CODEWITHSUNDEEP
pointersrustmemory-leaks
letsplayrust5346
letsplayrust5346

Reputation: 21

What makes returning a reference String in rust a dangling pointer?

fn dangle() -> &String { // dangle returns a reference to a String

    let s = String::from("hello"); // s is a new String

    &s // we return a reference to the String, s
}

Going through rust book and learning about ownership, How does returning a reference to a String make it a dangling pointer?

Upvotes: 2

Views: 767

Answers (1)

FloLo100
FloLo100

Reputation: 21

The string you're referencing lives inside the function (only). That means, that the management code to allocate and deallocate memory for this string will be put into this function by the compiler. Therefore the compiler has to deallocate the memory for s before returning to the caller. However, &s would now reference a deallocated item, that is a dangling pointer.

Upvotes: 2

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