Question

How severe is the efficiency loss between using memcpy and std::copy?

I have a situation where the vector implementation on my system doesn’t appear to use contiguous memory, which is making me have to std::copy its contents later on rather than doing memcpy(dest, &vec[0], size);. I’m not sure how badly this is likely to impact efficiency.

Answer 1

A reasonably decent implementation will have std::copy compile to a call memmove in the situations where this is possible (i.e. the element type is a POD).

If your implementation doesn’t have contiguous storage (the C++03 standard requires it), memmove might be faster than std::copy, but probably not too much. I would start worrying only when you have measurements to show it is indeed an issue.