[Tcl-bugs] [tcl] (Ticket 3598590fff - Change) UpdateStringOfList should use TclConvertElement length

[<tcl...@tc...>]

Repository: http://core.tcl.tk/tcl

Change Notification For
  [UpdateStringOfList should use TclConvertElement length]
  Ticket   http://core.tcl.tk/tcl/tktview?name=3598590fffffffffffffffffffffffffffffffff
  Artifact http://core.tcl.tk/tcl/tinfo?name=b43674f7e7c11e69c63ddc8e1b41e27562e833ea
  On       2013-11-12T12:39:32
  By       dkf

Changed Fields
  closedate: 2456609.02745837
  closer:    dkf
  comment:   tclListObj.c:UpdateStringOfList (which is what I'm cloning for an
             extension), loops TclScanElement to estimate size of buffer. It then
             sets Tcl_Obj.length as this estimate. As per source comments for
             TclScanElement this number is a *over*estimate and it is the lengths
             returned from TclConverElement that should be used. The only way it
             works as is if TclScanElement always returns a exact count, never an
             over estimate I can't actually get it to return an overestimate (yet)
             Either TclScanElement docs are wrong or the code needs to be fixed to
             use the lengths returned by TclConvertElement Yes, highly unlikely
             USOL does not work! But I think it is more likely the estimate is
             precise than the overallocation being harmless else you would get
             trailing garbage in some cases, I think (both the length field and the
             terminating null point to the end of allocated space) Other
             possibility is that the overestimate is some really arcane case that
             is not in the tests and will rarely (never?) occur in real life It
             appears as though the extra space happens (afaict) only when the
             CONVERT_ANY flag is passed in to TclScanElement.

             Since UpdateStringOfList does not pass this flag, it appears to be
             safe. However, to keep to the documented TclScanElement interface and
             guard against future changes, I think it should use the lengths
             returned by TclConvertElement instead.
  login:     dkf
  severity:  Minor
  status:    Closed