git.ozlabs.org Git - ccan/blob - ccan/tal/tal.c

   1 /* Licensed under BSD-MIT - see LICENSE file for details */
   2 #include <ccan/tal/tal.h>
   3 #include <ccan/compiler/compiler.h>
   4 #include <ccan/list/list.h>
   5 #include <ccan/take/take.h>
   6 #include <assert.h>
   7 #include <stdio.h>
   8 #include <stdarg.h>
   9 #include <stddef.h>
  10 #include <string.h>
  11 #include <limits.h>
  12 #include <errno.h>
  13
  14 //#define TAL_DEBUG 1
  15
  16 #define NOTIFY_IS_DESTRUCTOR 512
  17
  18 /* 32-bit type field, first byte 0 in either endianness. */
  19 enum prop_type {
  20         CHILDREN = 0x00c1d500,
  21         NAME = 0x00111100,
  22         NOTIFIER = 0x00071f00,
  23         LENGTH = 0x00515300
  24 };
  25
  26 struct tal_hdr {
  27         struct list_node list;
  28         struct prop_hdr *prop;
  29         struct children *parent_child;
  30 };
  31
  32 struct prop_hdr {
  33         enum prop_type type;
  34         struct prop_hdr *next;
  35 };
  36
  37 struct children {
  38         struct prop_hdr hdr; /* CHILDREN */
  39         struct tal_hdr *parent;
  40         struct list_head children; /* Head of siblings. */
  41 };
  42
  43 struct name {
  44         struct prop_hdr hdr; /* NAME */
  45         char name[];
  46 };
  47
  48 struct length {
  49         struct prop_hdr hdr; /* LENGTH */
  50         size_t count;
  51 };
  52
  53 struct notifier {
  54         struct prop_hdr hdr; /* NOTIFIER */
  55         enum tal_notify_type types;
  56         union {
  57                 void (*notifyfn)(tal_t *, enum tal_notify_type, void *);
  58                 void (*destroy)(tal_t *); /* If NOTIFY_IS_DESTRUCTOR set */
  59         } u;
  60 };
  61
  62 static struct {
  63         struct tal_hdr hdr;
  64         struct children c;
  65 } null_parent = { { { &null_parent.hdr.list, &null_parent.hdr.list },
  66                     &null_parent.c.hdr, NULL },
  67                   { { CHILDREN, NULL },
  68                     &null_parent.hdr,
  69                     { { &null_parent.c.children.n,
  70                         &null_parent.c.children.n } }
  71                   }
  72 };
  73
  74
  75 static void *(*allocfn)(size_t size) = malloc;
  76 static void *(*resizefn)(void *, size_t size) = realloc;
  77 static void (*freefn)(void *) = free;
  78 static void (*errorfn)(const char *msg) = (void *)abort;
  79 static bool initialized = false;
  80 /* Count on non-destrutor notifiers; often stays zero. */
  81 static size_t notifiers = 0;
  82
  83 static inline void COLD call_error(const char *msg)
  84 {
  85         errorfn(msg);
  86 }
  87
  88 static bool get_destroying_bit(struct children *parent_child)
  89 {
  90         return (size_t)parent_child & 1;
  91 }
  92
  93 static void set_destroying_bit(struct children **parent_child)
  94 {
  95         *parent_child = (void *)((size_t)*parent_child | 1);
  96 }
  97
  98 static struct children *ignore_destroying_bit(struct children *parent_child)
  99 {
 100         return (void *)((size_t)parent_child & ~(size_t)1);
 101 }
 102
 103 /* This means valgrind can see leaks. */
 104 static void tal_cleanup(void)
 105 {
 106         struct tal_hdr *i;
 107
 108         while ((i = list_top(&null_parent.c.children, struct tal_hdr, list)))
 109                 list_del(&i->list);
 110
 111         /* Cleanup any taken pointers. */
 112         take_cleanup();
 113 }
 114
 115 /* For allocation failures inside ccan/take */
 116 static void take_alloc_failed(const void *p)
 117 {
 118         tal_free(p);
 119 }
 120
 121 /* We carefully start all real properties with a zero byte. */
 122 static bool is_literal(const struct prop_hdr *prop)
 123 {
 124         return ((char *)prop)[0] != 0;
 125 }
 126
 127 #ifndef NDEBUG
 128 static const void *bounds_start, *bounds_end;
 129
 130 static void update_bounds(const void *new, size_t size)
 131 {
 132         if (unlikely(!bounds_start)) {
 133                 bounds_start = new;
 134                 bounds_end = (char *)new + size;
 135         } else if (new < bounds_start)
 136                 bounds_start = new;
 137         else if ((char *)new + size > (char *)bounds_end)
