readline: Add missing GCC_FMT_ATTR

This fixes a compiler warning with -Werror=missing-format-attribute
and allows improved compiler checks for variable argument lists.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

1 files changed, 2 insertions, 1 deletions

diff --git a/qemu-io.c b/qemu-io.c
index d6690289b8..7f459d8ffe 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -219,7 +219,8 @@ static char *get_prompt(void)
     return prompt;
 }
 
-static void readline_printf_func(void *opaque, const char *fmt, ...)
+static void GCC_FMT_ATTR(2, 3) readline_printf_func(void *opaque,
+                                                    const char *fmt, ...)
 {
     va_list ap;
     va_start(ap, fmt);