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[Qemu-devel] [PATCH RFC v3 08/20] qapi: Don't pass pre-existing error to
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH RFC v3 08/20] qapi: Don't pass pre-existing error to later call |
Date: |
Tue, 18 Aug 2015 07:19:50 -0700 |
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 a3a81c2..cea0414 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -49,8 +49,8 @@ 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);
}
@@ -142,9 +142,9 @@ 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);
}
@@ -173,9 +173,7 @@ 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);
}
@@ -232,9 +230,7 @@ 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);
}
@@ -326,10 +322,8 @@ 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 v3 00/20] post-introspection qapi cleanups, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 05/20] qapi: Test use of 'number' within alternates, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 01/20] qapi: use 'type' in generated C code to match QMP union wire form, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 06/20] qapi: Simplify visiting of alternate types, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 07/20] qapi: Fix alternates that accept 'number' but not 'int', Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 09/20] qapi: Use consistent generated code patterns, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 08/20] qapi: Don't pass pre-existing error to later call,
Eric Blake <=
- [Qemu-devel] [PATCH RFC v3 10/20] qapi: Add tests for empty unions, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 11/20] qapi: Rework deallocation of partial struct, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 04/20] qapi-visit: Remove redundant functions for flat union base, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 03/20] qapi: Unbox base members, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 02/20] vnc: hoist allocation of VncBasicInfo to callers, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 15/20] qapi: Remove dead visitor code, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 20/20] qapi: Support boxed unions, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 18/20] qapi: Plumb in 'box' to qapi generator lower levels, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 16/20] qapi: Document visitor interfaces, Eric Blake, 2015/08/18
- [Qemu-devel] [PATCH RFC v3 13/20] qapi: Forbid empty unions and useless alternates, Eric Blake, 2015/08/18