Extended Description

This bug hits us when building ICU as a DLL on Windows:

$ cat type.h
#ifdef DLL
#define API __declspec(dllexport)
#else
#define API __declspec(dllimport)
#endif

struct API VFoo {
virtual ~VFoo();
};

$ cat type.cpp
#include "type.h"

VFoo::~VFoo() {};

$ cat test.cpp
#include "type.h"

class XYZ : public VFoo {};

int main() {
new XYZ();
}

$ clang-cl -GR type.cpp -DDLL -link -dll -out:type.dll
Creating library type.lib and object type.exp

$ clang-cl -GR test.cpp type.lib -D_HAS_EXCEPTIONS=0
test-97d7d3.obj : error LNK2001: unresolved external symbol "struct VFoo RTTI Type Descriptor'" (??_R0?AUVFoo@@@8) test-97d7d3.obj : error LNK2001: unresolved external symbol "VFoo::RTTI Class Hierarchy Descriptor'" (??_R3VFoo@@8)
test.exe : fatal error LNK1120: 2 unresolved externals
clang-cl.exe: error: linker command failed with exit code 1120 (use -v to see invocation)