gc.c 17.2 KB
Newer Older
Damien's avatar
Damien committed
1
2
#include <stdio.h>
#include <string.h>
mux's avatar
mux committed
3
#include <stdbool.h>
Damien's avatar
Damien committed
4

5
#include "mpconfig.h"
Damien's avatar
Damien committed
6
7
#include "gc.h"

mux's avatar
mux committed
8
9
10
11
#include "misc.h"
#include "qstr.h"
#include "obj.h"

12
13
#if MICROPY_ENABLE_GC

14
15
#if 0 // print debugging info
#define DEBUG_PRINT (1)
16
#define DEBUG_printf DEBUG_printf
17
#else // don't print debugging info
18
#define DEBUG_printf(...) (void)0
19
20
#endif

Damien's avatar
Damien committed
21
22
23
24
25
26
typedef unsigned char byte;

#define WORDS_PER_BLOCK (4)
#define BYTES_PER_BLOCK (WORDS_PER_BLOCK * BYTES_PER_WORD)
#define STACK_SIZE (64) // tunable; minimum is 1

27
STATIC byte *gc_alloc_table_start;
mux's avatar
mux committed
28
STATIC byte *gc_mpobj_table_start;
29
STATIC machine_uint_t gc_alloc_table_byte_len;
mux's avatar
mux committed
30
STATIC machine_uint_t gc_mpobj_table_byte_len;
31
32
STATIC machine_uint_t *gc_pool_start;
STATIC machine_uint_t *gc_pool_end;
Damien's avatar
Damien committed
33

34
35
36
STATIC int gc_stack_overflow;
STATIC machine_uint_t gc_stack[STACK_SIZE];
STATIC machine_uint_t *gc_sp;
Damien's avatar
Damien committed
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67

// ATB = allocation table byte
// 0b00 = FREE -- free block
// 0b01 = HEAD -- head of a chain of blocks
// 0b10 = TAIL -- in the tail of a chain of blocks
// 0b11 = MARK -- marked head block

#define AT_FREE (0)
#define AT_HEAD (1)
#define AT_TAIL (2)
#define AT_MARK (3)

#define BLOCKS_PER_ATB (4)
#define ATB_MASK_0 (0x03)
#define ATB_MASK_1 (0x0c)
#define ATB_MASK_2 (0x30)
#define ATB_MASK_3 (0xc0)

#define ATB_0_IS_FREE(a) (((a) & ATB_MASK_0) == 0)
#define ATB_1_IS_FREE(a) (((a) & ATB_MASK_1) == 0)
#define ATB_2_IS_FREE(a) (((a) & ATB_MASK_2) == 0)
#define ATB_3_IS_FREE(a) (((a) & ATB_MASK_3) == 0)

#define BLOCK_SHIFT(block) (2 * ((block) & (BLOCKS_PER_ATB - 1)))
#define ATB_GET_KIND(block) ((gc_alloc_table_start[(block) / BLOCKS_PER_ATB] >> BLOCK_SHIFT(block)) & 3)
#define ATB_ANY_TO_FREE(block) do { gc_alloc_table_start[(block) / BLOCKS_PER_ATB] &= (~(AT_MARK << BLOCK_SHIFT(block))); } while (0)
#define ATB_FREE_TO_HEAD(block) do { gc_alloc_table_start[(block) / BLOCKS_PER_ATB] |= (AT_HEAD << BLOCK_SHIFT(block)); } while (0)
#define ATB_FREE_TO_TAIL(block) do { gc_alloc_table_start[(block) / BLOCKS_PER_ATB] |= (AT_TAIL << BLOCK_SHIFT(block)); } while (0)
#define ATB_HEAD_TO_MARK(block) do { gc_alloc_table_start[(block) / BLOCKS_PER_ATB] |= (AT_MARK << BLOCK_SHIFT(block)); } while (0)
#define ATB_MARK_TO_HEAD(block) do { gc_alloc_table_start[(block) / BLOCKS_PER_ATB] &= (~(AT_TAIL << BLOCK_SHIFT(block))); } while (0)

mux's avatar
mux committed
68
69
70
71
#define ATB_SET_MPOBJ(block) do { gc_mpobj_table_start[(block) / 8] |= (1<<(block%8)); } while (0)
#define ATB_CLR_MPOBJ(block) do { gc_mpobj_table_start[(block) / 8] &= (~(1<<(block%8))); } while (0)
#define ATB_IS_MPOBJ(block) ((gc_mpobj_table_start[(block) / 8]>>(block%8))&0x01)