 138                 bounds_end = (char *)new + size;
 139 }
 140
 141 static bool in_bounds(const void *p)
 142 {
 143         return !p
 144                 || (p >= (void *)&null_parent && p <= (void *)(&null_parent + 1))
 145                 || (p >= bounds_start && p <= bounds_end);
 146 }
 147 #else
 148 static void update_bounds(const void *new, size_t size)
 149 {
 150 }
 151
 152 static bool in_bounds(const void *p)
 153 {
 154         return true;
 155 }
 156 #endif
 157
 158 static void check_bounds(const void *p)
 159 {
 160         if (!in_bounds(p))
 161                 call_error("Not a valid header");
 162 }
 163
 164 static struct tal_hdr *to_tal_hdr(const void *ctx)
 165 {
 166         struct tal_hdr *t;
 167
 168         t = (struct tal_hdr *)((char *)ctx - sizeof(struct tal_hdr));
 169         check_bounds(t);
 170         check_bounds(ignore_destroying_bit(t->parent_child));
 171         check_bounds(t->list.next);
 172         check_bounds(t->list.prev);
 173         if (t->prop && !is_literal(t->prop))
 174                 check_bounds(t->prop);
 175         return t;
 176 }
 177
 178 static struct tal_hdr *to_tal_hdr_or_null(const void *ctx)
 179 {
 180         if (!ctx)
 181                 return &null_parent.hdr;
 182         return to_tal_hdr(ctx);
 183 }
 184
 185 static void *from_tal_hdr(const struct tal_hdr *hdr)
 186 {
 187         return (void *)(hdr + 1);
 188 }
 189
 190 #ifdef TAL_DEBUG
 191 static void *from_tal_hdr_or_null(struct tal_hdr *hdr)
 192 {
 193         if (hdr == &null_parent.hdr)
 194                 return NULL;
 195         return from_tal_hdr(hdr);
 196 }
 197
 198 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
 199 {
 200         tal_check(from_tal_hdr_or_null(tal), "TAL_DEBUG ");
 201         return tal;
 202 }
 203 #else
 204 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
 205 {
 206         return tal;
 207 }
 208 #endif
 209
 210 static void notify(const struct tal_hdr *ctx,
 211                    enum tal_notify_type type, const void *info)
 212 {
 213         const struct prop_hdr *p;
 214
 215         for (p = ctx->prop; p; p = p->next) {
 216                 struct notifier *n;
 217
 218                 if (is_literal(p))
 219                         break;
 220                 if (p->type != NOTIFIER)
 221                         continue;
 222                 n = (struct notifier *)p;
 223                 if (n->types & type) {
 224                         if (n->types & NOTIFY_IS_DESTRUCTOR)
 225                                 n->u.destroy(from_tal_hdr(ctx));
 226                         else
 227                                 n->u.notifyfn(from_tal_hdr(ctx), type,
 228                                               (void *)info);
 229                 }
 230         }
 231 }
 232
 233 static void *allocate(size_t size)
 234 {
 235         void *ret = allocfn(size);
 236         if (!ret)
 237                 call_error("allocation failed");
 238         else
 239                 update_bounds(ret, size);
 240         return ret;
 241 }
 242
 243 static struct prop_hdr **find_property_ptr(const struct tal_hdr *t,
 244                                            enum prop_type type)
 245 {
 246         struct prop_hdr **p;
 247
 248         for (p = (struct prop_hdr **)&t->prop; *p; p = &(*p)->next) {
 249                 if (is_literal(*p)) {
 250                         if (type == NAME)
 251                                 return p;
 252                         break;
 253                 }
 254                 if ((*p)->type == type)
 255                         return p;
 256         }
 257         return NULL;
 258 }
 259
 260 static void *find_property(const struct tal_hdr *parent, enum prop_type type)
 261 {
 262         struct prop_hdr **p = find_property_ptr(parent, type);
 263
 264         if (p)
 265                 return *p;
 266         return NULL;
 267 }
 268
 269 static void init_property(struct prop_hdr *hdr,
 270                           struct tal_hdr *parent,
 271                           enum prop_type type)
 272 {
 273         hdr->type = type;
 274         hdr->next = parent->prop;
 275         parent->prop = hdr;
 276 }
 277
