[PATCH] D11913: [dllimport] A non-imported class with an imported key can't have a key

Reid Kleckner via cfe-commits cfe-commits at lists.llvm.org
Mon Aug 10 11:19:27 PDT 2015

rnk created this revision.
rnk added reviewers: majnemer, hans.
rnk added a subscriber: cfe-commits.

The vtable takes its DLL storage class from the class, not the key
function. When they disagree, the vtable won't be exported by the DLL
that defines the key function. The easiest way to ensure that importers
of the class emit their own vtable is to say that the class has no key



Index: test/CodeGenCXX/dllimport-rtti.cpp
--- test/CodeGenCXX/dllimport-rtti.cpp
+++ test/CodeGenCXX/dllimport-rtti.cpp
@@ -22,3 +22,11 @@
 // GNU-DAG: @_ZTV1V = available_externally dllimport
 // GNU-DAG: @_ZTS1V = linkonce_odr
 // GNU-DAG: @_ZTI1V = linkonce_odr
+struct W {
+  __declspec(dllimport) virtual void f();
+  virtual void g();
+} w;
+// GNU-DAG: @_ZTV1W = linkonce_odr
+// GNU-DAG: @_ZTS1W = linkonce_odr
+// GNU-DAG: @_ZTI1W = linkonce_odr
Index: lib/AST/RecordLayoutBuilder.cpp
--- lib/AST/RecordLayoutBuilder.cpp
+++ lib/AST/RecordLayoutBuilder.cpp
@@ -2008,6 +2008,12 @@
+    // If the key function is dllimport but the class isn't, then the class has
+    // no key function. The DLL that exports the key function won't export the
+    // vtable in this case.
+    if (MD->hasAttr<DLLImportAttr>() && !RD->hasAttr<DLLImportAttr>())
+      return nullptr;
     // We found it.
     return MD;

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