Damien's avatar
Damien committed
72
73
74
75
#define BLOCK_FROM_PTR(ptr) (((ptr) - (machine_uint_t)gc_pool_start) / BYTES_PER_BLOCK)
#define PTR_FROM_BLOCK(block) (((block) * BYTES_PER_BLOCK + (machine_uint_t)gc_pool_start))
#define ATB_FROM_BLOCK(bl) ((bl) / BLOCKS_PER_ATB)

76
77
78
79
// TODO waste less memory; currently requires that all entries in alloc_table have a corresponding block in pool
void gc_init(void *start, void *end) {
    // align end pointer on block boundary
    end = (void*)((machine_uint_t)end & (~(BYTES_PER_BLOCK - 1)));
80
    DEBUG_printf("Initializing GC heap: %p-%p\n", start, end);
81
82
83
84
85

    // calculate parameters for GC
    machine_uint_t total_word_len = (machine_uint_t*)end - (machine_uint_t*)start;
    gc_alloc_table_byte_len = total_word_len * BYTES_PER_WORD / (1 + BITS_PER_BYTE / 2 * BYTES_PER_BLOCK);
    gc_alloc_table_start = (byte*)start;
mux's avatar
mux committed
86
87
88
89
90

    gc_mpobj_table_byte_len = (gc_alloc_table_byte_len * BITS_PER_BYTE / 2)/8;
    gc_mpobj_table_start = gc_alloc_table_start+gc_alloc_table_byte_len;

    machine_uint_t gc_pool_block_len = (gc_alloc_table_byte_len * BITS_PER_BYTE / 2) -(gc_mpobj_table_byte_len / BYTES_PER_BLOCK);
91
92
93
94
95
96
97
    machine_uint_t gc_pool_word_len = gc_pool_block_len * WORDS_PER_BLOCK;
    gc_pool_start = (machine_uint_t*)end - gc_pool_word_len;
    gc_pool_end = end;

    // clear ATBs
    memset(gc_alloc_table_start, 0, gc_alloc_table_byte_len);

mux's avatar
mux committed
98
99
100
    // clear MPOBJ flags
    memset(gc_mpobj_table_start, 0, gc_mpobj_table_byte_len);

101
102
103
104
105
106
107
    // allocate first block because gc_pool_start points there and it will never
    // be freed, so allocating 1 block with null pointers will minimise memory loss
    ATB_FREE_TO_HEAD(0);
    for (int i = 0; i < WORDS_PER_BLOCK; i++) {
        gc_pool_start[i] = 0;
    }

108
    DEBUG_printf("GC layout:\n");
109
110
    DEBUG_printf("  alloc table at %p, length " UINT_FMT " bytes\n", gc_alloc_table_start, gc_alloc_table_byte_len);
    DEBUG_printf("  pool at %p, length " UINT_FMT " blocks = " UINT_FMT " words = " UINT_FMT " bytes\n", gc_pool_start, gc_pool_block_len, gc_pool_word_len, gc_pool_word_len * BYTES_PER_WORD);
111
112
}

113
114
115
116
117
118
#define VERIFY_PTR(ptr) ( \
        (ptr & (BYTES_PER_BLOCK - 1)) == 0          /* must be aligned on a block */ \
        && ptr >= (machine_uint_t)gc_pool_start     /* must be above start of pool */ \
        && ptr < (machine_uint_t)gc_pool_end        /* must be below end of pool */ \
    )

Damien's avatar
Damien committed
119
120
#define VERIFY_MARK_AND_PUSH(ptr) \
    do { \
121
        if (VERIFY_PTR(ptr)) { \
Damien's avatar
Damien committed
122
123
124
125
126
127
128
129
130
131
132
133
134
            machine_uint_t _block = BLOCK_FROM_PTR(ptr); \
            if (ATB_GET_KIND(_block) == AT_HEAD) { \
                /* an unmarked head, mark it, and push it on gc stack */ \
                ATB_HEAD_TO_MARK(_block); \
                if (gc_sp < &gc_stack[STACK_SIZE]) { \
                    *gc_sp++ = _block; \
                } else { \
                    gc_stack_overflow = 1; \
                } \
            } \
        } \
    } while (0)

