Re: Running a preprocessor from GPS?

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 15-07-30 11:45 , EGarrulo wrote:
> On Thursday, July 30, 2015 at 10:23:23 AM UTC+2, Georg Bauhaus wrote:
>> On 30.07.15 10:03, EGarrulo wrote:
>>>   Not to mention
>>> the crippled support for exceptions in Ada.
>>
>> Do you mean that exceptions of Ada cannot be used for indirecting
>> non-local control flow with the help of exception objects?
>
> Exceptions in Ada cannot carry contextual information,   Where
> is the usefulness of knowing that something has gone awry,
> without any context?  For example: "'File not found?' What file
> was the program trying to open, and why?"

I suspect that you are conflating two possible uses of exception-handling:

1. To let the program detect and possibly recover automatically from 
run-time failures.

2. To inform the program's user about run-time failures so that the user 
can understand what went wrong and how to correct it.

Ada's exception facility was designed for (1), and is only indirectly 
useful for (2). The idea is that exceptions should be handled at a level 
that knows enough about the context to perform the recovery, or to 
describe the details of the failure to the user.

For example, the idiom for opening a file is:

    File_Name : String := ...

    begin

       Open (File, Name => File_Name, ...);

       -- Successful: do something with the File.

    exception when ... =>
       -- Here the handler knows which file we tried to open
       -- and can act accordingly.

    end;

This can be a bit cumbersome in case one needs to open several files in 
sequence, but then one must also consider if the program should (a) 
abort on the first missing file, or (b) attempt to open them all, so 
that it can give the user a complete list of missing files. Associating 
the name of the missing file with the exception occurrence would help 
with (a), but not really with the more user-friendly (b).

 > Exceptions in Ada cannot ... be chained

I'm not sure what you mean by "chained", but an Ada exception handler 
can either raise another exception, or re-raise the same exception, for 
handling at higher levels.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .