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From: "fabio de francesco" <fmdf@tiscali.it>
Newsgroups: comp.lang.ada
Subject: Re: tasks and protected types
Date: 29 Apr 2005 03:47:07 -0700
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Date: 2005-04-29T03:47:07-07:00
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Jacob Sparre Andersen wrote:
> Fabio de Francesco wrote:
>
> [...]
>
> >     G : Generator;
>
> Global objects are a _very_ bad idea when doing tasking.  Move it
into
> your task type.

Done.

>
> >     task body Door is
> >         Msg : String := "";
>
> Here you make the lenght of the string Msg 0.

Auch.

> >         Val : Positive;
> >         Times : Positive;
> >     begin
> >         accept Start( Str : in String; Tm : in Positive ) do
> >             Msg := Str;
>
> And here you try to assign a string of length 6 to a string of length
> 0.  It will fail with a Constraint_Error, but with tasking you don't
> always see the exceptions.
>
> And then I also prefer to keep the printing to a single protected
> object.

Why? Could lines come out intermixed? Does it mean that it is always
needed to protect every call to library functions and procedures? Do
they use global variables?

> Here's a modified version of your program using the advice above (and
> my pretty-printing style):
>
> [skip some code]
>

Why an error in using strings makes the program to behave as it was a
deadlock?

Thank you. Now the program runs without problems.

fabio de francesco