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[Qemu-devel] [PATCH RFC v4 14/29] qapi: Rework deallocation of partial s
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH RFC v4 14/29] qapi: Rework deallocation of partial struct |
Date: |
Wed, 9 Sep 2015 22:06:16 -0600 |
Commit cee2dedb noticed that if you have a partial flat union
(such as if an input parse failed due to a missing
discriminator), calling the dealloc visitor could result in
trying to dereference the NULL pointer. But the fix it proposed
requires the use of a 'data' member in the union, which may or
may not be the same size as other branches of the union
(consider a 32-bit platform where one of the branches is an
int64), so it feels fairly dirty. A better, and much shorter,
fix is to tweak all of the generated visit_type_implicit_FOO()
functions to avoid dereferencing NULL in the first place, to
not visit the fields if the struct pointer itself is not present,
at which point we no longer even need visit_start_union(), and
no one was implementing visit_end_union() callbacks. The change
keeps the contract that any successful use of
visit_start_implicit_struct() will be paired with a matching
visit_end_implicit_struct(), even if intermediate processing is
skipped.
The lack of documentation on the visitor interface is appalling,
but I'm not fixing it here.
Signed-off-by: Eric Blake <address@hidden>
---
include/qapi/visitor-impl.h | 2 --
include/qapi/visitor.h | 2 --
qapi/qapi-dealloc-visitor.c | 26 --------------------------
qapi/qapi-visit-core.c | 15 ---------------
scripts/qapi-visit.py | 12 ++++--------
5 files changed, 4 insertions(+), 53 deletions(-)
diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index c94e5a1..22539df 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -57,8 +57,6 @@ struct Visitor
void (*type_int64)(Visitor *v, int64_t *obj, const char *name, Error
**errp);
/* visit_type_size() falls back to (*type_uint64)() if type_size is unset
*/
void (*type_size)(Visitor *v, uint64_t *obj, const char *name, Error
**errp);
- bool (*start_union)(Visitor *v, bool data_present, Error **errp);
- void (*end_union)(Visitor *v, bool data_present, Error **errp);
};
void input_type_enum(Visitor *v, int *obj, const char * const strings[],
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index 6a93c87..d1e853c 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -59,7 +59,5 @@ void visit_type_bool(Visitor *v, bool *obj, const char *name,
Error **errp);
void visit_type_str(Visitor *v, char **obj, const char *name, Error **errp);
void visit_type_number(Visitor *v, double *obj, const char *name, Error
**errp);
void visit_type_any(Visitor *v, QObject **obj, const char *name, Error **errp);
-bool visit_start_union(Visitor *v, bool data_present, Error **errp);
-void visit_end_union(Visitor *v, bool data_present, Error **errp);
#endif
diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index 737deab..4989f50 100644
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -171,31 +171,6 @@ static void qapi_dealloc_type_enum(Visitor *v, int *obj,
{
}
-/* If there's no data present, the dealloc visitor has nothing to free.
- * Thus, indicate to visitor code that the subsequent union fields can
- * be skipped. This is not an error condition, since the cleanup of the
- * rest of an object can continue unhindered, so leave errp unset in
- * these cases.
- *
- * NOTE: In cases where we're attempting to deallocate an object that
- * may have missing fields, the field indicating the union type may
- * be missing. In such a case, it's possible we don't have enough
- * information to differentiate data_present == false from a case where
- * data *is* present but happens to be a scalar with a value of 0.
- * This is okay, since in the case of the dealloc visitor there's no
- * work that needs to done in either situation.
- *
- * The current inability in QAPI code to more thoroughly verify a union
- * type in such cases will likely need to be addressed if we wish to
- * implement this interface for other types of visitors in the future,
- * however.
- */
-static bool qapi_dealloc_start_union(Visitor *v, bool data_present,
- Error **errp)
-{
- return data_present;
-}
-
Visitor *qapi_dealloc_get_visitor(QapiDeallocVisitor *v)
{
return &v->visitor;
@@ -226,7 +201,6 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
v->visitor.type_number = qapi_dealloc_type_number;
v->visitor.type_any = qapi_dealloc_type_anything;
v->visitor.type_size = qapi_dealloc_type_size;
- v->visitor.start_union = qapi_dealloc_start_union;
QTAILQ_INIT(&v->stack);
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index 884fe94..82bfdd0 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -58,21 +58,6 @@ void visit_end_list(Visitor *v, Error **errp)
v->end_list(v, errp);
}
-bool visit_start_union(Visitor *v, bool data_present, Error **errp)
-{
- if (v->start_union) {
- return v->start_union(v, data_present, errp);
- }
- return true;
-}
-
-void visit_end_union(Visitor *v, bool data_present, Error **errp)
-{
- if (v->end_union) {
- v->end_union(v, data_present, errp);
- }
-}
-
void visit_optional(Visitor *v, bool *present, const char *name,
Error **errp)
{
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index d968642..81527ce 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -51,7 +51,9 @@ 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, &err);
+ if (!obj || *obj) {
+ visit_type_%(c_type)s_fields(m, obj, &err);
+ }
visit_end_implicit_struct(m, err ? NULL : &err);
}
error_propagate(errp, err);
@@ -209,7 +211,7 @@ void visit_type_%(c_name)s(Visitor *m, %(c_name)s **obj,
const char *name, Error
{
Error *err = NULL;
- visit_start_implicit_struct(m, (void**) obj, sizeof(%(c_name)s), &err);
+ visit_start_implicit_struct(m, (void **)obj, sizeof(%(c_name)s), &err);
if (err) {
goto out;
}
@@ -291,9 +293,6 @@ void visit_type_%(c_name)s(Visitor *m, %(c_name)s **obj,
const char *name, Error
if (err) {
goto out_obj;
}
- if (!visit_start_union(m, !!(*obj)->data, &err) || err) {
- goto out_obj;
- }
switch ((*obj)->%(c_name)s) {
''',
c_name=c_name(tag_key))
@@ -327,9 +326,6 @@ void visit_type_%(c_name)s(Visitor *m, %(c_name)s **obj,
const char *name, Error
abort();
}
out_obj:
- error_propagate(errp, err);
- err = NULL;
- visit_end_union(m, !!(*obj)->data, &err);
visit_end_struct(m, err ? NULL : &err);
out:
error_propagate(errp, err);
--
2.4.3
- [Qemu-devel] [PATCH RFC v4 04/29] vnc: hoist allocation of VncBasicInfo to callers, (continued)
- [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, 2015/09/10
- [Qemu-devel] [PATCH RFC v4 14/29] qapi: Rework deallocation of partial struct,
Eric Blake <=
- [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
- [Qemu-devel] [PATCH RFC v4 03/29] qapi: use 'type' in generated C code to match QMP union wire form, Eric Blake, 2015/09/10