135
STATIC void gc_drain_stack(void) {
Damien's avatar
Damien committed
136
137
138
139
    while (gc_sp > gc_stack) {
        // pop the next block off the stack
        machine_uint_t block = *--gc_sp;

140
        // work out number of consecutive blocks in the chain starting with this one
Damien's avatar
Damien committed
141
142
143
144
145
146
147
148
149
150
151
152
153
154
        machine_uint_t n_blocks = 0;
        do {
            n_blocks += 1;
        } while (ATB_GET_KIND(block + n_blocks) == AT_TAIL);

        // check this block's children
        machine_uint_t *scan = (machine_uint_t*)PTR_FROM_BLOCK(block);
        for (machine_uint_t i = n_blocks * WORDS_PER_BLOCK; i > 0; i--, scan++) {
            machine_uint_t ptr2 = *scan;
            VERIFY_MARK_AND_PUSH(ptr2);
        }
    }
}

155
STATIC void gc_deal_with_stack_overflow(void) {
Damien's avatar
Damien committed
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
    while (gc_stack_overflow) {
        gc_stack_overflow = 0;
        gc_sp = gc_stack;

        // scan entire memory looking for blocks which have been marked but not their children
        for (machine_uint_t block = 0; block < gc_alloc_table_byte_len * BLOCKS_PER_ATB; block++) {
            // trace (again) if mark bit set
            if (ATB_GET_KIND(block) == AT_MARK) {
                *gc_sp++ = block;
                gc_drain_stack();
            }
        }
    }
}

171
STATIC void gc_sweep(void) {
Damien's avatar
Damien committed
172
173
174
175
176
    // free unmarked heads and their tails
    int free_tail = 0;
    for (machine_uint_t block = 0; block < gc_alloc_table_byte_len * BLOCKS_PER_ATB; block++) {
        switch (ATB_GET_KIND(block)) {
            case AT_HEAD:
mux's avatar
mux committed
177
178
179
180
181
182
183
184
                if (ATB_IS_MPOBJ(block)) {
                    ATB_CLR_MPOBJ(block); // clear mpobj flag
                    mp_obj_t *self = (mp_obj_t*)PTR_FROM_BLOCK(block);
                    mp_obj_type_t *type= mp_obj_get_type(self);
                    if (type->del != NULL) {
                        type->del(self);
                    }
                }
Damien's avatar
Damien committed
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
                free_tail = 1;
                // fall through to free the head

            case AT_TAIL:
                if (free_tail) {
                    ATB_ANY_TO_FREE(block);
                }
                break;

            case AT_MARK:
                ATB_MARK_TO_HEAD(block);
                free_tail = 0;
                break;
        }
    }
}

202
void gc_collect_start(void) {
Damien's avatar
Damien committed
203
204
205
206
207
208
209
210
211
212
213
214
    gc_stack_overflow = 0;
    gc_sp = gc_stack;
}

void gc_collect_root(void **ptrs, machine_uint_t len) {
    for (machine_uint_t i = 0; i < len; i++) {
        machine_uint_t ptr = (machine_uint_t)ptrs[i];
        VERIFY_MARK_AND_PUSH(ptr);
        gc_drain_stack();
    }
}

215
void gc_collect_end(void) {
Damien's avatar
Damien committed
216
217
    gc_deal_with_stack_overflow();
    gc_sweep();
218
}
Damien's avatar
Damien committed
219

220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
void gc_info(gc_info_t *info) {
    info->total = (gc_pool_end - gc_pool_start) * sizeof(machine_uint_t);
    info->used = 0;
    info->free = 0;
    info->num_1block = 0;
    info->num_2block = 0;
    info->max_block = 0;
    for (machine_uint_t block = 0, len = 0; block < gc_alloc_table_byte_len * BLOCKS_PER_ATB; block++) {
        machine_uint_t kind = ATB_GET_KIND(block);
        if (kind == AT_FREE || kind == AT_HEAD) {
            if (len == 1) {
                info->num_1block += 1;
            } else if (len == 2) {
                info->num_2block += 1;
            }
            if (len > info->max_block) {
                info->max_block = len;
            }
        }
        switch (kind) {
Damien's avatar
Damien committed
240
            case AT_FREE:
241
242
                info->free += 1;
                len = 0;
Damien's avatar
Damien committed
243
244
245
                break;

            case AT_HEAD:
246
247
248
249
                info->used += 1;
                len = 1;
                break;

