std::unique_ptr: Default Ownership

intermediate25 min readLesson 108 of 204

make_unique, move-only transfer, and the signature discipline of not naming smart pointers in observers.

std::unique_ptr<T> is the default smart pointer: exclusive ownership, zero overhead over a raw pointer, deleted when the unique_ptr dies.

#include <memory>

auto p = std::make_unique<Widget>(arg1, arg2);  // prefer make_unique
p->draw();
auto q = std::move(p);       // ownership transfers; p is now nullptr
// p->draw();                // UB: p is empty — check it first

The rules:

Always make_unique, not new: one allocation, exception safety, no naked new in application code.
Non-copyable, movable. Copying would create two owners — the exact bug the type exists to prevent.
Arrays: std::unique_ptr<T[]> exists but std::vector<T> is almost always the right answer.
Pass unique_ptr when you transfer ownership; pass T& or T* when you merely use the object. Functions that observe should not name smart pointers in their signatures.

Now practice

unique_ptr practiceAn ownership-transferring command stack built on std::stack.2 challenges · · ~35 min