[COFF] Don't try to emit weak aliases on COFF
This comes up when a derived class destructor is equivalent to a base
class destructor defined in the same TU, and we try to alias them.
A COFF weak alias cannot satisfy a normal undefined symbol reference
from another TU. The other TU must also mark the referenced symbol as
weak, and we can't rely on that.
Clang already has a special case here for dllexport, but we failed to
realize that the problem also applies to other non-discardable symbols
such as those from explicit template instantiations.
Fixes PR25477.
llvm-svn: 252659
diff --git a/clang/test/CodeGenCXX/microsoft-abi-structors-alias.cpp b/clang/test/CodeGenCXX/microsoft-abi-structors-alias.cpp
index 6007e5a..08df374 100644
--- a/clang/test/CodeGenCXX/microsoft-abi-structors-alias.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-structors-alias.cpp
@@ -24,3 +24,19 @@
}
// CHECK-DAG: @"\01??1B@test2@@UAE@XZ" = alias void (%"struct.test2::B"*), bitcast (void (%"struct.test2::A"*)* @"\01??1A@test2@@UAE@XZ" to void (%"struct.test2::B"*)*)
}
+
+namespace test3 {
+struct A { virtual ~A(); };
+A::~A() {}
+}
+// CHECK-DAG: define x86_thiscallcc void @"\01??1A@test3@@UAE@XZ"(
+namespace test3 {
+template <typename T>
+struct B : A {
+ virtual ~B() { }
+};
+template struct B<int>;
+}
+// This has to be weak, and emitting weak aliases is fragile, so we don't do the
+// aliasing.
+// CHECK-DAG: define weak_odr x86_thiscallcc void @"\01??1?$B@H@test3@@UAE@XZ"(