[racket] 5.3's "mzc optimizer" log-debug, and log "facility" in general

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Thu Aug 30 12:52:20 EDT 2012

On Thu, Aug 30, 2012 at 9:32 AM, Greg Hendershott
<greghendershott at gmail.com> wrote:
> Thanks, Robby.
> Do you mean I could do something like this?
> (define (enable-log-output level)
>   (let ([r (make-log-receiver (current-logger) level)])
>     (thread
>      (lambda ()
>        (let loop ()
>          (match (sync r)
>                 [(vector lvl msg v)
>                  (printf "; [~a] ~a\n" lvl msg)])
>          (loop))))))
> (enable-log-output 'debug)

Yes, I think so.

> If so, then:
> 1. I don't see what you mean re being able to do more than string
> munging. `v' is a continuation-mark-set. Is that the struct you mean?

Yes, but perhaps this isn't helpful, as you'd need to use you own
logging macros to put something other than the continuation marks in
there. Maybe that makes this a non-starter for you.

> But stipulating I could filter in whatever fashion ...
> 2. Putting this in every source file doesn't seem practical? I'm
> talking about doing interactive development, using XREPL's ,log
> command. Open a file, evaluate it, make some changes, maybe use ,log
> to tweak the log output level, evaluate, move on to another file. That
> sort of work-flow.

IIUC, this is something you'd do instead of using ,log. You can
require some helper library with the function in it, or probably Eli
has some way to add more commands or something like that. Or maybe
even a patch to ,log that'd let you specify a regexp in the case that
string munging was the best option?

> 3. I have to ask users of my collections to use code like this, to
> avoid getting "drowned" in my log-debug output? That doesn't sound
> good.

You could designate a specific logger that you log to, instead of
logging to the current-logger. This would also require you to call you
own macros, not log-debug and co.

> ,log already does filtering on one "dimension" ("severity") without
> touching your source, which is great. It seems odd to have to use
> per-file code, in order to filter on another dimension ("facility" or
> "module").

I don't think there is any per-module requirement.


> On Thu, Aug 30, 2012 at 8:55 AM, Robby Findler
> <robby at eecs.northwestern.edu> wrote:
>> On Thu, Aug 30, 2012 at 6:29 AM, Greg Hendershott
>> <greghendershott at gmail.com> wrote:
>>> I have some code with copious log-debug calls. Occasionally I set
>>> ",log debug" to see the output.
>>> New in 5.3, I'm seeing many dozens of outputs like the following:
>>> ; [debug] mzc optimizer: inlining: involving: core727 in: unpack728 in
>>> module: 's3 size: 149 threshold: 320
>>> These are interleaved with and badly obscuring my own debug output.
>>> I've been trying to ignore these and live with it the last couple
>>> weeks, but it's proving difficult.
>>> 1. Narrow question: Is there a way I can disable the mzc debug output,
>>> while preserving my own?
>> You can set up your own log receiver and filter out the messages that
>> you want (note that you can filter based on racket data structures,
>> not just string munging as log messages have a value associated with
>> them that you can query).
>> Robby

Posted on the users mailing list.