How Can I Properly Transfer Ownership of a `unique_ptr` to a Lambda in C ?

Preserving Ownership in a Lambda with a Unique Pointer

In C , a unique_ptr is designed to manage ownership of a single object exclusively. When attempting to capture a unique_ptr into a lambda expression, ownership can become ambiguous. Here's how to address this issue:

Initially, an attempt to capture a unique_ptr as a reference in a lambda may fail to compile. To explicitly transfer ownership to the lambda, C 14 introduced lambda generalized capture:

auto getAction = [](std::unique_ptr<MyClass> psomething) {
    // Ownership now belongs to the lambda
    return [a = std::move(psomething)]() {
        a->do_something();
        // psomething is released after this point
    };
};

Ownership Transfer with Copy and Move Implementations:

In your updated code, you've defined copy and move functions to handle different types of references. To ensure proper ownership transfer, consider the following:

• move should only accept an lvalue reference because moving an rvalue (temporary object) is undefined behavior.
• Avoid declaring an rvalue version of move to prevent accidental movement of temporary objects.

With these modifications, your code should work as expected, preserving ownership within the lambda expression.

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