commit 61b146e49036a319d401d8b84c8a5e42eca2fe27
parent 0abe7d6823874577794e85502f761ea433567414
Author: Andres Navarro <canavarro82@gmail.com>
Date: Thu, 14 Apr 2011 16:24:19 -0300
Added some object definitions in preparation for the garbage collector.
Diffstat:
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/src/kobject.h b/src/kobject.h
@@ -47,8 +47,35 @@ typedef union GCObject GCObject;
** Common Header for all collectible objects (in macro form, to be
** included in other objects)
*/
-#define CommonHeader GCObject *next; uint8_t tt; uint8_t flags; uint16_t gct;
+#define CommonHeader GCObject *next; uint8_t tt; uint8_t flags; \
+ uint16_t gct; uint32_t padding; GCObject *gclist;
+
+/*
+** NOTE: this is next pointer comes from lua. This is a byproduct of the
+** lua allocator. Because objects come from an arbitrary allocator, they
+** can't be assumed to be contiguous; but in the sweep phase of garbage
+** collection there has to be a way to iterate over all allocated objects
+** and that is the function of the next pointer: for storing the white
+** list. Upon allocation objects are added to this white list, all linked
+** together by a succession of next pointers starting in a field of the
+** state struct. Likewise, during the tracing phase, gray objects are linked
+** by means of the gclist pointer. Technically this is necessary only for
+** objects that have references, but in klisp all objects except strings
+** have them so it is easier to just put it here. Re the use of the padding,
+** this is necessary (TODO add 32-bit check) in 32 bits because of the packed
+** attribute. Otherwise, all TValues would be misaligned. All of this,
+** assuming the compiler complies with it, but if not the padding doesn't
+** hurt.
+*/
+
+/*
+** MAYBE/REFACTOR: other way to do it would be to have a packed GCHeader
+** struct inside each object, but would have to change all references to
+** header objects from 'obj.*' to 'obj.h.*', or something like that. I
+** think the next C standard (C1X at this point) allows the use of
+** anonymous inner struct and unions for this use case
+*/
/*
** Common header in struct form
@@ -75,6 +102,8 @@ typedef struct __attribute__ ((__packed__)) GCheader {
** This gives us 256 types and as many as 8 flags per type.
*/
+/* TODO eliminate flags */
+
/*
** Macros for manipulating tags directly
*/
@@ -135,6 +164,9 @@ typedef struct __attribute__ ((__packed__)) GCheader {
/* this is used to test for numbers, as returned by ttype */
#define K_LAST_NUMBER_TYPE K_TCOMPLEX
+/* this is used to if the object is collectable */
+#define K_FIRST_GC_TYPE K_TPAIR
+
#define K_MAKE_VTAG(t) (K_TAG_TAGGED | (t))
/*
@@ -192,6 +224,7 @@ typedef struct __attribute__ ((__packed__)) GCheader {
#define ttisbigint(o) (tbasetype_(o) == K_TAG_FIXINT)
#define ttisinteger(o_) ({ int32_t t_ = tbasetype_(o_); \
t_ == K_TAG_FIXINT || t_ == K_TAG_BIGINT;})
+#define ttisnumber(o) (ttype(o) <= K_LAST_NUMBER_TYPE); })
#define ttiseinf(o) (tbasetype_(o) == K_TAG_EINF)
#define ttisiinf(o) (tbasetype_(o) == K_TAG_IINF)
#define ttisnil(o) (tbasetype_(o) == K_TAG_NIL)
@@ -203,6 +236,9 @@ typedef struct __attribute__ ((__packed__)) GCheader {
#define ttisdouble(o) ((ttag(o) & K_TAG_BASE_MASK) != K_TAG_TAGGED)
/* Complex types (value in heap) */
+#define ttiscollectable(o) (ttype(o) >= K_FIRST_GC_TYPE)
+#define ttiscollectible(o) ttiscollectable(o)
+
#define ttisstring(o) (tbasetype_(o) == K_TAG_STRING)
#define ttissymbol(o) (tbasetype_(o) == K_TAG_SYMBOL)
#define ttispair(o) (tbasetype_(o) == K_TAG_PAIR)
