Improve key-function computation for templates. In particular:

  - All classes can have a key function; templates don't change that.
  non-template classes when computing the key function.
  - We always mark all of the virtual member functions of class
  template instantiations. 
  - The vtable for an instantiation of a class template has weak
  linkage. 

We could probably use available_externally linkage for vtables of
classes instantiated by explicit instantiation declarations (extern
templates), but GCC doesn't do this and I'm not 100% that the ABI
permits it.

llvm-svn: 92753

1 files changed, 18 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/vtable-key-function.cpp b/clang/test/CodeGenCXX/vtable-key-function.cpp
index 90e8ea66f76..97a546f8c93 100644
--- a/clang/test/CodeGenCXX/vtable-key-function.cpp
+++ b/clang/test/CodeGenCXX/vtable-key-function.cpp
@@ -13,3 +13,21 @@ struct A {
 A::A() { }
 A::A(int) { }
 }
+
+// Make sure that we don't assert when building the vtable for a class
+// template specialization or explicit instantiation with a key
+// function.
+template<typename T>
+struct Base {
+  virtual ~Base();
+};
+
+template<typename T>
+struct Derived : public Base<T> { };
+
+template<>
+struct Derived<char> : public Base<char> {
+  virtual void anchor();
+};
+
+void Derived<char>::anchor() { }