 278 static struct notifier *add_notifier_property(struct tal_hdr *t,
 279                                               enum tal_notify_type types,
 280                                               void (*fn)(void *,
 281                                                          enum tal_notify_type,
 282                                                          void *))
 283 {
 284         struct notifier *prop = allocate(sizeof(*prop));
 285         if (prop) {
 286                 init_property(&prop->hdr, t, NOTIFIER);
 287                 prop->types = types;
 288                 prop->u.notifyfn = fn;
 289         }
 290         return prop;
 291 }
 292
 293 static enum tal_notify_type del_notifier_property(struct tal_hdr *t,
 294                                                   void (*fn)(tal_t *,
 295                                                              enum tal_notify_type,
 296                                                              void *))
 297 {
 298         struct prop_hdr **p;
 299
 300         for (p = (struct prop_hdr **)&t->prop; *p; p = &(*p)->next) {
 301                 struct notifier *n;
 302
 303                 if (is_literal(*p))
 304                         break;
 305                 if ((*p)->type != NOTIFIER)
 306                         continue;
 307                 n = (struct notifier *)*p;
 308                 if (n->u.notifyfn == fn) {
 309                         enum tal_notify_type types = n->types;
 310                         *p = (*p)->next;
 311                         freefn(n);
 312                         return types & ~NOTIFY_IS_DESTRUCTOR;
 313                 }
 314         }
 315         return 0;
 316 }
 317
 318 static struct name *add_name_property(struct tal_hdr *t, const char *name)
 319 {
 320         struct name *prop;
 321
 322         prop = allocate(sizeof(*prop) + strlen(name) + 1);
 323         if (prop) {
 324                 init_property(&prop->hdr, t, NAME);
 325                 strcpy(prop->name, name);
 326         }
 327         return prop;
 328 }
 329
 330 static struct length *add_length_property(struct tal_hdr *t, size_t count)
 331 {
 332         struct length *prop;
 333
 334         prop = allocate(sizeof(*prop));
 335         if (prop) {
 336                 init_property(&prop->hdr, t, LENGTH);
 337                 prop->count = count;
 338         }
 339         return prop;
 340 }
 341
 342 static struct children *add_child_property(struct tal_hdr *parent,
 343                                            struct tal_hdr *child)
 344 {
 345         struct children *prop = allocate(sizeof(*prop));
 346         if (prop) {
 347                 init_property(&prop->hdr, parent, CHILDREN);
 348                 prop->parent = parent;
 349                 list_head_init(&prop->children);
 350         }
 351         return prop;
 352 }
 353
 354 static bool add_child(struct tal_hdr *parent, struct tal_hdr *child)
 355 {
 356         struct children *children = find_property(parent, CHILDREN);
 357
 358         if (!children) {
 359                 if (unlikely(!initialized)) {
 360                         atexit(tal_cleanup);
 361                         take_allocfail(take_alloc_failed);
 362                         initialized = true;
 363                 }
 364                 children = add_child_property(parent, child);
 365                 if (!children)
 366                         return false;
 367         }
 368         list_add(&children->children, &child->list);
 369         child->parent_child = children;
 370         return true;
 371 }
 372
 373 static void del_tree(struct tal_hdr *t, const tal_t *orig)
 374 {
 375         struct prop_hdr **prop, *p, *next;
 376
 377         /* Already being destroyed?  Don't loop. */
 378         if (unlikely(get_destroying_bit(t->parent_child)))
 379                 return;
 380
 381         set_destroying_bit(&t->parent_child);
 382
 383         /* Call free notifiers. */
 384         notify(t, TAL_NOTIFY_FREE, (tal_t *)orig);
 385
 386         /* Now free children and groups. */
 387         prop = find_property_ptr(t, CHILDREN);
 388         if (prop) {
 389                 struct tal_hdr *i;
