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[Guile-commits] 03/07: Implement class redefinition on top of fixed stru
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From: |
Andy Wingo |
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Subject: |
[Guile-commits] 03/07: Implement class redefinition on top of fixed structs |
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Date: |
Thu, 14 Sep 2017 05:10:28 -0400 (EDT) |
wingo pushed a commit to branch master
in repository guile.
commit 48989599016c218da68899aee2af8264df98e34c
Author: Andy Wingo <address@hidden>
Date: Fri Sep 8 10:44:54 2017 +0200
Implement class redefinition on top of fixed structs
* libguile/struct.h: Steal another flag for GOOPS.
* libguile/goops.h (SCM_VTABLE_FLAG_GOOPS_INDIRECT)
(SCM_VTABLE_FLAG_GOOPS_NEEDS_MIGRATION): New flags.
(SCM_CLASSF_GOOPS_VALID, SCM_CLASSF_GOOPS_OR_VALID): Remove obsolete
definitions.
(SCM_IS_A_P): Use the scm_class_of function.
* libguile/goops.c (var_class_of_obsolete_indirect_instance): Rename
from var_migrate_instance.
(scm_is_generic, scm_is_method, scm_sys_init_layout_x): Use
scm_class_of instead of the SCM_CLASS_OF macro.
(get_indirect_slots): New helper.
(scm_class_of): This patch moves us in a direction where we won't be
able to separately address a struct's data and its identity.
Therefore to check whether a class needs migration, we check an
embedded pointer from a slot instead of the vtable data.
(scm_sys_struct_data): Remove this temporary function.
(scm_sys_modify_instance): Update to swap slot values instead of the
data pointers themselves.
(scm_sys_modify_class): Use scm_sys_modify_instance.
(scm_sys_goops_loaded): Capture class-of-obsolete-indirect-instance
instead of migrate-instance.
(scm_init_goops_builtins): Don't export the "valid" flag any more;
export instead the "indirect" and "needs-migration" flags.
* libguile/foreign-object.c (scm_assert_foreign_object_type): Add a
FIXME.
* libguile/vm-engine.c (class-of): Take away fast path for the time
being.
* module/oop/goops.scm (class-has-indirect-instances?)
(indirect-slots-need-migration?): New helpers.
(<class>, <slot>, %class-slot-definition, initialize): Remove use of
vtable-flag-goops-valid.
(define-class): Always push redefined values through
`class-redefinition'.
(<redefinable-class>): New public definition. Use it as a metaclass
for redefinable classes. Provide a compute-slots function that
declares the indirect slots mechanism. Add the "indirect" flag to
instances of <redefinable-class>. Create indirect-slots objects for
instances of those classes as part of their allocate-instance.
(change-object-class, class-of-obsolete-indirect-instance): Update for
new representation change.
* test-suite/tests/goops.test ("object update"): Add #:metaclass
<redefinable-class> to all redefinable classes. For the "hell" test,
make the new classes with class-direct-slots, not class-slots; this
was an error in the test.
---
libguile/foreign-object.c | 1 +
libguile/goops.c | 128 +++++-----
libguile/goops.h | 22 +-
libguile/struct.h | 12 +-
libguile/vm-engine.c | 3 +-
module/oop/goops.scm | 554 ++++++++++++++++++++++++++++----------------
test-suite/tests/goops.test | 39 ++--
7 files changed, 472 insertions(+), 287 deletions(-)
diff --git a/libguile/foreign-object.c b/libguile/foreign-object.c
index 830f73f..f074463 100644
--- a/libguile/foreign-object.c
+++ b/libguile/foreign-object.c
@@ -58,6 +58,7 @@ scm_make_foreign_object_type (SCM name, SCM slot_names,
void
scm_assert_foreign_object_type (SCM type, SCM val)
{
+ /* FIXME: Add fast path for when type == struct vtable */
if (!SCM_IS_A_P (val, type))
scm_error (scm_arg_type_key, NULL, "Wrong type (expecting ~A): ~S",
scm_list_2 (scm_class_name (type), val), scm_list_1 (val));
diff --git a/libguile/goops.c b/libguile/goops.c
index ed9dd1e..12a3687 100644
--- a/libguile/goops.c
+++ b/libguile/goops.c
@@ -68,7 +68,7 @@ SCM_GLOBAL_SYMBOL (scm_sym_args, "args");
static int goops_loaded_p = 0;
static SCM var_make_standard_class = SCM_BOOL_F;
-static SCM var_migrate_instance = SCM_BOOL_F;
+static SCM var_class_of_obsolete_indirect_instance = SCM_BOOL_F;
static SCM var_make = SCM_BOOL_F;
static SCM var_inherit_applicable = SCM_BOOL_F;
static SCM var_class_name = SCM_BOOL_F;
@@ -174,8 +174,8 @@ SCM_DEFINE (scm_sys_init_layout_x, "%init-layout!", 2, 0, 0,
