This seems to be most relavant question already asked.
Whats the difference between std::move and std::forward
But each answer is different and applies and says
In this case:
void push_back(T&& value)
{
resizeIfRequired();
moveBackInternal(std::forward(value)); // (1)
moveBackInternal(std::move(value)); // (2)
}
std::forward
and std::move(value)
are identical in this scenario (it doesn't matter between (1)
and (2)
... so use (2)
).
move
is an unconditional cast to xvalue. That line gives you an expression of type T&&
that's an rvalue, always.
forward
is a conditional cast. If T
is an lvalue reference type, it yields an lvalue. Otherwise (if it's either not a reference type or an rvalue reference type), it yields an rvalue. In our case, T
is not a reference type - so we get an rvalue.
Either way, we end up at the same point - we call moveBackInternal
with value
cast as an rvalue. Just move()
is a simpler way of getting there. forward
works, but it's unnecessary.