 390                 struct children *c = (struct children *)*prop;
 391
 392                 while ((i = list_top(&c->children, struct tal_hdr, list))) {
 393                         list_del(&i->list);
 394                         del_tree(i, orig);
 395                 }
 396         }
 397
 398         /* Finally free our properties. */
 399         for (p = t->prop; p && !is_literal(p); p = next) {
 400                 next = p->next;
 401                 freefn(p);
 402         }
 403         freefn(t);
 404 }
 405
 406 void *tal_alloc_(const tal_t *ctx, size_t size, bool clear, const char *label)
 407 {
 408         struct tal_hdr *child, *parent = debug_tal(to_tal_hdr_or_null(ctx));
 409
 410         child = allocate(sizeof(struct tal_hdr) + size);
 411         if (!child)
 412                 return NULL;
 413         if (clear)
 414                 memset(from_tal_hdr(child), 0, size);
 415         child->prop = (void *)label;
 416         if (!add_child(parent, child)) {
 417                 freefn(child);
 418                 return NULL;
 419         }
 420         debug_tal(parent);
 421         if (notifiers)
 422                 notify(parent, TAL_NOTIFY_ADD_CHILD, from_tal_hdr(child));
 423         return from_tal_hdr(debug_tal(child));
 424 }
 425
 426 static bool adjust_size(size_t *size, size_t count)
 427 {
 428         /* Multiplication wrap */
 429         if (count && unlikely(*size * count / *size != count))
 430                 goto overflow;
 431
 432         *size *= count;
 433
 434         /* Make sure we don't wrap adding header. */
 435         if (*size + sizeof(struct tal_hdr) < sizeof(struct tal_hdr))
 436                 goto overflow;
 437         return true;
 438 overflow:
 439         call_error("allocation size overflow");
 440         return false;
 441 }
 442
 443 void *tal_alloc_arr_(const tal_t *ctx, size_t size, size_t count, bool clear,
 444                      bool add_count, const char *label)
 445 {
 446         void *ret;
 447
 448         if (!adjust_size(&size, count))
 449                 return NULL;
 450
 451         ret = tal_alloc_(ctx, size, clear, label);
 452         if (likely(ret) && add_count) {
 453                 if (unlikely(!add_length_property(to_tal_hdr(ret), count)))
 454                         ret = tal_free(ret);
 455         }
 456         return ret;
 457 }
 458
 459 void *tal_free(const tal_t *ctx)
 460 {
 461         if (ctx) {
 462                 struct tal_hdr *t;
 463                 int saved_errno = errno;
 464                 t = debug_tal(to_tal_hdr(ctx));
 465                 if (notifiers)
 466                         notify(ignore_destroying_bit(t->parent_child)->parent,
 467                                TAL_NOTIFY_DEL_CHILD, ctx);
 468                 list_del(&t->list);
 469                 del_tree(t, ctx);
 470                 errno = saved_errno;
 471         }
 472         return NULL;
 473 }
 474
 475 void *tal_steal_(const tal_t *new_parent, const tal_t *ctx)
 476 {
 477         if (ctx) {
 478                 struct tal_hdr *newpar, *t, *old_parent;
 479
 480                 newpar = debug_tal(to_tal_hdr_or_null(new_parent));
 481                 t = debug_tal(to_tal_hdr(ctx));
 482
 483                 /* Unlink it from old parent. */
 484                 list_del(&t->list);
 485                 old_parent = ignore_destroying_bit(t->parent_child)->parent;
 486
 487                 if (unlikely(!add_child(newpar, t))) {
 488                         /* We can always add to old parent, becuase it has a
 489                          * children property already. */
 490                         if (!add_child(old_parent, t))
 491                                 abort();
 492                         return NULL;
 493                 }
 494                 debug_tal(newpar);
 495                 if (notifiers)
 496                         notify(t, TAL_NOTIFY_STEAL, new_parent);
 497         }
 498         return (void *)ctx;
 499 }
 500
 501 bool tal_add_destructor_(const tal_t *ctx, void (*destroy)(void *me))
 502 {
 503         tal_t *t = debug_tal(to_tal_hdr(ctx));
 504         return add_notifier_property(t, TAL_NOTIFY_FREE|NOTIFY_IS_DESTRUCTOR,
