monitor error: Make printf()-like functions return a value

printf() & friends return the number of characters written on success,
negative value on error.

monitor_printf(), monitor_vfprintf(), monitor_vprintf(),
error_printf(), error_printf_unless_qmp(), error_vprintf(), and
error_vprintf_unless_qmp() return void.  Some of them carry a TODO
comment asking for int instead.

Improve them to return int like printf() does.

This makes our use of monitor_printf() as fprintf_function slightly
less dirty: the function cast no longer adds a return value that isn't
there.  It still changes a parameter's pointer type.  That will be
addressed in a future commit.

monitor_vfprintf() always returns zero.  Improve it to return the
proper value.

Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190417190641.26814-11-armbru@redhat.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/stubs/error-printf.c b/stubs/error-printf.c
index 99c6406668..1f9d3b3714 100644
--- a/stubs/error-printf.c
+++ b/stubs/error-printf.c
@@ -2,19 +2,22 @@
 #include "qemu-common.h"
 #include "qemu/error-report.h"
 
-void error_vprintf(const char *fmt, va_list ap)
+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);
-    } else {
-        vfprintf(stderr, fmt, ap);
+        return ret;
     }
+    return vfprintf(stderr, fmt, ap);
 }
 
-void error_vprintf_unless_qmp(const char *fmt, va_list ap)
+int error_vprintf_unless_qmp(const char *fmt, va_list ap)
 {
-    error_vprintf(fmt, ap);
+    return error_vprintf(fmt, ap);
 }