Emit an error when trying to @encode an incomplete type.

There are APIs, e.g. [NSValue valueWithBytes:objCType:], which use the encoding to find out
the size of an object pointed to by a pointer. Make things safer by making it illegal to @encode
incomplete types.

llvm-svn: 131364

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2869,6 +2869,8 @@ def err_objc_pointer_cxx_catch_fragile : Error<
   "exception model">;
 def err_objc_object_catch : Error<
   "can't catch an Objective C object by value">;
+def err_incomplete_type_objc_at_encode : Error<
+  "'@encode' of incomplete type %0">;
 
 def warn_setter_getter_impl_required : Warning<
   "property %0 requires method %1 to be defined - "

clang/include/clang/Sema/Sema.h

@@ -3105,7 +3105,7 @@ public:
                                     Expr **Strings,
                                     unsigned NumStrings);
 
-  Expr *BuildObjCEncodeExpression(SourceLocation AtLoc,
+  ExprResult BuildObjCEncodeExpression(SourceLocation AtLoc,
                                   TypeSourceInfo *EncodedTypeInfo,
                                   SourceLocation RParenLoc);
   ExprResult BuildCXXMemberCallExpr(Expr *Exp, NamedDecl *FoundDecl,

clang/lib/Sema/SemaExprObjC.cpp

@@ -119,7 +119,7 @@ ExprResult Sema::ParseObjCStringLiteral(SourceLocation *AtLocs,
   return new (Context) ObjCStringLiteral(S, Ty, AtLocs[0]);
 }
 
-Expr *Sema::BuildObjCEncodeExpression(SourceLocation AtLoc,
+ExprResult Sema::BuildObjCEncodeExpression(SourceLocation AtLoc,
                                       TypeSourceInfo *EncodedTypeInfo,
                                       SourceLocation RParenLoc) {
   QualType EncodedType = EncodedTypeInfo->getType();
@@ -127,6 +127,12 @@ Expr *Sema::BuildObjCEncodeExpression(SourceLocation AtLoc,
   if (EncodedType->isDependentType())
     StrTy = Context.DependentTy;
   else {
+    if (!EncodedType->getAsArrayTypeUnsafe()) // Incomplete array is handled.
+      if (RequireCompleteType(AtLoc, EncodedType,
+                         PDiag(diag::err_incomplete_type_objc_at_encode)
+                             << EncodedTypeInfo->getTypeLoc().getSourceRange()))
+        return ExprError();
+
     std::string Str;
     Context.getObjCEncodingForType(EncodedType, Str);
 

clang/test/SemaObjC/exprs.m

@@ -32,3 +32,13 @@ void test3(Object *o) {
   // this is ok.
   __sync_bool_compare_and_swap(&g, 0, o);
 }
+
+@class Incomplete_ObjC_class;
+struct Incomplete_struct; // expected-note {{forward declaration}}
+
+void test_encode() {
+  (void)@encode(Incomplete_ObjC_class); // expected-error {{incomplete type}}
+  (void)@encode(struct Incomplete_struct); // expected-error {{incomplete type}}
+  (void)@encode(Incomplete_ObjC_class*);
+  (void)@encode(id);
+}