SCM_VALIDATE_STRING (2, layout);
SCM_SET_VTABLE_LAYOUT (class, scm_make_struct_layout (layout));
- scm_i_struct_inherit_vtable_magic (SCM_CLASS_OF (class), class);
- SCM_SET_CLASS_FLAGS (class, SCM_CLASSF_GOOPS_OR_VALID);
+ scm_i_struct_inherit_vtable_magic (scm_class_of (class), class);
+ SCM_SET_CLASS_FLAGS (class, SCM_VTABLE_FLAG_GOOPS_CLASS);
return SCM_UNSPECIFIED;
}
@@ -184,6 +184,17 @@ SCM_DEFINE (scm_sys_init_layout_x, "%init-layout!", 2, 0,
0,
+static SCM
+get_indirect_slots (SCM x)
+{
+ /* Precondition: X is an indirect instance. The indirect slots are in
+ the last field. */
+ scm_t_bits nfields =
+ SCM_STRUCT_DATA_REF (SCM_STRUCT_VTABLE (x), scm_vtable_index_size);
+
+ return SCM_STRUCT_SLOT_REF (x, nfields - 1);
+}
+
/* This function is used for efficient type dispatch. */
SCM_DEFINE (scm_class_of, "class-of", 1, 0, 0,
(SCM x),
@@ -283,24 +294,34 @@ SCM_DEFINE (scm_class_of, "class-of", 1, 0, 0,
return ptob->output_class;
}
case scm_tcs_struct:
- if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS_VALID)
- /* A GOOPS object with a valid class. */
- return SCM_CLASS_OF (x);
- else if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS)
- /* A GOOPS object whose class might have been redefined;
- try to migrate it over to the new class. */
- {
- scm_call_1 (scm_variable_ref (var_migrate_instance), x);
- /* At this point, either the migration succeeded, in which
- case SCM_CLASS_OF is the new class, or the migration
- failed because it's already in progress on the current
- thread, in which case we want to return the old class
- for the time being. SCM_CLASS_OF (x) is the right
- answer for both cases. */
- return SCM_CLASS_OF (x);
- }
- else
- return scm_i_define_class_for_vtable (SCM_CLASS_OF (x));
+ {
+ SCM vtable = SCM_STRUCT_VTABLE (x);
+ scm_t_bits flags = SCM_VTABLE_FLAGS (vtable);
+ scm_t_bits direct = SCM_VTABLE_FLAG_GOOPS_CLASS;
+ scm_t_bits indirect = direct | SCM_VTABLE_FLAG_GOOPS_INDIRECT;
+ scm_t_bits mask = indirect;
+ if ((flags & mask) == direct)
+ /* A direct GOOPS object. */
+ return vtable;
+ else if ((flags & mask) == indirect)
+ /* An indirect GOOPS object. If the vtable of the slots
+ object is flagged to indicate that there's a new class
+ definition available, migrate the instance before
+ returning the class. */
+ {
+ SCM slots = get_indirect_slots (x);
+ scm_t_bits slot_flags = SCM_OBJ_CLASS_FLAGS (slots);
+ if (slot_flags & SCM_VTABLE_FLAG_GOOPS_NEEDS_MIGRATION)
+ return scm_call_1
+ (scm_variable_ref
(var_class_of_obsolete_indirect_instance),
+ x);
+ else
+ return vtable;
+ }
+ else
+ /* A non-GOOPS struct. */
+ return scm_i_define_class_for_vtable (vtable);
+ }
default:
if (scm_is_pair (x))
return class_pair;
@@ -334,13 +355,13 @@ SCM_DEFINE (scm_instance_p, "instance?", 1, 0, 0,
int
scm_is_generic (SCM x)
{
- return SCM_INSTANCEP (x) && SCM_SUBCLASSP (SCM_CLASS_OF (x), class_generic);
+ return SCM_INSTANCEP (x) && SCM_SUBCLASSP (scm_class_of (x), class_generic);
}
int
scm_is_method (SCM x)
{
- return SCM_INSTANCEP (x) && SCM_SUBCLASSP (SCM_CLASS_OF (x), class_method);
+ return SCM_INSTANCEP (x) && SCM_SUBCLASSP (scm_class_of (x), class_method);
}
@@ -483,39 +504,40 @@ SCM_DEFINE (scm_sys_clear_fields_x, "%clear-fields!", 2,
0, 0,
static scm_i_pthread_mutex_t goops_lock = SCM_I_PTHREAD_MUTEX_INITIALIZER;
-SCM_INTERNAL SCM scm_sys_struct_data (SCM);
-SCM_DEFINE (scm_sys_struct_data, "%struct-data", 1, 0, 0,
- (SCM s),
- "Internal function used when migrating classes")
-#define FUNC_NAME s_scm_sys_struct_data
-{
- SCM_VALIDATE_INSTANCE (1, s);
- return scm_from_uintptr_t (SCM_CELL_WORD_1 (s));
-}
-#undef FUNC_NAME
-
SCM_DEFINE (scm_sys_modify_instance, "%modify-instance", 2, 0, 0,
(SCM old, SCM new),
"Used by change-class to modify objects in place.")
#define FUNC_NAME s_scm_sys_modify_instance
{
+ scm_t_bits i, old_nfields, new_nfields;
+
SCM_VALIDATE_INSTANCE (1, old);
SCM_VALIDATE_INSTANCE (2, new);
+ old_nfields = SCM_STRUCT_DATA_REF (SCM_STRUCT_VTABLE (old),
+ scm_vtable_index_size);
+ new_nfields = SCM_STRUCT_DATA_REF (SCM_STRUCT_VTABLE (new),
+ scm_vtable_index_size);
+ SCM_ASSERT (old_nfields == new_nfields, new, SCM_ARG2, FUNC_NAME);
+
/* Exchange the data contained in old and new. We exchange rather than
* scratch the old value with new to be correct with GC.
* See "Class redefinition protocol above".