 505                                      (void *)destroy);
 506 }
 507
 508 bool tal_add_notifier_(const tal_t *ctx, enum tal_notify_type types,
 509                        void (*callback)(tal_t *, enum tal_notify_type, void *))
 510 {
 511         tal_t *t = debug_tal(to_tal_hdr(ctx));
 512         struct notifier *n;
 513
 514         assert(types);
 515         assert((types & ~(TAL_NOTIFY_FREE | TAL_NOTIFY_STEAL | TAL_NOTIFY_MOVE
 516                           | TAL_NOTIFY_RESIZE | TAL_NOTIFY_RENAME
 517                           | TAL_NOTIFY_ADD_CHILD | TAL_NOTIFY_DEL_CHILD
 518                           | TAL_NOTIFY_ADD_NOTIFIER
 519                           | TAL_NOTIFY_DEL_NOTIFIER)) == 0);
 520
 521         /* Don't call notifier about itself: set types after! */
 522         n = add_notifier_property(t, 0, callback);
 523         if (unlikely(!n))
 524                 return false;
 525
 526         if (notifiers)
 527                 notify(t, TAL_NOTIFY_ADD_NOTIFIER, callback);
 528
 529         n->types = types;
 530         if (types != TAL_NOTIFY_FREE)
 531                 notifiers++;
 532         return true;
 533 }
 534
 535 bool tal_del_notifier_(const tal_t *ctx,
 536                        void (*callback)(tal_t *, enum tal_notify_type, void *))
 537 {
 538         struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
 539         enum tal_notify_type types;
 540
 541         types = del_notifier_property(t, callback);
 542         if (types) {
 543                 notify(t, TAL_NOTIFY_DEL_NOTIFIER, callback);
 544                 if (types != TAL_NOTIFY_FREE)
 545                         notifiers--;
 546                 return true;
 547         }
 548         return false;
 549 }
 550
 551 bool tal_del_destructor_(const tal_t *ctx, void (*destroy)(void *me))
 552 {
 553         return tal_del_notifier_(ctx, (void *)destroy);
 554 }
 555
 556 bool tal_set_name_(tal_t *ctx, const char *name, bool literal)
 557 {
 558         struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
 559         struct prop_hdr **prop = find_property_ptr(t, NAME);
 560
 561         /* Get rid of any old name */
 562         if (prop) {
 563                 struct name *name = (struct name *)*prop;
 564                 if (is_literal(&name->hdr))
 565                         *prop = NULL;
 566                 else {
 567                         *prop = name->hdr.next;
 568                         freefn(name);
 569                 }
 570         }
 571
 572         if (literal && name[0]) {
 573                 struct prop_hdr **p;
 574
 575                 /* Append literal. */
 576                 for (p = &t->prop; *p && !is_literal(*p); p = &(*p)->next);
 577                 *p = (struct prop_hdr *)name;
 578         } else if (!add_name_property(t, name))
 579                 return false;
 580
 581         debug_tal(t);
 582         if (notifiers)
 583                 notify(t, TAL_NOTIFY_RENAME, name);
 584         return true;
 585 }
 586
 587 const char *tal_name(const tal_t *t)
 588 {
 589         struct name *n;
 590
 591         n = find_property(debug_tal(to_tal_hdr(t)), NAME);
 592         if (!n)
 593                 return NULL;
 594
 595         if (is_literal(&n->hdr))
 596                 return (const char *)n;
 597         return n->name;
 598 }
 599
 600 size_t tal_count(const tal_t *ptr)
 601 {
 602         struct length *l;
 603
 604         l = find_property(debug_tal(to_tal_hdr(ptr)), LENGTH);
 605         if (!l)
 606                 return 0;
 607         return l->count;
 608 }
 609
 610 /* Start one past first child: make stopping natural in circ. list. */
 611 static struct tal_hdr *first_child(struct tal_hdr *parent)
 612 {
 613         struct children *child;
 614
 615         child = find_property(parent, CHILDREN);
 616         if (!child)
 617                 return NULL;
 618
 619         return list_top(&child->children, struct tal_hdr, list);
 620 }
 621
 622 tal_t *tal_first(const tal_t *root)
 623 {
 624         struct tal_hdr *c, *t = debug_tal(to_tal_hdr_or_null(root));
 625
 626         c = first_child(t);
 627         if (!c)
 628                 return NULL;
 629         return from_tal_hdr(c);
