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gc.c
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gc.c
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/* Copyright 2009-2024
* Kaz Kylheku <kaz@kylheku.com>
* Vancouver, Canada
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stddef.h>
#include <assert.h>
#include <wchar.h>
#include <signal.h>
#include "config.h"
#include "alloca.h"
#if HAVE_VALGRIND
#include <valgrind/memcheck.h>
#endif
#if HAVE_RLIMIT
#include <sys/resource.h>
#endif
#include "lib.h"
#include "stream.h"
#include "hash.h"
#include "eval.h"
#include "gc.h"
#include "signal.h"
#include "unwind.h"
#include "args.h"
#define PROT_STACK_SIZE 1024
#if CONFIG_SMALL_MEM
#define HEAP_SIZE 4096
#define CHECKOBJ_VEC_SIZE HEAP_SIZE
#define MUTOBJ_VEC_SIZE HEAP_SIZE
#define FULL_GC_INTERVAL 20
#define FRESHOBJ_VEC_SIZE (2 * HEAP_SIZE)
#define DFL_MALLOC_DELTA_THRESH (16L * 1024 * 1024)
#define DFL_STACK_LIMIT (128 * 1024L)
#else
#define HEAP_SIZE 16384
#define CHECKOBJ_VEC_SIZE (2 * HEAP_SIZE)
#define MUTOBJ_VEC_SIZE (2 * HEAP_SIZE)
#define FULL_GC_INTERVAL 40
#define FRESHOBJ_VEC_SIZE (8 * HEAP_SIZE)
#define DFL_MALLOC_DELTA_THRESH (64L * 1024 * 1024)
#define DFL_STACK_LIMIT (16384 * 1024L)
#endif
#define MIN_STACK_LIMIT 32768
#if HAVE_MEMALIGN || HAVE_POSIX_MEMALIGN
#define OBJ_ALIGN (sizeof (obj_t))
#else
#define OBJ_ALIGN 8
#endif
typedef struct heap {
obj_t block[HEAP_SIZE];
struct heap *next;
#if CONFIG_NAN_BOXING_STRIP_TAG
ucnum tag;
#endif
} heap_t;
typedef struct mach_context {
struct jmp buf;
} mach_context_t;
#define save_context(X) jmp_save(&(X).buf)
int opt_gc_debug;
#if HAVE_VALGRIND
int opt_vg_debug;
#endif
val *gc_stack_bottom;
val *gc_stack_limit;
static val *prot_stack[PROT_STACK_SIZE];
static val **prot_stack_limit = prot_stack + PROT_STACK_SIZE;
val **gc_prot_top = prot_stack;
static val free_list, *free_tail = &free_list;
static heap_t *heap_list;
static val heap_min_bound, heap_max_bound;
alloc_bytes_t gc_bytes;
static alloc_bytes_t prev_malloc_bytes;
alloc_bytes_t opt_gc_delta = DFL_MALLOC_DELTA_THRESH;
int gc_enabled = 1;
static int inprogress;
static struct fin_reg {
struct fin_reg *next;
val obj;
val fun;
int reachable;
} *final_list, **final_tail = &final_list;
#if CONFIG_GEN_GC
static val checkobj[CHECKOBJ_VEC_SIZE];
static int checkobj_idx;
static val mutobj[MUTOBJ_VEC_SIZE];
static int mutobj_idx;
static val freshobj[FRESHOBJ_VEC_SIZE];
static int freshobj_idx;
int full_gc;
#endif
#if CONFIG_EXTRA_DEBUGGING
val break_obj;
#endif
struct prot_array {
cnum size;
val self;
val arr[FLEX_ARRAY];
};
val gc_prot_array_s;
struct cobj_class *prot_array_cls;
val prot1(val *loc)
{
assert (gc_prot_top < prot_stack_limit);
assert (loc != 0);
*gc_prot_top++ = loc;
return nil; /* for use in macros */
}
void protect(val *first, ...)
