Re: How to get nice with GNAT?

[brbarkstrom@gmail.com]

On Tuesday, November 25, 2014 2:18:21 PM UTC-5, G.B. wrote:
> On 25.11.14 16:07, ake.ragnar.dahlgren wrote:
> > Of course I always listen seriously to Jeff Carter but it's not obvious to me that doing "C in Ada" is bad. If I remember correctly Google employees are recommended to avoid using exceptions when doing C++. The designers of Google Go has gone great lengths to avoid the exception concept as much as possible. In addition SPARK forbids usage of exceptions.
> 
> Tucker Taft, designer of both Ada 95 and ParaSail has not
> put Ada's exceptions in his ParaSail language(*). The latter
> language does presume a lot of checking at compile time, though,
> of logical expressions etc.; all of this is almost entirely absent
> from C programs.
> 
> That's not without consequences for a fair comparison.
> 
> Some static analyzers re-interpret the C language by adding
> rules and information that is not present in either C programs
> or in the C language. The interpretation may likely be what
> the programmers would have intended, but still inference cannot
> magically add all of the same logical information to a C program
> that would be present in a ParaSail program. Moreover, a program's
> meaning then begins to essentially depend on the QoI of a compiler,
> not on the language or on your own expressions as a program's author.
> 
> As these and previous efforts both at language design and
> at compiler technology will influence AdaCore, it seems likely
> that Ada 2012's contracts can both reduce the need for checks
> at run-time and add assurance based on real expressions,
> while also improving diagnostic messages if provers look at
> the assertions, the calls, and the implementations.
> 
> There are the beginnings specific mentions of exception
> identifiers in post-conditions, IIUC.
> 
>     Post => that_will_be_true(...) or else raise  ...;
> 
> ParaSail...
> "eliminates run-time exception handling -- strong compile-time
>   checking of preconditions and support for parallel event-handling
>   provides a safer alternative;"
> 
> __
> (*)https://forge.open-do.org/plugins/moinmoin/parasail/

Thanks to the last two posters for clarifying the situation with
references to documents I haven't consulted.  For now, it looks like
raising exceptions and using exception handlers is quite legal.
In the code development I'm doing, these tools are helpful and
fairly easy to understand.  Personally, I don't like to have code
that raises warnings.  Thus, when using a local exception handler
removes the two warnings that appear when there isn't a handler,
I feel more confident that the code will work.

Bruce B.