Damien's avatar
Damien committed
250
            case AT_TAIL:
251
252
                info->used += 1;
                len += 1;
Damien's avatar
Damien committed
253
254
255
                break;

            case AT_MARK:
256
                // shouldn't happen
Damien's avatar
Damien committed
257
258
259
260
                break;
        }
    }

261
262
    info->used *= BYTES_PER_BLOCK;
    info->free *= BYTES_PER_BLOCK;
Damien's avatar
Damien committed
263
264
}

mux's avatar
mux committed
265
void *_gc_alloc(machine_uint_t n_bytes, bool is_mpobj) {
Damien's avatar
Damien committed
266
    machine_uint_t n_blocks = ((n_bytes + BYTES_PER_BLOCK - 1) & (~(BYTES_PER_BLOCK - 1))) / BYTES_PER_BLOCK;
267
    DEBUG_printf("gc_alloc(" UINT_FMT " bytes -> " UINT_FMT " blocks)\n", n_bytes, n_blocks);
Damien's avatar
Damien committed
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293

    // check for 0 allocation
    if (n_blocks == 0) {
        return NULL;
    }

    machine_uint_t i;
    machine_uint_t end_block;
    machine_uint_t start_block;
    machine_uint_t n_free = 0;
    int collected = 0;
    for (;;) {

        // look for a run of n_blocks available blocks
        for (i = 0; i < gc_alloc_table_byte_len; i++) {
            byte a = gc_alloc_table_start[i];
            if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
            if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
            if (ATB_2_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 2; goto found; } } else { n_free = 0; }
            if (ATB_3_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 3; goto found; } } else { n_free = 0; }
        }

        // nothing found!
        if (collected) {
            return NULL;
        }
294
        DEBUG_printf("gc_alloc(" UINT_FMT "): no free mem, triggering GC\n", n_bytes);
Damien's avatar
Damien committed
295
296
297
298
299
300
301
302
303
304
305
306
307
        gc_collect();
        collected = 1;
    }

    // found, ending at block i inclusive
found:
    // get starting and end blocks, both inclusive
    end_block = i;
    start_block = i - n_free + 1;

    // mark first block as used head
    ATB_FREE_TO_HEAD(start_block);

mux's avatar
mux committed
308
309
310
311
    if (is_mpobj) {
        ATB_SET_MPOBJ(start_block);
    }

Damien's avatar
Damien committed
312
313
314
315
316
317
318
319
320
321
    // mark rest of blocks as used tail
    // TODO for a run of many blocks can make this more efficient
    for (machine_uint_t bl = start_block + 1; bl <= end_block; bl++) {
        ATB_FREE_TO_TAIL(bl);
    }

    // return pointer to first block
    return (void*)(gc_pool_start + start_block * WORDS_PER_BLOCK);
}

mux's avatar
mux committed
322
323
324
325
326
327
328
329
void *gc_alloc(machine_uint_t n_bytes) {
    return _gc_alloc(n_bytes, false);
}

void *gc_alloc_mp_obj(machine_uint_t n_bytes) {
    return _gc_alloc(n_bytes, true);
}

330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
// force the freeing of a piece of memory
void gc_free(void *ptr_in) {
    machine_uint_t ptr = (machine_uint_t)ptr_in;

    if (VERIFY_PTR(ptr)) {
        machine_uint_t block = BLOCK_FROM_PTR(ptr);
        if (ATB_GET_KIND(block) == AT_HEAD) {
            // free head and all of its tail blocks
            do {
                ATB_ANY_TO_FREE(block);
                block += 1;
            } while (ATB_GET_KIND(block) == AT_TAIL);
        }
    }
}

Damien's avatar
Damien committed
346
347
348
machine_uint_t gc_nbytes(void *ptr_in) {
    machine_uint_t ptr = (machine_uint_t)ptr_in;

