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c++inheritancec++20weak-ptr

How to not allow conversion from temporary shared_ptr to weak_ptr for derived types

I have asked this question for concrete types. The provided solution is sufficient for those, but when it comes to inheritance, it fails. Would there be a solution to that as well?

Lets have a inheritance of classes Foo and IFoo such that class Foo: public IFoo and a function void use_weak_ptr(std::weak_ptr<IFoo>).

Is it possible to ensure that this compiles:

auto shared = std::make_shared<Foo>();
use_weak_ptr(shared);

And this does not:

use_weak_ptr(std::make_shared<Foo>());

Godbolt

Solution

  • One of the possible solutions - overload use_weak_ptr for all std::shared_ptr.

    template <typename T>
void use_weak_ptr(std::shared_ptr<T>&&) = delete;

    https://godbolt.org/z/Tj1a134bd

    The linked answer is not a good answer. const std::shared_ptr<IFoo>&& - const is redundant.