Is it safe to call vector.resize(0) after moving its content [duplicate]

Question

In other words is the following code sound(defined behavior,portable,...)

   std::vector<int> vec(100,42);
   std::vector<int> other = std::move(vec);
   vec.resize(0);//is this sound

   //using vec like an empty vector

Answer 1

Yes, it is safe.

From §23.3.6.5:

If sz <= size(), equivalent to calling pop_back() size() - sz times. If size() < sz, appends sz - size() default-inserted elements to the sequence.

So basically, when you call resize(0), it calls pop_back() until every element is removed from the vector.

It doesn't matter that you moved vec, because even though the state of vec is unspecified, it is still a valid vector that you can modify.

So, the std::vector will be empty after a call to resize(0).