--- /dev/null
+/*
+ * 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
+
+#ifdef __cplusplus
+ extern "C" {
+#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 describing 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 if 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 must 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
+
+GC_API void * GC_least_plausible_heap_addr;
+GC_API void * GC_greatest_plausible_heap_addr;
+ /* Bounds on the heap. Guaranteed valid */
+ /* Likely to include future heap expansion. */
+ /* Hence usually includes not-yet-mapped */
+ /* memory. */
+
+/* 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. */
+GC_API struct GC_ms_entry * GC_CALL 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))
+
+GC_API 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. */
+GC_API void ** GC_CALL GC_new_free_list(void);
+GC_API void ** GC_CALL GC_new_free_list_inner(void);
+
+/* Return a new kind, as specified. */
+GC_API unsigned GC_CALL 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. */
+GC_API unsigned GC_CALL 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. */
+GC_API unsigned GC_CALL GC_new_proc(GC_mark_proc);
+GC_API unsigned GC_CALL 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. */
+GC_API void * GC_CALL GC_generic_malloc(size_t /* lb */, int /* k */);
+
+typedef void (GC_CALLBACK * 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
+
+GC_API void GC_CALL GC_register_describe_type_fn(int /* kind */,
+ GC_describe_type_fn);
+ /* Register a describe_type function */
+ /* to be used when printing objects */
+ /* of a particular kind. */
+
+/* Clear some of the inaccessible part of the stack. Returns its */
+/* argument, so it can be used in a tail call position, hence clearing */
+/* another frame. Argument may be NULL. */
+GC_API void * GC_CALL GC_clear_stack(void *);
+
+/* Set and get the client notifier on collections. The client function */
+/* is called at the start of every full GC (called with the allocation */
+/* lock held). May be 0. This is a really tricky interface to use */
+/* correctly. Unless you really understand the collector internals, */
+/* the callback should not, directly or indirectly, make any GC_ or */
+/* potentially blocking calls. In particular, it is not safe to */
+/* allocate memory using the garbage collector from within the callback */
+/* function. Both the setter and getter acquire the GC lock. */
+typedef void (GC_CALLBACK * GC_start_callback_proc)(void);
+GC_API void GC_CALL GC_set_start_callback(GC_start_callback_proc);
+GC_API GC_start_callback_proc GC_CALL GC_get_start_callback(void);
+
+#ifdef __cplusplus
+ } /* end of extern "C" */
+#endif
+
+#endif /* GC_MARK_H */
projects / hs-boehmgc.git / blobdiff