[ms-cxxabi] Elide dtor access checks for pass-by-val objects in callees

The ABI requires the destructor to be invoked in the callee, but the
standard does not require access checks here so we avoid doing direct
access checks on the destructor.

If we end up needing to define an implicit destructor, we don't skip
access checks for the base class, etc. Those checks are effectively part
of generating the destructor definition, and aren't affected by which TU
the check is performed in.

Differential Revision: http://llvm-reviews.chandlerc.com/D2409

llvm-svn: 199120

clang/lib/Sema/SemaChecking.cpp

@@ -6241,12 +6241,21 @@ bool Sema::CheckParmsForFunctionDef(ParmVarDecl *const *P,
 
     // MSVC destroys objects passed by value in the callee.  Therefore a
     // function definition which takes such a parameter must be able to call the
-    // object's destructor.
+    // object's destructor.  However, we don't perform any direct access check
+    // on the dtor.
     if (getLangOpts().CPlusPlus && Context.getTargetInfo()
                                        .getCXXABI()
                                        .areArgsDestroyedLeftToRightInCallee()) {
-      if (const RecordType *RT = Param->getType()->getAs<RecordType>())
-        FinalizeVarWithDestructor(Param, RT);
+      if (const RecordType *RT = Param->getType()->getAs<RecordType>()) {
+        CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(RT->getDecl());
+        if (!ClassDecl->isInvalidDecl() &&
+            !ClassDecl->hasIrrelevantDestructor() &&
+            !ClassDecl->isDependentContext()) {
+          CXXDestructorDecl *Destructor = LookupDestructor(ClassDecl);
+          MarkFunctionReferenced(Param->getLocation(), Destructor);
+          DiagnoseUseOfDecl(Destructor, Param->getLocation());
+        }
+      }
     }
   }
 

clang/test/SemaCXX/microsoft-dtor-lookup.cpp

@@ -32,10 +32,9 @@ namespace Test2 {
 // requires a dtor for B, but we can't implicitly define it because ~A is
 // private.  bar should be able to call A's private dtor without error, even
 // though MSVC rejects bar.
-
 class A {
 private:
-  ~A(); // expected-note 2{{declared private here}}
+  ~A(); // expected-note {{declared private here}}
   int a;
 };
 
@@ -54,7 +53,7 @@ struct D {
 };
 
 void foo(B b) { } // expected-note {{implicit destructor for 'Test2::B' first required here}}
-void bar(A a) { } // expected-error {{variable of type 'Test2::A' has private destructor}}
+void bar(A a) { } // no error; MSVC rejects this, but we skip the direct access check.
 void baz(D d) { } // no error
 
 }
@@ -64,13 +63,13 @@ namespace Test3 {
 
 class A {
   A();
-  ~A(); // expected-note 2{{implicitly declared private here}}
+  ~A(); // expected-note {{implicitly declared private here}}
   friend void bar(A);
   int a;
 };
 
 void bar(A a) { }
-void baz(A a) { } // expected-error {{variable of type 'Test3::A' has private destructor}}
+void baz(A a) { } // no error; MSVC rejects this, but the standard allows it.
 
 // MSVC accepts foo() but we reject it for consistency with Itanium.  MSVC also
 // rejects this if A has a copy ctor or if we call A's ctor.

clang/test/SemaObjCXX/microsoft-abi-byval.mm

@@ -1,7 +1,8 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -cxx-abi microsoft -Wno-objc-root-class %s
+// expected-no-diagnostics
 
 class Foo {
-  ~Foo(); // expected-note {{implicitly declared private here}}
+  ~Foo();
 };
 
 @interface bar
@@ -9,6 +10,6 @@ class Foo {
 @end
 
 @implementation bar
-- (void) my_method: (Foo)arg { // expected-error {{variable of type 'Foo' has private destructor}}
+- (void) my_method: (Foo)arg { // no error; MS ABI will call Foo's dtor, but we skip the access check.
 }
 @end