329 lines
18 KiB
C
329 lines
18 KiB
C
/*
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* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
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* Copyright (c) 2001 by Hewlett-Packard Company. All rights reserved.
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*
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* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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*
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* Permission is hereby granted to use or copy this program
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* for any purpose, provided the above notices are retained on all copies.
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* Permission to modify the code and to distribute modified code is granted,
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* provided the above notices are retained, and a notice that the code was
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* modified is included with the above copyright notice.
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*
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*/
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/*
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* This contains interfaces to the GC marker that are likely to be useful to
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* clients that provide detailed heap layout information to the collector.
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* This interface should not be used by normal C or C++ clients.
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* It will be useful to runtimes for other languages.
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*
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* This is an experts-only interface! There are many ways to break the
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* collector in subtle ways by using this functionality.
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*/
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#ifndef GC_MARK_H
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#define GC_MARK_H
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#ifndef GC_H
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# include "gc.h"
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* A client supplied mark procedure. Returns new mark stack pointer. */
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/* Primary effect should be to push new entries on the mark stack. */
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/* Mark stack pointer values are passed and returned explicitly. */
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/* Global variables describing mark stack are not necessarily valid. */
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/* (This usually saves a few cycles by keeping things in registers.) */
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/* Assumed to scan about GC_PROC_BYTES on average. If it needs to do */
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/* much more work than that, it should do it in smaller pieces by */
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/* pushing itself back on the mark stack. */
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/* Note that it should always do some work (defined as marking some */
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/* objects) before pushing more than one entry on the mark stack. */
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/* This is required to ensure termination in the event of mark stack */
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/* overflows. */
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/* This procedure is always called with at least one empty entry on the */
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/* mark stack. */
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/* Currently we require that mark procedures look for pointers in a */
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/* subset of the places the conservative marker would. It must be safe */
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/* to invoke the normal mark procedure instead. */
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/* WARNING: Such a mark procedure may be invoked on an unused object */
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/* residing on a free list. Such objects are cleared, except for a */
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/* free list link field in the first word. Thus mark procedures may */
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/* not count on the presence of a type descriptor, and must handle this */
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/* case correctly somehow. */
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#define GC_PROC_BYTES 100
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#if defined(GC_BUILD) || defined(NOT_GCBUILD)
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struct GC_ms_entry;
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#else
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struct GC_ms_entry { void *opaque; };
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#endif
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typedef struct GC_ms_entry * (*GC_mark_proc)(GC_word * /* addr */,
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struct GC_ms_entry * /* mark_stack_ptr */,
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struct GC_ms_entry * /* mark_stack_limit */,
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GC_word /* env */);
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#define GC_LOG_MAX_MARK_PROCS 6
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#define GC_MAX_MARK_PROCS (1 << GC_LOG_MAX_MARK_PROCS)
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/* In a few cases it's necessary to assign statically known indices to */
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/* certain mark procs. Thus we reserve a few for well known clients. */
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/* (This is necessary if mark descriptors are compiler generated.) */
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#define GC_RESERVED_MARK_PROCS 8
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#define GC_GCJ_RESERVED_MARK_PROC_INDEX 0
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/* Object descriptors on mark stack or in objects. Low order two */
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/* bits are tags distinguishing among the following 4 possibilities */
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/* for the high order 30 bits. */
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#define GC_DS_TAG_BITS 2
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#define GC_DS_TAGS ((1 << GC_DS_TAG_BITS) - 1)
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#define GC_DS_LENGTH 0 /* The entire word is a length in bytes that */
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/* must be a multiple of 4. */
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#define GC_DS_BITMAP 1 /* 30 (62) bits are a bitmap describing pointer */
