Merge remote-tracking branch 'remotes/armbru/tags/pull-error-2017-01-19' into staging

Error reporting patches for 2017-01-19

# gpg: Signature made Thu 19 Jan 2017 14:51:17 GMT
# gpg:                using RSA key 0x3870B400EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-error-2017-01-19:
  error: Report certain hints on stderr when no monitor
  error: error_setg_errno(): errno gets preserved
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

include/qapi/error.h

@@ -170,6 +170,9 @@ void error_setg_internal(Error **errp,
  * Just like error_setg(), with @os_error info added to the message.
  * If @os_error is non-zero, ": " + strerror(os_error) is appended to
  * the human-readable error message.
+ *
+ * The value of errno (which usually can get clobbered by almost any
+ * function call) will be preserved.
  */
 #define error_setg_errno(errp, os_error, fmt, ...)                      \
     error_setg_errno_internal((errp), __FILE__, __LINE__, __func__,     \

monitor.c

@@ -3973,6 +3973,8 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
 {
     if (cur_mon && !monitor_cur_is_qmp()) {
         monitor_vprintf(cur_mon, fmt, ap);
+    } else if (!cur_mon) {
+        vfprintf(stderr, fmt, ap);
     }
 }