2 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
4 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
5 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
7 * Permission is hereby granted to use or copy this program
8 * for any purpose, provided the above notices are retained on all copies.
9 * Permission to modify the code and to distribute modified code is granted,
10 * provided the above notices are retained, and a notice that the code was
11 * modified is included with the above copyright notice.
14 #include "private/gc_pmark.h"
17 * These are checking routines calls to which could be inserted by a
18 * preprocessor to validate C pointer arithmetic.
21 STATIC void GC_CALLBACK GC_default_same_obj_print_proc(void * p, void * q)
23 ABORT_ARG2("GC_same_obj test failed",
24 ": %p and %p are not in the same object", p, q);
27 void (GC_CALLBACK *GC_same_obj_print_proc) (void *, void *)
28 = GC_default_same_obj_print_proc;
30 /* Check that p and q point to the same object. Call */
31 /* *GC_same_obj_print_proc if they don't. */
32 /* Returns the first argument. (Return value may be hard */
33 /* to use due to typing issues. But if we had a suitable */
34 /* preprocessor...) */
35 /* Succeeds if neither p nor q points to the heap. */
36 /* We assume this is performance critical. (It shouldn't */
37 /* be called by production code, but this can easily make */
38 /* debugging intolerably slow.) */
39 GC_API void * GC_CALL GC_same_obj(void *p, void *q)
46 if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
49 if (divHBLKSZ((word)p) != divHBLKSZ((word)q)
50 && HDR((word)q) != 0) {
55 /* If it's a pointer to the middle of a large object, move it */
56 /* to the beginning. */
57 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
58 h = HBLKPTR(p) - (word)hhdr;
60 while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
61 h = FORWARDED_ADDR(h, hhdr);
64 limit = (ptr_t)h + hhdr -> hb_sz;
65 if ((word)p >= (word)limit || (word)q >= (word)limit
66 || (word)q < (word)h) {
72 if (sz > MAXOBJBYTES) {
73 base = (ptr_t)HBLKPTR(p);
75 if ((word)p >= (word)limit) {
80 size_t pdispl = HBLKDISPL(p);
83 if (HBLKPTR(p) != HBLKPTR(q)) goto fail;
84 /* W/o this check, we might miss an error if */
85 /* q points to the first object on a page, and */
86 /* points just before the page. */
87 base = (ptr_t)p - offset;
90 /* [base, limit) delimits the object containing p, if any. */
91 /* If p is not inside a valid object, then either q is */
92 /* also outside any valid object, or it is outside */
94 if ((word)q >= (word)limit || (word)q < (word)base) {
99 (*GC_same_obj_print_proc)((ptr_t)p, (ptr_t)q);
103 STATIC void GC_CALLBACK GC_default_is_valid_displacement_print_proc (void *p)
105 ABORT_ARG1("GC_is_valid_displacement test failed", ": %p not valid", p);
108 void (GC_CALLBACK *GC_is_valid_displacement_print_proc)(void *) =
109 GC_default_is_valid_displacement_print_proc;
111 /* Check that if p is a pointer to a heap page, then it points to */
112 /* a valid displacement within a heap object. */
113 /* Uninteresting with GC_all_interior_pointers. */
114 /* Always returns its argument. */
115 /* Note that we don't lock, since nothing relevant about the header */
116 /* should change while we have a valid object pointer to the block. */
117 GC_API void * GC_CALL GC_is_valid_displacement(void *p)
125 if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
127 if (hhdr == 0) return(p);
129 if (GC_all_interior_pointers) {
130 while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
131 h = FORWARDED_ADDR(h, hhdr);
134 } else if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
138 pdispl = HBLKDISPL(p);
139 offset = pdispl % sz;
140 if ((sz > MAXOBJBYTES && (word)p >= (word)h + sz)
141 || !GC_valid_offsets[offset]
142 || ((word)p + (sz - offset) > (word)(h + 1)
143 && !IS_FORWARDING_ADDR_OR_NIL(HDR(h + 1)))) {
148 (*GC_is_valid_displacement_print_proc)((ptr_t)p);
152 STATIC void GC_CALLBACK GC_default_is_visible_print_proc(void * p)
154 ABORT_ARG1("GC_is_visible test failed", ": %p not GC-visible", p);
157 void (GC_CALLBACK *GC_is_visible_print_proc)(void * p) =
158 GC_default_is_visible_print_proc;
161 /* Could p be a stack address? */
162 STATIC GC_bool GC_on_stack(void *p)
164 # ifdef STACK_GROWS_DOWN
165 if ((word)p >= (word)GC_approx_sp()
166 && (word)p < (word)GC_stackbottom) {
170 if ((word)p <= (word)GC_approx_sp()
171 && (word)p > (word)GC_stackbottom) {
179 /* Check that p is visible */
180 /* to the collector as a possibly pointer containing location. */
181 /* If it isn't, invoke *GC_is_visible_print_proc. */
182 /* Returns the argument in all cases. May erroneously succeed */
183 /* in hard cases. (This is intended for debugging use with */
184 /* untyped allocations. The idea is that it should be possible, though */
185 /* slow, to add such a call to all indirect pointer stores.) */
186 /* Currently useless for the multi-threaded worlds. */
187 GC_API void * GC_CALL GC_is_visible(void *p)
191 if ((word)p & (ALIGNMENT - 1)) goto fail;
192 if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
195 if (hhdr != 0 && GC_base(p) == 0) {
198 /* May be inside thread stack. We can't do much. */
202 /* Check stack first: */
203 if (GC_on_stack(p)) return(p);
206 if (GC_is_static_root(p)) return(p);
207 /* Else do it again correctly: */
208 # if defined(DYNAMIC_LOADING) || defined(MSWIN32) \
209 || defined(MSWINCE) || defined(CYGWIN32) || defined(PCR)
210 GC_register_dynamic_libraries();
211 if (GC_is_static_root(p))
216 /* p points to the heap. */
218 ptr_t base = (ptr_t)GC_base(p);
219 /* TODO: should GC_base be manually inlined? */
221 if (NULL == base) goto fail;
222 if (HBLKPTR(base) != HBLKPTR(p))
224 descr = hhdr -> hb_descr;
226 switch(descr & GC_DS_TAGS) {
228 if ((word)p - (word)base > descr) goto fail;
231 if ((word)p - (word)base >= WORDS_TO_BYTES(BITMAP_BITS)
232 || ((word)p & (sizeof(word) - 1))) goto fail;
233 if (!(((word)1 << (WORDSZ - ((ptr_t)p - (ptr_t)base) - 1))
237 /* We could try to decipher this partially. */
238 /* For now we just punt. */
240 case GC_DS_PER_OBJECT:
241 if ((signed_word)descr >= 0) {
242 descr = *(word *)((ptr_t)base + (descr & ~GC_DS_TAGS));
244 ptr_t type_descr = *(ptr_t *)base;
245 descr = *(word *)(type_descr
246 - (descr - (word)(GC_DS_PER_OBJECT
247 - GC_INDIR_PER_OBJ_BIAS)));
255 (*GC_is_visible_print_proc)((ptr_t)p);
259 GC_API void * GC_CALL GC_pre_incr (void **p, ptrdiff_t how_much)
262 void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
264 if (!GC_all_interior_pointers) {
265 (void) GC_is_valid_displacement(result);
267 return (*p = result);
270 GC_API void * GC_CALL GC_post_incr (void **p, ptrdiff_t how_much)
273 void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
275 if (!GC_all_interior_pointers) {
276 (void) GC_is_valid_displacement(result);