Question

When I do something like this:

int my_array[5] = {1, 2, 3, 4, 5};
for (int &x : my_array) {
    x *= 2;
}

C++11 obviously knows that my array only has 5 elements. Is this information stored somewhere in the my_array object?

If so, is there any good reason why it is not made available to me as a developer (or is it?!?!?)? It seems that a lot of the world’s problems would be solved if C++ devs always knew the bounds of the arrays they’re dealing with.

Answer 1

This is simply something that the language requires to work, and the compiler must implement. Obviously the complete type of my_array is int[5] (i.e. the size is part of the type), so this information is readily available.

Contrary to popular belief, there is no use of the free std::begin()/std::end() functions in play, although those would naively seem to be able to do the trick (but there’s a catch involving ADL that would break this approach).