[MauranKilom]

What? That's one of the primary motivations!

"I have created an object and will pass its unique ownership to you." -> std::unique_ptr

"This routine needs a function that takes two ints and returns a float (without putting all my code into headers)." -> std::function<float(int, int)>.

Can you elaborate in what circumstance you should not pass std::types across API boundaries?

[jfkebwjsbx]

The heap allocation is an implementation detail.

std::function is useful in some situations, but "without putting all my code into headers" is not a good argument.