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/hash/hash.h>
   5 #include <ccan/list/list.h>
   6 #include <ccan/take/take.h>
   7 #include <assert.h>
   8 #include <stdio.h>
   9 #include <stdarg.h>
  10 #include <stddef.h>
  11 #include <string.h>
  12 #include <limits.h>
  13 #include <errno.h>
  14
  15 //#define TAL_DEBUG 1
  16
  17 /* How large should grouips get? */
  18 #define GROUP_NODE_AVERAGE 32
  19
  20 /* 32-bit type field, first byte 0 in either endianness. */
  21 enum prop_type {
  22         CHILDREN = 0x00c1d500,
  23         GROUP = 0x00600d00,
  24         DESTRUCTOR = 0x00de5700,
  25         NAME = 0x00111100,
  26 };
  27
  28 struct tal_hdr {
  29         struct tal_hdr *next;
  30         struct prop_hdr *prop;
  31 };
  32
  33 struct prop_hdr {
  34         enum prop_type type;
  35         struct prop_hdr *next;
  36 };
  37
  38 /* Unlike other properties, this is owned by parent, not child! */
  39 struct group {
  40         struct prop_hdr hdr; /* GROUP */
  41         struct list_head list; /* Head for child->group, node for others. */
  42         /* We point to parent's children property, as it doesn't move! */
  43         struct children *parent_child;
  44         struct tal_hdr *first_child;
  45 };
  46
  47 struct children {
  48         struct prop_hdr hdr; /* CHILDREN */
  49         struct tal_hdr *parent;
  50         /* We always have one group.  Others may be added. */
  51         struct group group;
  52 };
  53
  54 struct destructor {
  55         struct prop_hdr hdr; /* DESTRUCTOR */
  56         void (*destroy)(void *me);
  57 };
  58
  59 struct name {
  60         struct prop_hdr hdr; /* NAME */
  61         char name[];
  62 };
  63
  64 static struct {
  65         struct tal_hdr hdr;
  66         struct children c;
  67 } null_parent = { { NULL, &null_parent.c.hdr },
  68                   { { CHILDREN, NULL },
  69                     &null_parent.hdr,
  70                     { { GROUP, NULL },
  71                       { { &null_parent.c.group.list.n,
  72                           &null_parent.c.group.list.n } },
  73                       &null_parent.c, NULL } }
  74 };
  75
  76
  77 static void *(*allocfn)(size_t size) = malloc;
  78 static void *(*resizefn)(void *, size_t size) = realloc;
  79 static void (*freefn)(void *) = free;
  80 static void (*errorfn)(const char *msg) = (void *)abort;
  81
  82 static inline void COLD call_error(const char *msg)
  83 {
  84         errorfn(msg);
  85 }
  86
  87 static bool get_destroying_bit(struct tal_hdr *next)
  88 {
  89         return (size_t)next & 1;
  90 }
  91
  92 static void set_destroying_bit(struct tal_hdr **next)
  93 {
  94         *next = (void *)((size_t)next | 1);
  95 }
  96
  97 static struct tal_hdr *ignore_destroying_bit(struct tal_hdr *next)
  98 {
  99         return (void *)((size_t)next & ~(size_t)1);
 100 }
 101
 102 static struct group *next_group(struct group *group)
 103 {
 104         return list_entry(group->list.n.next, struct group, list.n);
 105 }
 106
 107 static bool initialized = false;
 108
 109 /* This means valgrind can see leaks. */
 110 static void tal_cleanup(void)
 111 {
 112         struct group *i, *next;
 113
 114         /* Unlink null_parent. */
 115         for (i = next_group(&null_parent.c.group);
 116              i != &null_parent.c.group;
 117              i = next) {
 118                 next = next_group(i);
 119                 freefn(i);
 120         }
 121         null_parent.c.group.first_child = NULL;
 122
 123         /* Cleanup any taken pointers. */
 124         take_cleanup();
 125 }
 126
 127 /* For allocation failures inside ccan/take */
 128 static void take_alloc_failed(const void *p)
 129 {
 130         tal_free(p);
 131 }
 132
 133 #ifndef NDEBUG
 134 static const void *bounds_start, *bounds_end;
 135
 136 static void update_bounds(const void *new)
 137 {
 138         if (unlikely(!bounds_start))
 139                 bounds_start = bounds_end = new;
 140         else if (new < bounds_start)
 141                 bounds_start = new;
 142         else if (new > bounds_end)
 143                 bounds_end = new;
 144 }
 145
 146 static bool in_bounds(const void *p)
 147 {
