Our existing input visitors were not very consistent on errors in a function taking 'TYPE **obj' (that is, start_struct(), start_alternate(), next_list(), type_str(), and type_any()). 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 '*obj' is assigned on exit, even on failures. Add assertions to enforce it.
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 <ebl...@redhat.com> --- v15: enhance commit message, hoist assertions from later in series v14: no change v13: no change v12: new patch --- qapi/qapi-visit-core.c | 34 ++++++++++++++++++++++++++++++---- qapi/opts-visitor.c | 3 ++- qapi/qmp-input-visitor.c | 4 ++++ qapi/string-input-visitor.c | 1 + tests/test-qmp-input-strict.c | 2 +- 5 files changed, 38 insertions(+), 6 deletions(-) diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c index 3cd7edc..3a131ce 100644 --- a/qapi/qapi-visit-core.c +++ b/qapi/qapi-visit-core.c @@ -23,7 +23,13 @@ void visit_start_struct(Visitor *v, const char *name, void **obj, size_t size, Error **errp) { - v->start_struct(v, name, obj, size, errp); + Error *err = NULL; + + v->start_struct(v, name, obj, size, &err); + if (obj && v->type == VISITOR_INPUT) { + assert(err || *obj); + } + error_propagate(errp, err); } void visit_end_struct(Visitor *v, Error **errp) @@ -51,9 +57,15 @@ void visit_start_alternate(Visitor *v, const char *name, GenericAlternate **obj, size_t size, bool promote_int, Error **errp) { + Error *err = NULL; + assert(obj && size >= sizeof(GenericAlternate)); if (v->start_alternate) { - v->start_alternate(v, name, obj, size, promote_int, errp); + v->start_alternate(v, name, obj, size, promote_int, &err); + if (v->type == VISITOR_INPUT) { + assert(err || *obj); + } + error_propagate(errp, err); } } @@ -188,7 +200,14 @@ void visit_type_bool(Visitor *v, const char *name, bool *obj, Error **errp) void visit_type_str(Visitor *v, const char *name, char **obj, Error **errp) { - v->type_str(v, name, obj, errp); + Error *err = NULL; + + assert(obj); + v->type_str(v, name, obj, &err); + if (v->type == VISITOR_INPUT) { + assert(err || *obj); + } + error_propagate(errp, err); } void visit_type_number(Visitor *v, const char *name, double *obj, @@ -199,7 +218,14 @@ void visit_type_number(Visitor *v, const char *name, double *obj, void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp) { - v->type_any(v, name, obj, errp); + Error *err = NULL; + + assert(obj); + v->type_any(v, name, obj, &err); + if (v->type == VISITOR_INPUT) { + assert(err || *obj); + } + error_propagate(errp, err); } static void output_type_enum(Visitor *v, const char *name, int *obj, diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c index 66aeaed..4cb6436 100644 --- a/qapi/opts-visitor.c +++ b/qapi/opts-visitor.c @@ -133,7 +133,7 @@ opts_start_struct(Visitor *v, const char *name, void **obj, const QemuOpt *opt; if (obj) { - *obj = g_malloc0(size > 0 ? size : 1); + *obj = g_malloc0(size); } if (ov->depth++ > 0) { return; @@ -314,6 +314,7 @@ opts_type_str(Visitor *v, const char *name, char **obj, Error **errp) opt = lookup_scalar(ov, name, errp); if (!opt) { + *obj = NULL; return; } *obj = g_strdup(opt->str ? opt->str : ""); 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; diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c index d604575..797973a 100644 --- a/qapi/string-input-visitor.c +++ b/qapi/string-input-visitor.c @@ -293,6 +293,7 @@ static void parse_type_str(Visitor *v, const char *name, char **obj, if (siv->string) { *obj = g_strdup(siv->string); } else { + *obj = NULL; error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "string"); } diff --git a/tests/test-qmp-input-strict.c b/tests/test-qmp-input-strict.c index d71727e..d5f80ec 100644 --- a/tests/test-qmp-input-strict.c +++ b/tests/test-qmp-input-strict.c @@ -263,7 +263,7 @@ static void test_validate_fail_union_flat_no_discrim(TestInputVisitorData *data, static void test_validate_fail_alternate(TestInputVisitorData *data, const void *unused) { - UserDefAlternate *tmp = NULL; + UserDefAlternate *tmp; Visitor *v; Error *err = NULL; -- 2.5.5