Question

If I never use the address of a static const variable, is memory allocated for it when using a reasonably modern compiler?

Answer 1

It depends on the type of the variable, and on whether “constant” also means “constant expression”. Example:

static const Foo = get_foo(std::cin);

static const int q = argc * 3;

static const std::string s(gets());

These variables are const, but blatantly need an actual allocation.

On the other hand, the following constant expression may never have physical storage:

static const int N = 1000;

static const std::shared_ptr<void> vp();  // constexpr constructor!

Most importantly, static constexpr member variables don’t need a definition if you’re careful:

struct Bar
{
  int size() const { return N; }
  static const int N = 8;
};
// does NOT need "const int Bar::N;"