Review of Jose Armando Garcia Sancio's std.log

[Andrei Alexandrescu]

On 3/6/12 7:43 PM, Jonathan M Davis wrote:
> Because the level that you log something at and what you want to do in terms
> of exceptions aren't necessarily related at all. It could easily be that you
> want to log something and then do some series of operations before throwing -
> even if the log level is the most severe level, and you intend to throw an
> Error to kill the program. And as others have pointed out, you might want to
> log a series of messages. Having std.log throw on the first one makes it so
> that you can't log any others.

Then I guess you'd be well advised to use the function that "logs to the 
error log", not the one that "logs to the error log and then throws". 
No? I mean you're explaining how a screwdriver is not appropriate for 
pounding nails.

>>> std.log shouldn't be declaring _any_
>>> exception types unless they're related to setting up the logging (_none_
>>> which relate to functions which log).
>>
>> Why?
>
> Because as others have asserted, logging should not affect program flow.
> It's
> printing out messages to a log, which doesn't necessarily have _anything_ to
> do with throwing exceptions.

It does, because, as I mentioned, frequently one is interested in 
logging erroneous events that are followed by a breakage of flow.

> It's merely for providing information about what
> the program is doing. If you have it throwing exceptions - _especially_
> exceptions which are specific to it - you're conflating two separate concepts:
> logging to a log file and having the program report errors. They _can_ be
> related, but they often aren't.

Well all I can say is they are in my experience. Some logging libraries 
have primitives that throw, some don't. I prefer a library that has the 
option in it because I use it all the time with glog.

> And when you _do_ throw an exception, why on earth would anyone want a
> LoggingException (or whatever std.log would call its exception type)? You want
> an exception which relates to what went wrong, not what threw it. The fact
> that you logged a message before throwing is incidental. Nothing that catches
> the exception is going to care.

That I do agree with.


Andrei