tests: Clean up string interpolation into QMP input (simple cases)

When you build QMP input manually like this

    cmd = g_strdup_printf("{ 'execute': 'migrate',"
                          "'arguments': { 'uri': '%s' } }",
                          uri);
    rsp = qmp(cmd);
    g_free(cmd);

you're responsible for escaping the interpolated values for JSON.  Not
done here, and therefore works only for sufficiently nice @uri.  For
instance, if @uri contained a single "'", qobject_from_vjsonf_nofail()
would abort.  A sufficiently nasty @uri could even inject unwanted
members into the arguments object.

Leaving interpolation into JSON to qmp() is more robust:

    rsp = qmp("{ 'execute': 'migrate', 'arguments': { 'uri': %s } }", uri);

It's also more concise.

Clean up the simple cases where we interpolate exactly a JSON value.

Bonus: gets rid of non-literal format strings.  A step towards
compile-time format string checking without triggering
-Wformat-nonliteral.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180806065344.7103-13-armbru@redhat.com>

1 files changed, 2 insertions, 5 deletions

diff --git a/tests/libqtest.c b/tests/libqtest.c
index 9e3870bb7d..81b17f6fc9 100644
--- a/tests/libqtest.c
+++ b/tests/libqtest.c
@@ -1054,12 +1054,9 @@ void qtest_qmp_device_add(const char *driver, const char *id, const char *fmt,
 void qtest_qmp_device_del(const char *id)
 {
     QDict *response1, *response2, *event = NULL;
-    char *cmd;
 
-    cmd = g_strdup_printf("{'execute': 'device_del',"
-                          " 'arguments': { 'id': '%s' }}", id);
-    response1 = qmp(cmd);
-    g_free(cmd);
+    response1 = qmp("{'execute': 'device_del', 'arguments': {'id': %s}}",
+                    id);
     g_assert(response1);
     g_assert(!qdict_haskey(response1, "error"));