*/
scm_i_pthread_mutex_lock (&goops_lock);
+ /* Swap vtables. */
{
- scm_t_bits word0, word1;
- word0 = SCM_CELL_WORD_0 (old);
- word1 = SCM_CELL_WORD_1 (old);
+ scm_t_bits tmp = SCM_CELL_WORD_0 (old);
SCM_SET_CELL_WORD_0 (old, SCM_CELL_WORD_0 (new));
- SCM_SET_CELL_WORD_1 (old, SCM_CELL_WORD_1 (new));
- SCM_SET_CELL_WORD_0 (new, word0);
- SCM_SET_CELL_WORD_1 (new, word1);
+ SCM_SET_CELL_WORD_0 (new, tmp);
}
+ /* Swap data. */
+ for (i = 0; i < old_nfields; i++)
+ {
+ scm_t_bits tmp = SCM_STRUCT_DATA_REF (old, i);
+ SCM_STRUCT_DATA_SET (old, i, SCM_STRUCT_DATA_REF (new, i));
+ SCM_STRUCT_DATA_SET (new, i, tmp);
+ }
scm_i_pthread_mutex_unlock (&goops_lock);
return SCM_UNSPECIFIED;
}
@@ -529,19 +551,10 @@ SCM_DEFINE (scm_sys_modify_class, "%modify-class", 2, 0,
0,
SCM_VALIDATE_CLASS (1, old);
SCM_VALIDATE_CLASS (2, new);
- scm_i_pthread_mutex_lock (&goops_lock);
- {
- scm_t_bits word0, word1;
- word0 = SCM_CELL_WORD_0 (old);
- word1 = SCM_CELL_WORD_1 (old);
- SCM_SET_CELL_WORD_0 (old, SCM_CELL_WORD_0 (new));
- SCM_SET_CELL_WORD_1 (old, SCM_CELL_WORD_1 (new));
- SCM_STRUCT_DATA (old)[scm_vtable_index_self] = SCM_UNPACK (old);
- SCM_SET_CELL_WORD_0 (new, word0);
- SCM_SET_CELL_WORD_1 (new, word1);
- SCM_STRUCT_DATA (new)[scm_vtable_index_self] = SCM_UNPACK (new);
- }
- scm_i_pthread_mutex_unlock (&goops_lock);
+ scm_sys_modify_instance (old, new);
+ SCM_STRUCT_DATA (old)[scm_vtable_index_self] = SCM_UNPACK (old);
+ SCM_STRUCT_DATA (new)[scm_vtable_index_self] = SCM_UNPACK (new);
+
return SCM_UNSPECIFIED;
}
#undef FUNC_NAME
@@ -997,7 +1010,8 @@ SCM_DEFINE (scm_sys_goops_loaded, "%goops-loaded", 0, 0, 0,
var_method_specializers = scm_c_lookup ("method-specializers");
var_method_procedure = scm_c_lookup ("method-procedure");
- var_migrate_instance = scm_c_lookup ("migrate-instance");
+ var_class_of_obsolete_indirect_instance =
+ scm_c_lookup ("class-of-obsolete-indirect-instance");
return SCM_UNSPECIFIED;
}
@@ -1020,12 +1034,14 @@ scm_init_goops_builtins (void *unused)
scm_from_int (SCM_VTABLE_FLAG_VALIDATED));
scm_c_define ("vtable-flag-goops-class",
scm_from_int (SCM_VTABLE_FLAG_GOOPS_CLASS));
- scm_c_define ("vtable-flag-goops-valid",
- scm_from_int (SCM_VTABLE_FLAG_GOOPS_VALID));
scm_c_define ("vtable-flag-goops-slot",
scm_from_int (SCM_VTABLE_FLAG_GOOPS_SLOT));
scm_c_define ("vtable-flag-goops-static-slot-allocation",
scm_from_int (SCM_VTABLE_FLAG_GOOPS_STATIC_SLOT_ALLOCATION));
+ scm_c_define ("vtable-flag-goops-indirect",
+ scm_from_int (SCM_VTABLE_FLAG_GOOPS_INDIRECT));
+ scm_c_define ("vtable-flag-goops-needs-migration",
+ scm_from_int (SCM_VTABLE_FLAG_GOOPS_NEEDS_MIGRATION));
}
void
diff --git a/libguile/goops.h b/libguile/goops.h
index 8565f4f..202fef9 100644
--- a/libguile/goops.h
+++ b/libguile/goops.h
@@ -40,10 +40,22 @@
* certain class or its subclasses when traversal of the inheritance
* graph would be too costly.
*/
+/* Set for all GOOPS classes. */
#define SCM_VTABLE_FLAG_GOOPS_CLASS SCM_VTABLE_FLAG_GOOPS_0
-#define SCM_VTABLE_FLAG_GOOPS_VALID SCM_VTABLE_FLAG_GOOPS_1
-#define SCM_VTABLE_FLAG_GOOPS_SLOT SCM_VTABLE_FLAG_GOOPS_2
-#define SCM_VTABLE_FLAG_GOOPS_STATIC_SLOT_ALLOCATION SCM_VTABLE_FLAG_GOOPS_3
+/* Set for GOOPS classes whose instances are <slot> objects. */
+#define SCM_VTABLE_FLAG_GOOPS_SLOT SCM_VTABLE_FLAG_GOOPS_1
+/* Set for GOOPS classes whose instance's slots must always be allocated
+ to the same indices, for all concrete subclasses. */
+#define SCM_VTABLE_FLAG_GOOPS_STATIC_SLOT_ALLOCATION SCM_VTABLE_FLAG_GOOPS_2
+/* Set for GOOPS classes whose instances are "indirect", meaning they
+ just have one slot that indirects to a direct instance with the
+ slots. For non-class instances, this is at struct slot 0. For class
+ instances, it's the first slot after the <class> fixed slots. */
+#define SCM_VTABLE_FLAG_GOOPS_INDIRECT SCM_VTABLE_FLAG_GOOPS_3
+/* For indirect classes, the slots object itself has a direct vtable.
+ This flag will be set on that vtable if the instance needs to migrate
+ to a new class. */
+#define SCM_VTABLE_FLAG_GOOPS_NEEDS_MIGRATION SCM_VTABLE_FLAG_GOOPS_4
#define SCM_CLASS_OF(x) SCM_STRUCT_VTABLE (x)
#define SCM_CLASS_FLAGS(class) (SCM_VTABLE_FLAGS (class))
@@ -52,9 +64,7 @@
#define SCM_CLEAR_CLASS_FLAGS(c, f) (SCM_CLEAR_VTABLE_FLAGS (c, f))
#define SCM_CLASSF_METACLASS
(SCM_VTABLE_FLAG_GOOPS_CLASS|SCM_VTABLE_FLAG_VTABLE)
-#define SCM_CLASSF_GOOPS_VALID SCM_VTABLE_FLAG_GOOPS_VALID
#define SCM_CLASSF_GOOPS SCM_VTABLE_FLAG_GOOPS_CLASS
-#define SCM_CLASSF_GOOPS_OR_VALID (SCM_CLASSF_GOOPS | SCM_CLASSF_GOOPS_VALID)
#define SCM_CLASS_OF(x) SCM_STRUCT_VTABLE (x)
@@ -72,7 +82,7 @@
#define SCM_SUBCLASSP(c1, c2) \
(scm_is_true (scm_c_memq (c2, scm_class_precedence_list (c1))))
#define SCM_IS_A_P(x, c) \
- (SCM_INSTANCEP (x) && SCM_SUBCLASSP (SCM_CLASS_OF (x), c))
+ (SCM_INSTANCEP (x) && SCM_SUBCLASSP (scm_class_of (x), c))
#define SCM_GENERICP(x) (scm_is_generic (x))
#define SCM_VALIDATE_GENERIC(pos, x) SCM_MAKE_VALIDATE_MSG (pos, x, GENERICP,
"generic function")
diff --git a/libguile/struct.h b/libguile/struct.h
index e8db316..e7007b7 100644
--- a/libguile/struct.h
+++ b/libguile/struct.h
@@ -112,12 +112,12 @@
#define SCM_VTABLE_FLAG_SIMPLE_RW (1L << 7) /* instances of this vtable have
