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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!rjh
From: rjh@cs.purdue.EDU (Bob Hathaway)
Newsgroups: comp.lang.ada
Subject: Re: Two Questions on tasking
Message-ID: <6358@medusa.cs.purdue.edu>
Date: 31 Mar 89 21:42:29 GMT
References: <890331161111.20401e9f@elcc.epfl.ch>
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Reply-To: rjh@cs.purdue.edu (Bob Hathaway)
Organization: Department of Computer Science, Purdue University
List-Id: <comp.lang.ada>

In article <890331161111.20401e9f@elcc.epfl.ch> madmats@elma.epfl.ch (Mats Weber) writes:
>> 1. When an exception is raised and not handled in a task body, the task
>>    is terminated and the exception is not further propagated, without
>>    notice (11.4.1.8).  Why is this?
>
>This is because the execution of the task is independent of its creator.

According to section 9.4.1: "Each task depends on at least one master.".

>If the exception were propagated to the task's creator, the exception 
>handler in the creator could get exceptions from all tasks he has created.
>For example, if task A creates A.B, A.C and A.D and A.B raises Exception_B
>and A.C raises exception Exception_C, how would the handler in A deal with
>them ?
>The Ada rules on exceptions state that only one exception may be active in
>any thread of execution.

According to section 9.3.3, if any child task does not have a handler for 
a raised exception, the exception TASKING_ERROR is propagated to the master
upon conclusion of the activation of all sibling tasks and is propagated
to the master only once for any number of concluded child tasks.  What is 
being asserted above? 

Bob Hathaway
rjh@purdue.edu