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[Qemu-devel] [PATCH RFC v4 11/29] qapi: Don't pass pre-existing error to
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH RFC v4 11/29] qapi: Don't pass pre-existing error to later call |
Date: |
Wed, 9 Sep 2015 22:06:13 -0600 |
Due to the existing semantics of the error_set() family,
generated sequences in the qapi visitors such as:
visit_start_implicit_struct(m, (void **)obj, sizeof(FOO), &err);
if (!err) {
visit_type_FOO_fields(m, obj, errp);
visit_end_implicit_struct(m, &err);
}
error_propagate(errp, err);
are risky: if visit_type_FOO_fields() sets errp, and then
visit_end_implicit_struct() also encounters an error, the
attempt to overwrite the first error will cause an abort().
Obviously, we weren't triggering this situation (none of the
existing callbacks for visit_end_implicit_struct() currently
try to set an error), but it is better to not even cause the
problem in the first place.
Meanwhile, in spite of the poor documentation of the qapi
visitors, we want to guarantee that if a visit_start_*()
succeeds, then the matching visit_end_*() will be called.
The options are to either propagate and clear a local err
multiple times:
visit_start_implicit_struct(m, (void **)obj, sizeof(FOO), &err);
if (!err) {
visit_type_FOO_fields(m, obj, &err);
if (err) {
error_propagate(errp, err);
err = NULL;
}
visit_end_implicit_struct(m, &err);
}
error_propagate(errp, err);
or, as this patch does, just pass in NULL to ignore further
errors once an error has occurred.
visit_start_implicit_struct(m, (void **)obj, sizeof(FOO), &err);
if (!err) {
visit_type_FOO_fields(m, obj, &err);
visit_end_implicit_struct(m, err ? NULL : &err);
}
error_propagate(errp, err);
Signed-off-by: Eric Blake <address@hidden>
---
scripts/qapi-visit.py | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 22d325f..5d4fb3a 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -51,8 +51,8 @@ static void visit_type_implicit_%(c_type)s(Visitor *m,
%(c_type)s **obj, Error *
visit_start_implicit_struct(m, (void **)obj, sizeof(%(c_type)s), &err);
if (!err) {
- visit_type_%(c_type)s_fields(m, obj, errp);
- visit_end_implicit_struct(m, &err);
+ visit_type_%(c_type)s_fields(m, obj, &err);
+ visit_end_implicit_struct(m, err ? NULL : &err);
}
error_propagate(errp, err);
}
@@ -146,9 +146,9 @@ void visit_type_%(c_name)s(Visitor *m, %(c_name)s **obj,
const char *name, Error
visit_start_struct(m, (void **)obj, "%(name)s", name, sizeof(%(c_name)s),
&err);
if (!err) {
if (*obj) {
- visit_type_%(c_name)s_fields(m, obj, errp);
+ visit_type_%(c_name)s_fields(m, obj, &err);
}
- visit_end_struct(m, &err);
+ visit_end_struct(m, err ? NULL : &err);
}
error_propagate(errp, err);
}
@@ -178,9 +178,7 @@ void visit_type_%(c_name)s(Visitor *m, %(c_name)s **obj,
const char *name, Error
visit_type_%(c_elt_type)s(m, &native_i->value, NULL, &err);
}
- error_propagate(errp, err);
- err = NULL;
- visit_end_list(m, &err);
+ visit_end_list(m, err ? NULL : &err);
out:
error_propagate(errp, err);
}
@@ -239,9 +237,7 @@ void visit_type_%(c_name)s(Visitor *m, %(c_name)s **obj,
const char *name, Error
"%(name)s");
}
out_end:
- error_propagate(errp, err);
- err = NULL;
- visit_end_implicit_struct(m, &err);
+ visit_end_implicit_struct(m, err ? NULL : &err);
out:
error_propagate(errp, err);
}
@@ -332,10 +328,8 @@ out_obj:
error_propagate(errp, err);
err = NULL;
visit_end_union(m, !!(*obj)->data, &err);
- error_propagate(errp, err);
- err = NULL;
}
- visit_end_struct(m, &err);
+ visit_end_struct(m, err ? NULL : &err);
out:
error_propagate(errp, err);
}
--
2.4.3
- [Qemu-devel] [PATCH RFC v4 01/29] qapi: Provide nicer array names in introspection, (continued)
- [Qemu-devel] [PATCH RFC v4 01/29] qapi: Provide nicer array names in introspection, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 04/29] vnc: hoist allocation of VncBasicInfo to callers, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 06/29] qapi-visit: Remove redundant functions for flat union base, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 02/29] net: use Netdev instead of NetClientOptions in client init, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 05/29] qapi: Unbox base members, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 07/29] qapi: Test use of 'number' within alternates, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 09/29] qapi: Hide tag_name data member of variants, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 08/29] qapi: Simplify visiting of alternate types, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 12/29] qapi: Use consistent generated code patterns, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 17/29] qapi: Drop useless 'data' member of unions, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 11/29] qapi: Don't pass pre-existing error to later call,
Eric Blake <=
- [Qemu-devel] [PATCH RFC v4 14/29] qapi: Rework deallocation of partial struct, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 10/29] qapi: Fix alternates that accept 'number' but not 'int', Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 13/29] qapi: Add tests for empty unions, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 16/29] qapi: Forbid empty unions and useless alternates, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 15/29] qapi: Avoid use of 'data' member of qapi unions, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 18/29] qapi: Remove dead visitor code, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 21/29] qapi: Test failure in middle of array parse, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 19/29] qapi: Document visitor interfaces, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 20/29] qapi: Plug leaks in test-qmp-input-visitor, Eric Blake, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 22/29] qapi: Change visit_type_FOO() to no longer return partial objects, Eric Blake, 2015/09/10