Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
678 views
in Technique[技术] by (71.8m points)

c++ - std::vector capacity after copying

  • Does vector::operator= change vector capacity? If so, how?
  • Does vector's copy constructor copy capacity?

I looked through documentation but could not find a specific answer. Is it implementation dependent?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

All you're guaranteed is that:

  1. The vector has enough capacity to store its elements. (Obviously.)
  2. The vector won't get a new capacity until it's current capacity is full.*

So how much extra or little an implementation wants to put is up to the implementation. I think most will make capacity match size, when copying, but it cannot lower capacity. (Because of number 2 above; reallocating while there's enough room is not allowed.)

* Mostly. See Charles' comments below.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...