[PATCH] [-cxx-abi microsoft] Emit thunks for pointers to virtual member functions

[Reid Kleckner]

  LGTM with one last fix


================
Comment at: lib/CodeGen/MicrosoftCXXABI.cpp:993
@@ +992,3 @@
+  LinkageInfo LV = MD->getLinkageAndVisibility();
+  ThunkFn->setLinkage(LV.getLinkage() != ExternalLinkage
+                          ? llvm::GlobalValue::InternalLinkage
----------------
I think you really want MD->isExternallyVisible() to handle the VisibleNoLinkage case, which would be triggered by something evil like:

  inline __forceinline bool foo(bool set_mp) {
    struct B {
      virtual void f() {}
      static bool compare_mps(void (B::*mp1)(), void (B::*mp2)()) {
        return mp1 == mp2;
      }
    };
    if (set_mp)
      mp = reinterpret_cast<void (A::*)()>(&B::f);
    return B::compare_mps(&B::f, reinterpret_cast<void (B::*)()>(mp));
  }

If you use internal linkage here, you'll get two distinct thunks, and the comparison will be false when it shouldn't be.


http://llvm-reviews.chandlerc.com/D2104