Commit ee16ce93 authored May 02, 2014 by Markus Armbruster Committed by Luiz Capitulino May 09, 2014

qapi: Clean up fragile use of error_is_set()



Using error_is_set(ERRP) to find out whether a function failed is
either wrong, fragile, or unnecessarily opaque.  It's wrong when ERRP
may be null, because errors go undetected when it is.  It's fragile
when proving ERRP non-null involves a non-local argument.  Else, it's
unnecessarily opaque (see commit 84d18f06).

The error_is_set(errp) in do_qmp_dispatch() is merely fragile, because
the caller never passes a null errp argument.

Make the code more robust and more obviously correct: receive the
error in a local variable, then propagate it through the parameter.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

parent 196857f8

qapi/qmp-dispatch.c

+8 −7

Original line number	Diff line number	Diff line
		@@ -62,6 +62,7 @@ static QDict qmp_dispatch_check_obj(const QObject request, Error **errp)

		static QObject do_qmp_dispatch(QObject request, Error **errp)
		{
		Error *local_err = NULL;
		const char *command;
		QDict args, dict;
		QmpCommand *cmd;
		@@ -93,14 +94,14 @@ static QObject do_qmp_dispatch(QObject request, Error **errp)

		switch (cmd->type) {
		case QCT_NORMAL:
		cmd->fn(args, &ret, errp);
		if (!error_is_set(errp)) {
		if (cmd->options & QCO_NO_SUCCESS_RESP) {
		cmd->fn(args, &ret, &local_err);
		if (local_err) {
		error_propagate(errp, local_err);
		} else if (cmd->options & QCO_NO_SUCCESS_RESP) {
		g_assert(!ret);
		} else if (!ret) {
		ret = QOBJECT(qdict_new());
		}
		}
		break;
		}