How to export the virtual destructor in Xcode?

Question

I'm working on a sample project with two modules: A and B(which links to A), using Xcode 4.4.

In module A, the symbols are hidden by the compiler flag -fvisibility=hidden. I have a class whose destructor is virtual and exported:

class utx
{
    int mm;
public:
    __attribute__ ((visibility("default"))) utx(int m);
    __attribute__ ((visibility("default"))) virtual ~utx();
};

And it's implemented as:

utx::utx(int m) : mm(m) { }
utx::~utx() { }

In module B, MyUtx derives from utx as below:

class MyUtx : public utx
{
public:
    MyUtx() : utx(5) { }
    virtual ~MyUtx() { }
}Ins;

While, I always get below link error for module B:

Undefined symbols for architecture x86_x64:
    "typeinfo for utx", referenced from:
        typeinfo for MyUtx in main.o

If the utx's destructor is non-virtual, the problem goes away.

Answer 1

Have you tried:

class __attribute__ ((visibility("default"))) utx
{
  ...

According to http://gcc.gnu.org/wiki/Visibility typeinfo generation depends on whether your class has vfptr and adding virtual destructor can change that (if you have no other virtual functions).