Developers of Sympa

[Guillaume Rousse <address@concealed>]

Le 07/12/2012 11:03, David Verdin a écrit :
> Hi guys,
>
> I see an alarmingly growing number of croak calls in the Sympa code. I
> think I misunderstand what this function does.
> As far as I understand it, it simply kills the program after having
> issued a last log. However, it looks like Sympa doesn't die any time
> corak is called, so I think I don't fully understand what exactly is the
> effect of croak.
croak has the same effect as die: it raises an exception.

The only difference is in the context reported:
- with die(), the file and line number is the one from the called code
- with croak(), the file and line number is the one from the caller code

See the attached test case for an example.

That usually refered as 'dying from the caller perspective', and it's 
considered a best practice for general-purpose modules, meaning code 
intended to be used by other people. Indeed, if there is an exception in 
IO::Socket::SSL, for instance, you're not really interested in debugging 
this module, but rather where did your own code call it.

For Sympa private modules, intended to be used in sympa code only, I 
don't think we have any interest in croak vs die.

> In which cases, in our code, will croak actually kill the process?
> Because we must not kill our processes on errors. Errors will happen all
> the time. We must warn users, send mail, but never kill the processes,
> except if they can't access vital ressources, such as database.
If the exception is not caught, the process will get killed. So any code 
susceptible of raising an exception should be enclosed in an eval block. 
Think of a try/catch block in many other languages.

eval {
    run_dangerous_code;
};
if ($EVAL_ERROR) {
    something wrong happened...
}

--
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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Description: Perl program

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