[PATCH v2 1/2] tests/qtest: migration-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: e5553c1b8d28 ("tests/qtest: migration-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/migration-test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index ef4427ff4d..aa1ba179fa 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -2481,8 +2481,8 @@ int main(int argc, char **argv)
 
     tmpfs = g_dir_make_tmp("migration-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_assert(tmpfs);
 
-- 
2.34.1