[PATCH v2 2/2] tests/qtest: vhost-user-test: Fix [-Werror=format-overflow=] build warning

[Bin Meng <bmeng.cn@gmail.com>]

From: Bin Meng <bin.meng@windriver.com>

When tmpfs is NULL, a build warning is seen with GCC 9.3.0.
It's strange that GCC 11.2.0 on Ubuntu 22.04 does not catch this,
neither did the QEMU CI.

While we are here, improve the error message as well.

Reported-by: Shengjiang Wu <shengjiang.wu@windriver.com>
Fixes: e6efe236c1d1 ("tests/qtest: vhost-user-test: Avoid using hardcoded /tmp")
Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
---

Changes in v2:
- improve the error message

 tests/qtest/vhost-user-test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/qtest/vhost-user-test.c b/tests/qtest/vhost-user-test.c
index e8d2da7228..bf9f7c4248 100644
--- a/tests/qtest/vhost-user-test.c
+++ b/tests/qtest/vhost-user-test.c
@@ -571,8 +571,8 @@ static TestServer *test_server_new(const gchar *name,
 
     tmpfs = g_dir_make_tmp("vhost-test-XXXXXX", &err);
     if (!tmpfs) {
-        g_test_message("g_dir_make_tmp on path (%s): %s", tmpfs,
-                       err->message);
+        g_test_message("Can't create temporary directory in %s: %s",
+                       g_get_tmp_dir(), err->message);
         g_error_free(err);
     }
     g_assert(tmpfs);
-- 
2.34.1