The following code compiles and works on clang, but fails with "error: invalid use of non-static data member ‘Outer::a’" on gcc:
#include <functional>
#include <vector>
#include <assert.h>
#include <iostream>
#include <memory>
class Outer
{
public:
bool a = false;
virtual void f() = 0;
template <typename T>
class Inner : public T
{
public:
virtual void f() override
{
a = true; // Note: accessed through inheritance, not through outer scope
}
};
};
struct Foo : Outer { };
int main()
{
Outer::Inner<Foo> f;
f.f();
}
Adding "this->a" to the inner class makes it work on both compilers, but I'm wondering what's the correct behavior and what the standards says about this.
Interestingly the above code works with as part of a larger code base in VS2017 at work, but when I try it at home with VS2017 in isolation, it fails with the same error as GCC.
You can try compiling it here:
