Re: ANN: PLplot plotting library with Ada bindings

["Randy Brukardt" <randy@rrsoftware.com>]

"Jerry" <lanceboyle@qwest.net> wrote in message 
news:9006bf4b-e682-4803-a5e3-b0363ecb61d1@googlegroups.com...
On Tuesday, October 1, 2013 5:45:57 PM UTC-7, Jeffrey Carter wrote:
> On 10/01/2013 05:31 PM, Jerry wrote:
...
>>  >     ...
>> >     End_PLplot;        -- Call this only once.
>>
>> Why not use finalization to do this?
>
>...
>I don't know what happens if the library doesn't get finalized but it 
>probably ties up
>resources so an automatic process would be wise in that sense.

The problem with requiring manual finalization is that it doesn't work when 
the program propagates an exception. In that case, the user's explicit call 
doesn't get executed. You could try to require them to handle such 
exceptions and do the finalization in a handler, but that's both a mess and 
something that's easy to forget. And even that doesn't work in the face of 
abort (although that's probably not a significant concern in this case).

Thus, I think you always want automatic finalization if any is needed. It 
might make sense to also support a manual version (especially in this case, 
where you wouldn't want to force an incompatibility on any of your users, 
which you would if you completely got rid of the End_PLPlot routine.) -- but 
you don't want that manual version to be required. (Of course, this assumes 
that the finalization actually does something important; if the OS cleans up 
well enough after an program that terminated unexpectedly, then this doesn't 
apply.)

Even if *correct* programs would be fine with manual finalization, remember 
that the program will fail many times while you're creating and debugging 
it. You don't want that to suck up resources on the user's computer.

                                  Randy.