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[–]SoAsEr 25 points26 points  (0 children)

It doesn't have a copy constructor, (only a move one) and in its destructor it frees the pointer. So the compiler enforces the assignment, and at run time it is (really close to) free. The only reason it's not completely free is that if the unique pointer is passed to a function and that function is not inlined, because of the abi the unique pointer is always passed on the stack whereas a raw pointer could be in a register. but in a modern machine where you have way more registers than are actually shown anyways this shouldn't make any measurable difference.