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/* fields. The msb is 1 if the first word */
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/* is a pointer. */
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/* (This unconventional ordering sometimes */
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/* makes the marker slightly faster.) */
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/* Zeroes indicate definite nonpointers. Ones */
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/* indicate possible pointers. */
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/* Only usable if pointers are word aligned. */
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#define GC_DS_PROC 2
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/* The objects referenced by this object can be */
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/* pushed on the mark stack by invoking */
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/* PROC(descr). ENV(descr) is passed as the */
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/* last argument. */
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#define GC_MAKE_PROC(proc_index, env) \
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(((((env) << GC_LOG_MAX_MARK_PROCS) \
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| (proc_index)) << GC_DS_TAG_BITS) | GC_DS_PROC)
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#define GC_DS_PER_OBJECT 3 /* The real descriptor is at the */
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/* byte displacement from the beginning of the */
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/* object given by descr & ~GC_DS_TAGS. */
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/* If the descriptor is negative, the real */
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/* descriptor is at (*<object_start>) - */
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/* (descr&~GC_DS_TAGS) - GC_INDIR_PER_OBJ_BIAS */
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/* The latter alternative can be used if each */
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/* object contains a type descriptor in the */
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/* first word. */
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/* Note that in the multi-threaded environments */
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/* per-object descriptors must be located in */
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/* either the first two or last two words of */
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/* the object, since only those are guaranteed */
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/* to be cleared while the allocation lock is */
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/* held. */
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#define GC_INDIR_PER_OBJ_BIAS 0x10
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GC_API void * GC_least_plausible_heap_addr;
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GC_API void * GC_greatest_plausible_heap_addr;
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/* Bounds on the heap. Guaranteed valid */
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/* Likely to include future heap expansion. */
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/* Hence usually includes not-yet-mapped */
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/* memory. */
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/* Handle nested references in a custom mark procedure. */
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/* Check if obj is a valid object. If so, ensure that it is marked. */
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/* If it was not previously marked, push its contents onto the mark */
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/* stack for future scanning. The object will then be scanned using */
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/* its mark descriptor. */
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/* Returns the new mark stack pointer. */
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/* Handles mark stack overflows correctly. */
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/* Since this marks first, it makes progress even if there are mark */
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/* stack overflows. */
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/* Src is the address of the pointer to obj, which is used only */
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/* for back pointer-based heap debugging. */
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/* It is strongly recommended that most objects be handled without mark */
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/* procedures, e.g. with bitmap descriptors, and that mark procedures */
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/* be reserved for exceptional cases. That will ensure that */
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/* performance of this call is not extremely performance critical. */
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/* (Otherwise we would need to inline GC_mark_and_push completely, */
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/* which would tie the client code to a fixed collector version.) */
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/* Note that mark procedures should explicitly call FIXUP_POINTER() */
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/* if required. */
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GC_API struct GC_ms_entry * GC_CALL GC_mark_and_push(void * /* obj */,
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struct GC_ms_entry * /* mark_stack_ptr */,
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struct GC_ms_entry * /* mark_stack_limit */,
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void ** /* src */);
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#define GC_MARK_AND_PUSH(obj, msp, lim, src) \
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((GC_word)(obj) >= (GC_word)GC_least_plausible_heap_addr && \
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(GC_word)(obj) <= (GC_word)GC_greatest_plausible_heap_addr ? \
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GC_mark_and_push(obj, msp, lim, src) : (msp))
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/* The size of the header added to objects allocated through the */
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/* GC_debug routines. Defined as a function so that client mark */
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/* procedures do not need to be recompiled for the collector library */
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/* version changes. */
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GC_API GC_ATTR_CONST size_t GC_CALL GC_get_debug_header_size(void);
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#define GC_USR_PTR_FROM_BASE(p) \
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((void *)((char *)(p) + GC_get_debug_header_size()))
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/* The same but defined as a variable. Exists only for the backward */
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/* compatibility. Some compilers do not accept "const" together with */
