monitor: QError support

This commit adds QError support in the Monitor.

A QError member is added to the Monitor struct. This new member
stores error information and is also used to check if an error
has occurred when the called handler returns.

Additionally, a new macro called qemu_error_new() is introduced.
It builds on top of the QemuErrorSink API and should be used in
place of qemu_error().

When all conversion to qemu_error_new() is done, qemu_error() can
be turned private.

Basically, Monitor's error flow is something like this:

1. An error occurs in the handler, it calls qemu_error_new()
2. qemu_error_new() builds a new QError object and stores it in
   the Monitor struct
3. The handler returns
4. Top level Monitor code checks the Monitor struct and calls
   qerror_print() to print the error

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

2 files changed, 49 insertions, 1 deletions

diff --git a/monitor.c b/monitor.c
index 3286ba2b00..da05bf45e5 100644
--- a/monitor.c
+++ b/monitor.c
@@ -49,6 +49,7 @@
 #include "qlist.h"
 #include "qdict.h"
 #include "qstring.h"
+#include "qerror.h"
 
 //#define DEBUG
 //#define DEBUG_COMPLETION
@@ -103,6 +104,7 @@ struct Monitor {
     CPUState *mon_cpu;
     BlockDriverCompletionFunc *password_completion_cb;
     void *password_opaque;
+    QError *error;
     QLIST_HEAD(,mon_fd_t) fds;
     QLIST_ENTRY(Monitor) entry;
 };
@@ -224,6 +226,11 @@ static inline int monitor_handler_ported(const mon_cmd_t *cmd)
     return cmd->user_print != NULL;
 }
 
+static inline int monitor_has_error(const Monitor *mon)
+{
+    return mon->error != NULL;
+}
+
 static void monitor_print_qobject(Monitor *mon, const QObject *data)
 {
     switch (qobject_type(data)) {
@@ -3168,6 +3175,13 @@ fail:
     return NULL;
 }
 
+static void monitor_print_error(Monitor *mon)
+{
+    qerror_print(mon->error);
+    QDECREF(mon->error);
+    mon->error = NULL;
+}
+
 static void monitor_handle_command(Monitor *mon, const char *cmdline)
 {
     QDict *qdict;
@@ -3193,7 +3207,10 @@ static void monitor_handle_command(Monitor *mon, const char *cmdline)
         cmd->mhandler.cmd(mon, qdict);
     }
 
-   qemu_errors_to_previous();
+    if (monitor_has_error(mon))
+        monitor_print_error(mon);
+
+    qemu_errors_to_previous();
 
 out:
     QDECREF(qdict);
@@ -3644,3 +3661,27 @@ void qemu_error(const char *fmt, ...)
         break;
     }
 }
+
+void qemu_error_internal(const char *file, int linenr, const char *func,
+                         const char *fmt, ...)
+{
+    va_list va;
+    QError *qerror;
+
+    assert(qemu_error_sink != NULL);
+
+    va_start(va, fmt);
+    qerror = qerror_from_info(file, linenr, func, fmt, &va);
+    va_end(va);
+
+    switch (qemu_error_sink->dest) {
+    case ERR_SINK_FILE:
+        qerror_print(qerror);
+        QDECREF(qerror);
+        break;
+    case ERR_SINK_MONITOR:
+        assert(qemu_error_sink->mon->error == NULL);
+        qemu_error_sink->mon->error = qerror;
+        break;
+    }
+}
diff --git a/sysemu.h b/sysemu.h
index b1887ef1f4..70a2b044df 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -7,6 +7,7 @@
 #include "qemu-queue.h"
 #include "qemu-timer.h"
 #include "qdict.h"
+#include "qerror.h"
 
 #ifdef _WIN32
 #include <windows.h>
@@ -71,6 +72,12 @@ void qemu_errors_to_file(FILE *fp);
 void qemu_errors_to_mon(Monitor *mon);
 void qemu_errors_to_previous(void);
 void qemu_error(const char *fmt, ...) __attribute__ ((format(printf, 1, 2)));
+void qemu_error_internal(const char *file, int linenr, const char *func,
+                         const char *fmt, ...)
+                         __attribute__ ((format(printf, 4, 5)));
+
+#define qemu_error_new(fmt, ...) \
+    qemu_error_internal(__FILE__, __LINE__, __func__, fmt, ## __VA_ARGS__)
 
 #ifdef _WIN32
 /* Polling handling */