Question

Suppose I have VectorA and VectorB are two std::vector<SameType>, both initilized (i mean VectorA.size() > 0 and VectorB.size() > 0)

If I do:

VectorA = VectorB;

the memory previosly allocated for VectorA is automatically freed?

Answer 1

It is freed in the sense that the destructors of all contained objects are called, and the vector no longer owns the memory.¹

But really, it’s just returned to the allocator, which may or may not actually return it to the OS.

So long as there isn’t a bug in the allocator being used, you haven’t created a memory leak, if that’s what your concern is.

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_{1. As @David points out in the comment below, the memory isn’t necessarily deallocated, depending on whether the size needs to change or not.}