 148         return !p || (p >= bounds_start && p <= bounds_end);
 149 }
 150 #else
 151 static void update_bounds(const void *new)
 152 {
 153 }
 154
 155 static bool in_bounds(const void *p)
 156 {
 157         return true;
 158 }
 159 #endif
 160
 161 static void check_bounds(const void *p)
 162 {
 163         if (!in_bounds(p))
 164                 call_error("Not a valid header");
 165 }
 166
 167 static struct tal_hdr *to_tal_hdr(const void *ctx)
 168 {
 169         struct tal_hdr *t;
 170
 171         t = (struct tal_hdr *)((char *)ctx - sizeof(struct tal_hdr));
 172         check_bounds(t);
 173         check_bounds(ignore_destroying_bit(t->next));
 174         return t;
 175 }
 176
 177 static struct tal_hdr *to_tal_hdr_or_null(const void *ctx)
 178 {
 179         if (!ctx)
 180                 return &null_parent.hdr;
 181         return to_tal_hdr(ctx);
 182 }
 183
 184 static void *from_tal_hdr(struct tal_hdr *hdr)
 185 {
 186         return hdr + 1;
 187 }
 188
 189 #ifdef TAL_DEBUG
 190 static void *from_tal_hdr_or_null(struct tal_hdr *hdr)
 191 {
 192         if (hdr == &null_parent.hdr)
 193                 return NULL;
 194         return from_tal_hdr(hdr);
 195 }
 196
 197 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
 198 {
 199         tal_check(from_tal_hdr_or_null(tal), "TAL_DEBUG ");
 200         return tal;
 201 }
 202 #else
 203 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
 204 {
 205         return tal;
 206 }
 207 #endif
 208
 209 static void *allocate(size_t size)
 210 {
 211         void *ret;
 212
 213         /* Don't hand silly sizes to malloc. */
 214         if (size >> (CHAR_BIT*sizeof(size) - 1)) {
 215                 call_error("allocation size overflow");
 216                 return NULL;
 217         }
 218
 219         ret = allocfn(size);
 220         if (!ret)
 221                 call_error("allocation failed");
 222         else
 223                 update_bounds(ret);
 224         return ret;
 225 }
 226
 227 /* We carefully start all real properties with a zero byte. */
 228 static bool is_literal(const struct prop_hdr *prop)
 229 {
 230         return ((char *)prop)[0] != 0;
 231 }
 232
 233 static struct prop_hdr **find_property_ptr(const struct tal_hdr *t,
 234                                            enum prop_type type)
 235 {
 236         struct prop_hdr **p;
 237
 238         for (p = (struct prop_hdr **)&t->prop; *p; p = &(*p)->next) {
 239                 if (is_literal(*p)) {
 240                         if (type == NAME)
 241                                 return p;
 242                         break;
 243                 }
 244                 if ((*p)->type == type)
 245                         return p;
 246         }
 247         return NULL;
 248 }
 249
 250 static void *find_property(const struct tal_hdr *parent, enum prop_type type)
 251 {
 252         struct prop_hdr **p = find_property_ptr(parent, type);
 253
 254         if (p)
 255                 return *p;
 256         return NULL;
 257 }
 258
 259 static void init_property(struct prop_hdr *hdr,
 260                           struct tal_hdr *parent,
 261                           enum prop_type type)
 262 {
 263         hdr->type = type;
 264         hdr->next = parent->prop;
 265         parent->prop = hdr;
 266 }
 267
 268 static struct destructor *add_destructor_property(struct tal_hdr *t,
 269                                                   void (*destroy)(void *))
 270 {
 271         struct destructor *prop = allocate(sizeof(*prop));
 272         if (prop) {
 273                 init_property(&prop->hdr, t, DESTRUCTOR);
 274                 prop->destroy = destroy;
 275         }
 276         return prop;
 277 }
 278
 279 static struct name *add_name_property(struct tal_hdr *t, const char *name)
 280 {
 281         struct name *prop;
 282
 283         prop = allocate(sizeof(*prop) + strlen(name) + 1);
 284         if (prop) {
 285                 init_property(&prop->hdr, t, NAME);
 286                 strcpy(prop->name, name);
 287         }
 288         return prop;
 289 }
 290
 291 static void init_group_property(struct group *group,
 292                                 struct children *parent_child,
 293                                 struct tal_hdr *child)
 294 {
