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mirror of https://github.com/janet-lang/janet synced 2024-06-21 12:43:15 +00:00
janet/core/gc.c
Calvin Rose d84cc5342e Fix write after free bug.
Remove caching from strings, tuples, and structs.
Keyword style strings removed, now are just symbols. The
compiler can decide to treat symbols with a leading ':'
differently for mostly the same effect. This was done because
as strings are no longer interned, symbols are cheaper to look
up and check for equality.
2017-11-27 14:03:34 -05:00

343 lines
11 KiB
C

/*
* Copyright (c) 2017 Calvin Rose
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <dst/dst.h>
#include "symcache.h"
/* GC State */
void *dst_vm_blocks;
uint32_t dst_vm_memory_interval;
uint32_t dst_vm_next_collection;
/* Helpers for marking the various gc types */
static void dst_mark_funcenv(DstFuncEnv *env);
static void dst_mark_funcdef(DstFuncDef *def);
static void dst_mark_function(DstFunction *func);
static void dst_mark_array(DstArray *array);
static void dst_mark_table(DstTable *table);
static void dst_mark_struct(const DstValue *st);
static void dst_mark_tuple(const DstValue *tuple);
static void dst_mark_buffer(DstBuffer *buffer);
static void dst_mark_string(const uint8_t *str);
static void dst_mark_fiber(DstFiber *fiber);
static void dst_mark_udata(void *udata);
/* Mark a value */
void dst_mark(DstValue x) {
switch (x.type) {
default: break;
case DST_STRING:
case DST_SYMBOL: dst_mark_string(x.as.string); break;
case DST_FUNCTION: dst_mark_function(x.as.function); break;
case DST_ARRAY: dst_mark_array(x.as.array); break;
case DST_TABLE: dst_mark_table(x.as.table); break;
case DST_STRUCT: dst_mark_struct(x.as.st); break;
case DST_TUPLE: dst_mark_tuple(x.as.tuple); break;
case DST_BUFFER: dst_mark_buffer(x.as.buffer); break;
case DST_FIBER: dst_mark_fiber(x.as.fiber); break;
case DST_USERDATA: dst_mark_udata(x.as.pointer); break;
}
}
/* Pin a value. This prevents a value from being garbage collected.
* Needed if the valueis not accesible to the garbage collector, but
* still in use by the program. For example, a c function that
* creates a table, and then runs the garbage collector without
* ever saving the table anywhere (except on the c stack, which
* the gc cannot inspect). */
void dst_pin(DstValue x) {
switch (x.type) {
default: break;
case DST_STRING:
case DST_SYMBOL: dst_pin_string(x.as.string); break;
case DST_FUNCTION: dst_pin_function(x.as.function); break;
case DST_ARRAY: dst_pin_array(x.as.array); break;
case DST_TABLE: dst_pin_table(x.as.table); break;
case DST_STRUCT: dst_pin_struct(x.as.st); break;
case DST_TUPLE: dst_pin_tuple(x.as.tuple); break;
case DST_BUFFER: dst_pin_buffer(x.as.buffer); break;
case DST_FIBER: dst_pin_fiber(x.as.fiber); break;
case DST_USERDATA: dst_pin_userdata(x.as.pointer); break;
}
}
/* Unpin a value. This enables the GC to collect the value's
* memory again. */
void dst_unpin(DstValue x) {
switch (x.type) {
default: break;
case DST_STRING:
case DST_SYMBOL: dst_unpin_string(x.as.string); break;
case DST_FUNCTION: dst_unpin_function(x.as.function); break;
case DST_ARRAY: dst_unpin_array(x.as.array); break;
case DST_TABLE: dst_unpin_table(x.as.table); break;
case DST_STRUCT: dst_unpin_struct(x.as.st); break;
case DST_TUPLE: dst_unpin_tuple(x.as.tuple); break;
case DST_BUFFER: dst_unpin_buffer(x.as.buffer); break;
case DST_FIBER: dst_unpin_fiber(x.as.fiber); break;
case DST_USERDATA: dst_unpin_userdata(x.as.pointer); break;
}
}
static void dst_mark_string(const uint8_t *str) {
dst_gc_mark(dst_string_raw(str));
}
static void dst_mark_buffer(DstBuffer *buffer) {
dst_gc_mark(buffer);
}
static void dst_mark_udata(void *udata) {
dst_gc_mark(dst_userdata_header(udata));
}
/* Mark a bunch of items in memory */
static void dst_mark_many(const DstValue *values, uint32_t n) {
const DstValue *end = values + n;
while (values < end) {
dst_mark(*values);
values += 1;
}
}
static void dst_mark_array(DstArray *array) {
if (dst_gc_reachable(array))
return;
dst_gc_mark(array);
dst_mark_many(array->data, array->count);
}
static void dst_mark_table(DstTable *table) {
if (dst_gc_reachable(table))
return;
dst_gc_mark(table);
dst_mark_many(table->data, table->capacity);
}
static void dst_mark_struct(const DstValue *st) {
if (dst_gc_reachable(dst_struct_raw(st)))
return;
dst_gc_mark(dst_struct_raw(st));
dst_mark_many(st, dst_struct_capacity(st));
}
