good code to return const reference to function local object?

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  • George2
    #1

    good code to return const reference to function local object?

    Hello everyone,


    1. Returning non-const reference to function local object is not
    correct. But is it correct to return const reference to function local
    object?

    2. If in (1), it is correct to return const reference to function
    local object, the process is a new temporary object is created (based
    on the function local object) and the const reference is binded to the
    temporary object, and the life time of the temporary object is
    extended to the life time of const reference?

    Or no need to create such a temporary object, just let the const
    reference binded to the function local object itself?


    thanks in advance,
    George
    Tags: None
    • James Kanze
      #2
      Re: good code to return const reference to function local object?

      On Jan 23, 12:26 pm, George2 <george4acade.. .@yahoo.comwrot e:
      1. Returning non-const reference to function local object is not
      correct. But is it correct to return const reference to function local
      object?
      No. What would that change?
      2. If in (1), it is correct to return const reference to function
      local object, the process is a new temporary object is created (based
      on the function local object) and the const reference is binded to the
      temporary object, and the life time of the temporary object is
      extended to the life time of const reference?
      No. To begin with, a temporary is never created when a
      reference is initialized with an lvalue. And even if it were,
      "A temporary bound to the [reference type] return value of a
      function persists until the function exits".
      Or no need to create such a temporary object, just let the
      const reference binded to the function local object itself?
      Const or not, the reference binds to the function local object,
      which is destructed when the function exits.

      --
      James Kanze (GABI Software) email:james.kan ze@gmail.com
      Conseils en informatique orientée objet/
      Beratung in objektorientier ter Datenverarbeitu ng
      9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34

        Comment

        • Kira Yamato
          #3
          Re: good code to return const reference to function local object?

          On 2008-01-24 12:48:23 -0500, varung@gmail.co m said:
          According to http://herbsutter.spac es.live.com/blog/cns!2D4327CC297 151BB!378
          .entry
          You CAN return a const reference to a function local object and it IS
          kept alive
          as long as the reference lives.
          You're confusing C++ with java.
          >
          [...]
          --

          -kira

            Comment

            • James Kanze
              #4
              Re: good code to return const reference to function local object?

              On Jan 24, 6:48 pm, var...@gmail.co m wrote:
              According
              tohttp://herbsutter.spac es.live.com/blog/cns!2D4327CC297 151BB!378.entry
              You CAN return a const reference to a function local object
              and it IS kept alive as long as the reference lives.
              According to the standard, you cannot. And I'd suggest you read
              the article you site; there is no mention of any reference type
              return values at all in it.

              --
              James Kanze (GABI Software) email:james.kan ze@gmail.com
              Conseils en informatique orientée objet/
              Beratung in objektorientier ter Datenverarbeitu ng
              9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34

                Comment

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