 295         init_property(&group->hdr, child, GROUP);
 296         group->parent_child = parent_child;
 297         group->first_child = child;
 298 }
 299
 300 static struct children *add_child_property(struct tal_hdr *parent,
 301                                            struct tal_hdr *child)
 302 {
 303         struct children *prop = allocate(sizeof(*prop));
 304         if (prop) {
 305                 init_property(&prop->hdr, parent, CHILDREN);
 306                 prop->parent = parent;
 307
 308                 init_group_property(&prop->group, prop, child);
 309                 list_head_init(&prop->group.list);
 310                 update_bounds(&prop->group);
 311         }
 312         return prop;
 313 }
 314
 315 static struct group *add_group_property(struct tal_hdr *child,
 316                                         struct children *parent_child)
 317 {
 318         struct group *prop = allocate(sizeof(*prop));
 319         if (prop)
 320                 init_group_property(prop, parent_child, child);
 321         return prop;
 322 }
 323
 324 static bool add_child(struct tal_hdr *parent, struct tal_hdr *child)
 325 {
 326         struct group *group;
 327         struct children *children = find_property(parent, CHILDREN);
 328
 329         if (!children) {
 330                 children = add_child_property(parent, child);
 331                 if (!children)
 332                         return false;
 333                 list_head_init(&children->group.list);
 334
 335                 /* Child links to itself. */
 336                 child->next = child;
 337                 return true;
 338         }
 339
 340         /* Last one (may be children->group itself). */
 341         group = next_group(&children->group);
 342
 343         /* Empty group can happen: null_parent, or all children freed. */
 344         if (unlikely(!group->first_child)) {
 345                 assert(group == &children->group);
 346                 /* This hits on first child appended to null parent. */
 347                 if (unlikely(!initialized)) {
 348                         atexit(tal_cleanup);
 349                         take_allocfail(take_alloc_failed);
 350                         initialized = true;
 351                 }
 352                 /* Link group into this child, make it the first one. */
 353                 group->hdr.next = child->prop;
 354                 child->prop = &group->hdr;
 355                 group->first_child = child;
 356
 357                 /* Child links to itself. */
 358                 child->next = child;
 359                 return true;
 360         }
 361
 362         if (unlikely(hash_pointer(child, 0) % GROUP_NODE_AVERAGE == 0)) {
 363                 struct group *newgroup;
 364
 365                 newgroup = add_group_property(child, children);
 366                 if (likely(newgroup)) {
 367                         list_add(&children->group.list, &newgroup->list.n);
 368
 369                         /* Child links to itself. */
 370                         child->next = child;
 371                         return true;
 372                 }
 373                 /* Fall through: on allocation failure reuse old group. */
 374         }
 375
 376         /* We insert after head, otherwise we'd need to find end. */
 377         child->next = group->first_child->next;
 378         group->first_child->next = child;
 379         return true;
 380 }
 381
 382 static void del_tree(struct tal_hdr *t)
 383 {
 384         struct prop_hdr **prop, *p, *next;
 385
 386         /* Already being destroyed?  Don't loop. */
 387         if (unlikely(get_destroying_bit(t->next)))
 388                 return;
 389
 390         set_destroying_bit(&t->next);
 391
 392         /* Carefully call destructors, removing as we go. */
 393         while ((prop = find_property_ptr(t, DESTRUCTOR))) {
 394                 struct destructor *d = (struct destructor *)*prop;
 395                 d->destroy(from_tal_hdr(t));
 396                 *prop = d->hdr.next;
 397                 freefn(d);
 398         }
 399
 400         /* Now free children and groups. */
 401         prop = find_property_ptr(t, CHILDREN);
 402         if (prop) {