 630 }
 631
 632 tal_t *tal_next(const tal_t *root, const tal_t *prev)
 633 {
 634         struct tal_hdr *c, *t = debug_tal(to_tal_hdr(prev)), *top;
 635
 636         /* Children? */
 637         c = first_child(t);
 638         if (c)
 639                 return from_tal_hdr(c);
 640
 641         top = to_tal_hdr_or_null(root);
 642         do {
 643                 struct tal_hdr *next;
 644                 struct list_node *end;
 645
 646                 end = &ignore_destroying_bit(t->parent_child)->children.n;
 647
 648                 next = list_entry(t->list.next, struct tal_hdr, list);
 649                 if (&next->list != end)
 650                         return from_tal_hdr(next);
 651
 652                 /* OK, go back to parent. */
 653                 t = ignore_destroying_bit(t->parent_child)->parent;
 654         } while (t != top);
 655
 656         return NULL;
 657 }
 658
 659 tal_t *tal_parent(const tal_t *ctx)
 660 {
 661         struct tal_hdr *t;
 662
 663         if (!ctx)
 664                 return NULL;
 665
 666         t = debug_tal(to_tal_hdr(ctx));
 667         if (ignore_destroying_bit(t->parent_child)->parent == &null_parent.hdr)
 668                 return NULL;
 669         return from_tal_hdr(ignore_destroying_bit(t->parent_child)->parent);
 670 }
 671
 672 bool tal_resize_(tal_t **ctxp, size_t size, size_t count)
 673 {
 674         struct tal_hdr *old_t, *t;
 675         struct children *child;
 676         struct length *len;
 677
 678         old_t = debug_tal(to_tal_hdr(*ctxp));
 679
 680         if (!adjust_size(&size, count))
 681                 return false;
 682
 683         t = resizefn(old_t, size + sizeof(struct tal_hdr));
 684         if (!t) {
 685                 call_error("Reallocation failure");
 686                 return false;
 687         }
 688
 689         /* If it didn't move, we're done! */
 690         if (t != old_t) {
 691                 update_bounds(t, size + sizeof(struct tal_hdr));
 692
 693                 /* Fix up linked list pointers. */
 694                 if (list_entry(t->list.next, struct tal_hdr, list) != old_t)
 695                         t->list.next->prev = t->list.prev->next = &t->list;
 696
 697                 /* Fix up child property's parent pointer. */
 698                 child = find_property(t, CHILDREN);
 699                 if (child) {
 700                         assert(child->parent == old_t);
 701                         child->parent = t;
 702                 }
 703                 *ctxp = from_tal_hdr(debug_tal(t));
 704                 if (notifiers)
 705                         notify(t, TAL_NOTIFY_MOVE, from_tal_hdr(old_t));
 706         }
 707         len = find_property(t, LENGTH);
 708         if (len)
 709                 len->count = count;
 710         if (notifiers)
 711                 notify(t, TAL_NOTIFY_RESIZE, (void *)size);
 712
 713         return true;
 714 }
 715
 716 char *tal_strdup(const tal_t *ctx, const char *p)
 717 {
 718         /* We have to let through NULL for take(). */
 719         return tal_dup_(ctx, p, 1, p ? strlen(p) + 1: 1, 0, false,
 720                         TAL_LABEL(char, "[]"));
 721 }
 722
 723 char *tal_strndup(const tal_t *ctx, const char *p, size_t n)
 724 {
 725         size_t len;
 726         char *ret;
 727
 728         /* We have to let through NULL for take(). */
 729         if (likely(p)) {
 730                 len = strlen(p);
 731                 if (len > n)
 732                         len = n;
 733         } else
 734                 len = n;
 735
 736         ret = tal_dup_(ctx, p, 1, len, 1, false, TAL_LABEL(char, "[]"));
 737         if (ret)
 738                 ret[len] = '\0';
 739         return ret;
 740 }
 741
 742 void *tal_dup_(const tal_t *ctx, const void *p, size_t size,
 743                size_t n, size_t extra, bool add_count,
 744                const char *label)
 745 {
 746         void *ret;
 747         size_t nbytes = size;
 748
 749         if (!adjust_size(&nbytes, n)) {
 750                 if (taken(p))
 751                         tal_free(p);
 752                 return NULL;
 753         }
 754
 755         /* Beware addition overflow! */