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/* deprecated or dllimport attributes, so the symbol is exported as */
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/* a non-constant one. */
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GC_API GC_ATTR_DEPRECATED
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# ifdef GC_BUILD
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const
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# endif
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size_t GC_debug_header_size;
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/* And some routines to support creation of new "kinds", e.g. with */
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/* custom mark procedures, by language runtimes. */
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/* The _inner versions assume the caller holds the allocation lock. */
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/* Return a new free list array. */
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GC_API void ** GC_CALL GC_new_free_list(void);
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GC_API void ** GC_CALL GC_new_free_list_inner(void);
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/* Return a new kind, as specified. */
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GC_API unsigned GC_CALL GC_new_kind(void ** /* free_list */,
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GC_word /* mark_descriptor_template */,
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int /* add_size_to_descriptor */,
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int /* clear_new_objects */) GC_ATTR_NONNULL(1);
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/* The last two parameters must be zero or one. */
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GC_API unsigned GC_CALL GC_new_kind_inner(void ** /* free_list */,
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GC_word /* mark_descriptor_template */,
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int /* add_size_to_descriptor */,
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int /* clear_new_objects */) GC_ATTR_NONNULL(1);
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/* Return a new mark procedure identifier, suitable for use as */
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/* the first argument in GC_MAKE_PROC. */
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GC_API unsigned GC_CALL GC_new_proc(GC_mark_proc);
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GC_API unsigned GC_CALL GC_new_proc_inner(GC_mark_proc);
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/* Allocate an object of a given kind. By default, there are only */
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/* a few kinds: composite (pointerful), atomic, uncollectible, etc. */
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/* We claim it is possible for clever client code that understands the */
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/* GC internals to add more, e.g. to communicate object layout */
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/* information to the collector. Note that in the multi-threaded */
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/* contexts, this is usually unsafe for kinds that have the descriptor */
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/* in the object itself, since there is otherwise a window in which */
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/* the descriptor is not correct. Even in the single-threaded case, */
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/* we need to be sure that cleared objects on a free list don't */
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/* cause a GC crash if they are accidentally traced. */
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GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(1) void * GC_CALL GC_generic_malloc(
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size_t /* lb */,
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int /* knd */);
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GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(1) void * GC_CALL
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GC_generic_malloc_ignore_off_page(
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size_t /* lb */, int /* knd */);
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/* As above, but pointers to past the */
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/* first page of the resulting object */
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/* are ignored. */
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/* Generalized version of GC_malloc_[atomic_]uncollectable. */
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GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(1) void * GC_CALL
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GC_generic_malloc_uncollectable(
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size_t /* lb */, int /* knd */);
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/* Same as above but primary for allocating an object of the same kind */
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/* as an existing one (kind obtained by GC_get_kind_and_size). */
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/* Not suitable for GCJ and typed-malloc kinds. */
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GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(1) void * GC_CALL
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GC_generic_or_special_malloc(
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size_t /* size */, int /* knd */);
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GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(1) void * GC_CALL
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GC_debug_generic_or_special_malloc(
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size_t /* size */, int /* knd */,
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GC_EXTRA_PARAMS);
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#ifdef GC_DEBUG
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# define GC_GENERIC_OR_SPECIAL_MALLOC(sz, knd) \
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GC_debug_generic_or_special_malloc(sz, knd, GC_EXTRAS)
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#else
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# define GC_GENERIC_OR_SPECIAL_MALLOC(sz, knd) \
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GC_generic_or_special_malloc(sz, knd)
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#endif /* !GC_DEBUG */
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/* Similar to GC_size but returns object kind. Size is returned too */
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/* if psize is not NULL. */
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GC_API int GC_CALL GC_get_kind_and_size(const void *, size_t * /* psize */)
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GC_ATTR_NONNULL(1);
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typedef void (GC_CALLBACK * GC_describe_type_fn)(void * /* p */,
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char * /* out_buf */);
