/*
* Copyright (c) 1991-1994 by Xerox Corporation. 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.
*/
#include "private/gc_pmark.h"
/*
* These are checking routines calls to which could be inserted by a
* preprocessor to validate C pointer arithmetic.
*/
STATIC void GC_CALLBACK GC_default_same_obj_print_proc(void * p, void * q)
{
ABORT_ARG2("GC_same_obj test failed",
": %p and %p are not in the same object", p, q);
}
void (GC_CALLBACK *GC_same_obj_print_proc) (void *, void *)
= GC_default_same_obj_print_proc;
/* Check that p and q point to the same object. Call */
/* *GC_same_obj_print_proc if they don't. */
/* Returns the first argument. (Return value may be hard */
/* to use due to typing issues. But if we had a suitable */
/* preprocessor...) */
/* Succeeds if neither p nor q points to the heap. */
/* We assume this is performance critical. (It shouldn't */
/* be called by production code, but this can easily make */
/* debugging intolerably slow.) */
GC_API void * GC_CALL GC_same_obj(void *p, void *q)
{
struct hblk *h;
hdr *hhdr;
ptr_t base, limit;
word sz;
if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
hhdr = HDR((word)p);
if (hhdr == 0) {
if (divHBLKSZ((word)p) != divHBLKSZ((word)q)
&& HDR((word)q) != 0) {
goto fail;
}
return(p);
}
/* If it's a pointer to the middle of a large object, move it */
/* to the beginning. */
if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
h = HBLKPTR(p) - (word)hhdr;
hhdr = HDR(h);
while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
h = FORWARDED_ADDR(h, hhdr);
hhdr = HDR(h);
}
limit = (ptr_t)h + hhdr -> hb_sz;
if ((word)p >= (word)limit || (word)q >= (word)limit
|| (word)q < (word)h) {
goto fail;
}
return(p);
}
sz = hhdr -> hb_sz;
if (sz > MAXOBJBYTES) {
base = (ptr_t)HBLKPTR(p);
limit = base + sz;
if ((word)p >= (word)limit) {
goto fail;
}
} else {
size_t offset;
size_t pdispl = HBLKDISPL(p);
offset = pdispl % sz;
if (HBLKPTR(p) != HBLKPTR(q)) goto fail;
/* W/o this check, we might miss an error if */
/* q points to the first object on a page, and */
/* points just before the page. */
base = (ptr_t)p - offset;
limit = base + sz;
}
/* [base, limit) delimits the object containing p, if any. */
/* If p is not inside a valid object, then either q is */
/* also outside any valid object, or it is outside */
/* [base, limit). */
if ((word)q >= (word)limit || (word)q < (word)base) {
goto fail;
}
return(p);
fail:
(*GC_same_obj_print_proc)((ptr_t)p, (ptr_t)q);
return(p);
}
STATIC void GC_CALLBACK GC_default_is_valid_displacement_print_proc (void *p)
{
ABORT_ARG1("GC_is_valid_displacement test failed", ": %p not valid", p);
}
void (GC_CALLBACK *GC_is_valid_displacement_print_proc)(void *) =
GC_default_is_valid_displacement_print_proc;
/* Check that if p is a pointer to a heap page, then it points to */
/* a valid displacement within a heap object. */
/* Uninteresting with GC_all_interior_pointers. */
/* Always returns its argument. */
/* Note that we don't lock, since nothing relevant about the header */
/* should change while we have a valid object pointer to the block. */
GC_API void * GC_CALL GC_is_valid_displacement(void *p)
{
hdr *hhdr;
word pdispl;
word offset;
struct hblk *h;
word sz;
if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
hhdr = HDR((word)p);
if (hhdr == 0) return(p);
h = HBLKPTR(p);
if (GC_all_interior_pointers) {
while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
h = FORWARDED_ADDR(h, hhdr);
hhdr = HDR(h);
}
}
if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
