MS ABI: Don't always instantiate all members of dllexported class templates (PR20163)

Normally we mark all members of exported classes referenced to get them emitted.

However, MSVC doesn't do this for class templates that are implicitly specialized or
just have an explicit instantiation declaration. For such specializations, the members
are emitted when referenced.

The exception is the case when the dllexport attribute is propagated from a base class
to a base class template that doesn't have an explicit attribute: in this case all
methods of the base class template do get instantiated.

llvm-svn: 216145

1 files changed, 3 insertions, 4 deletions

diff --git a/clang/test/CodeGenCXX/dllexport.cpp b/clang/test/CodeGenCXX/dllexport.cpp
index 846978dbb19..4cf6005134c 100644
--- a/clang/test/CodeGenCXX/dllexport.cpp
+++ b/clang/test/CodeGenCXX/dllexport.cpp
@@ -509,11 +509,9 @@ USEVAR(T::b)
 int T::c;
 
 template <typename T> struct __declspec(dllexport) U { void foo() {} };
-// The U<int> specialization below must cause the following to be emitted:
-// M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?foo@?$U@H@@QAEXXZ"
-// M32-DAG: define weak_odr dllexport x86_thiscallcc dereferenceable({{[0-9]+}}) %struct.U* @"\01??4?$U@H@@QAEAAU0@ABU0@@Z"
 struct __declspec(dllexport) V : public U<int> { };
-
+// U<int>'s assignment operator is emitted.
+// M32-DAG: define weak_odr dllexport x86_thiscallcc dereferenceable({{[0-9]+}}) %struct.U* @"\01??4?$U@H@@QAEAAU0@ABU0@@Z"
 
 struct __declspec(dllexport) W { virtual void foo() {} };
 // Default ctor:
@@ -618,6 +616,7 @@ USEMEMFUNC(DerivedFromTemplate, func)
 
 // ExportedTemplate is explicitly exported.
 struct __declspec(dllexport) DerivedFromExportedTemplate : public ExportedClassTemplate<int> {};
+USEMEMFUNC(DerivedFromExportedTemplate, func)
 // M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?func@?$ExportedClassTemplate@H@@QAEXXZ"
 // G32-DAG: define weak_odr dllexport x86_thiscallcc void @_ZN21ExportedClassTemplateIiE4funcEv