Re: terminate applications

[Marin David Condic <nobody@noplace.com>]

Sure, its possible that an uberkill could leave a database corrupt - 
especially one that didn't properly implement the concept of a 
"transaction" that keeps things pending until there is a "commit". But 
just because one can imagine some corner-case in which an uberkill might 
make a mess of things doesn't mean it shouldn't exist. Sometimes one has 
to trust the programmer not to do something stupid with a language feature.

Yes, a clean shutdown is desirable. I suspect where I have my program 
hanging trying to terminate the environment task is within some OS fault 
- or "feature". But so long as the user has a control-C key on his 
keyboard, there exists the possibility of a direct headshot to a 
program, so it must be possible to do that from under program control. 
People invented those sorts of things for a reason. Sometimes, its a 
good thing to be able to kill some runaway program. Sometimes its 
convenient to say "I'm done with you now and I don't care what you're 
doing, just stop and go away...." Perhaps programs of better (or at 
least different) design might not require such a feature, but that 
doesn't mean it shouldn't exist.

I know Ada tends to dislike features that might in some way be 
"dangerous", but absolute safety is for people who don't have the 
testicular fortitude to live in the real world. :-) It is probably wise 
not to have the ability to create pointers capabile of pointing to 
anything because it is "dangerous" - but mostly because the programmer 
doesn't really have much need to do so. Alternatives exist and only 
someone stuck in a C idiom would find it difficult to get the job done 
without it. But when programming a cruise missile, sooner or later you 
need to execute the "Ignite the explosives" instruction and pretty much 
by definition, that's "dangerous". ;-) Ada should have one of those 
instructions or its tough to break into the cruise missile business.

MDC



Robert I. Eachus wrote:
> 
> But note that this cannot and should not be the normal behaviour of 
> aborting the environment task, or any task.  This is not ideological 
> purity.  Think of it this way.  Using your �berkill on a program that 
> interfaces to a database will not only kill the program, it will break 
> transactions and corrupt the database.  Yes, cycling the power can do 
> the same thing, but correctly written Ada programs will not, even if the 
> main program is aborted.  (It will of course abort transactions in 
> progress, which is fine.  But the (correct) use of abort deferred 
> regions will allow the main program to be aborted cleanly without 
> corrupting any external files.
> 

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Marin David Condic
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