{
val *next = first;
va_list vl;
va_start (vl, first);
while (next) {
prot1(next);
next = va_arg(vl, val *);
}
va_end (vl);
}
static void more(void)
{
#if CONFIG_NAN_BOXING_STRIP_TAG
ucnum tagged_ptr = coerce(cnum, chk_malloc_gc_more(sizeof (heap_t)));
heap_t *heap = coerce(heap_t *, tagged_ptr & ~TAG_BIGMASK);
#else
heap_t *heap = coerce(heap_t *, chk_malloc_gc_more(sizeof *heap));
#endif
obj_t *block = heap->block, *end = heap->block + HEAP_SIZE;
#if CONFIG_NAN_BOXING_STRIP_TAG
heap->tag = tagged_ptr >> TAG_BIGSHIFT;
#endif
if (free_list == 0)
free_tail = &heap->block[0].t.next;
if (!heap_max_bound || end > heap_max_bound)
heap_max_bound = end;
if (!heap_min_bound || block < heap_min_bound)
heap_min_bound = block;
while (block < end) {
block->t.next = free_list;
block->t.type = convert(type_t, FREE);
#if CONFIG_EXTRA_DEBUGGING
if (block == break_obj) {
#if HAVE_VALGRIND
VALGRIND_PRINTF_BACKTRACE("object %p newly added to free list\n", convert(void *, block));
#endif
breakpt();
}
#endif
free_list = block++;
}
heap->next = heap_list;
heap_list = heap;
#if HAVE_VALGRIND
if (opt_vg_debug)
VALGRIND_MAKE_MEM_NOACCESS(&heap->block, sizeof heap->block);
#endif
}
val make_obj(void)
{
int tries;
alloc_bytes_t malloc_delta = malloc_bytes - prev_malloc_bytes;
assert (!async_sig_enabled);
#if CONFIG_GEN_GC
if ((opt_gc_debug || freshobj_idx >= FRESHOBJ_VEC_SIZE ||
malloc_delta >= opt_gc_delta) &&
gc_enabled)
{
gc();
}
if (freshobj_idx >= FRESHOBJ_VEC_SIZE)
full_gc = 1;
#else
if ((opt_gc_debug || malloc_delta >= opt_gc_delta) && gc_enabled) {
gc();
}
#endif
for (tries = 0; tries < 3; tries++) {
if (free_list) {
val ret = free_list;
#if HAVE_VALGRIND
if (opt_vg_debug)
VALGRIND_MAKE_MEM_DEFINED(free_list, sizeof *free_list);
#endif
free_list = free_list->t.next;
if (free_list == 0)
free_tail = &free_list;
#if HAVE_VALGRIND
if (opt_vg_debug)
VALGRIND_MAKE_MEM_UNDEFINED(ret, sizeof *ret);
#endif
#if CONFIG_GEN_GC
ret->t.gen = 0;
ret->t.fincount = 0;
if (!full_gc)
freshobj[freshobj_idx++] = ret;
#endif
gc_bytes += sizeof (obj_t);
#if CONFIG_EXTRA_DEBUGGING
if (ret == break_obj) {
#if HAVE_VALGRIND
VALGRIND_PRINTF_BACKTRACE("object %p allocated\n", convert(void *, ret));
#endif
breakpt();
}
#endif
return ret;
}
#if CONFIG_GEN_GC
if (!full_gc && freshobj_idx < FRESHOBJ_VEC_SIZE) {
more();
continue;
}
#endif
switch (tries) {
case 0:
if (gc_enabled) {
gc();
break;
}
/* fallthrough */
case 1:
more();
break;
}
}
abort();
}
val copy_obj(val orig)
{
val copy = make_obj();
*copy = *orig;
#if CONFIG_GEN_GC
copy->t.fincount = 0;
copy->t.gen = 0;
#endif
return copy;
}
static void finalize(val obj)
{
switch (convert(type_t, obj->t.type)) {
case NIL:
case CONS:
case CHR:
case NUM:
case LIT:
case PKG:
case FUN:
case LCONS:
case ENV:
case FLNUM:
case RNG:
case TNOD:
return;
case SYM:
free(obj->s.slot_cache);
obj->s.slot_cache = 0;
return;
case STR:
free(obj->st.str);
obj->st.str = 0;
return;
case LSTR:
free(obj->ls.props);