only "pw" fields and no tail array */
#define SCM_VTABLE_FLAG_RESERVED_0 (1L << 8)
#define SCM_VTABLE_FLAG_RESERVED_1 (1L << 9)
-#define SCM_VTABLE_FLAG_RESERVED_2 (1L << 10)
-#define SCM_VTABLE_FLAG_SMOB_0 (1L << 11)
-#define SCM_VTABLE_FLAG_GOOPS_0 (1L << 12)
-#define SCM_VTABLE_FLAG_GOOPS_1 (1L << 13)
-#define SCM_VTABLE_FLAG_GOOPS_2 (1L << 14)
-#define SCM_VTABLE_FLAG_GOOPS_3 (1L << 15)
+#define SCM_VTABLE_FLAG_SMOB_0 (1L << 10)
+#define SCM_VTABLE_FLAG_GOOPS_0 (1L << 11)
+#define SCM_VTABLE_FLAG_GOOPS_1 (1L << 12)
+#define SCM_VTABLE_FLAG_GOOPS_2 (1L << 13)
+#define SCM_VTABLE_FLAG_GOOPS_3 (1L << 14)
+#define SCM_VTABLE_FLAG_GOOPS_4 (1L << 15)
#define SCM_VTABLE_USER_FLAG_SHIFT 16
typedef void (*scm_t_struct_finalize) (SCM obj);
diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index 6c88ebf..bd91919 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -2905,8 +2905,7 @@ VM_NAME (scm_i_thread *thread, struct scm_vm *vp,
VM_DEFINE_OP (113, class_of, "class-of", OP1 (X8_S12_S12) | OP_DST)
{
ARGS1 (obj);
- if (SCM_INSTANCEP (obj))
- RETURN (SCM_CLASS_OF (obj));
+ /* FIXME: restore fast path for direct instances. */
RETURN_EXP (scm_class_of (obj));
}
diff --git a/module/oop/goops.scm b/module/oop/goops.scm
index 3e72524..f943324 100644
--- a/module/oop/goops.scm
+++ b/module/oop/goops.scm
@@ -46,6 +46,9 @@
<protected-hidden-slot> <protected-read-only-slot>
<scm-slot> <int-slot> <float-slot> <double-slot>
+ ;; Redefinable classes.
+ <redefinable-class>
+
;; Methods are implementations of generic functions.
<method> <accessor-method>
@@ -250,9 +253,11 @@
;;; a vtable are themselves vtables, and `vtable-flag-validated'
;;; indicates that the struct's layout has been validated. goops.c
;;; defines a few additional flags: one to indicate that a vtable is
-;;; actually a class, one to indicate that the class is "valid" (meaning
-;;; that it hasn't been redefined), and one to indicate that instances
-;;; of a class are slot definition objects (<slot> instances).
+;;; actually a class, one to indicate that instances of a class are slot
+;;; definition objects (<slot> instances), one to indicate that this
+;;; class has "static slot allocation" (meaning that its slots must
+;;; always be allocated to the same indices in all subclasses), and two
+;;; more flags used for redefinable classes (more below).
;;;
(define vtable-flag-goops-metaclass
(logior vtable-flag-vtable vtable-flag-goops-class))
@@ -282,6 +287,12 @@
(define (class-has-statically-allocated-slots? class)
(class-has-flags? class vtable-flag-goops-static-slot-allocation))
+(define (class-has-indirect-instances? class)
+ (class-has-flags? class vtable-flag-goops-indirect))
+
+(define (indirect-slots-need-migration? slots)
+ (class-has-flags? (struct-vtable slots) vtable-flag-goops-needs-migration))
+
;;;
;;; Now that we know the slots that must be present in classes, and
;;; their offsets, we can create the root of the class hierarchy.
@@ -311,8 +322,7 @@
(let* ((layout (fold-class-slots macro-fold-right cons-layout ""))
(nfields (/ (string-length layout) 2))
(<class> (%make-vtable-vtable layout)))
- (class-add-flags! <class> (logior vtable-flag-goops-class
- vtable-flag-goops-valid))
+ (class-add-flags! <class> vtable-flag-goops-class)
(struct-set! <class> class-index-name '<class>)
(struct-set! <class> class-index-nfields nfields)
(struct-set! <class> class-index-direct-supers '())
@@ -422,8 +432,7 @@ followed by its associated value. If @var{l} does not hold
a value for
(nfields (/ (string-length layout) 2))
(<slot> (make-struct/no-tail <class> (make-struct-layout layout))))
(class-add-flags! <slot> (logior vtable-flag-goops-class
- vtable-flag-goops-slot
- vtable-flag-goops-valid))
+ vtable-flag-goops-slot))
(struct-set! <slot> class-index-name '<slot>)
(struct-set! <slot> class-index-nfields nfields)
(struct-set! <slot> class-index-direct-supers '())
@@ -1094,8 +1103,7 @@ function."
(#:body body ())
(#:make-procedure make-procedure #f))))
((memq <class> (class-precedence-list class))
- (class-add-flags! z (logior vtable-flag-goops-class
- vtable-flag-goops-valid))
+ (class-add-flags! z vtable-flag-goops-class)
(for-each (match-lambda
((kw slot default)
(slot-set! z slot (get-keyword kw args default))))
@@ -1112,18 +1120,6 @@ function."
;;;
;;; Slot access.
;;;
-;;; Before we go on, some notes about class redefinition. In GOOPS,
-;;; classes can be redefined. Redefinition of a class marks the class
-;;; as invalid, and instances will be lazily migrated over to the new
-;;; representation as they are accessed. Migration happens when
-;;; `class-of' is called on an instance. For more technical details on
-;;; object redefinition, see struct.h.
-;;;
-;;; In the following interfaces, class-of handles the redefinition
-;;; protocol. I would think though that there is some thread-unsafety
-;;; here though as the { class, object data } pair needs to be accessed
-;;; atomically, not the { class, object } pair.
-;;;
(define-inlinable (%class-slot-definition class slot-name kt kf)
(let lp ((slots (struct-ref class class-index-slots)))
(match slots
@@ -1716,12 +1712,12 @@ function."
(define-syntax-rule (define-class name supers slot ...)
