Re: How to get nice with GNAT?

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 11/23/2014 09:13 AM, brbarkstrom@gmail.com wrote:
> 
> That is not correct.  I routinely set OK := False; at the beginning
> of the procedure and only set it to True when the procedure has completed
> correctly.  The output from the procedure does provide the last value
> of OK before the procedure raises the exception -- if the procedure doesn't
> handle the exception.

This is compiler-dependent behavior. Your code is not portable.

>    if (Bad_Condition = True) then

if Bad_Condition then

Comparing Boolean variables to Boolean literals usually indicates someone who
doesn't understand Booleans.

> The code that calls This_Procedure can choose how it wants to handle
> the exception.  For example, 
> 
> ...
>     This_Procedure(OK      => OK,
>                    Err_Msg => Err_Msg);
>     if not OK then
>        Put_Line(Vstring.To_String(Err_Msg));
>        -- Take other exception handling steps
>     end if;

If the call to This_Procedure raises an exception, execution will not get to the
if statement.

> ...
> 
> will print out the error message.  I'll grant the programmer may have
> to handle complex chains of exception handling.  However, it does work
> and can provide the thread of exceptions for understanding what happened.
> 
> Also, this is one strategy for dealing with exceptions in Web interfaces,
> where it's important to avoid a fatal error that shuts down a working
> program that's interacting with users.
> 
> I use this approach routinely.  It is a big help during debugging.  If
> the exception handling is left in, it can also catch problems when the
> debugging has moved along and you've forgotten about it.  That saves
> time.
> 
> Bruce B.
> 


-- 
Jeff Carter
"This school was here before you came,
and it'll be here before you go."
Horse Feathers
48