obj->ls.props = 0;
return;
case VEC:
free(obj->v.vec-2);
obj->v.vec = 0;
return;
case COBJ:
case CPTR:
obj->co.ops->destroy(obj);
obj->co.handle = 0;
return;
case BGNUM:
mp_clear(mp(obj));
return;
case BUF:
if (obj->b.size) {
free(obj->b.data);
obj->b.data = 0;
}
return;
case DARG:
free(obj->a.args);
obj->a.args = 0;
return;
}
assert (0 && "corrupt type field");
}
void cobj_destroy_stub_op(val obj)
{
(void) obj;
}
void cobj_destroy_free_op(val obj)
{
free(obj->co.handle);
}
static void mark_obj(val obj)
{
val self = lit("gc");
type_t t;
tail_call:
#define mark_obj_tail(o) do { obj = (o); goto tail_call; } while (0)
if (!is_ptr(obj))
return;
t = obj->t.type;
if ((t & REACHABLE) != 0)
return;
#if CONFIG_GEN_GC
if (!full_gc && obj->t.gen > 0)
return;
#endif
if ((t & FREE) != 0)
abort();
#if CONFIG_GEN_GC
if (obj->t.gen == -1)
obj->t.gen = 0; /* Will be promoted to generation 1 by sweep_one */
#endif
obj->t.type = convert(type_t, t | REACHABLE);
#if CONFIG_EXTRA_DEBUGGING
if (obj == break_obj) {
#if HAVE_VALGRIND
VALGRIND_PRINTF_BACKTRACE("object %p marked\n", convert(void *, obj));
#endif
breakpt();
}
#endif
switch (t) {
case NIL:
case CHR:
case NUM:
case LIT:
case BGNUM:
case FLNUM:
return;
case CONS:
mark_obj(obj->c.car);
mark_obj_tail(obj->c.cdr);
case STR:
mark_obj_tail(obj->st.len);
case SYM:
mark_obj(obj->s.name);
mark_obj_tail(obj->s.package);
case PKG:
mark_obj(obj->pk.name);
mark_obj(obj->pk.hidhash);
mark_obj_tail(obj->pk.symhash);
case FUN:
switch (obj->f.functype) {
case FINTERP:
mark_obj(obj->f.f.interp_fun);
break;
case FVM:
mark_obj(obj->f.f.vm_desc);
break;
}
mark_obj_tail(obj->f.env);
case VEC:
{
val alloc_size = obj->v.vec[vec_alloc];
val len = obj->v.vec[vec_length];
cnum i, fp = c_num(len, self);
mark_obj(alloc_size);
mark_obj(len);
for (i = 0; i < fp; i++)
mark_obj(obj->v.vec[i]);
}
return;
case LCONS:
mark_obj(obj->lc.func);
mark_obj(obj->lc.car);
mark_obj_tail(obj->lc.cdr);
case LSTR:
mark_obj(obj->ls.prefix);
mark_obj(obj->ls.props->limit);
mark_obj(obj->ls.props->term);
mark_obj_tail(obj->ls.list);
case COBJ:
obj->co.ops->mark(obj);
return;
case CPTR:
obj->co.ops->mark(obj);
mark_obj_tail(obj->cp.cls);
case ENV:
mark_obj(obj->e.vbindings);
mark_obj(obj->e.fbindings);
mark_obj_tail(obj->e.up_env);
case RNG:
mark_obj(obj->rn.from);
mark_obj_tail(obj->rn.to);
case BUF:
mark_obj(obj->b.len);
mark_obj_tail(obj->b.size);
case TNOD:
mark_obj(obj->tn.left);
mark_obj(obj->tn.right);
mark_obj_tail(obj->tn.key);
case DARG:
{
varg args = obj->a.args;
cnum i, n = args->fill;
val *arg = args->arg;
mark_obj(obj->a.car);
mark_obj(obj->a.cdr);
for (i = 0; i < n; i++)
mark_obj(arg[i]);
mark_obj_tail(args->list);
}
}
assert (0 && "corrupt type field");
}
static void mark_obj_norec(val obj)
{
type_t t;
if (!is_ptr(obj))
return;
t = obj->t.type;
if ((t & REACHABLE) != 0)
return;
#if CONFIG_GEN_GC
if (!full_gc && obj->t.gen > 0)
return;
#endif
if ((t & FREE) != 0)
abort();
#if CONFIG_GEN_GC