(begin
(define-class-pre-definitions (slot ...))
- (if (and (defined? 'name)
- (is-a? name <class>)
- (memq <object> (class-precedence-list name)))
- (class-redefinition name
- (class supers slot ... #:name 'name))
- (toplevel-define! 'name (class supers slot ... #:name 'name)))))
+ (let ((cls (class supers slot ... #:name 'name)))
+ (toplevel-define!
+ 'name
+ (if (defined? 'name)
+ (class-redefinition name cls)
+ cls)))))
(define-syntax-rule (standard-define-class arg ...)
(define-class arg ...))
@@ -2118,14 +2114,14 @@ function."
;;; have a rest argument.
;;;
-(define (map* fn . l) ; A map which accepts dotted lists (arg lists
+(define (map* fn . l) ; A map which accepts dotted lists (arg lists
(cond ; must be "isomorph"
((null? (car l)) '())
((pair? (car l)) (cons (apply fn (map car l))
(apply map* fn (map cdr l))))
(else (apply fn l))))
-(define (for-each* fn . l) ; A for-each which accepts dotted lists (arg
lists
+(define (for-each* fn . l) ; A for-each which accepts dotted lists (arg
lists
(cond ; must be "isomorph"
((null? (car l)) '())
((pair? (car l)) (apply fn (map car l)) (apply for-each* fn (map cdr l)))
@@ -2517,115 +2513,6 @@ function."
clone))
;;;
-;;; {Class redefinition utilities}
-;;;
-
-;;; (class-redefinition OLD NEW)
-;;;
-
-;;; Has correct the following conditions:
-
-;;; Methods
-;;;
-;;; 1. New accessor specializers refer to new header
-;;;
-;;; Classes
-;;;
-;;; 1. New class cpl refers to the new class header
-;;; 2. Old class header exists on old super classes direct-subclass lists
-;;; 3. New class header exists on new super classes direct-subclass lists
-
-(define-method (class-redefinition (old <class>) (new <class>))
- ;; Work on direct methods:
- ;; 1. Remove accessor methods from the old class
- ;; 2. Patch the occurences of new in the specializers by old
- ;; 3. Displace the methods from old to new
- (remove-class-accessors! old) ;; -1-
- (let ((methods (class-direct-methods new)))
- (for-each (lambda (m)
- (update-direct-method! m new old)) ;; -2-
- methods)
- (struct-set! new
- class-index-direct-methods
- (append methods (class-direct-methods old))))
-
- ;; Substitute old for new in new cpl
- (set-car! (struct-ref new class-index-cpl) old)
-
- ;; Remove the old class from the direct-subclasses list of its super classes
- (for-each (lambda (c) (struct-set! c class-index-direct-subclasses
- (delv! old (class-direct-subclasses c))))
- (class-direct-supers old))
-
- ;; Replace the new class with the old in the direct-subclasses of the supers
- (for-each (lambda (c)
- (struct-set! c class-index-direct-subclasses
- (cons old (delv! new (class-direct-subclasses c)))))
- (class-direct-supers new))
-
- ;; Swap object headers
- (%modify-class old new)
-
- ;; Now old is NEW!
-
- ;; Redefine all the subclasses of old to take into account modification
- (for-each
- (lambda (c)
- (update-direct-subclass! c new old))
- (class-direct-subclasses new))
-
- ;; Invalidate class so that subsequent instances slot accesses invoke
- ;; change-object-class
- (struct-set! new class-index-redefined old)
- (class-clear-flags! new vtable-flag-goops-valid) ;must come after slot-set!
-
- old)
-
-;;;
-;;; remove-class-accessors!
-;;;
-
-(define-method (remove-class-accessors! (c <class>))
- (for-each (lambda (m)
- (when (is-a? m <accessor-method>)
- (let ((gf (slot-ref m 'generic-function)))
- ;; remove the method from its GF
- (slot-set! gf 'methods
- (delq1! m (slot-ref gf 'methods)))
- (invalidate-method-cache! gf)
- ;; remove the method from its specializers
- (remove-method-in-classes! m))))
- (class-direct-methods c)))
-
-;;;
-;;; update-direct-method!
-;;;
-
-(define-method (update-direct-method! (m <method>)
- (old <class>)
- (new <class>))
- (let loop ((l (method-specializers m)))
- ;; Note: the <top> in dotted list is never used.
- ;; So we can work as if we had only proper lists.
- (when (pair? l)
- (when (eqv? (car l) old)
- (set-car! l new))
- (loop (cdr l)))))
-
-;;;
-;;; update-direct-subclass!
-;;;
-
-(define-method (update-direct-subclass! (c <class>)
- (old <class>)
- (new <class>))
- (class-redefinition c
- (make-class (class-direct-supers c)
- (class-direct-slots c)
- #:name (class-name c)
- #:metaclass (class-of c))))
-
-;;;
;;; {Utilities for INITIALIZE methods}
;;;
@@ -2807,8 +2694,7 @@ var{initargs}."
(compute-direct-slot-definition class initargs)))
(next-method)
- (class-add-flags! class (logior vtable-flag-goops-class
- vtable-flag-goops-valid))
+ (class-add-flags! class vtable-flag-goops-class)
(struct-set! class class-index-name (get-keyword #:name initargs '???))
(struct-set! class class-index-nfields 0)
(struct-set! class class-index-direct-supers
@@ -2898,68 +2784,6 @@ var{initargs}."
