[PATCH v2 11/15] qapi: Assert non-input visitors see only valid alternate tags

[Markus Armbruster <armbru@redhat.com>]

An alternate type's visit_type_FOO() fails when it runs into an
invalid ->type.

This is appropriate with an input visitor: visit_start_alternate()
sets ->type according to the input, and bad input can lead to bad
->type.

It should never happen with an output, clone or dealloc visitor: if it
did, the alternate being output, cloned or deallocated would be messed
up beyond repair.  Assert that.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 scripts/qapi/visit.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 678109dfb5..d5d7a1031f 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -232,6 +232,7 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
     case QTYPE_NONE:
         abort();
     default:
+        assert(visit_is_input(v));
         error_setg(&err, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
                    "%(name)s");
         /* Avoid passing invalid *obj to qapi_free_%(c_name)s() */
-- 
2.21.1