goto fail;
}
sz = hhdr -> hb_sz;
pdispl = HBLKDISPL(p);
offset = pdispl % sz;
if ((sz > MAXOBJBYTES && (word)p >= (word)h + sz)
|| !GC_valid_offsets[offset]
|| (word)p - offset + sz > (word)(h + 1)) {
goto fail;
}
return(p);
fail:
(*GC_is_valid_displacement_print_proc)((ptr_t)p);
return(p);
}
STATIC void GC_CALLBACK GC_default_is_visible_print_proc(void * p)
{
ABORT_ARG1("GC_is_visible test failed", ": %p not GC-visible", p);
}
void (GC_CALLBACK *GC_is_visible_print_proc)(void * p) =
GC_default_is_visible_print_proc;
#ifndef THREADS
/* Could p be a stack address? */
STATIC GC_bool GC_on_stack(ptr_t p)
{
# ifdef STACK_GROWS_DOWN
if ((word)p >= (word)GC_approx_sp()
&& (word)p < (word)GC_stackbottom) {
return(TRUE);
}
# else
if ((word)p <= (word)GC_approx_sp()
&& (word)p > (word)GC_stackbottom) {
return(TRUE);
}
# endif
return(FALSE);
}
#endif
/* Check that p is visible */
/* to the collector as a possibly pointer containing location. */
/* If it isn't, invoke *GC_is_visible_print_proc. */
/* Returns the argument in all cases. May erroneously succeed */
/* in hard cases. (This is intended for debugging use with */
/* untyped allocations. The idea is that it should be possible, though */
/* slow, to add such a call to all indirect pointer stores.) */
/* Currently useless for the multi-threaded worlds. */
GC_API void * GC_CALL GC_is_visible(void *p)
{
hdr *hhdr;
if ((word)p & (ALIGNMENT - 1)) goto fail;
if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
# ifdef THREADS
hhdr = HDR((word)p);
if (hhdr != 0 && GC_base(p) == 0) {
goto fail;
} else {
/* May be inside thread stack. We can't do much. */
return(p);
}
# else
/* Check stack first: */
if (GC_on_stack(p)) return(p);
hhdr = HDR((word)p);
if (hhdr == 0) {
if (GC_is_static_root(p)) return(p);
/* Else do it again correctly: */
# if defined(DYNAMIC_LOADING) || defined(MSWIN32) \
|| defined(MSWINCE) || defined(CYGWIN32) || defined(PCR)
GC_register_dynamic_libraries();
if (GC_is_static_root(p))
return(p);
# endif
goto fail;
} else {
/* p points to the heap. */
word descr;
ptr_t base = GC_base(p); /* Should be manually inlined? */
if (base == 0) goto fail;
if (HBLKPTR(base) != HBLKPTR(p)) hhdr = HDR((word)p);
descr = hhdr -> hb_descr;
retry:
switch(descr & GC_DS_TAGS) {
case GC_DS_LENGTH:
if ((word)p - (word)base > descr) goto fail;
break;
case GC_DS_BITMAP:
if ((word)p - (word)base >= WORDS_TO_BYTES(BITMAP_BITS)
|| ((word)p & (sizeof(word) - 1))) goto fail;
if (!(((word)1 << (WORDSZ - ((ptr_t)p - (ptr_t)base) - 1))
& descr)) goto fail;
break;
case GC_DS_PROC:
/* We could try to decipher this partially. */
/* For now we just punt. */
break;
case GC_DS_PER_OBJECT:
if ((signed_word)descr >= 0) {
descr = *(word *)((ptr_t)base + (descr & ~GC_DS_TAGS));
} else {
ptr_t type_descr = *(ptr_t *)base;
descr = *(word *)(type_descr
- (descr - (word)(GC_DS_PER_OBJECT
- GC_INDIR_PER_OBJ_BIAS)));
}
goto retry;
}
return(p);
}
# endif
fail:
(*GC_is_visible_print_proc)((ptr_t)p);
return(p);
}
GC_API void * GC_CALL GC_pre_incr (void **p, ptrdiff_t how_much)
{
void * initial = *p;
void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
if (!GC_all_interior_pointers) {
(void) GC_is_valid_displacement(result);
}
return (*p = result);
}
GC_API void * GC_CALL GC_post_incr (void **p, ptrdiff_t how_much)
{
void * initial = *p;
void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
if (!GC_all_interior_pointers) {
(void) GC_is_valid_displacement(result);
}
*p = result;
return(initial);
}