Re: [boost] [log] Comments

Subject: Re: [boost] [log] Comments
From: Vladimir Prus (ghost_at_[hidden])
Date: 2010-03-15 16:31:36

On Monday 15 March 2010 22:50:59 Steven Watanabe wrote:

> > 	// myproject.hpp
> > 	#ifndef COMPONENT
> > 	#define COMPONENT "unspecified"
> > 	#endif
> >
> > 	#define DEBUG BOOST_LOG_XXX(mygloballogger, COMPONENT, debug)
> >   
> 
> I guess that what I'd like is a way to specify arbitrary attributes when
> logging, so BOOST_LOG_XXX would be defined like
> 
> #define BOOST_LOG_XXX(lg, component, severity) BOOST_LOG_WITH_ATTRS(lg, 
> ("Severity", severity)("Channel", component))

Yes, I think this would be nice.

There's another thing about component/severity logging that I have apparently
forgot about -- filtering. It is surely necessary to change filtered components
dynamically -- either while the application is running, or between runs, therefore
lambda expression that compares to a fixed string will not be enough -- we need
a lookup in a map. It's not obvious to me how to form a lambda expression
to do a lookup in a map using the library, e.g. something like:

        enabled_components.count(attr<string>("Component"))

So I wonder:

1. What is the actual syntax to do this inside lambda expression.
2. Can we implement a more convenient out-of-box mechanism.
For example: 

        logging::core()->enabled_components().add("c1")

where this automatically affects the "Component" attribute.

- Volodya