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/* A procedure which */
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/* produces a human-readable */
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/* description of the "type" of object */
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/* p into the buffer out_buf of length */
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/* GC_TYPE_DESCR_LEN. This is used by */
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/* the debug support when printing */
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/* objects. */
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/* These functions should be as robust */
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/* as possible, though we do avoid */
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/* invoking them on objects on the */
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/* global free list. */
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#define GC_TYPE_DESCR_LEN 40
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GC_API void GC_CALL GC_register_describe_type_fn(int /* kind */,
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GC_describe_type_fn);
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/* Register a describe_type function */
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/* to be used when printing objects */
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/* of a particular kind. */
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/* Clear some of the inaccessible part of the stack. Returns its */
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/* argument, so it can be used in a tail call position, hence clearing */
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/* another frame. Argument may be NULL. */
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GC_API void * GC_CALL GC_clear_stack(void *);
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/* Set and get the client notifier on collections. The client function */
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/* is called at the start of every full GC (called with the allocation */
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/* lock held). May be 0. This is a really tricky interface to use */
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/* correctly. Unless you really understand the collector internals, */
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/* the callback should not, directly or indirectly, make any GC_ or */
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/* potentially blocking calls. In particular, it is not safe to */
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/* allocate memory using the garbage collector from within the callback */
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/* function. Both the setter and getter acquire the GC lock. */
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typedef void (GC_CALLBACK * GC_start_callback_proc)(void);
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GC_API void GC_CALL GC_set_start_callback(GC_start_callback_proc);
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GC_API GC_start_callback_proc GC_CALL GC_get_start_callback(void);
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/* Slow/general mark bit manipulation. The caller must hold the */
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/* allocation lock. GC_is_marked returns 1 (TRUE) or 0. */
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GC_API int GC_CALL GC_is_marked(const void *) GC_ATTR_NONNULL(1);
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GC_API void GC_CALL GC_clear_mark_bit(const void *) GC_ATTR_NONNULL(1);
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GC_API void GC_CALL GC_set_mark_bit(const void *) GC_ATTR_NONNULL(1);
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/* Push everything in the given range onto the mark stack. */
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/* (GC_push_conditional pushes either all or only dirty pages depending */
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/* on the third argument.) GC_push_all_eager also ensures that stack */
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/* is scanned immediately, not just scheduled for scanning. */
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GC_API void GC_CALL GC_push_all(void * /* bottom */, void * /* top */);
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GC_API void GC_CALL GC_push_all_eager(void * /* bottom */, void * /* top */);
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GC_API void GC_CALL GC_push_conditional(void * /* bottom */, void * /* top */,
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int /* bool all */);
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GC_API void GC_CALL GC_push_finalizer_structures(void);
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/* Set and get the client push-other-roots procedure. A client */
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/* supplied procedure should also call the original procedure. */
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/* Note that both the setter and getter require some external */
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/* synchronization to avoid data race. */
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typedef void (GC_CALLBACK * GC_push_other_roots_proc)(void);
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GC_API void GC_CALL GC_set_push_other_roots(GC_push_other_roots_proc);
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GC_API GC_push_other_roots_proc GC_CALL GC_get_push_other_roots(void);
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/* Walk the GC heap visiting all reachable objects. Assume the caller */
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/* holds the allocation lock. Object base pointer, object size and */
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/* client custom data are passed to the callback (holding the lock). */
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typedef void (GC_CALLBACK *GC_reachable_object_proc)(void * /* obj */,
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size_t /* bytes */,
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void * /* client_data */);
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GC_API void GC_CALL GC_enumerate_reachable_objects_inner(
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GC_reachable_object_proc,
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void * /* client_data */) GC_ATTR_NONNULL(1);
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GC_API int GC_CALL GC_is_tmp_root(void *);
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GC_API void GC_CALL GC_print_trace(GC_word /* gc_no */);
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GC_API void GC_CALL GC_print_trace_inner(GC_word /* gc_no */);
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#ifdef __cplusplus
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} /* extern "C" */
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#endif
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#endif /* GC_MARK_H */
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