function template specialization in a namespace

I want to specialize a function template. This function is declared in a namespace:

namespace foo
{
   template <int>
   void function();
}

(For simplicity, the template is based on an int, whereas in my production code, it is an enum class, but it is the same issue. The same goes for a type based template)

Now I want to specialize it for a specific value:

template <>
void foo::function<0>()
{
}

This fails to compile with g++ -std=c++11 (versions 4.6, 4.7, 4.8 and 4.9):

specialization of ‘template void foo::function()’ in different namespace [-fpermissive]

clang++ -std=c++11 accepts this code.

g++ also accepts the following piece:

namespace foo
{
   template <>
   void function<0>()
   {
   }
}

Who's right, gcc or clang?