Re: ANN: PLplot plotting library with Ada bindings

[Jerry <lanceboyle@qwest.net>]

On Friday, October 18, 2013 7:27:50 PM UTC-7, Randy Brukardt wrote:
> "Jerry"  wrote in message 
> 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.

Good point. Thanks, Randy. I think I'll work this into the next release.
Jerry