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Diffstat (limited to 'boehm-gc/include/gc_mark.h')
| -rw-r--r-- | boehm-gc/include/gc_mark.h | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/boehm-gc/include/gc_mark.h b/boehm-gc/include/gc_mark.h new file mode 100644 index 000000000..953bb74dc --- /dev/null +++ b/boehm-gc/include/gc_mark.h @@ -0,0 +1,203 @@ +/* + * 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_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 collector version.) */ +/* Note that mark procedures should explicitly call FIXUP_POINTER() */ +/* if required. */ +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) + +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) ((GC_PTR)((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 GC_PROTO((void)); +void ** GC_new_free_list_inner GC_PROTO((void)); + +/* Return a new kind, as specified. */ +int GC_new_kind GC_PROTO((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. */ +int GC_new_kind_inner GC_PROTO((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. */ +int GC_new_proc GC_PROTO((GC_mark_proc)); +int GC_new_proc_inner GC_PROTO((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. */ +/* ptr_t */char * GC_generic_malloc GC_PROTO((GC_word lb, int k)); + +/* FIXME - Should return void *, but that requires other changes. */ + +typedef void (*GC_describe_type_fn) GC_PROTO((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 GC_PROTO((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 */ + |