Re: Advantages

[Hyman Rosen <hyrosen@mail.com>]

Randy Brukardt wrote:
 > It is a bounded error to use a blocking operation in protected
> action (see 9.5.1(8-17)). It's defined to either be detected
 > (and raise Program_Error) or otherwise "may result in deadlock".
> 
> Since GNAT detected the error at compile-time (thus the warning), there
> couldn't be any run-time overhead for detecting the error. It should
> therefore have raised Program_Error (allowing a known deadlock condition
> seems like a very bad thing). But perhaps there is some customer of ACT's
> that likes living dangerously? Or, perhaps the case just never came up,
> because people rarely try to do the obviously bad...

If I'm not mistaken, normal Ada I/O is potentially blocking and is
therefore technically not allowed in protected actions. I believe
ACT's customers found this to be too restrictive, and that's why
GNAT doesn't prevent potentially blocking actions from being called.
I seem to recall threads on this subject back when Dewar was still
here.