qemu-log: default to stderr for logging output

Switch the default for qemu_log logging output from "/tmp/qemu.log"
to stderr. This is an incompatible change in some sense, but logging
is mostly used for debugging purposes so it shouldn't affect production
use. The previous behaviour can be obtained by adding "-D /tmp/qemu.log"
to the command line.

This change requires us to:
 * update all the documentation/help text (we take the opportunity
   to smooth out minor inconsistencies between the phrasing in
   linux-user/bsd-user/system help messages)
 * make linux-user and bsd-user defer to qemu-log for the default
   logging destination rather than overriding it themselves
 * ensure that all logfile closing is done via qemu_log_close()
   and that that function doesn't close stderr
as well as the obvious change to the behaviour of do_qemu_set_log()
when no logfile name has been specified.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1361901160-28729-1-git-send-email-peter.maydell@linaro.org
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/qemu/log.h b/include/qemu/log.h
index 452700329e..6b0db02efc 100644
--- a/include/qemu/log.h
+++ b/include/qemu/log.h
@@ -116,8 +116,12 @@ static inline void qemu_log_flush(void)
 /* Close the log file */
 static inline void qemu_log_close(void)
 {
-    fclose(qemu_logfile);
-    qemu_logfile = NULL;
+    if (qemu_logfile) {
+        if (qemu_logfile != stderr) {
+            fclose(qemu_logfile);
+        }
+        qemu_logfile = NULL;
+    }
 }
 
 /* Set up a new log file */