349
    if (VERIFY_PTR(ptr)) {
Damien's avatar
Damien committed
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
        machine_uint_t block = BLOCK_FROM_PTR(ptr);
        if (ATB_GET_KIND(block) == AT_HEAD) {
            // work out number of consecutive blocks in the chain starting with this on
            machine_uint_t n_blocks = 0;
            do {
                n_blocks += 1;
            } while (ATB_GET_KIND(block + n_blocks) == AT_TAIL);
            return n_blocks * BYTES_PER_BLOCK;
        }
    }

    // invalid pointer
    return 0;
}

mux's avatar
mux committed
365
#if 0
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
// use this realloc for now, one below is broken
void *gc_realloc(void *ptr, machine_uint_t n_bytes) {
    machine_uint_t n_existing = gc_nbytes(ptr);
    if (n_bytes <= n_existing) {
        return ptr;
    } else {
        // TODO check if we can grow inplace
        void *ptr2 = gc_alloc(n_bytes);
        if (ptr2 == NULL) {
            return ptr2;
        }
        memcpy(ptr2, ptr, n_existing);
        gc_free(ptr);
        return ptr2;
    }
}
mux's avatar
mux committed
382
#else
mux's avatar
mux committed
383
384
void *gc_realloc(void *ptr_in, machine_uint_t n_bytes) {
    void *ptr_out = NULL;
385
    machine_uint_t block = 0;
mux's avatar
mux committed
386
387
388
389
390
391
    machine_uint_t ptr = (machine_uint_t)ptr_in;

    if (ptr_in == NULL) {
        return gc_alloc(n_bytes);
    }

Damien George's avatar
Damien George committed
392
393
394
    if (VERIFY_PTR(ptr)                         // verify pointer
        && (block = BLOCK_FROM_PTR(ptr))        // get first block
        && ATB_GET_KIND(block) == AT_HEAD) {    // make sure it's a HEAD block
mux's avatar
mux committed
395
396
397

        byte block_type;
        machine_uint_t n_free   = 0;
Damien George's avatar
Damien George committed
398
        machine_uint_t n_blocks = 1; // counting HEAD block
mux's avatar
mux committed
399
        machine_uint_t max_block = gc_alloc_table_byte_len * BLOCKS_PER_ATB;
mux's avatar
mux committed
400

Damien George's avatar
Damien George committed
401
402
403
        // get the number of consecutive tail blocks and
        // the number of free blocks after last tail block
        // stop if we reach (or are at) end of heap
mux's avatar
mux committed
404
        while ((block + n_blocks + n_free) < max_block
Damien George's avatar
Damien George committed
405
                // stop as soon as we find enough blocks for n_bytes
mux's avatar
mux committed
406
                && (n_bytes > ((n_blocks+n_free) * BYTES_PER_BLOCK))
Damien George's avatar
Damien George committed
407
                // stop if block is HEAD
mux's avatar
mux committed
408
                && (block_type = ATB_GET_KIND(block + n_blocks + n_free)) != AT_HEAD) {
mux's avatar
mux committed
409
410
411
412
413
            switch (block_type) {
                case AT_FREE: n_free++; break;
                case AT_TAIL: n_blocks++; break;
                default: break;
            }
mux's avatar
mux committed
414
        }
Damien George's avatar
Damien George committed
415
        // number of allocated bytes
mux's avatar
mux committed
416
417
        machine_uint_t n_existing = n_blocks * BYTES_PER_BLOCK;

Damien George's avatar
Damien George committed
418
        // check if realloc'ing to a smaller size
mux's avatar
mux committed
419
420
        if (n_bytes <= n_existing) {
            ptr_out = ptr_in;
Damien George's avatar
Damien George committed
421
            // free unneeded tail blocks
422
423
            for (machine_uint_t bl = block + n_blocks; ATB_GET_KIND(bl) == AT_TAIL; bl++) {
                ATB_ANY_TO_FREE(bl);
mux's avatar
mux committed
424
425
            }

Damien George's avatar
Damien George committed
426
        // check if we can expand in place
mux's avatar
mux committed
427
        } else if (n_bytes <= (n_existing + (n_free * BYTES_PER_BLOCK))) {
Damien George's avatar
Damien George committed
428
            // number of blocks needed to expand +1 if there's a remainder
mux's avatar
mux committed
429
430
431
432
433
434
            machine_uint_t n_diff = ( n_bytes - n_existing)/BYTES_PER_BLOCK+
                                    ((n_bytes - n_existing)%BYTES_PER_BLOCK!=0);