if (obj->t.gen == -1)
obj->t.gen = 0; /* Will be promoted to generation 1 by sweep_one */
#endif
obj->t.type = convert(type_t, t | REACHABLE);
#if CONFIG_EXTRA_DEBUGGING
if (obj == break_obj) {
#if HAVE_VALGRIND
VALGRIND_PRINTF_BACKTRACE("object %p marked\n", convert(void *, obj));
#endif
breakpt();
}
#endif
}
void cobj_mark_op(val obj)
{
(void) obj;
}
static int in_heap(val ptr)
{
heap_t *heap;
if (!is_ptr(ptr))
return 0;
if (coerce(uint_ptr_t, ptr) % OBJ_ALIGN != 0)
return 0;
if (ptr < heap_min_bound || ptr >= heap_max_bound)
return 0;
for (heap = heap_list; heap != 0; heap = heap->next) {
if (ptr >= heap->block && ptr < heap->block + HEAP_SIZE) {
#if HAVE_MEMALIGN || HAVE_POSIX_MEMALIGN
return 1;
#else
if ((coerce(char *, ptr) -
coerce(char *, heap->block)) % sizeof (obj_t) == 0)
return 1;
#endif
}
}
return 0;
}
static void mark_obj_maybe(val maybe_obj)
{
#if HAVE_VALGRIND
VALGRIND_MAKE_MEM_DEFINED(&maybe_obj, sizeof maybe_obj);
#endif
if (in_heap(maybe_obj)) {
type_t t;
#if HAVE_VALGRIND
if (opt_vg_debug)
VALGRIND_MAKE_MEM_DEFINED(maybe_obj, SIZEOF_PTR);
#endif
t = maybe_obj->t.type;
if ((t & FREE) == 0) {
mark_obj(maybe_obj);
} else {
#if HAVE_VALGRIND
if (opt_vg_debug)
VALGRIND_MAKE_MEM_NOACCESS(maybe_obj, sizeof *maybe_obj);
#endif
}
}
}
static void mark_mem_region(val *low, val *high)
{
if (low > high) {
val *tmp = high;
high = low;
low = tmp;
}
for (; low < high; low++)
mark_obj_maybe(*low);
}
NOINLINE static void mark(val *gc_stack_top)
{
val **rootloc;
/*
* First, scan the officially registered locations.
*/
for (rootloc = prot_stack; rootloc != gc_prot_top; rootloc++)
mark_obj(**rootloc);
#if CONFIG_GEN_GC
/*
* Mark the additional objects indicated for marking.
*/
if (!full_gc)
{
int i;
for (i = 0; i < checkobj_idx; i++)
mark_obj(checkobj[i]);
for (i = 0; i < mutobj_idx; i++)
mark_obj(mutobj[i]);
}
#endif
/*
* Finally, the stack.
*/
mark_mem_region(gc_stack_top, gc_stack_bottom);
}
static int sweep_one(obj_t *block)
{
#if HAVE_VALGRIND
const int vg_dbg = opt_vg_debug;
#else
const int vg_dbg = 0;
#endif
#if CONFIG_EXTRA_DEBUGGING
if (block == break_obj && (block->t.type & FREE) == 0) {
#if HAVE_VALGRIND
VALGRIND_PRINTF_BACKTRACE("object %p swept (type = %x)\n",
convert(void *, block),
convert(unsigned int, block->t.type));
#endif
breakpt();
}
#endif
#if CONFIG_GEN_GC
if (!full_gc && block->t.gen > 0)
abort();
#endif
if ((block->t.type & (REACHABLE | FREE)) == (REACHABLE | FREE))
abort();
if (block->t.type & REACHABLE) {
#if CONFIG_GEN_GC
block->t.gen = 1;
#endif
block->t.type = convert(type_t, block->t.type & ~REACHABLE);
return 0;
}
if (block->t.type & FREE) {
#if HAVE_VALGRIND
if (vg_dbg)
VALGRIND_MAKE_MEM_NOACCESS(block, sizeof *block);
#endif
return 1;
}
finalize(block);
block->t.type = convert(type_t, block->t.type | FREE);
/* If debugging is turned on, we want to catch instances
where a reachable object is wrongly freed. This is difficult
to do if the object is recycled soon after.
