/libs/headers/gc/gc_mark.h
http://github.com/nddrylliog/ooc · C++ Header · 201 lines · 52 code · 19 blank · 130 comment · 1 complexity · 4aaa35de76b4d0cfe7db368c06f6d506 MD5 · raw file
- /*
- * 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.
- *
- * This is an experts-only interface! There are many ways to break the
- * collector in subtle ways by using this functionality.
- */
- #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_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 void * GC_least_plausible_heap_addr;
- extern void * 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 collector version.) */
- /* Note that mark procedures should explicitly call FIXUP_POINTER() */
- /* if required. */
- struct GC_ms_entry *GC_mark_and_push(void * obj,
- struct GC_ms_entry * mark_stack_ptr,
- struct GC_ms_entry * mark_stack_limit,
- void * *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)
- extern size_t GC_debug_header_size;
- /* The size of the header added to objects allocated through */
- /* the GC_debug routines. */
- /* Defined as a variable so that client mark procedures don't */
- /* need to be recompiled for collector version changes. */
- #define GC_USR_PTR_FROM_BASE(p) ((void *)((char *)(p) + GC_debug_header_size))
- /* And some routines to support creation of new "kinds", e.g. with */
- /* custom mark procedures, by language runtimes. */
- /* The _inner versions assume the caller holds the allocation lock. */
- /* Return a new free list array. */
- void ** GC_new_free_list(void);
- void ** GC_new_free_list_inner(void);
- /* Return a new kind, as specified. */
- unsigned GC_new_kind(void **free_list, GC_word mark_descriptor_template,
- int add_size_to_descriptor, int clear_new_objects);
- /* The last two parameters must be zero or one. */
- unsigned GC_new_kind_inner(void **free_list,
- GC_word mark_descriptor_template,
- int add_size_to_descriptor,
- int clear_new_objects);
- /* Return a new mark procedure identifier, suitable for use as */
- /* the first argument in GC_MAKE_PROC. */
- unsigned GC_new_proc(GC_mark_proc);
- unsigned GC_new_proc_inner(GC_mark_proc);
- /* Allocate an object of a given kind. Note that in multithreaded */
- /* contexts, this is usually unsafe for kinds that have the descriptor */
- /* in the object itself, since there is otherwise a window in which */
- /* the descriptor is not correct. Even in the single-threaded case, */
- /* we need to be sure that cleared objects on a free list don't */
- /* cause a GC crash if they are accidentally traced. */
- void * GC_generic_malloc(size_t lb, int k);
- typedef void (*GC_describe_type_fn) (void *p, char *out_buf);
- /* A procedure which */
- /* produces a human-readable */
- /* description of the "type" of object */
- /* p into the buffer out_buf of length */
- /* GC_TYPE_DESCR_LEN. This is used by */
- /* the debug support when printing */
- /* objects. */
- /* These functions should be as robust */
- /* as possible, though we do avoid */
- /* invoking them on objects on the */
- /* global free list. */
- # define GC_TYPE_DESCR_LEN 40
- void GC_register_describe_type_fn(int kind, GC_describe_type_fn knd);
- /* Register a describe_type function */
- /* to be used when printing objects */
- /* of a particular kind. */
- #endif /* GC_MARK_H */