🚀 go-pugleaf

In article <42sf4t$9im@eurybia.rz.uni-konstanz.de>
kuehl@horn.rz.uni-konstanz.de (Dietmar Kuehl) writes:

|> Rogier Goossens (goossens@cs.few.eur.nl) wrote:
|> : I have two more remarks:
|> : 
|> : >   template<class T>
|> : >   inline void operator=(auto_ptr<T>& rhs)
|> : >   { ptr = rhs.release; }
|> : 
|> : Don't forget to delete the previous object ptr pointed to.

|> The standard doesn't say something about deleting the old pointer!  My
|> interpretation is this: auto_ptr is not supposed to delete all pointers
|> but only the one it is holding when it gets destructed.  This semantic
|> is indeed useful if it is possible that an exception is thrown while
|> nothing else takes care of the allocated object or some memory should
|> be released when exiting a function. In the meantime the programmer has
|> still to care for the pointer if it is replaced.

The draft standard does say that the semantics of assignment include a
call to reset.  It doesn't say anything about the semantics of reset,
but the original proposal did.

>From 94-0202R1/N0289R1: 

   Semantics
   ---------
   An auto_ptr<X> object holds a pointer to an object of class X, presented
   here as X* px. In the following table: p and px are pointers to an object
   of class X or a class derived from X for which delete(X*) is defined and
   accessible, or else null; d is an auto_ptr<D> where D is X or a class
   derived from X; a is an auto_ptr<X>; and m is a member of X.

      Expression           Value             Effect
      ------------------   ---------------   ---------------------
      auto_ptr<X> a(p)                       a.px = p
      auto_ptr<X> a(d)                       a.px = d.release()
      a.~auto_ptr<X>()                       delete a.px
      a = d                reference to a    a.reset(d.release())
      *a                   *a.px
      a->m                 a.px->m
      a.get()              a.px
      a.release()          a.px              a.px = 0
      a.reset(p)                             delete a.px, a.px = p

IMHO, these are the only semantics which make sense; if I *don't*
delete the old pointer in assignment, who will?
--

James Kanze         Tel.: (+33) 88 14 49 00        email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs-Bourgeois, F-67000 Strasbourg, France
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