Re: [Qemu-devel] [PATCH v4] log: Make glib logging go through QEMU

[Christophe Fergeau]

Hey,

On Thu, Jan 03, 2019 at 10:54:25AM +0000, Stefan Hajnoczi wrote:
> On Fri, Dec 14, 2018 at 11:56:42AM +0100, Christophe Fergeau wrote:
> > +static void qemu_log_func(const gchar *log_domain,
> > +                          GLogLevelFlags log_level,
> > +                          const gchar *message,
> > +                          gpointer user_data)
> > +{
> > +    switch (log_level & G_LOG_LEVEL_MASK) {
> > +    case G_LOG_LEVEL_DEBUG:
> > +        /* Use same G_MESSAGES_DEBUG logic as glib to enable/disable debug
> > +         * messages
> > +         */
> > +        if (qemu_glog_domains == NULL) {
> > +            break;
> > +        }
> > +        if (strcmp(qemu_glog_domains, "all") != 0 &&
> > +          (log_domain == NULL || !strstr(qemu_glog_domains, log_domain))) {
> > +            break;
> > +        }
> > +        /* Fall through */
> > +    case G_LOG_LEVEL_INFO:
> > +        /* Fall through */
> > +    case G_LOG_LEVEL_MESSAGE:
> > +        info_report("%s: %s", log_domain, message);
> 
> QEMU itself uses glib, so what happens if *_report() emit more log
> messages?  Can this result in an infinite loop?

If *_report try to output messages through the g_log API, glib will
catch it and will abort, so not an infinite loop, but not a
desirable outcome either.

Some low-level logging functions which are going to dump the message
without glib (or using g_log_default_handler()) are needed.
The timestamping/prepending of 'error:', 'warning:' to the error message
is done right below *_report (in vreport) so this looked like a good
place for that.

Christophe

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