Substring

[dietao234]

How does substr() in the string class work?? Does it copy over each character linearly?

Thanks in advance

[Lindley]

It probably depends on the implementation. A reference-counted copy-on-write implementation is possible, although I think the next version of the standard will require substr() to actually make an O(n) copy, yes. (Trying to use copy-on-write in conjunction with multithreading would be....interesting.)

[ninja9578]

Yes, here's a way to show:

std::string test("Hello World");
std::cout << (void*)test.data() << " - " << (void*)test.substr(0, 5).data() << std::endl;

If they're the same they're copy on write, else, literal copy.