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authorEric Blake <eblake@redhat.com>2016-04-28 15:45:27 -0600
committerMarkus Armbruster <armbru@redhat.com>2016-05-12 09:47:55 +0200
commit15c2f669e3fb2bc97f7b42d1871f595c0ac24af8 (patch)
treed5baa8f103d90e6d13d51d351b869b6cde427413 /include/qapi
parent56a6f02b8ce1fe41a2a9077593e46eca7d98267d (diff)
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qapi: Split visit_end_struct() into pieces
As mentioned in previous patches, we want to call visit_end_struct() functions unconditionally, so that visitors can release resources tied up since the matching visit_start_struct() without also having to worry about error priority if more than one error occurs. Even though error_propagate() can be safely used to ignore a second error during cleanup caused by a first error, it is simpler if the cleanup cannot set an error. So, split out the error checking portion (basically, input visitors checking for unvisited keys) into a new function visit_check_struct(), which can be safely skipped if any earlier errors are encountered, and leave the cleanup portion (which never fails, but must be called unconditionally if visit_start_struct() succeeded) in visit_end_struct(). Generated code in qapi-visit.c has diffs resembling: |@@ -59,10 +59,12 @@ void visit_type_ACPIOSTInfo(Visitor *v, | goto out_obj; | } | visit_type_ACPIOSTInfo_members(v, obj, &err); |- error_propagate(errp, err); |- err = NULL; |+ if (err) { |+ goto out_obj; |+ } |+ visit_check_struct(v, &err); | out_obj: |- visit_end_struct(v, &err); |+ visit_end_struct(v); | out: and in qapi-event.c: @@ -47,7 +47,10 @@ void qapi_event_send_acpi_device_ost(ACP | goto out; | } | visit_type_q_obj_ACPI_DEVICE_OST_arg_members(v, &param, &err); |- visit_end_struct(v, err ? NULL : &err); |+ if (!err) { |+ visit_check_struct(v, &err); |+ } |+ visit_end_struct(v); | if (err) { | goto out; Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-20-git-send-email-eblake@redhat.com> [Conflict with a doc fixup resolved] Signed-off-by: Markus Armbruster <armbru@redhat.com>
Diffstat (limited to 'include/qapi')
-rw-r--r--include/qapi/visitor-impl.h5
-rw-r--r--include/qapi/visitor.h21
2 files changed, 20 insertions, 6 deletions
diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 88d27d5..b20a922 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -43,8 +43,11 @@ struct Visitor
void (*start_struct)(Visitor *v, const char *name, void **obj,
size_t size, Error **errp);
+ /* Optional; intended for input visitors */
+ void (*check_struct)(Visitor *v, Error **errp);
+
/* Must be set to visit structs */
- void (*end_struct)(Visitor *v, Error **errp);
+ void (*end_struct)(Visitor *v);
/* Must be set */
void (*start_list)(Visitor *v, const char *name, Error **errp);
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index 709cca0..fe268fe 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -192,10 +192,11 @@
* }
* outlist:
* visit_end_list(v);
+ * if (!err) {
+ * visit_check_struct(v, &err);
+ * }
* outobj:
- * error_propagate(errp, err);
- * err = NULL;
- * visit_end_struct(v, &err);
+ * visit_end_struct(v);
* out:
* error_propagate(errp, err);
* ...clean up v...
@@ -249,17 +250,27 @@ void visit_start_struct(Visitor *v, const char *name, void **obj,
size_t size, Error **errp);
/*
- * Complete an object visit started earlier.
+ * Prepare for completing an object visit.
*
* @errp obeys typical error usage, and reports failures such as
* unparsed keys remaining in the input stream.
*
+ * Should be called prior to visit_end_struct() if all other
+ * intermediate visit steps were successful, to allow the visitor one
+ * last chance to report errors. May be skipped on a cleanup path,
+ * where there is no need to check for further errors.
+ */
+void visit_check_struct(Visitor *v, Error **errp);
+
+/*
+ * Complete an object visit started earlier.
+ *
* Must be called after any successful use of visit_start_struct(),
* even if intermediate processing was skipped due to errors, to allow
* the backend to release any resources. Destroying the visitor early
* behaves as if this was implicitly called.
*/
-void visit_end_struct(Visitor *v, Error **errp);
+void visit_end_struct(Visitor *v);
/*** Visiting lists ***/