Re: Passing the same actual as both in and out formal parameters?

[Jean-Pierre Rosen <rosen@adalog.fr>]

Ludovic Brenta a �crit :

> procedure P (A : in T; B : out T) is
> begin
>    B.L := A.M; -- does this change A.L too?
Yes
>    B.M := A.L; -- bug: A.L has been clobbered, now B.M = B.L?
> end P;
> 
> My concern stems from the fact that T is tagged (I cannot change
> that), so Object is passed by reference as both A and B.
> 
> Am I right to be concerned?
> 
Depend on what your concern is ;-)
The semantic is well defined: tagged types are by-reference type. If you
want to swap two fields of different parameters of the same type, use a
local variable.

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           J-P. Rosen (rosen@adalog.fr)
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