From e58d695e6c3a5cfa0aa2fc91b87ade017ef28b05 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 28 Apr 2016 15:45:10 -0600 Subject: qapi: Guarantee NULL obj on input visitor callback error Our existing input visitors were not very consistent on errors in a function taking 'TYPE **obj'. These are start_struct(), start_alternate(), type_str(), and type_any(). next_list() is similar, but can't fail (see commit 08f9541). While all of them set '*obj' to allocated storage on success, it was not obvious whether '*obj' was guaranteed safe on failure, or whether it was left uninitialized. But a future patch wants to guarantee that visit_type_FOO() does not leak a partially-constructed obj back to the caller; it is easier to implement this if we can reliably state that input visitors assign '*obj' regardless of success or failure, and that on failure *obj is NULL. Add assertions to enforce consistency in the final setting of err vs. *obj. The opts-visitor start_struct() doesn't set an error, but it also was doing a weird check for 0 size; all callers pass in non-zero size if obj is non-NULL. The testsuite has at least one spot where we no longer need to pre-initialize a variable prior to a visit; valgrind confirms that the test is still fine with the cleanup. A later patch will document the design constraint implemented here. Signed-off-by: Eric Blake Message-Id: <1461879932-9020-3-git-send-email-eblake@redhat.com> [visit_start_alternate()'s assertion tightened, commit message tweaked] Signed-off-by: Markus Armbruster --- qapi/qmp-input-visitor.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'qapi/qmp-input-visitor.c') diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c index 02d4233..77cce8b 100644 --- a/qapi/qmp-input-visitor.c +++ b/qapi/qmp-input-visitor.c @@ -120,6 +120,9 @@ static void qmp_input_start_struct(Visitor *v, const char *name, void **obj, QObject *qobj = qmp_input_get_object(qiv, name, true); Error *err = NULL; + if (obj) { + *obj = NULL; + } if (!qobj || qobject_type(qobj) != QTYPE_QDICT) { error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "QDict"); @@ -267,6 +270,7 @@ static void qmp_input_type_str(Visitor *v, const char *name, char **obj, QString *qstr = qobject_to_qstring(qmp_input_get_object(qiv, name, true)); if (!qstr) { + *obj = NULL; error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "string"); return; -- cgit v1.1