;;;
-;;; {Change-class}
-;;;
-
-(define (change-object-class old-instance old-class new-class)
- (let ((new-instance (allocate-instance new-class '())))
- ;; Initialize the slots of the new instance
- (for-each
- (lambda (slot)
- (if (and (slot-exists? old-instance slot)
- (eq? (%slot-definition-allocation
- (class-slot-definition old-class slot))
- #:instance)
- (slot-bound? old-instance slot))
- ;; Slot was present and allocated in old instance; copy it
- (slot-set! new-instance slot (slot-ref old-instance slot))
- ;; slot was absent; initialize it with its default value
- (let ((init (slot-init-function new-class slot)))
- (when init
- (slot-set! new-instance slot (init))))))
- (map slot-definition-name (class-slots new-class)))
- ;; Exchange old and new instance in place to keep pointers valid
- (%modify-instance old-instance new-instance)
- ;; Allow class specific updates of instances (which now are swapped)
- (update-instance-for-different-class new-instance old-instance)
- old-instance))
-
-
-(define-method (update-instance-for-different-class (old-instance <object>)
- (new-instance
- <object>))
- ;;not really important what we do, we just need a default method
- new-instance)
-
-(define-method (change-class (old-instance <object>) (new-class <class>))
- (change-object-class old-instance (class-of old-instance) new-class))
-
-(define migrate-instance
- (let ((lock (make-mutex))
- (stack '()))
- (lambda (instance)
- (let ((key (%struct-data instance)))
- (let/ec return
- (dynamic-wind
- (lambda ()
- (with-mutex lock
- (if (memv key stack)
- (return #f)
- (set! stack (cons key stack)))))
- (lambda ()
- (let* ((old-class (struct-vtable instance))
- (new-class (slot-ref old-class 'redefined)))
- ;; Although migrate-indirect-instance-if-needed should
- ;; only be called if the "valid" flag is not present on
- ;; the old-class, it's possible that multiple threads can
- ;; race, so we need to check again here.
- (when new-class
- (change-class instance new-class))))
- (lambda ()
- (with-mutex lock
- (set! stack (delq! key stack))))))))))
-
-;;;
;;; {make}
;;;
;;; A new definition which overwrites the previous one which was built-in
@@ -3077,6 +2901,332 @@ var{initargs}."
no-method
))
+
+
+;;;
+;;; Class redefinition
+;;;
+
+;;; GOOPS has a facility to allow a user to change the definition of
+;;; class. This will cause instances of that class to lazily migrate
+;;; over to the new definition. Implementing this is tricky because
+;;; identity is a fundamental part of object-oriented programming; you
+;;; can't just make a new class and start using it, just like that. In
+;;; GOOPS, classes are objects too and need to be addressable by
+;;; identity (by `eq?'). Classes need the ability to change their
+;;; definition "in place". The same goes for instances; redefining a
+;;; class might change the amount of storage associated with each
+;;; instance, and yet we need to update the instances in place, and
+;;; without having classes maintain a list of all of their instances.
+;;;
+;;; The way that we implement this is by adding an indirection. An
+;;; instance of a redefinable class becomes a small object containing
+;;; only a single field, a reference to an external "slots" objects that
+;;; holds the actual slots. There is an exception however for objects
+;;; that have statically allocated slots, most importantly classes -- in
+;;; that case the indirected slots are allocated "directly" in the
+;;; object.
+;;;
+;;; Instances update by checking the class of their their indirected
+;;; slots object. In addition to describing the slots of the indirected
+;;; slots object, that slots class (which is a direct class) has a
+;;; "redefined" slot. If the indirect slots object is current, this
+;;; value is #f. Otherwise it points to the old class definition
+;;; corresponding to its instances.
+;;;
+;;; To try to clarify things, here is a diagram of the "normal" state of
+;;; affairs. The redefinable class has an associated slots class. When
+;;; it makes instances, the instances have a pointer to the indirect
+;;; "slots" object. The class of the indirect slots object is the slots
+;;; class associated with the instance's class. The "V" arrows indicate
+;;; a vtable (class-of) relationship. Dashed arrows indicate a reference
+;;; from a struct slot to an object.
+;;;
+;;; Initial state.
+;;; +-------------+ +------------------------------+
+;;; | class ----> slots class, redefined: #f |
+;;; +-V-----------+ +-V----------------------------+
+;;; V V
+;;; +-V-----------+ +-V----------------------------+
+;;; | instance ----> slots ... |
+;;; +-------------+ +------------------------------+
+;;;
+;;; When a class is redefined, it is updated in place. However existing
+;;; instances are only migrated lazily. So after a class has been
+;;; redefined but before the instance has been updated, the state looks
+;;; like this:
+;;;
+;;; Redefined state.
+;;; ,-------------------------------------------.
+;;; | |
+;;; +-v-----------+ +----------------------------|-+
+;;; | old class ----> old slots class, redefined:' VVV
+;;; +-------------+ +------------------------------+ V
+;;; V
+;;; +-------------+ +------------------------------+ V
+;;; | new class ----> new slots class, redefined:#f| V
+;;; +-V-----------+ +------------------------------+ V
+;;; V V
+;;; +-V-----------+ +------------------------------+ V
+;;; | old inst ----> slots ... VVV
+;;; +-------------+ +------------------------------+
+;;;
+;;; That is to say, because the class was updated in place, the old
+;;; instance's vtable is the new class, even though the old instance's
+;;; slots still correspond to the old class. The vtable of the old slots
+;;; has the "redefined" field, which has been set to point to a fresh
+;;; object containing the direct slots of the old class, and a pointer to
+;;; the old slots class -- as if it were the old class, but with a new
+;;; temporary identity. This allows us to then call
+;;;
+;;; (change-object-class obj old-class new-class)
+;;;
+;;; which will allocate a fresh slots object for the old instance
+;;; corresponding to the new class, completing the migration for that
+;;; instance.
+;;;
+;;; Lazy instance migration is triggered by "class-of". Calling
+;;; "class-of" on an indirect instance will check the indirect slots to
+;;; see if they need redefinition. If so, we construct a fresh instance
+;;; of the new class and swap fields with the old instance (including
+;;; the indirect-slots field). Unfortunately there is some
+;;; thread-unsafety here, as retrieving the class is unsynchronized with
+;;; retrieving the indirect slots.
+;;;
+(define-class <indirect-slots-class> (<class>)
+ (%redefined #:init-value #f))
+(define-class <redefinable-class> (<class>)
+ (indirect-slots-class))
+
+(define-method (compute-slots (class <redefinable-class>))
+ (let* ((slots (next-method))
+ ;; The base method ensured that at most one superclass has
+ ;; statically allocated slots.
+ (static-slots
+ (match (filter class-has-statically-allocated-slots?
+ (cdr (class-precedence-list class)))
+ (() '())
+ ((class) (struct-ref class class-index-direct-slots)))))
+ (define (simplify-slot-definition s)
+ ;; Here we take a slot definition and strip it to just be a plain
+ ;; old name, suitable for use as a slot for the plain-old-data
+ ;; indirect-slots class.