 756         if (n + extra < n) {
 757                 call_error("dup size overflow");
 758                 if (taken(p))
 759                         tal_free(p);
 760                 return NULL;
 761         }
 762
 763         if (taken(p)) {
 764                 if (unlikely(!p))
 765                         return NULL;
 766                 if (unlikely(!tal_resize_((void **)&p, size, n + extra)))
 767                         return tal_free(p);
 768                 if (unlikely(!tal_steal(ctx, p)))
 769                         return tal_free(p);
 770                 return (void *)p;
 771         }
 772
 773         ret = tal_alloc_arr_(ctx, size, n + extra, false, add_count, label);
 774         if (ret)
 775                 memcpy(ret, p, nbytes);
 776         return ret;
 777 }
 778
 779 char *tal_asprintf(const tal_t *ctx, const char *fmt, ...)
 780 {
 781         va_list ap;
 782         char *ret;
 783
 784         va_start(ap, fmt);
 785         ret = tal_vasprintf(ctx, fmt, ap);
 786         va_end(ap);
 787
 788         return ret;
 789 }
 790
 791 char *tal_vasprintf(const tal_t *ctx, const char *fmt, va_list ap)
 792 {
 793         size_t max;
 794         char *buf;
 795         int ret;
 796
 797         if (!fmt && taken(fmt))
 798                 return NULL;
 799
 800         /* A decent guess to start. */
 801         max = strlen(fmt) * 2;
 802         buf = tal_arr(ctx, char, max);
 803         while (buf) {
 804                 va_list ap2;
 805
 806                 va_copy(ap2, ap);
 807                 ret = vsnprintf(buf, max, fmt, ap2);
 808                 va_end(ap2);
 809
 810                 if (ret < max)
 811                         break;
 812                 if (!tal_resize(&buf, max *= 2))
 813                         buf = tal_free(buf);
 814         }
 815         if (taken(fmt))
 816                 tal_free(fmt);
 817         return buf;
 818 }
 819
 820 void tal_set_backend(void *(*alloc_fn)(size_t size),
 821                      void *(*resize_fn)(void *, size_t size),
 822                      void (*free_fn)(void *),
 823                      void (*error_fn)(const char *msg))
 824 {
 825         if (alloc_fn)
 826                 allocfn = alloc_fn;
 827         if (resize_fn)
 828                 resizefn = resize_fn;
 829         if (free_fn)
 830                 freefn = free_fn;
 831         if (error_fn)
 832                 errorfn = error_fn;
 833 }
 834
 835 #ifdef CCAN_TAL_DEBUG
 836 static void dump_node(unsigned int indent, const struct tal_hdr *t)
 837 {
 838         unsigned int i;
 839         const struct prop_hdr *p;
 840
 841         for (i = 0; i < indent; i++)
 842                 printf("  ");
 843         printf("%p", t);
 844         for (p = t->prop; p; p = p->next) {
 845                 struct children *c;
 846                 struct name *n;
 847                 struct notifier *no;
 848                 struct length *l;
 849                 if (is_literal(p)) {
 850                         printf(" \"%s\"", (const char *)p);
 851                         break;
 852                 }
 853                 switch (p->type) {
 854                 case CHILDREN:
 855                         c = (struct children *)p;
 856                         printf(" CHILDREN(%p):parent=%p,children={%p,%p}\n",
 857                                p, c->parent,
 858                                c->children.n.prev, c->children.n.next);
 859                         break;
 860                 case NAME:
 861                         n = (struct name *)p;
 862                         printf(" NAME(%p):%s", p, n->name);
 863                         break;
 864                 case NOTIFIER:
 865                         no = (struct notifier *)p;
 866                         printf(" NOTIFIER(%p):fn=%p", p, no->u.notifyfn);
 867                         break;
 868                 case LENGTH:
 869                         l = (struct length *)p;
 870                         printf(" LENGTH(%p):count=%zu", p, l->count);
 871                         break;
 872                 default:
 873                         printf(" **UNKNOWN(%p):%i**", p, p->type);
 874                 }
 875         }
