Developers of Sympa

[Guillaume Rousse <address@concealed>]

Le 07/08/2013 18:08, IKEDA Soji a écrit :
> > > - fatal_err() vs. croak().
> > >
> > >     fatal_err() seems to be replaced by croak() in most cases.
> > >     Former requires Sympa module, while latter needs just a standard
> > >     Carp module.
> > >
> > >     What are pros to use fatal_err()?
> > It just predates usage of exceptions, and should better be dropped in
> > favor a exception handler in top-level code.
>
> You proposed it before.  I have carefully thought on it for
> a while, and personally concluded that it would not be adopted.
>
> Perl5 does not have true exception handling such as
> "try-except-finally-else" structure and "raise" statement (e.g. in
> Python).  Behaviors of eval() and die() [or croak()] sometimes look
> similar, however, they may be rather a Perl version of setjmp(3) and
> longjmp(3).
>
> To express exception handling by Perl5, code will be forced to be
> slightly complex.  Though some CPAN modules have been proposed to
> ease it, they often fail to implement perfect syntax for exception
> handling.
>
> So my conclusion is: We should not try to emulate exception handling
> on Perl5, although I deeply feel how better Perl5 had supported it.
First, you're confusing catching and analysing exceptions here. Second, 
even string-based exceptions, such as raised by die() or croak() already 
allow minimal analysis. We really don't care if that's a "false" or 
"true" model, as long as it works sufficiently for our needs.

fatal_error("foobar") logs "foobar", send a notification to listmaster, 
then call exit. It doesn't have any understanding of what exact the 
problem is, it just ensure proper recording of the event before exiting. 
You can achieve exactly the same result by wrapping the main infinite 
loop of all daemons:

eval {
    while (1) {
       # do some stuff here...
    }
};
if ($EVAL_ERROR) {
    log("something wrong happened: $EVAL_ERROR");
    notify("something wrong happened: $EVAL_ERROR");
    exit(1);
}

Code using fatal_error("foobar") hardcodes the logic "foobar message 
goes to syslog then to sendmail command, then everything stops". Code 
using croak("foobar") instead is much more flexible, as the error flow 
can be handled differently according to the context. When recovery is 
possible, for instance, there is no reason to quit. In unit testing 
scenario, you also need to re-route the error message without having to 
dig in actual syslog content. Etc...

Morevoer, you were the first one to implement such an exception handler 
in Sympa::Site, so I really don't understand this sudden change of mind...
--
Guillaume Rousse
INRIA, Direction des systèmes d'information
Domaine de Voluceau
Rocquencourt - BP 105
78153 Le Chesnay
Tel: 01 39 63 58 31

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