How does this code create a dangling reference?

Asked Jun 28 '22 at 12:31

Active Jun 28 '22 at 12:43

Viewed 114 times

There is a good post in [1] about move semantics. I'm fairly comfortable with them, but there are still some edge cases that I'm not sure about -- specifically, about returning rvalue references. For example, the link says that this creates a dangling reference:

unique_ptr<Shape>&& flawed_attempt()   // DO NOT DO THIS!
{
    unique_ptr<Shape> very_bad_idea(new Square);
    return std::move(very_bad_idea);   // WRONG!
}

I don't quite understand the error. The function is declared to return an rvalue ref, and it's doing that with the std::move().

How is the dangling reference created?

[1] What is move semantics?

asked Jun 28 '22 at 12:31

Dess

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Ask yourself: When does the `very_bad_idea` object get destroyed? – NathanOliver Jun 28 '22 at 12:32
1

Do you understand why the equivalent code, but returning an lvalue reference and not going through std::move, would also create a dangling reference? – Sneftel Jun 28 '22 at 12:39
The `unique_ptr&&` rvalue reference is a **reference**. – Eljay Jun 28 '22 at 12:39

How does this code create a dangling reference?

0 Answers0