+ (and (eq? (slot-definition-allocation s) #:instance)
+ (make (class-of s) #:name (slot-definition-name s))))
+ (define (maybe-make-indirect-slot-definition s)
+ ;; Here we copy over all the frippery of a slot definition
+ ;; (accessors, init-keywords, and so on), but we change the slot
+ ;; to have virtual allocation and we provide explicit
+ ;; slot-ref/slot-set! functions that access the slot value through
+ ;; the indirect slots object. For slot definitions without
+ ;; instance allocation though, we just pass them through.
+ (cond
+ ((eq? (slot-definition-allocation s) #:instance)
+ (let* ((s* (class-slot-definition (slot-ref class
'indirect-slots-class)
+ (slot-definition-name s)))
+ (ref (slot-definition-slot-ref/raw s*))
+ (set! (slot-definition-slot-set! s*)))
+ (make (class-of s) #:name (slot-definition-name s)
+ #:getter (slot-definition-getter s)
+ #:setter (slot-definition-setter s)
+ #:accessor (slot-definition-accessor s)
+ #:init-keyword (slot-definition-init-keyword s)
+ #:init-thunk (slot-definition-init-thunk s)
+ #:allocation #:virtual
+ ;; TODO: Make faster.
+ #:slot-ref (lambda (o)
+ (ref (slot-ref o 'indirect-slots)))
+ #:slot-set! (lambda (o v)
+ (set! (slot-ref o 'indirect-slots) v)))))
+ (else s)))
+ (unless (equal? (list-head slots (length static-slots))
+ static-slots)
+ (error "unexpected slots"))
+ (let* ((indirect-slots (list-tail slots (length static-slots)))
+ (indirect-slots-class
+ (make-class '()
+ (filter-map simplify-slot-definition
+ indirect-slots)
+ #:name 'indirect-slots
+ #:metaclass <indirect-slots-class>)))
+ (slot-set! class 'indirect-slots-class indirect-slots-class)
+ (append static-slots
+ (cons (make <slot> #:name 'indirect-slots)
+ (map maybe-make-indirect-slot-definition
+ indirect-slots))))))
+
+(define-method (initialize (class <redefinable-class>) initargs)
+ (next-method)
+ (class-add-flags! class vtable-flag-goops-indirect))
+
+(define-method (allocate-instance (class <redefinable-class>) initargs)
+ (let ((instance (next-method))
+ (nfields (struct-ref class class-index-nfields))
+ (indirect-slots-class (slot-ref class 'indirect-slots-class)))
+ ;; Indirect slots will be last struct field.
+ (struct-set! instance (1- nfields) (make indirect-slots-class))
+ instance))
+
+;; Called when redefining an existing binding, and the new binding is a
+;; class. Two arguments: the old value, and the new.
+(define-generic class-redefinition)
+
+(define-method (class-redefinition (old <top>) (new <class>))
+ ;; Default class-redefinition method is to just replace old binding
+ ;; with the class.
+ new)
+
+(define-method (class-redefinition (old <redefinable-class>)
+ (new <redefinable-class>))
+ ;; When redefining a redefinable class with a redefinable class, we
+ ;; migrate the old definition and its instances to become the new
+ ;; definition.
+ ;;
+ ;; Work on direct methods:
+ ;; 1. Remove accessor methods from the old class
+ ;; 2. Patch the occurences of new in the specializers by old
+ ;; 3. Displace the methods from old to new
+ (remove-class-accessors! old) ;; -1-
+ (let ((methods (class-direct-methods new)))
+ (for-each (lambda (m)
+ (update-direct-method! m new old)) ;; -2-
+ methods)
+ (struct-set! new
+ class-index-direct-methods
+ (append methods (class-direct-methods old))))
+
+ ;; Substitute old for new in new cpl
+ (set-car! (struct-ref new class-index-cpl) old)
+
+ ;; Remove the old class from the direct-subclasses list of its super classes
+ (for-each (lambda (c) (struct-set! c class-index-direct-subclasses
+ (delv! old (class-direct-subclasses c))))
+ (class-direct-supers old))
+
+ ;; Replace the new class with the old in the direct-subclasses of the supers
+ (for-each (lambda (c)
+ (struct-set! c class-index-direct-subclasses
+ (cons old (delv! new (class-direct-subclasses c)))))
+ (class-direct-supers new))
+
+ ;; Swap object headers
+ (%modify-class old new)
+
+ ;; Now old is NEW!
+
+ ;; Redefine all the subclasses of old to take into account modification
+ (for-each
+ (lambda (c)
+ (update-direct-subclass! c new old))
+ (class-direct-subclasses new))
+
+ ;; Invalidate class so that subsequent instance slot accesses invoke
+ ;; change-object-class
+ (let ((slots-class (slot-ref new 'indirect-slots-class)))
+ (slot-set! slots-class '%redefined new)
+ (class-add-flags! slots-class vtable-flag-goops-needs-migration))
+
+ old)
+
+(define-method (remove-class-accessors! (c <class>))
+ (for-each (lambda (m)
+ (when (is-a? m <accessor-method>)
+ (let ((gf (slot-ref m 'generic-function)))
+ ;; remove the method from its GF
+ (slot-set! gf 'methods
+ (delq1! m (slot-ref gf 'methods)))
+ (invalidate-method-cache! gf)
+ ;; remove the method from its specializers
+ (remove-method-in-classes! m))))
+ (class-direct-methods c)))
+
+(define-method (update-direct-method! (m <method>)
+ (old <class>)
+ (new <class>))
+ (let loop ((l (method-specializers m)))
+ ;; Note: the <top> in dotted list is never used.
+ ;; So we can work as if we had only proper lists.
