log: Make glib logging go through QEMU

This commit adds a error_init() helper which calls
g_log_set_default_handler() so that glib logs (g_log, g_warning, ...)
are handled similarly to other QEMU logs. This means they will get a
timestamp if timestamps are enabled, and they will go through the
HMP monitor if one is configured.

This commit also adds a call to error_init() to the binaries
installed by QEMU. Since error_init() also calls error_set_progname(),
this means that *-linux-user, *-bsd-user and qemu-pr-helper messages
output with error_report, info_report, ... will slightly change: they
will be prefixed by the binary name.

glib debug messages are enabled through G_MESSAGES_DEBUG similarly to
the glib default log handler.

At the moment, this change will mostly impact SPICE logging if your
spice version is >= 0.14.1. With older spice versions, this is not going
to work as expected, but will not have any ill effect, so this call is
not conditional on the SPICE version.

Signed-off-by: Christophe Fergeau <cfergeau@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20190131164614.19209-3-cfergeau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 54 insertions, 1 deletions

diff --git a/util/qemu-error.c b/util/qemu-error.c
index fcbe8a1f74..d08139d9ac 100644
--- a/util/qemu-error.c
+++ b/util/qemu-error.c
@@ -142,7 +142,7 @@ static const char *progname;
 /*
  * Set the program name for error_print_loc().
  */
-void error_set_progname(const char *argv0)
+static void error_set_progname(const char *argv0)
 {
     const char *p = strrchr(argv0, '/');
     progname = p ? p + 1 : argv0;
@@ -345,3 +345,56 @@ bool warn_report_once_cond(bool *printed, const char *fmt, ...)
     va_end(ap);
     return true;
 }
+
+static char *qemu_glog_domains;
+
+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:
+    case G_LOG_LEVEL_INFO:
+        /*
+         * 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_MESSAGE:
+        info_report("%s%s%s",
+                    log_domain ?: "", log_domain ? ": " : "", message);
+
+        break;
+    case G_LOG_LEVEL_WARNING:
+        warn_report("%s%s%s",
+                    log_domain ?: "", log_domain ? ": " : "", message);
+        break;
+    case G_LOG_LEVEL_CRITICAL:
+    case G_LOG_LEVEL_ERROR:
+        error_report("%s%s%s",
+                     log_domain ?: "", log_domain ? ": " : "", message);
+        break;
+    }
+}
+
+void error_init(const char *argv0)
+{
+    /* Set the program name for error_print_loc(). */
+    error_set_progname(argv0);
+
+    /*
+     * This sets up glib logging so libraries using it also print their logs
+     * through error_report(), warn_report(), info_report().
+     */
+    g_log_set_default_handler(qemu_log_func, NULL);
+    g_warn_if_fail(qemu_glog_domains == NULL);
+    qemu_glog_domains = g_strdup(g_getenv("G_MESSAGES_DEBUG"));
+}