[MS] Emit exported complete/vbase destructors

Summary:
Fixes PR44205

I checked, and deleting destructors are not affected.

Reviewers: hans

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70931

Author: rnk

clang/lib/CodeGen/MicrosoftCXXABI.cpp

@@ -1343,6 +1343,13 @@ void MicrosoftCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
   // The TU defining a dtor is only guaranteed to emit a base destructor.  All
   // other destructor variants are delegating thunks.
   CGM.EmitGlobal(GlobalDecl(D, Dtor_Base));
+
+  // If the class is dllexported, emit the complete (vbase) destructor wherever
+  // the base dtor is emitted.
+  // FIXME: To match MSVC, this should only be done when the class is exported
+  // with -fdllexport-inlines enabled.
+  if (D->getParent()->getNumVBases() > 0 && D->hasAttr<DLLExportAttr>())
+    CGM.EmitGlobal(GlobalDecl(D, Dtor_Complete));
 }
 
 CharUnits

clang/test/CodeGenCXX/dllexport-dtor-thunks.cpp

@@ -1,5 +1,12 @@
 // RUN: %clang_cc1 -mconstructor-aliases -fms-extensions %s -emit-llvm -o - -triple x86_64-windows-msvc | FileCheck %s
 
+namespace test1 {
+struct A { ~A(); };
+struct __declspec(dllexport) B : virtual A { };
+// CHECK: define weak_odr dso_local dllexport void @"??1B@test1@@QEAA@XZ"
+// CHECK: define weak_odr dso_local dllexport void @"??_DB@test1@@QEAAXXZ"
+}
+
 struct __declspec(dllexport) A { virtual ~A(); };
 struct __declspec(dllexport) B { virtual ~B(); };
 struct __declspec(dllexport) C : A, B { virtual ~C(); };

clang/test/CodeGenCXX/dllimport-dtor-thunks.cpp

@@ -19,9 +19,9 @@ struct __declspec(dllimport) ImportOverrideVDtor : public BaseClass {
   virtual ~ImportOverrideVDtor() {}
 };
 
-// Virtually inherits from a non-dllimport base class. This time we need to call
-// the complete destructor and emit it inline. It's not exported from the DLL,
-// and it must be emitted.
+// Virtually inherits from a non-dllimport base class. In this case, we can
+// expect the DLL to provide a definition of the complete dtor. See
+// dllexport-dtor-thunks.cpp.
 struct __declspec(dllimport) ImportVBaseOverrideVDtor
     : public virtual BaseClass {
   virtual ~ImportVBaseOverrideVDtor() {}