+ (when (pair? l)
+ (when (eqv? (car l) old)
+ (set-car! l new))
+ (loop (cdr l)))))
+
+(define-method (update-direct-subclass! (c <class>)
+ (old <class>)
+ (new <class>))
+ (class-redefinition c
+ (make-class (class-direct-supers c)
+ (class-direct-slots c)
+ #:name (class-name c)
+ #:metaclass (class-of c))))
+
+(define (change-object-class old-instance old-class new-class)
+ (let ((new-instance (allocate-instance new-class '())))
+ ;; Initialize the slots of the new instance
+ (for-each
+ (lambda (slot)
+ (unless (eq? slot 'indirect-slots)
+ (if (and (slot-exists? old-instance slot)
+ (memq (%slot-definition-allocation
+ (class-slot-definition old-class slot))
+ '(#:instance #:virtual))
+ (slot-bound? old-instance slot))
+ ;; Slot was present and allocated in old instance; copy it
+ (slot-set! new-instance slot (slot-ref old-instance slot))
+ ;; slot was absent; initialize it with its default value
+ (let ((init (slot-init-function new-class slot)))
+ (when init
+ (slot-set! new-instance slot (init)))))))
+ (map slot-definition-name (class-slots new-class)))
+ ;; Exchange old and new instance in place to keep pointers valid
+ (%modify-instance old-instance new-instance)
+ ;; Allow class specific updates of instances (which now are swapped)
+ (update-instance-for-different-class new-instance old-instance)
+ old-instance))
+
+
+(define-method (update-instance-for-different-class (old-instance <object>)
+ (new-instance
+ <object>))
+ ;;not really important what we do, we just need a default method
+ new-instance)
+
+(define-method (change-class (old-instance <object>)
+ (new-class <redefinable-class>))
+ (unless (is-a? (class-of old-instance) <redefinable-class>)
+ (error (string-append
+ "Default change-class implementation only works on"
+ " instances of redefinable classes")))
+ (change-object-class old-instance (class-of old-instance) new-class))
+
+(define class-of-obsolete-indirect-instance
+ (let ((lock (make-mutex))
+ (stack '()))
+ (lambda (instance)
+ (let* ((new-class (struct-vtable instance))
+ (nfields (struct-ref new-class class-index-nfields))
+ ;; Indirect slots are in last instance slot. For normal
+ ;; instances last slot is 0 of course.
+ (slots (struct-ref instance (1- nfields)))
+ (old-class (slot-ref (class-of slots) '%redefined)))
+ (let/ec return
+ (dynamic-wind
+ (lambda ()
+ (with-mutex lock
+ (if (memv slots stack)
+ (return (or old-class new-class))
+ (set! stack (cons slots stack)))))
+ (lambda ()
+ (when old-class
+ (change-class instance new-class))
+ new-class)
+ (lambda ()
+ (with-mutex lock
+ (set! stack (delq! slots stack))))))))))
+
+
+
+
;;;
;;; {Final initialization}
;;;
diff --git a/test-suite/tests/goops.test b/test-suite/tests/goops.test
index 6c66604..390cd8c 100644
--- a/test-suite/tests/goops.test
+++ b/test-suite/tests/goops.test
@@ -337,25 +337,31 @@
(with-test-prefix "object update"
(pass-if "defining class"
(eval '(define-class <foo> ()
- (x #:accessor x #:init-value 123)
- (z #:accessor z #:init-value 789))
- (current-module))
+ (x #:accessor x #:init-value 123)
+ (z #:accessor z #:init-value 789)
+ #:metaclass <redefinable-class>)
+ (current-module))
(eval '(is-a? <foo> <class>) (current-module)))
(pass-if "making instance"
(eval '(define foo (make <foo>)) (current-module))
(eval '(and (is-a? foo <foo>) (= (x foo) 123)) (current-module)))
(pass-if "redefining class"
(eval '(define-class <foo> ()
- (x #:accessor x #:init-value 123)
- (y #:accessor y #:init-value 456)
- (z #:accessor z #:init-value 789))
- (current-module))
+ (x #:accessor x #:init-value 123)
+ (y #:accessor y #:init-value 456)
+ (z #:accessor z #:init-value 789)
+ #:metaclass <redefinable-class>)
+ (current-module))
(eval '(and (= (y foo) 456) (= (z foo) 789)) (current-module)))
(pass-if "changing class"
- (let* ((c1 (class () (the-slot #:init-keyword #:value)))
- (c2 (class () (the-slot #:init-keyword #:value)
- (the-other-slot #:init-value 888)))
+ (let* ((c1 (class ()
+ (the-slot #:init-keyword #:value)
+ #:metaclass <redefinable-class>))
+ (c2 (class ()
+ (the-slot #:init-keyword #:value)
+ (the-other-slot #:init-value 888)
+ #:metaclass <redefinable-class>))
(o1 (make c1 #:value 777)))
(and (is-a? o1 c1)
(not (is-a? o1 c2))
@@ -373,7 +379,8 @@
;; array, leading to out-of-bounds accesses.
(let* ((parent-class (class ()
- #:name '<class-that-will-be-redefined>))
+ #:name '<class-that-will-be-redefined>
+ #:metaclass <redefinable-class>))
(classes
(unfold (lambda (i) (>= i 20))
(lambda (i)
@@ -383,7 +390,8 @@
#:name (string->symbol
(string-append "<foo-to-redefine-"
(number->string i)
- ">"))))
+ ">"))
+ #:metaclass <redefinable-class>))
(lambda (i)
(+ 1 i))
0))
@@ -393,7 +401,7 @@
classes)))
(define-method (change-class (foo parent-class)
- (new <class>))
+ (new <redefinable-class>))
;; Called by `scm_change_object_class ()', via `purgatory ()'.
(if (null? classes)
(next-method)
@@ -407,8 +415,9 @@
;; nested `scm_change_object_class ()' calls, which increases
;; the size of HELL and increments N_HELL.
(class-redefinition class
- (make-class '() (class-slots class)
- #:name (class-name class)))
+ (make-class '() (class-direct-slots class)
+ #:name (class-name class)
+ #:metaclass <redefinable-class>))
;; Use `slot-ref' to trigger the `scm_change_object_class ()'
;; and `go_to_hell ()' calls.
- [Guile-commits] branch master updated (cfe2279 -> ed549da), Andy Wingo, 2017/09/14
- [Guile-commits] 01/07: GOOPS instance migration implemented in Scheme, Andy Wingo, 2017/09/14
- [Guile-commits] 02/07: Change name of "static" flag indicating static slot allocation, Andy Wingo, 2017/09/14
- [Guile-commits] 06/07: Remove "redefined" class slot, Andy Wingo, 2017/09/14
- [Guile-commits] 05/07: remove self field of vtables, Andy Wingo, 2017/09/14
- [Guile-commits] 04/07: Remove indirection in structs, Andy Wingo, 2017/09/14
- [Guile-commits] 07/07: Document class redefinition change, Andy Wingo, 2017/09/14
- [Guile-commits] 03/07: Implement class redefinition on top of fixed structs,
Andy Wingo <=