 403                 struct children *c = (struct children *)*prop;
 404                 struct group *group, *next;
 405
 406                 group = &c->group;
 407                 do {
 408                         next = next_group(group);
 409                         if (group->first_child) {
 410                                 struct tal_hdr *i, *nextc;
 411
 412                                 i = group->first_child;
 413                                 do {
 414                                         nextc = i->next;
 415                                         del_tree(i);
 416                                         i = nextc;
 417                                 } while (i != group->first_child);
 418                         }
 419                         if (group != &c->group)
 420                                 freefn(group);
 421                         group = next;
 422                 } while (group != &c->group);
 423         }
 424
 425         /* Finally free our properties (groups are freed by parent). */
 426         for (p = t->prop; p && !is_literal(p); p = next) {
 427                 next = p->next;
 428                 if (p->type != GROUP)
 429                         freefn(p);
 430         }
 431         freefn(t);
 432 }
 433
 434 void *tal_alloc_(const tal_t *ctx, size_t size, bool clear, const char *label)
 435 {
 436         struct tal_hdr *child, *parent = debug_tal(to_tal_hdr_or_null(ctx));
 437
 438         child = allocate(sizeof(struct tal_hdr) + size);
 439         if (!child)
 440                 return NULL;
 441         if (clear)
 442                 memset(from_tal_hdr(child), 0, size);
 443         child->prop = (void *)label;
 444         if (!add_child(parent, child)) {
 445                 freefn(child);
 446                 return NULL;
 447         }
 448         debug_tal(parent);
 449         return from_tal_hdr(debug_tal(child));
 450 }
 451
 452 /* Update back ptrs, etc, as required.
 453  * May return pointer to parent. */
 454 static struct tal_hdr *remove_node(struct tal_hdr *t)
 455 {
 456         struct prop_hdr **prop;
 457         struct tal_hdr *prev;
 458
 459         /* Loop around to find previous node. */
 460         for (prev = t->next; prev->next != t; prev = prev->next);
 461
 462         /* Unlink ourselves. */
 463         prev->next = t->next;
 464
 465         /* Are we the node with the group property? */
 466         prop = find_property_ptr(t, GROUP);
 467         if (prop) {
 468                 struct group *group = (struct group *)*prop;
 469
 470                 /* Are we the only one? */
 471                 if (prev == t) {
 472                         struct prop_hdr *next = (*prop)->next;
 473                         struct children *c = group->parent_child;
 474                         /* Is this the group embedded in the child property? */
 475                         if (group == &c->group) {
 476                                 group->first_child = NULL;
 477                         } else {
 478                                 /* Empty group, so free it. */
 479                                 list_del_from(&c->group.list, &group->list.n);
 480                                 freefn(group);
 481                         }
 482                         *prop = next;
 483                         return c->parent;
 484                 } else {
 485                         /* Move property to next node. */
 486                         group->first_child = t->next;
 487
 488                         *prop = group->hdr.next;
 489                         group->hdr.next = t->next->prop;
 490                         t->next->prop = &group->hdr;
 491                 }
 492         }
 493         return NULL;
 494 }
 495
 496 void tal_free(const tal_t *ctx)
 497 {
 498         struct tal_hdr *t;
 499         int saved_errno = errno;
 500
 501         if (!ctx)
 502                 return;
 503
 504         t = debug_tal(to_tal_hdr(ctx));
 505         remove_node(t);
 506         del_tree(t);
 507         errno = saved_errno;
 508 }
 509
 510 void *tal_steal_(const tal_t *new_parent, const tal_t *ctx)
 511 {
 512         if (ctx) {
 513                 struct tal_hdr *newpar, *t, *old_next, *old_parent;
 514