            DEBUG_printf("gc_realloc: expanding " UINT_FMT " blocks (" UINT_FMT " bytes) to " UINT_FMT " blocks (" UINT_FMT " bytes)\n",
                    n_existing/BYTES_PER_BLOCK, n_existing, n_existing/BYTES_PER_BLOCK+n_diff, n_existing + n_diff*BYTES_PER_BLOCK);

Damien George's avatar
Damien George committed
435
            // mark rest of blocks as used tail
436
            for (machine_uint_t bl = block + n_blocks; bl < (block + n_blocks + n_diff); bl++) {
mux's avatar
mux committed
437
438
439
440
                ATB_FREE_TO_TAIL(bl);
            }
            ptr_out = ptr_in;

Damien George's avatar
Damien George committed
441
        // try to find a new contiguous chain
mux's avatar
mux committed
442
        } else if ((ptr_out = gc_alloc(n_bytes)) != NULL) {
Damien George's avatar
Damien George committed
443
            DEBUG_printf("gc_realloc: allocating new block\n");
mux's avatar
mux committed
444
445
            memcpy(ptr_out, ptr_in, n_existing);
            gc_free(ptr_in);
446
        }
Damien's avatar
Damien committed
447
    }
mux's avatar
mux committed
448
449

    return ptr_out;
Damien's avatar
Damien committed
450
}
mux's avatar
mux committed
451

452
#endif
Damien's avatar
Damien committed
453

454
455
456
457
458
459
460
461
void gc_dump_info() {
    gc_info_t info;
    gc_info(&info);
    printf("GC: total: " UINT_FMT ", used: " UINT_FMT ", free: " UINT_FMT "\n", info.total, info.used, info.free);
    printf(" No. of 1-blocks: " UINT_FMT ", 2-blocks: " UINT_FMT ", max blk sz: " UINT_FMT "\n",
           info.num_1block, info.num_2block, info.max_block);
}

462
463
void gc_dump_alloc_table(void) {
    printf("GC memory layout:");
464
    for (machine_uint_t bl = 0; bl < gc_alloc_table_byte_len * BLOCKS_PER_ATB; bl++) {
465
466
467
468
        if (bl % 64 == 0) {
            printf("\n%04x: ", (uint)bl);
        }
        int c = ' ';
469
        switch (ATB_GET_KIND(bl)) {
470
471
472
473
            case AT_FREE: c = '.'; break;
            case AT_HEAD: c = 'h'; break;
            case AT_TAIL: c = 't'; break;
            case AT_MARK: c = 'm'; break;
474
        }
475
        printf("%c", c);
476
    }
477
    printf("\n");
478
479
}

480
#if DEBUG_PRINT
481
482
void gc_test(void) {
    machine_uint_t len = 500;
Damien's avatar
Damien committed
483
484
485
486
    machine_uint_t *heap = malloc(len);
    gc_init(heap, heap + len / sizeof(machine_uint_t));
    void *ptrs[100];
    {
487
        machine_uint_t **p = gc_alloc(16);
Damien's avatar
Damien committed
488
489
490
491
        p[0] = gc_alloc(64);
        p[1] = gc_alloc(1);
        p[2] = gc_alloc(1);
        p[3] = gc_alloc(1);
492
        machine_uint_t ***p2 = gc_alloc(16);
Damien's avatar
Damien committed
493
494
495
496
        p2[0] = p;
        p2[1] = p;
        ptrs[0] = p2;
    }
497
    for (int i = 0; i < 25; i+=2) {
Damien's avatar
Damien committed
498
499
500
501
502
503
504
        machine_uint_t *p = gc_alloc(i);
        printf("p=%p\n", p);
        if (i & 3) {
            //ptrs[i] = p;
        }
    }

505
    printf("Before GC:\n");
506
    gc_dump_alloc_table();
507
508
509
510
511
    printf("Starting GC...\n");
    gc_collect_start();
    gc_collect_root(ptrs, sizeof(ptrs) / sizeof(void*));
    gc_collect_end();
    printf("After GC:\n");
512
    gc_dump_alloc_table();
Damien's avatar
Damien committed
513
}
514
#endif
515
516

#endif // MICROPY_ENABLE_GC