C++ std::unique_ptr with STL container

Question

I got a piece of code which uses a std::set to keep a bunch of pointer.

I used this to be sure of that each pointer will present only once in my container.

Then, I heard about std::unique_ptr that ensure the pointer will exists only once in my entire code, and that's exactly what I need.

So my question is quite simple, should I change my container type to std::vector ? Or It won't changes anything leaving a std::set ?

std::unique_ptr doesn't ensure that only one pointer points to a certain address. — Timo
– Timo, Commented Apr 19, 2018 at 13:47
Yes, but if I create my object with new std::unique_ptr< ... >(new ...()), or std::make_unique< ... >( ... ) ? — Sébastien Bémelmans
– Sébastien Bémelmans, Commented Apr 19, 2018 at 13:49
Should the container own the objects pointed to by the pointers? Do you even need pointers in the first place? — Caleth
– Caleth, Commented Apr 19, 2018 at 13:54
You are pretty safe when using make_unique. But you won't get total safety at any point. I.e. auto x = new xyz(); auto a = unique_ptr(x), b = unique_ptr(x); and don't use new to create a unique_ptr, you will lose the advantages smart pointers give you. — Timo
– Timo, Commented Apr 19, 2018 at 13:57

Gem Taylor · Accepted Answer · 2018-04-19 18:37:09Z

I think the job your set is doing is probably different to unique_ptr.

Your set is likely recording some events, and ensuring that only 1 event is recorded for each object that triggers, using these terms very loosely.
An example might be tracing through a mesh and recording all the nodes that are passed through.
The objects themselves already exist and are owned elsewhere.

The purpose of unique_ptr is to ensure that there is only one owner for a dynamically allocated object, and ensure automatic destruction of the object. Your objects already have owners, they don't need new ones!

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