Re: Ada.Text_IO and protected objects (Was: [newbie question] tasks and protected types)

["Björn Lundin" <bnl@spray.se>]

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2005-04-29 kl. 14.45 skrev Jacob Sparre Andersen:

> Adrien Plisson wrote:
>> Jacob Sparre Andersen wrote:
>
>>> If calls to Ada.Text_IO _are_ potentially blocking operations,
>>> that means that one has to move the calls to a task.
>>
>> and what about putting them into an entry of a protected object?
>


> I think I need an explanation of the difference between entries and
> procedures of protected objects.  Any suggestion of some reading
> materials?
>
  Ada As A Second Language by Norman Cohen

<http://www.amazon.com/exec/obidos/tg/detail/-/0070116075/103-0300811 
-4955053?v=glance>
Has a nice and long chapter about protected objects and tasking

As a remark to the issue of text_io being potentially blocking, I've  
developed code
that works as it should with Windows and gnat, but came to a total  
freeze of the process
when compiled with Object Ada. The freeze occured when calling text_io  
inside a protected procedure.
Replacing the protected object with another task solved it.

In the book above, the author mentions that io inside protected objects  
will either freeze the process,
or work, but with the protection disabled, or work very well? Anyway, I  
will always be carefull with
protected objects in the future.

/Björn
Björn Lundin
bnl at spray dot se

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2005-04-29 kl. 14.45 skrev Jacob Sparre Andersen:


<excerpt>Adrien Plisson wrote:

<excerpt>Jacob Sparre Andersen wrote:

</excerpt>

<excerpt><excerpt>If calls to Ada.Text_IO _are_ potentially blocking
operations,

that means that one has to move the calls to a task.

</excerpt>

and what about putting them into an entry of a protected object?

</excerpt>

</excerpt>


<excerpt>I think I need an explanation of the difference between
entries and

procedures of protected objects.  Any suggestion of some reading

materials?


</excerpt><fontfamily><param>Arial</param><x-tad-bigger>
</x-tad-bigger><bold><x-tad-bigger>Ada</x-tad-bigger></bold><x-tad-bigger>
As A
</x-tad-bigger><bold><x-tad-bigger>Second</x-tad-bigger></bold><x-tad-bigger> </x-tad-bigger><bold><x-tad-bigger>Language</x-tad-bigger></bold><x-tad-bigger>
by Norman Cohen


<<http://www.amazon.com/exec/obidos/tg/detail/-/0070116075/103-0300811-4955053?v=glance>

Has a nice and long chapter about protected objects and tasking


</x-tad-bigger></fontfamily>As a remark to the issue of text_io being
potentially blocking, I've developed code

that works as it should with Windows and gnat, but came to a total
freeze of the process

when compiled with Object Ada. The freeze occured when calling text_io
inside a protected procedure.

Replacing the protected object with another task solved it.


In the book above, the author mentions that io inside protected
objects will either freeze the process, 

or work, but with the protection disabled, or work very well? Anyway,
I will always be carefull with

protected objects in the future.


/Björn

Björn Lundin

bnl at spray dot se