 876         printf("\n");
 877 }
 878
 879 static void tal_dump_(unsigned int level, const struct tal_hdr *t)
 880 {
 881         struct children *children;
 882
 883         dump_node(level, t);
 884
 885         children = find_property(t, CHILDREN);
 886         if (children) {
 887                 struct tal_hdr *i;
 888
 889                 list_for_each(&children->children, i, list)
 890                         tal_dump_(level + 1, i);
 891         }
 892 }
 893
 894 void tal_dump(void)
 895 {
 896         tal_dump_(0, &null_parent.hdr);
 897 }
 898 #endif /* CCAN_TAL_DEBUG */
 899
 900 #ifndef NDEBUG
 901 static bool check_err(struct tal_hdr *t, const char *errorstr,
 902                       const char *errmsg)
 903 {
 904         if (errorstr) {
 905                 /* Try not to malloc: it may be corrupted. */
 906                 char msg[strlen(errorstr) + 20 + strlen(errmsg) + 1];
 907                 sprintf(msg, "%s:%p %s", errorstr, from_tal_hdr(t), errmsg);
 908                 call_error(msg);
 909         }
 910         return false;
 911 }
 912
 913 static bool check_node(struct children *parent_child,
 914                        struct tal_hdr *t, const char *errorstr)
 915 {
 916         struct prop_hdr *p;
 917         struct name *name = NULL;
 918         struct children *children = NULL;
 919         struct length *length = NULL;
 920
 921         if (!in_bounds(t))
 922                 return check_err(t, errorstr, "invalid pointer");
 923
 924         if (ignore_destroying_bit(t->parent_child) != parent_child)
 925                 return check_err(t, errorstr, "incorrect parent");
 926
 927         for (p = t->prop; p; p = p->next) {
 928                 if (is_literal(p)) {
 929                         if (name)
 930                                 return check_err(t, errorstr,
 931                                                  "has extra literal");
 932                         name = (struct name *)p;
 933                         break;
 934                 }
 935                 if (!in_bounds(p))
 936                         return check_err(t, errorstr,
 937                                          "has bad property pointer");
 938
 939                 switch (p->type) {
 940                 case CHILDREN:
 941                         if (children)
 942                                 return check_err(t, errorstr,
 943                                                  "has two child nodes");
 944                         children = (struct children *)p;
 945                         break;
 946                 case LENGTH:
 947                         if (length)
 948                                 return check_err(t, errorstr,
 949                                                  "has two lengths");
 950                         length = (struct length *)p;
 951                         break;
 952                 case NOTIFIER:
 953                         break;
 954                 case NAME:
 955                         if (name)
 956                                 return check_err(t, errorstr,
 957                                                  "has two names");
 958                         name = (struct name *)p;
 959                         break;
 960                 default:
 961                         return check_err(t, errorstr, "has unknown property");
 962                 }
 963         }
 964         if (children) {
 965                 struct tal_hdr *i;
 966
 967                 if (!list_check(&children->children, errorstr))
 968                         return false;
 969                 list_for_each(&children->children, i, list) {
 970                         if (!check_node(children, i, errorstr))
 971                                 return false;
 972                 }
 973         }
 974         return true;
 975 }
 976
 977 bool tal_check(const tal_t *ctx, const char *errorstr)
 978 {
 979         struct tal_hdr *t = to_tal_hdr_or_null(ctx);
 980
 981         return check_node(ignore_destroying_bit(t->parent_child), t, errorstr);
 982 }
 983 #else /* NDEBUG */
 984 bool tal_check(const tal_t *ctx, const char *errorstr)
 985 {
 986         return true;
 987 }
 988 #endif