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+/*
+ * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
+ * Copyright (c) 2001 by Hewlett-Packard Company. All rights reserved.
+ *
+ * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+ * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
+ *
+ * Permission is hereby granted to use or copy this program
+ * for any purpose, provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is granted,
+ * provided the above notices are retained, and a notice that the code was
+ * modified is included with the above copyright notice.
+ *
+ */
+
+/*
+ * This contains interfaces to the GC marker that are likely to be useful to
+ * clients that provide detailed heap layout information to the collector.
+ * This interface should not be used by normal C or C++ clients.
+ * It will be useful to runtimes for other languages.
+ *
+ * Note that this file is not "namespace-clean", i.e. it introduces names
+ * not prefixed with GC_, which may collide with the client's names. It
+ * should be included only in those few places that directly provide
+ * information to the collector.
+ */
+#ifndef GC_MARK_H
+# define GC_MARK_H
+
+# ifndef GC_H
+# include "gc.h"
+# endif
+
+/* A client supplied mark procedure. Returns new mark stack pointer. */
+/* Primary effect should be to push new entries on the mark stack. */
+/* Mark stack pointer values are passed and returned explicitly. */
+/* Global variables decribing mark stack are not necessarily valid. */
+/* (This usually saves a few cycles by keeping things in registers.) */
+/* Assumed to scan about GC_PROC_BYTES on average. If it needs to do */
+/* much more work than that, it should do it in smaller pieces by */
+/* pushing itself back on the mark stack. */
+/* Note that it should always do some work (defined as marking some */
+/* objects) before pushing more than one entry on the mark stack. */
+/* This is required to ensure termination in the event of mark stack */
+/* overflows. */
+/* This procedure is always called with at least one empty entry on the */
+/* mark stack. */
+/* Currently we require that mark procedures look for pointers in a */
+/* subset of the places the conservative marker would. It must be safe */
+/* to invoke the normal mark procedure instead. */
+/* WARNING: Such a mark procedure may be invoked on an unused object */
+/* residing on a free list. Such objects are cleared, except for a */
+/* free list link field in the first word. Thus mark procedures may */
+/* not count on the presence of a type descriptor, and must handle this */
+/* case correctly somehow. */
+# define GC_PROC_BYTES 100
+struct GC_ms_entry;
+typedef struct GC_ms_entry * (*GC_mark_proc) GC_PROTO((
+ GC_word * addr, struct GC_ms_entry * mark_stack_ptr,
+ struct GC_ms_entry * mark_stack_limit, GC_word env));
+
+# define GC_LOG_MAX_MARK_PROCS 6
+# define GC_MAX_MARK_PROCS (1 << GC_LOG_MAX_MARK_PROCS)
+
+/* In a few cases it's necessary to assign statically known indices to */
+/* certain mark procs. Thus we reserve a few for well known clients. */
+/* (This is necessary if mark descriptors are compiler generated.) */
+#define GC_RESERVED_MARK_PROCS 8
+# define GC_GCJ_RESERVED_MARK_PROC_INDEX 0
+
+/* Object descriptors on mark stack or in objects. Low order two */
+/* bits are tags distinguishing among the following 4 possibilities */
+/* for the high order 30 bits. */
+#define GC_DS_TAG_BITS 2
+#define GC_DS_TAGS ((1 << GC_DS_TAG_BITS) - 1)
+#define GC_DS_LENGTH 0 /* The entire word is a length in bytes that */
+ /* must be a multiple of 4. */
+#define GC_DS_BITMAP 1 /* 30 (62) bits are a bitmap describing pointer */
+ /* fields. The msb is 1 iff the first word */
+ /* is a pointer. */
+ /* (This unconventional ordering sometimes */
+ /* makes the marker slightly faster.) */
+ /* Zeroes indicate definite nonpointers. Ones */
+ /* indicate possible pointers. */
+ /* Only usable if pointers are word aligned. */
+#define GC_DS_PROC 2
+ /* The objects referenced by this object can be */
+ /* pushed on the mark stack by invoking */
+ /* PROC(descr). ENV(descr) is passed as the */
+ /* last argument. */
+# define GC_MAKE_PROC(proc_index, env) \
+ (((((env) << GC_LOG_MAX_MARK_PROCS) \
+ | (proc_index)) << GC_DS_TAG_BITS) | GC_DS_PROC)
+#define GC_DS_PER_OBJECT 3 /* The real descriptor is at the */
+ /* byte displacement from the beginning of the */
+ /* object given by descr & ~DS_TAGS */
+ /* If the descriptor is negative, the real */
+ /* descriptor is at (*<object_start>) - */
+ /* (descr & ~DS_TAGS) - GC_INDIR_PER_OBJ_BIAS */
+ /* The latter alternative can be used if each */
+ /* object contains a type descriptor in the */
+ /* first word. */
+ /* Note that in multithreaded environments */
+ /* per object descriptors maust be located in */
+ /* either the first two or last two words of */
+ /* the object, since only those are guaranteed */
+ /* to be cleared while the allocation lock is */
+ /* held. */
+#define GC_INDIR_PER_OBJ_BIAS 0x10
+
+extern GC_PTR GC_least_plausible_heap_addr;
+extern GC_PTR GC_greatest_plausible_heap_addr;
+ /* Bounds on the heap. Guaranteed valid */
+ /* Likely to include future heap expansion. */
+
+/* Handle nested references in a custom mark procedure. */
+/* Check if obj is a valid object. If so, ensure that it is marked. */
+/* If it was not previously marked, push its contents onto the mark */
+/* stack for future scanning. The object will then be scanned using */
+/* its mark descriptor. */
+/* Returns the new mark stack pointer. */
+/* Handles mark stack overflows correctly. */
+/* Since this marks first, it makes progress even if there are mark */
+/* stack overflows. */
+/* Src is the address of the pointer to obj, which is used only */
+/* for back pointer-based heap debugging. */
+/* It is strongly recommended that most objects be handled without mark */
+/* procedures, e.g. with bitmap descriptors, and that mark procedures */
+/* be reserved for exceptional cases. That will ensure that */
+/* performance of this call is not extremely performance critical. */
+/* (Otherwise we would need to inline GC_mark_and_push completely, */
+/* which would tie the client code to a fixed colllector version.) */
+struct GC_ms_entry *GC_mark_and_push
+ GC_PROTO((GC_PTR obj,
+ struct GC_ms_entry * mark_stack_ptr,
+ struct GC_ms_entry * mark_stack_limit, GC_PTR *src));
+
+#define GC_MARK_AND_PUSH(obj, msp, lim, src) \
+ (((GC_word)obj >= (GC_word)GC_least_plausible_heap_addr && \
+ (GC_word)obj <= (GC_word)GC_greatest_plausible_heap_addr)? \
+ GC_mark_and_push(obj, msp, lim, src) : \
+ msp)
+
+#endif /* GC_MARK_H */
+