So when debugging is on, the free list is FIFO
rather than LIFO, which increases our chances that the
code which is still using the object will trip on
the freed object before it is recycled. */
if (vg_dbg || opt_gc_debug) {
#if HAVE_VALGRIND
if (vg_dbg && free_tail != &free_list)
VALGRIND_MAKE_MEM_DEFINED(free_tail, sizeof *free_tail);
#endif
*free_tail = block;
block->t.next = nil;
#if HAVE_VALGRIND
if (vg_dbg) {
if (free_tail != &free_list)
VALGRIND_MAKE_MEM_NOACCESS(free_tail, sizeof *free_tail);
VALGRIND_MAKE_MEM_NOACCESS(block, sizeof *block);
}
#endif
free_tail = &block->t.next;
} else {
block->t.next = free_list;
free_list = block;
}
return 1;
}
NOINLINE static int_ptr_t sweep(void)
{
int_ptr_t free_count = 0;
heap_t **pph;
val hminb = nil, hmaxb = nil;
#if HAVE_VALGRIND
const int vg_dbg = opt_vg_debug;
#endif
#if CONFIG_GEN_GC
if (!full_gc) {
int i;
/* No need to mark block defined via Valgrind API; everything
in the freshobj is an allocated node! */
for (i = 0; i < freshobj_idx; i++)
free_count += sweep_one(freshobj[i]);
/* Generation 1 objects that were indicated for dangerous
mutation must have their REACHABLE flag flipped off,
and must be returned to gen 1. */
for (i = 0; i < mutobj_idx; i++)
sweep_one(mutobj[i]);
return free_count;
}
#endif
for (pph = &heap_list; *pph != 0; ) {
obj_t *block, *end;
heap_t *heap = *pph;
int_ptr_t old_count = free_count;
val old_free_list = free_list;
#if HAVE_VALGRIND
if (vg_dbg)
VALGRIND_MAKE_MEM_DEFINED(&heap->block, sizeof heap->block);
#endif
for (block = heap->block, end = heap->block + HEAP_SIZE;
block < end;
block++)
{
free_count += sweep_one(block);
}
if (free_count - old_count == HEAP_SIZE) {
val *ppf;
free_list = old_free_list;
#if HAVE_VALGRIND
if (vg_dbg) {
val iter;
for (iter = free_list; iter; iter = iter->t.next)
VALGRIND_MAKE_MEM_DEFINED(iter, sizeof *iter);
}
#endif
for (ppf = &free_list; *ppf != nil; ) {
val block = *ppf;
if (block >= heap->block && block < end) {
if ((*ppf = block->t.next) == 0)
free_tail = ppf;
} else {
ppf = &block->t.next;
}
}
*pph = heap->next;
#if CONFIG_NAN_BOXING_STRIP_TAG
free(coerce(heap_t *, coerce(ucnum, heap) | (heap->tag << TAG_BIGSHIFT)));
#else
free(heap);
#endif
#if HAVE_VALGRIND
if (vg_dbg) {
val iter, next;
for (iter = free_list; iter; iter = next) {
next = iter->t.next;
VALGRIND_MAKE_MEM_NOACCESS(iter, sizeof *iter);
}
}
#endif
} else {
if (!hmaxb || end > hmaxb)
hmaxb = end;
if (!hminb || heap->block < hminb)
hminb = heap->block;
pph = &(*pph)->next;
}
}
heap_min_bound = hminb;
heap_max_bound = hmaxb;
return free_count;
}
static int is_reachable(val obj)
{
type_t t;
#if CONFIG_GEN_GC
if (!full_gc && obj->t.gen > 0)
return 1;
#endif
t = obj->t.type;
return (t & REACHABLE) != 0;
}
NOINLINE static void prepare_finals(void)
{
struct fin_reg *f;
