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qapi: Split visit_end_struct() into pieces

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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>
This commit is contained in:
Eric Blake
2016-04-28 15:45:27 -06:00
committed by Markus Armbruster
parent 56a6f02b8c
commit 15c2f669e3
18 changed files with 128 additions and 73 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
scripts/qapi-visit.py
View File

@@ -186,9 +186,10 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
break;
}
visit_type_%(c_type)s_members(v, &(*obj)->u.%(c_name)s, &err);
error_propagate(errp, err);
err = NULL;
visit_end_struct(v, &err);
if (!err) {
visit_check_struct(v, &err);
}
visit_end_struct(v);
''',
c_type=var.type.c_name(),
c_name=c_name(var.name))
@@ -236,10 +237,12 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
goto out_obj;
}
visit_type_%(c_name)s_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:
error_propagate(errp, err);
}