safe to delete null pointer?

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  • Songling
    #1

    safe to delete null pointer?

    Hi gurus,

    Just learnt from my co-worker that it's safe to delete a null pointer. I
    tried it on sun box
    (and linux), nothing bad happens. So it seems to be true. But does it apply
    to all platforms?

    Also if I delete a pointer twice, and don't nullify the pointer after the
    first delete, it's going
    to trap. If I do the nullify, no trap. Does it just confirm that it's safe
    to delete null pointer?

    Btw I ran my test on SunOS 5.8 and Linux 2.4.18-3.

    Thanks for your reply!

    Songling


    Tags: delete null;
    • Artie Gold
      #2
      Re: safe to delete null pointer?

      Songling wrote:[color=blue]
      > Hi gurus,
      >
      > Just learnt from my co-worker that it's safe to delete a null pointer. I
      > tried it on sun box
      > (and linux), nothing bad happens. So it seems to be true. But does it apply
      > to all platforms?
      >
      > Also if I delete a pointer twice, and don't nullify the pointer after the
      > first delete, it's going
      > to trap. If I do the nullify, no trap. Does it just confirm that it's safe
      > to delete null pointer?
      >
      > Btw I ran my test on SunOS 5.8 and Linux 2.4.18-3.
      >
      > Thanks for your reply!
      >
      > Songling
      >
      >[/color]
      Calling delete on a null pointer is a no-op -- and, by the standard, no
      problem. Of course, the fact that you're deleting a null pointer may
      indicate the existence of a bug in your program -- but not necessarily.

      HTH,
      --ag

      --
      Artie Gold -- Austin, Texas

      http://it-matters.blogspot.com http://www.cafepress.com/goldsays

        Comment

        • Sumit Rajan
          #3
          Re: safe to delete null pointer?

          Songling wrote:[color=blue]
          > Hi gurus,
          >
          > Just learnt from my co-worker that it's safe to delete a null pointer. I
          > tried it on sun box
          > (and linux), nothing bad happens. So it seems to be true. But does it apply
          > to all platforms?
          >
          > Also if I delete a pointer twice, and don't nullify the pointer after the
          > first delete, it's going
          > to trap. If I do the nullify, no trap. Does it just confirm that it's safe
          > to delete null pointer?[/color]


          Deleting a null pointer is safe. 5.3.5/2 of the Standard:

          "In either alternative, if the value of the operand of delete is the
          null pointer the operation has no effect."

          Regards,
          Sumit.
          --
          Sumit Rajan <sumit.rajan@gm ail.com>

            Comment

            • Stuart Gerchick
              #4
              Re: safe to delete null pointer?

              "Songling" <yangsong@norte lnetworks.com> wrote in message news:<coq847$p1 0$1@zcars0v6.ca .nortel.com>...[color=blue]
              > Hi gurus,
              >
              > Just learnt from my co-worker that it's safe to delete a null pointer. I
              > tried it on sun box
              > (and linux), nothing bad happens. So it seems to be true. But does it apply
              > to all platforms?
              >
              > Also if I delete a pointer twice, and don't nullify the pointer after the
              > first delete, it's going
              > to trap. If I do the nullify, no trap. Does it just confirm that it's safe
              > to delete null pointer?
              >
              > Btw I ran my test on SunOS 5.8 and Linux 2.4.18-3.
              >
              > Thanks for your reply!
              >
              > Songling[/color]

              Deleting a null poiner is fine. It will have no effect and will behave as expected

                Comment

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