Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-01-28' into staging

QAPI patches patches for 2021-01-28

# gpg: Signature made Thu 28 Jan 2021 07:10:21 GMT
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2021-01-28:
  qapi: More complex uses of QAPI_LIST_APPEND
  qapi: Use QAPI_LIST_APPEND in trivial cases
  qapi: Introduce QAPI_LIST_APPEND
  qapi: A couple more QAPI_LIST_PREPEND() stragglers
  net: Clarify early exit condition

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

include/qapi/util.h

@@ -37,4 +37,17 @@ int parse_qapi_name(const char *name, bool complete);
     (list) = _tmp; \
 } while (0)
 
+/*
+ * For any pointer to a GenericList @tail (usually the 'next' member of a
+ * list element), insert @element at the back and update the tail.
+ *
+ * Note that this macro evaluates @element exactly once, so it is safe
+ * to have side-effects with that argument.
+ */
+#define QAPI_LIST_APPEND(tail, element) do { \
+    *(tail) = g_malloc0(sizeof(**(tail))); \
+    (*(tail))->value = (element); \
+    (tail) = &(*(tail))->next; \
+} while (0)
+
 #endif