How to define static const member?

Question

My Test class has a const static member of a subtype. I usually define this const static member as follows.

class Test 
{
public:
    class Dummy {};

private:
    static Dummy const dummy;

};

Test::Dummy const Test::dummy;             // ERROR HERE

int main() 
{
    return 0;
}

When compiling this source with gcc-4.6, it gives no error and compiles correctly.

When compiling this same source with gcc-4.4, it gives the following error: error: uninitialized const ‘Test::dummy’ on the marked line.

• Is there another way to define this static const member variable?
• Is this a limitation of gcc-4.4?
• Is there a workaround?

Answer 1

Say:

Test::Dummy const Test::dummy = { };

Answer 2

See http://gcc.gnu.org/wiki/VerboseDiagnostics#uninitialized_const (which gives the relevant reference to the standard) and also the GCC 4.6 release notes which say

In 4.6.0 and 4.6.1 G++ no longer allows objects of const-qualified type to be default initialized unless the type has a user-declared default constructor. In 4.6.2 G++ implements the proposed resolution of DR 253, so default initialization is allowed if it initializes all subobjects. Code that fails to compile can be fixed by providing an initializer e.g.

struct A { A(); };
struct B : A { int i; };
const B b = B();

Use -fpermissive to allow the old, non-conforming behaviour.