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.
15 * These are checking routines calls to which could be inserted by a
16 * preprocessor to validate C pointer arithmetic.
21 #include "private/gc_pmark.h"
23 void GC_default_same_obj_print_proc(void * p, void * q)
25 GC_err_printf("%p and %p are not in the same object\n", p, q);
26 ABORT("GC_same_obj test failed");
29 void (*GC_same_obj_print_proc) (void *, void *)
30 = GC_default_same_obj_print_proc;
32 /* Check that p and q point to the same object. Call */
33 /* *GC_same_obj_print_proc if they don't. */
34 /* Returns the first argument. (Return value may be hard */
35 /* to use,due to typing issues. But if we had a suitable */
36 /* preprocessor ...) */
37 /* Succeeds if neither p nor q points to the heap. */
38 /* We assume this is performance critical. (It shouldn't */
39 /* be called by production code, but this can easily make */
40 /* debugging intolerably slow.) */
41 void * GC_same_obj(void *p, void *q)
48 if (!GC_is_initialized) GC_init();
51 if (divHBLKSZ((word)p) != divHBLKSZ((word)q)
52 && HDR((word)q) != 0) {
57 /* If it's a pointer to the middle of a large object, move it */
58 /* to the beginning. */
59 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
60 h = HBLKPTR(p) - (word)hhdr;
62 while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
63 h = FORWARDED_ADDR(h, hhdr);
66 limit = (ptr_t)h + hhdr -> hb_sz;
67 if ((ptr_t)p >= limit || (ptr_t)q >= limit || (ptr_t)q < (ptr_t)h ) {
73 if (sz > MAXOBJBYTES) {
74 base = (ptr_t)HBLKPTR(p);
76 if ((ptr_t)p >= limit) {
81 size_t pdispl = HBLKDISPL(p);
84 if (HBLKPTR(p) != HBLKPTR(q)) goto fail;
85 /* W/o this check, we might miss an error if */
86 /* q points to the first object on a page, and */
87 /* points just before the page. */
88 base = (ptr_t)p - offset;
91 /* [base, limit) delimits the object containing p, if any. */
92 /* If p is not inside a valid object, then either q is */
93 /* also outside any valid object, or it is outside */
95 if ((ptr_t)q >= limit || (ptr_t)q < base) {
100 (*GC_same_obj_print_proc)((ptr_t)p, (ptr_t)q);
104 void GC_default_is_valid_displacement_print_proc (void *p)
106 GC_err_printf("%p does not point to valid object displacement\n", p);
107 ABORT("GC_is_valid_displacement test failed");
110 void (*GC_is_valid_displacement_print_proc)(void *) =
111 GC_default_is_valid_displacement_print_proc;
113 /* Check that if p is a pointer to a heap page, then it points to */
114 /* a valid displacement within a heap object. */
115 /* Uninteresting with GC_all_interior_pointers. */
116 /* Always returns its argument. */
117 /* Note that we don't lock, since nothing relevant about the header */
118 /* should change while we have a valid object pointer to the block. */
119 void * GC_is_valid_displacement(void *p)
127 if (!GC_is_initialized) GC_init();
129 if (hhdr == 0) return(p);
131 if (GC_all_interior_pointers) {
132 while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
133 h = FORWARDED_ADDR(h, hhdr);
137 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
141 pdispl = HBLKDISPL(p);
142 offset = pdispl % sz;
143 if ((sz > MAXOBJBYTES && (ptr_t)p >= (ptr_t)h + sz)
144 || !GC_valid_offsets[offset]
145 || (ptr_t)p - offset + sz > (ptr_t)(h + 1)) {
150 (*GC_is_valid_displacement_print_proc)((ptr_t)p);
154 void GC_default_is_visible_print_proc(void * p)
156 GC_err_printf("%p is not a GC visible pointer location\n", p);
157 ABORT("GC_is_visible test failed");
160 void (*GC_is_visible_print_proc)(void * p) = GC_default_is_visible_print_proc;
162 /* Could p be a stack address? */
163 GC_bool GC_on_stack(ptr_t p)
169 # ifdef STACK_GROWS_DOWN
170 if ((ptr_t)p >= (ptr_t)(&dummy) && (ptr_t)p < GC_stackbottom ) {
174 if ((ptr_t)p <= (ptr_t)(&dummy) && (ptr_t)p > GC_stackbottom ) {
182 /* Check that p is visible */
183 /* to the collector as a possibly pointer containing location. */
184 /* If it isn't invoke *GC_is_visible_print_proc. */
185 /* Returns the argument in all cases. May erroneously succeed */
186 /* in hard cases. (This is intended for debugging use with */
187 /* untyped allocations. The idea is that it should be possible, though */
188 /* slow, to add such a call to all indirect pointer stores.) */
189 /* Currently useless for multithreaded worlds. */
190 void * GC_is_visible(void *p)
194 if ((word)p & (ALIGNMENT - 1)) goto fail;
195 if (!GC_is_initialized) GC_init();
198 if (hhdr != 0 && GC_base(p) == 0) {
201 /* May be inside thread stack. We can't do much. */
205 /* Check stack first: */
206 if (GC_on_stack(p)) return(p);
211 if (GC_is_static_root(p)) return(p);
212 /* Else do it again correctly: */
213 # if (defined(DYNAMIC_LOADING) || defined(MSWIN32) || \
214 defined(MSWINCE) || defined(PCR))
215 GC_register_dynamic_libraries();
216 result = GC_is_static_root(p);
217 if (result) return(p);
221 /* p points to the heap. */
223 ptr_t base = GC_base(p); /* Should be manually inlined? */
225 if (base == 0) goto fail;
226 if (HBLKPTR(base) != HBLKPTR(p)) hhdr = HDR((word)p);
227 descr = hhdr -> hb_descr;
229 switch(descr & GC_DS_TAGS) {
231 if ((word)((ptr_t)p - (ptr_t)base) > (word)descr) goto fail;
234 if ((ptr_t)p - (ptr_t)base
235 >= WORDS_TO_BYTES(BITMAP_BITS)
236 || ((word)p & (sizeof(word) - 1))) goto fail;
237 if (!((1 << (WORDSZ - ((ptr_t)p - (ptr_t)base) - 1))
241 /* We could try to decipher this partially. */
242 /* For now we just punt. */
244 case GC_DS_PER_OBJECT:
245 if ((signed_word)descr >= 0) {
246 descr = *(word *)((ptr_t)base + (descr & ~GC_DS_TAGS));
248 ptr_t type_descr = *(ptr_t *)base;
249 descr = *(word *)(type_descr
250 - (descr - (GC_DS_PER_OBJECT
251 - GC_INDIR_PER_OBJ_BIAS)));
259 (*GC_is_visible_print_proc)((ptr_t)p);
264 void * GC_pre_incr (void **p, size_t how_much)
267 void * result = GC_same_obj((void *)((word)initial + how_much), initial);
269 if (!GC_all_interior_pointers) {
270 (void) GC_is_valid_displacement(result);
272 return (*p = result);
275 void * GC_post_incr (void **p, size_t how_much)
278 void * result = GC_same_obj((void *)((word)initial + how_much), initial);
280 if (!GC_all_interior_pointers) {
281 (void) GC_is_valid_displacement(result);