static void dst_mark_tuple(const DstValue *tuple) {
if (dst_gc_reachable(dst_tuple_raw(tuple)))
return;
dst_gc_mark(dst_tuple_raw(tuple));
dst_mark_many(tuple, dst_tuple_length(tuple));
}
/* Helper to mark function environments */
static void dst_mark_funcenv(DstFuncEnv *env) {
if (dst_gc_reachable(env))
return;
dst_gc_mark(env);
if (env->offset) {
/* On stack */
dst_mark_fiber(env->as.fiber);
} else {
/* Not on stack */
dst_mark_many(env->as.values, env->length);
}
}
/* GC helper to mark a FuncDef */
static void dst_mark_funcdef(DstFuncDef *def) {
uint32_t count, i;
if (dst_gc_reachable(def))
return;
dst_gc_mark(def);
if (def->constants) {
count = def->constants_length;
for (i = 0; i < count; ++i) {
DstValue v = def->constants[i];
/* Funcdefs use boolean literals to store other funcdefs */
if (v.type == DST_BOOLEAN) {
dst_mark_funcdef((DstFuncDef *) v.as.pointer);
} else {
dst_mark(v);
}
}
}
}
static void dst_mark_function(DstFunction *func) {
uint32_t i;
uint32_t numenvs;
if (dst_gc_reachable(func))
return;
dst_gc_mark(func);
numenvs = func->def->environments_length;
if (NULL != func->envs)
for (i = 0; i < numenvs; ++i)
if (NULL != func->envs[i])
dst_mark_funcenv(func->envs[i]);
dst_mark_funcdef(func->def);
}
static void dst_mark_fiber(DstFiber *fiber) {
uint32_t i, j;
DstStackFrame *frame;
if (dst_gc_reachable(fiber))
return;
dst_gc_mark(fiber);
i = fiber->frame;
j = fiber->frametop;
while (i != 0) {
frame = (DstStackFrame *)(fiber->data + i - DST_FRAME_SIZE);
if (NULL != frame->func)
dst_mark_function(frame->func);
/* Mark all values in the stack frame */
dst_mark_many(fiber->data + i, j - i);
j = i - DST_FRAME_SIZE;
i = frame->prevframe;
}
if (NULL != fiber->parent)
dst_mark_fiber(fiber->parent);
dst_mark(fiber->ret);
}
/* Deinitialize a block of memory */
static void dst_deinit_block(DstGCMemoryHeader *block) {
void *mem = ((char *)(block + 1));
DstUserdataHeader *h = (DstUserdataHeader *)mem;
switch (block->flags & DST_MEM_TYPEBITS) {
default:
break; /* Do nothing for non gc types */
case DST_MEMORY_SYMBOL:
dst_symbol_deinit((const uint8_t *)mem + 2 * sizeof(uint32_t));
break;
case DST_MEMORY_ARRAY:
dst_array_deinit((DstArray*) mem);
break;
case DST_MEMORY_TABLE:
dst_table_deinit((DstTable*) mem);
break;
case DST_MEMORY_FIBER:
free(((DstFiber *) mem)->data);
break;
case DST_MEMORY_BUFFER:
dst_buffer_deinit((DstBuffer *) mem);
break;
case DST_MEMORY_FUNCTION:
free(((DstFunction *)mem)->envs);
break;
case DST_MEMORY_USERDATA:
if (h->type->finalize)
h->type->finalize((void *)(h + 1), h->size);
break;
case DST_MEMORY_FUNCENV:
{
DstFuncEnv *env = (DstFuncEnv *)mem;
if (0 == env->offset)
free(env->as.values);
}
break;
case DST_MEMORY_FUNCDEF:
{
DstFuncDef *def = (DstFuncDef *)mem;
/* TODO - get this all with one alloc and one free */
free(def->environments);
free(def->constants);
free(def->bytecode);
}
break;
}
}
/* Iterate over all allocated memory, and free memory that is not
* marked as reachable. Flip the gc color flag for next sweep. */
void dst_sweep() {
DstGCMemoryHeader *previous = NULL;
DstGCMemoryHeader *current = dst_vm_blocks;
DstGCMemoryHeader *next;
while (NULL != current) {
next = current->next;
if (current->flags & (DST_MEM_REACHABLE | DST_MEM_DISABLED)) {
previous = current;
current->flags &= ~DST_MEM_REACHABLE;
} else {
dst_deinit_block(current);
if (NULL != previous) {
previous->next = next;
} else {
dst_vm_blocks = next;
}
free(current);
}
current = next;
}
}
/* Allocate some memory that is tracked for garbage collection */
void *dst_alloc(DstMemoryType type, size_t size) {
DstGCMemoryHeader *mdata;
size_t total = size + sizeof(DstGCMemoryHeader);
/* Make sure everything is inited */
if (NULL == dst_vm_cache) {
DST_PLEASE_INIT;
}
void *mem = malloc(total);
/* Check for bad malloc */
if (NULL == mem) {
DST_OUT_OF_MEMORY;
}
mdata = (DstGCMemoryHeader *)mem;
/* Configure block */
mdata->flags = type;
/* Prepend block to heap list */
dst_vm_next_collection += size;
mdata->next = dst_vm_blocks;
dst_vm_blocks = mdata;
return mem + sizeof(DstGCMemoryHeader);
}
/* Run garbage collection */
void dst_collect() {
if (dst_vm_fiber)
dst_mark_fiber(dst_vm_fiber);
dst_sweep();
dst_vm_next_collection = 0;
}
/* Free all allocated memory */
void dst_clear_memory() {
DstGCMemoryHeader *current = dst_vm_blocks;
while (current) {
dst_deinit_block(current);
DstGCMemoryHeader *next = current->next;
free(current);
current = next;
}
dst_vm_blocks = NULL;
}