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From: Robert Dewar <robert_dewar@my-deja.com>
Newsgroups: comp.lang.ada
Subject: Re: Parameter Modes, In In Out and Out
Date: Thu, 11 Jan 2001 04:23:12 GMT
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In article <3A5CF57A.225BC5B5@averstar.com>,
  Tucker Taft <stt@averstar.com> wrote:

> Unless you can prove that passing them by reference would be
> equivalent, of course.

Well when we say that something must be passed by copy, we are
not making statements about generated code, but about
semantics. After all the compiler can do anything it likes
if it makes no difference. For example, if it knows that the
result of a call to the cosine function is not needed, then the
compiler can call the sine function instead, but that's not
really relevant in talking about semantics.




  E.g., for [in] out parameters, we generally pass an address
> of something.  Usually that something is a temp which is
initialized
> by copy from the actual parameter.  However, if we can prove
that
> it is safe to pass the address of the actual parameter itself
> (which involves checking for the presence of things like
exception
> handlers, local task units, aliasing, etc.) then we can do
so,
> and thereby avoid the space and copy [in/]out for the temp.
>
> --
> -Tucker Taft   stt@avercom.net
http://www.averstar.com/~stt/
> Chief Technology Officer, AverCom, Inc. (A Titan Company)
Burlington, MA  USA
> (AverCom was formed 1/1/01 from the Commercial Division of
AverStar)
>
(http://www.averstar.com/services/ebusiness_applications.html)
>


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