qmp-event: Avoid qobject_from_jsonf("%"PRId64)

The qobject_from_jsonf() function implements a pseudo-printf
language for creating a QObject; however, it is hard-coded to
only parse a subset of formats understood by -Wformat, and is
not a straight synonym to bare printf().  In particular, any
use of an int64_t integer works only if the system's
definition of PRId64 matches what the parser expects; which
works on glibc (%lld or %ld depending on 32- vs. 64-bit) and
mingw (%I64d), but not on Mac OS (%qd).  Rather than enhance
the parser, it is just as easy to use 'long long', which we
know always works.  There are few enough callers of
qobject_from_json[fv]() that it is easy to audit that this is
the only non-testsuite caller that was actually relying on
this particular conversion.

Reported by: G 3 <programmingkidx@gmail.com>
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1479922617-4400-2-git-send-email-eblake@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
[Cast tv.tv_sec, tv.tv_usec to long long for type correctness]
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

qapi/qmp-event.c

@@ -35,21 +35,12 @@ static void timestamp_put(QDict *qdict)
     int err;
     QObject *obj;
     qemu_timeval tv;
-    int64_t sec, usec;
 
     err = qemu_gettimeofday(&tv);
-    if (err < 0) {
-        /* Put -1 to indicate failure of getting host time */
-        sec = -1;
-        usec = -1;
-    } else {
-        sec = tv.tv_sec;
-        usec = tv.tv_usec;
-    }
-
-    obj = qobject_from_jsonf("{ 'seconds': %" PRId64 ", "
-                             "'microseconds': %" PRId64 " }",
-                             sec, usec);
+    /* Put -1 to indicate failure of getting host time */
+    obj = qobject_from_jsonf("{ 'seconds': %lld, 'microseconds': %lld }",
+                             err < 0 ? -1LL : (long long)tv.tv_sec,
+                             err < 0 ? -1LL : (long long)tv.tv_usec);
     qdict_put_obj(qdict, "timestamp", obj);
 }