Not all visitor implementations supply the full set of visitor callback functions. For example, the string output visitor does not provide 'start_struct' and friends. If you don't know this and feed it an object that uses structs, you'll get a crash:
Segmentation fault (core dumped) Crashing is fine, because this is a programmer mistake, but we can improve the error message upon crash to make it obvious what failed by adding assert()s: qapi/qapi-visit-core.c:32: visit_start_struct: Assertion `v->start_struct != ((void *)0)' failed. Signed-off-by: Daniel P. Berrange <berra...@redhat.com> --- qapi/qapi-visit-core.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c index eada467..3b5efbe 100644 --- a/qapi/qapi-visit-core.c +++ b/qapi/qapi-visit-core.c @@ -29,6 +29,7 @@ void visit_start_struct(Visitor *v, const char *name, void **obj, assert(size); assert(v->type != VISITOR_OUTPUT || *obj); } + assert(v->start_struct != NULL); v->start_struct(v, name, obj, size, &err); if (obj && v->type == VISITOR_INPUT) { assert(!err != !*obj); @@ -45,6 +46,7 @@ void visit_check_struct(Visitor *v, Error **errp) void visit_end_struct(Visitor *v) { + assert(v->end_struct != NULL); v->end_struct(v); } @@ -54,6 +56,7 @@ void visit_start_list(Visitor *v, const char *name, GenericList **list, Error *err = NULL; assert(!list || size >= sizeof(GenericList)); + assert(v->start_list != NULL); v->start_list(v, name, list, size, &err); if (list && v->type == VISITOR_INPUT) { assert(!(err && *list)); @@ -64,11 +67,13 @@ void visit_start_list(Visitor *v, const char *name, GenericList **list, GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size) { assert(tail && size >= sizeof(GenericList)); + assert(v->next_list != NULL); return v->next_list(v, tail, size); } void visit_end_list(Visitor *v) { + assert(v->end_list != NULL); v->end_list(v); } @@ -112,6 +117,7 @@ bool visit_is_input(Visitor *v) void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp) { assert(obj); + assert(v->type_int64 != NULL); v->type_int64(v, name, obj, errp); } @@ -121,6 +127,7 @@ static void visit_type_uintN(Visitor *v, uint64_t *obj, const char *name, Error *err = NULL; uint64_t value = *obj; + assert(v->type_uint64 != NULL); v->type_uint64(v, name, &value, &err); if (err) { error_propagate(errp, err); @@ -160,6 +167,7 @@ void visit_type_uint64(Visitor *v, const char *name, uint64_t *obj, Error **errp) { assert(obj); + assert(v->type_uint64 != NULL); v->type_uint64(v, name, obj, errp); } @@ -170,6 +178,7 @@ static void visit_type_intN(Visitor *v, int64_t *obj, const char *name, Error *err = NULL; int64_t value = *obj; + assert(v->type_int64 != NULL); v->type_int64(v, name, &value, &err); if (err) { error_propagate(errp, err); @@ -218,6 +227,7 @@ void visit_type_size(Visitor *v, const char *name, uint64_t *obj, if (v->type_size) { v->type_size(v, name, obj, errp); } else { + assert(v->type_uint64 != NULL); v->type_uint64(v, name, obj, errp); } } @@ -225,6 +235,7 @@ void visit_type_size(Visitor *v, const char *name, uint64_t *obj, void visit_type_bool(Visitor *v, const char *name, bool *obj, Error **errp) { assert(obj); + assert(v->type_bool != NULL); v->type_bool(v, name, obj, errp); } @@ -237,6 +248,7 @@ void visit_type_str(Visitor *v, const char *name, char **obj, Error **errp) * can enable: assert(v->type != VISITOR_OUTPUT || *obj); */ + assert(v->type_str != NULL); v->type_str(v, name, obj, &err); if (v->type == VISITOR_INPUT) { assert(!err != !*obj); @@ -248,6 +260,7 @@ void visit_type_number(Visitor *v, const char *name, double *obj, Error **errp) { assert(obj); + assert(v->type_number != NULL); v->type_number(v, name, obj, errp); } @@ -257,6 +270,7 @@ void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp) assert(obj); assert(v->type != VISITOR_OUTPUT || *obj); + assert(v->type_any != NULL); v->type_any(v, name, obj, &err); if (v->type == VISITOR_INPUT) { assert(!err != !*obj); @@ -266,6 +280,7 @@ void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp) void visit_type_null(Visitor *v, const char *name, Error **errp) { + assert(v->type_null != NULL); v->type_null(v, name, errp); } -- 2.5.5