Re: [boost] Debug/Stream Libraries?

From: David A. Greene (greened_at_[hidden])
Date: 2001-11-24 16:11:43

Jesse Jones wrote:

>>I've written a class template that takes as template
>>value parameter the number of streams logging messages
>>should go to.
> 
> Personally I don't like using iostreams for debug logging. I 
> experimented with this with CodeWarrior Pro 6 (I think it was) and 
> got insane amounts of bloat. 

I haven't noticed such problems, though admittedly I haven't
looked for them either.  :)  I find iostreams much too convenient
to just dismiss them out-of-hand.  Often I want to dump the
state of some object and iostreams is the only way to do it
nicely.

>>Each stream can be bound to a different
>>ostream, and each stream has its own threshold (to
>>prioritize logging messages).
> 
> I do this a bit differently. When clients want to log something they 
> can specify a logging category (eg LOG("Sockets", "Sent ", bytes, " 
> bytes to ", address, ".\n")). When LOG is called it assembles the 
> string (using overloaded ToStr functions) and passes the string and 
> the category to the logger.  

Here is where I find iostreams nice to use.  My simple debug
macro is used like this:

DEBUG("Sent " << bytes << " bytes to " << address, <other_args>);

where <other_args> includes categories, levels, etc.  I haven't
implemented anything beyond a simple global debug level since
I didn't want to spend all my time writing debugging code.  This
is one of the reasons I asked whether Boost might provide such
facilities.  :)

There is no need for ToStr functions as iostreams takes care
of it.  Plus it works with objects.

> The nice thing about this is that it's simple to use, messages are 
> filtered with a meaningful name instead of a number, there's no bloat 
> yet it's still type safe and extensible, and it can be easily 
> customized with different sinks.

How do you specify different sinks?  Is LOG a vararg macro?
I don't know why, but I feel a bit uncomfortable channelling
based on a string.  You're right in that it gives you a
friendlier category tag than a number, but there's something
that just doesn't "feel" right to me.  Maybe it's that the
compiler can't check whether a valid channel is being specified.

Has anyone ever come up with a nice solution to the "stringified
enum" idiom?  I've seen countless preprocessor hacks but is
there a better way?

                                -Dave

-- 
"Some little people have music in them, but Fats, he was all music,
  and you know how big he was."  --  James P. Johnson