vector push_back calling copy_constructor more than once?

Question

I am a bit confused with the way vector push_back behaves, with the following snippet I expected the copy constructor to be invoked only twice, but the output suggest otherw

Answer 1

You're correct in assuming the additional invocation of the copy constructor comes from internal restructuring of the vector.

See this answer for more detail: https://stackoverflow.com/a/10368636/3708904

Or this answer for the reason why copy construction is necessary: https://stackoverflow.com/a/11166959/3708904