if (!final_list)
return;
for (f = final_list; f; f = f->next)
f->reachable = is_reachable(f->obj);
for (f = final_list; f; f = f->next) {
if (!f->reachable) {
mark_obj(f->obj);
}
mark_obj(f->fun);
}
}
static val call_finalizers_impl(val ctx,
int (*should_call)(struct fin_reg *, val))
{
val ret = nil;
for (;;) {
struct fin_reg *f, **tail;
struct fin_reg *found = 0, **ftail = &found;
for (f = final_list, tail = &final_list; f; ) {
struct fin_reg *next = f->next;
if (should_call(f, ctx)) {
*ftail = f;
ftail = &f->next;
} else {
*tail = f;
tail = &f->next;
}
f = next;
}
*ftail = 0;
*tail = 0;
final_tail = tail;
if (!found)
break;
do {
struct fin_reg *next = found->next;
val obj = found->obj;
funcall1(found->fun, obj);
#if CONFIG_GEN_GC
if (--obj->t.fincount == 0 && inprogress &&
!full_gc && !found->reachable)
{
if (freshobj_idx < FRESHOBJ_VEC_SIZE) {
obj->t.gen = 0;
freshobj[freshobj_idx++] = obj;
} else {
full_gc = 1;
}
}
#endif
free(found);
found = next;
ret = t;
} while (found);
}
return ret;
}
static int is_unreachable_final(struct fin_reg *f, val ctx)
{
(void) ctx;
return !f->reachable;
}
NOINLINE static void call_finals(void)
{
(void) call_finalizers_impl(nil, is_unreachable_final);
}
void gc(void)
{
#if CONFIG_GEN_GC
int exhausted = (free_list == 0);
int full_gc_next_time = 0;
static int gc_counter;
#endif
int swept;
mach_context_t *pmc = convert(mach_context_t *, alloca(sizeof *pmc));
assert (gc_enabled);
if (inprogress++)
assert(0 && "gc re-entered");
#if CONFIG_GEN_GC
if (malloc_bytes - prev_malloc_bytes >= opt_gc_delta)
full_gc = 1;
#endif
save_context(*pmc);
gc_enabled = 0;
rcyc_empty();
iobuf_list_empty();
mark(coerce(val *, pmc));
hash_process_weak();
prepare_finals();
swept = sweep();
#if CONFIG_GEN_GC
if (++gc_counter >= FULL_GC_INTERVAL ||
freshobj_idx >= FRESHOBJ_VEC_SIZE)
{
full_gc_next_time = 1;
gc_counter = 0;
}
if (exhausted && full_gc && swept < 3 * HEAP_SIZE / 4)
more();
#else
if (swept < 3 * HEAP_SIZE / 4)
more();
#endif
#if CONFIG_GEN_GC
checkobj_idx = 0;
mutobj_idx = 0;
freshobj_idx = 0;
full_gc = full_gc_next_time;
#endif
call_finals();
gc_enabled = 1;
prev_malloc_bytes = malloc_bytes;
inprogress--;
}
int gc_state(int enabled)
{
int old = gc_enabled;
gc_enabled = enabled;
return old;
}
int gc_inprogress(void)
{
return inprogress;
}
void gc_init(val *stack_bottom)
{
gc_stack_bottom = stack_bottom;
gc_stack_limit = gc_stack_bottom - DFL_STACK_LIMIT / sizeof (val);
#if HAVE_RLIMIT
{
struct rlimit rl;
if (getrlimit(RLIMIT_STACK, &rl) == 0) {
rlim_t lim = rl.rlim_cur;
if (lim != RLIM_INFINITY) {
ptrdiff_t delta = (lim >= MIN_STACK_LIMIT
? (lim - lim / 16)
: MIN_STACK_LIMIT) / sizeof (val);
gc_stack_limit = gc_stack_bottom - delta;
}
}
}
#endif
}
void gc_mark(val obj)
{
mark_obj(obj);
}
void gc_mark_norec(val obj)