Certainly std::sort and friends are recursive in all C++ implementations I've looked at. In C++ it's hard to make the efficient and non-recursive. You can have

Certainly std::sort and friends are recursive in all C++ implementations I've looked at. In C++ it's hard to make the efficient and non-recursive. You can have a fixed-sized buffer (limits depth), or call malloc for a buffer (a single call to malloc can be more expensive than just doing the sort on the stack, and in general the C++ standard library tries hard to avoid mallocing).