monitor: move error_vprintf back to error-report.c

The current unit tests rely on monitor.o not being linked, such
that the monitor stubs get linked instead. Since error_vprintf
is in monitor.o this allows a stub error_vprintf impl to be used
that calls g_test_message.

This takes a different approach, with error_vprintf moving
back to error-report.c such that it is always linked into the
tests. The monitor_vprintf() stub is then changed to use
g_test_message if QTEST_SILENT_ERRORS is set, otherwise it will
return -1 and trigger error_vprintf to call vfprintf.

The end result is functionally equivalent for the purposes of
the unit tests.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

monitor/monitor.c

@@ -268,24 +268,6 @@ void monitor_printc(Monitor *mon, int c)
     monitor_printf(mon, "'");
 }
 
-/*
- * Print to the current human monitor if we have one, else to stderr.
- */
-int error_vprintf(const char *fmt, va_list ap)
-{
-    Monitor *cur_mon = monitor_cur();
-    /*
-     * This will return -1 if 'cur_mon' is NULL, or is QMP.
-     * IOW this will only print if in HMP, otherwise we
-     * fallback to stderr for QMP / no-monitor scenarios.
-     */
-    int ret = monitor_vprintf(cur_mon, fmt, ap);
-    if (ret == -1) {
-        ret = vfprintf(stderr, fmt, ap);
-    }
-    return ret;
-}
-
 static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
     /* Limit guest-triggerable events to 1 per second */
     [QAPI_EVENT_RTC_CHANGE]        = { 1000 * SCALE_MS },

stubs/error-printf.c

@@ -1,18 +0,0 @@
-#include "qemu/osdep.h"
-#include "qemu/error-report.h"
-#include "monitor/monitor.h"
-
-int error_vprintf(const char *fmt, va_list ap)
-{
-    int ret;
-
-    if (g_test_initialized() && !g_test_subprocess() &&
-        getenv("QTEST_SILENT_ERRORS")) {
-        char *msg = g_strdup_vprintf(fmt, ap);
-        g_test_message("%s", msg);
-        ret = strlen(msg);
-        g_free(msg);
-        return ret;
-    }
-    return vfprintf(stderr, fmt, ap);
-}

stubs/meson.build

@@ -3,7 +3,6 @@
 # below, so that it is clear who needs the stubbed functionality.
 
 stub_ss.add(files('cpu-get-clock.c'))
-stub_ss.add(files('error-printf.c'))
 stub_ss.add(files('fdset.c'))
 stub_ss.add(files('iothread-lock.c'))
 stub_ss.add(files('is-daemonized.c'))

stubs/monitor-core.c

@@ -18,5 +18,17 @@ void qapi_event_emit(QAPIEvent event, QDict *qdict)
 
 int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
 {
-    abort();
+    /*
+     * Pretend 'g_test_message' is our monitor console to
+     * stop the caller sending messages to stderr
+     */
+    if (g_test_initialized() && !g_test_subprocess() &&
+        getenv("QTEST_SILENT_ERRORS")) {
+        char *msg = g_strdup_vprintf(fmt, ap);
+        g_test_message("%s", msg);
+        size_t ret = strlen(msg);
+        g_free(msg);
+        return ret;
+    }
+    return -1;
 }

util/error-report.c

@@ -29,6 +29,24 @@ bool message_with_timestamp;
 bool error_with_guestname;
 const char *error_guest_name;
 
+/*
+ * Print to the current human monitor if we have one, else to stderr.
+ */
+int error_vprintf(const char *fmt, va_list ap)
+{
+    Monitor *cur_mon = monitor_cur();
+    /*
+     * This will return -1 if 'cur_mon' is NULL, or is QMP.
+     * IOW this will only print if in HMP, otherwise we
+     * fallback to stderr for QMP / no-monitor scenarios.
+     */
+    int ret = monitor_vprintf(cur_mon, fmt, ap);
+    if (ret == -1) {
+        ret = vfprintf(stderr, fmt, ap);
+    }
+    return ret;
+}
+
 int error_printf(const char *fmt, ...)
 {
     va_list ap;