From 15c2f669e3fb2bc97f7b42d1871f595c0ac24af8 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 28 Apr 2016 15:45:27 -0600 Subject: 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, ¶m, &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 Message-Id: <1461879932-9020-20-git-send-email-eblake@redhat.com> [Conflict with a doc fixup resolved] Signed-off-by: Markus Armbruster --- include/qapi/visitor-impl.h | 5 ++++- include/qapi/visitor.h | 21 ++++++++++++++++----- 2 files changed, 20 insertions(+), 6 deletions(-) (limited to 'include/qapi') diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h index 88d27d58de..b20a9226e0 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 709cca0774..fe268fe78d 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 ***/ -- cgit v1.2.3