Reates a temporary which is freed while still in use

help
1

Hi
I have the dreaded creates temporary which is freed error . I tried doing the clone but that does not solve the error. I also looked at the other posts in the forum on the same topic .
This is inside a match fragment.The code is below and the error is also attached

let mut client_ip_address = "";
if dns.additionals.len() != 0 {
    let additionals = dns.additionals;
    match &additionals[0] {
        dns_message_parser::rr::RR::OPT(m) => {
            if m.edns_options.len() > 0 {
                let edns_options = &m.edns_options;
                let edns_options = match &edns_options[0] {
                dns_message_parser::rr::edns::EDNSOption::ECS(m1) => {
                                   
                    m1
                }

                _ =>{
                        eprintln!("Found a non EDNS message ");
                        return Err("Error ".into());
                }
            };
      // ERROR
                            
            let x1 = &edns_options.get_address().to_string().clone();
            client_ip_address = x1;
        }
    }
    _ => {
            eprintln!("Found a non OPT message ");
            return Err("Error ".into());
         }
    }
}
println!("{:}",client_ip_address);

error[E0716]: temporary value dropped while borrowed
    
    |
    |                             let x1 = &edns_options.get_address().to_string().clone();
    |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
    |                             client_ip_address = x1;
    |                         }
    |                         - temporary value is freed at the end of this statement
...
    |                     client_ip_address,
    |                     ----------------- borrow later used here
    |
    = note: consider using a `let` binding to create a longer lived value
2

The problem is that edns_options.get_address().to_string() (with or without .clone()) is producing a String that isn't being stored anywhere, so it gets freed at the end of the statement. You then take a reference to it with &, which can't live longer than the temporary. The easiest fix is to store the String instead of a reference:

let mut client_ip_address: String = String::new();
// ...
client_ip_address = edns_options.get_address().to_string();

Depending on how dns_message_parser is built, this might also work, as it doesn't create a temporary String; I haven't checked:

let mut client_ip_address = "";
// ...
client_ip_address = edns_options.get_address();
3

This worked very well. Thanks .The 2nd option did not work since it is returning an Enum

4

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