'}}
+  return [foo conformsToProtocol:@protocol(TestProtocol)]; // expected-error {{@protocol is using a forward protocol declaration of 'TestProtocol'}}
 }
 
 int doesConformSuper(id foo) {
-  return [foo conformsToProtocol:@protocol(SuperProtocol)]; // expected-warning {{@protocol is using a forward protocol declaration of 'SuperProtocol'}}
+  return [foo conformsToProtocol:@protocol(SuperProtocol)]; // expected-error {{@protocol is using a forward protocol declaration of 'SuperProtocol'}}
 }