Re: 'Read for pointers

["Pat Rogers" <progers@NOclasswideSPAM.com>]

<tmoran@bix.com> wrote in message
news:xRLf5.61$M35.39742@news.pacbell.net...
> >I'm not sure I see your point, given the context.
>   The "out" parameter is not set to null so if the procedure has a
bug
> so that it isn't set, it will retain its previous value.  Any
> uninitialized variable bug can be hard to find.  But a pointer is
> especially hard, and in fact most pointers are automatically
> initialized to null, which helps a lot.  Here the "out" parameter
> pointer in fact points to an internally correct data structure, just
> the wrong one, or one that might have been deallocated.  I think
such
> a bug might take a while to track down.

Having parsed the above a couple of times, let me try to restate what
you're saying, just  to be sure I understand it.  What I believe
you're saying -- and if so I agree with it (which is why I question my
understanding of it:) -- is this: Given that the value of the actual
is copied in for an access type formal parameter of mode out, if the
subprogram has a bug such that the formal is not updated then the
actual will retain the old value, and this would be a hard bug to
find.  If that's what you mean I agree, but it is preferable to
copying back junk, which can certainly happen with by-copy types other
than access types.  At least we don't go off into the weeds when
dereferencing the pointer.

--
Pat Rogers                            Consulting and Training in:
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