Re: [Qemu-devel] qemu-ga and logging domain

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting David Gibson (2015-04-30 20:29:23)
> Michael,
> 
> I was just looking at some of the logging stuff in qemu-ga, and it
> seems to be doing something very odd with the "domain".
> 
> static void ga_log(const gchar *domain, GLogLevelFlags level,
>                    const gchar *msg, gpointer opaque)
> {
>     GAState *s = opaque;
>     GTimeVal time;
>     const char *level_str = ga_log_level_str(level);
> 
>     if (!ga_logging_enabled(s)) {
>         return;
>     }
> 
>     level &= G_LOG_LEVEL_MASK;
> #ifndef _WIN32
>     if (domain && strcmp(domain, "syslog") == 0) {
>         syslog(LOG_INFO, "%s: %s", level_str, msg);
>     } else if (level & s->log_level) {
> #else
>     if (level & s->log_level) {
> #endif
>         g_get_current_time(&time);
>         fprintf(s->log_file,
>                 "%lu.%lu: %s: %s\n", time.tv_sec, time.tv_usec, level_str, msg);
>         fflush(s->log_file);
>     }
> }
> 
> This is sending messages to syslog instead of a logfile if domain is
> set to "syslog".  But the log domain is usually about where the
> messages came from, not where they're going.
> 
> What's up with this?

Hmm, good question... IIRC I originally wanted a way to extend
GLogLevelFlags to support a syslog log-level, but failing that
I ended up re-purposing the unused domain field as a sort of
hack instead.

As for why I felt the need to have slog() hook into this instead
of calling syslog() directly... I think maybe I wanted to avoid
having a global GAState *s in the qga/command* code for
ga_logging_enable(s), but that could simply be done by having
the slog() implementation live in qga/main.c. Then we can drop
the need to re-purpose g_logv()'s 'domain' field.

> 
> -- 
> David Gibson                    | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
>                                 | _way_ _around_!
> http://www.ozlabs.org/~dgibson