 515                 newpar = debug_tal(to_tal_hdr_or_null(new_parent));
 516                 t = debug_tal(to_tal_hdr(ctx));
 517
 518                 /* Save enough data to get us back if we fail! */
 519                 old_next = t->next;
 520
 521                 /* Unlink it from old parent. */
 522                 old_parent = remove_node(t);
 523                 if (unlikely(!add_child(newpar, t))) {
 524                         /* If we were last child, parent returned by
 525                          * remove_node, otherwise search old siblings
 526                          * for it. */
 527                         if (!old_parent) {
 528                                 struct group *g;
 529                                 while (!(g = find_property(old_next, GROUP)))
 530                                         old_next = old_next->next;
 531                                 old_parent = g->parent_child->parent;
 532                         }
 533                         /* We can always add to old parent, becuase it has one
 534                          * group already. */
 535                         if (!add_child(old_parent, t))
 536                                 abort();
 537                         return NULL;
 538                 }
 539                 debug_tal(newpar);
 540         }
 541         return (void *)ctx;
 542 }
 543
 544 bool tal_add_destructor_(tal_t *ctx, void (*destroy)(void *me))
 545 {
 546         return add_destructor_property(debug_tal(to_tal_hdr(ctx)), destroy);
 547 }
 548
 549 bool tal_set_name_(tal_t *ctx, const char *name, bool literal)
 550 {
 551         struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
 552         struct prop_hdr **prop = find_property_ptr(t, NAME);
 553
 554         /* Get rid of any old name */
 555         if (prop) {
 556                 struct name *name = (struct name *)*prop;
 557                 if (is_literal(&name->hdr))
 558                         *prop = NULL;
 559                 else {
 560                         *prop = name->hdr.next;
 561                         freefn(name);
 562                 }
 563         }
 564
 565         if (literal && name[0]) {
 566                 struct prop_hdr **p;
 567
 568                 /* Append literal. */
 569                 for (p = &t->prop; *p && !is_literal(*p); p = &(*p)->next);
 570                 *p = (struct prop_hdr *)name;
 571                 return true;
 572         }
 573         if (!add_name_property(t, name))
 574                 return false;
 575         debug_tal(t);
 576         return true;
 577 }
 578
 579 const char *tal_name(const tal_t *t)
 580 {
 581         struct name *n;
 582
 583         n = find_property(debug_tal(to_tal_hdr(t)), NAME);
 584         if (!n)
 585                 return NULL;
 586
 587         if (is_literal(&n->hdr))
 588                 return (const char *)n;
 589         return n->name;
 590 }
 591
 592 /* Start one past first child: make stopping natural in circ. list. */
 593 static struct tal_hdr *first_child(struct tal_hdr *parent)
 594 {
 595         struct children *child;
 596         struct group *group;
 597
 598         child = find_property(parent, CHILDREN);
 599         if (!child)
 600                 return NULL;
 601
 602         /* Careful of empty group embedded in child property. */
 603         if (child->group.first_child)
 604                 return child->group.first_child->next;
 605
 606         /* There could still be another group! */
 607         group = next_group(&child->group);
 608         if (group == &child->group)
 609                 return NULL;
 610
 611         return group->first_child->next;
 612 }
 613
 614 tal_t *tal_first(const tal_t *root)
 615 {
 616         struct tal_hdr *c, *t = debug_tal(to_tal_hdr_or_null(root));
 617
 618         c = first_child(t);
 619         if (!c)
 620                 return NULL;
 621         return from_tal_hdr(c);
 622 }
 623
 624 tal_t *tal_next(const tal_t *root, const tal_t *prev)
 625 {
 626         struct tal_hdr *c, *t = debug_tal(to_tal_hdr(prev)), *top;
 627         struct group *group;
 628
 629         /* Children? */
 630         c = first_child(t);
 631         if (c)
 632                 return from_tal_hdr(c);
 633
 634         top = to_tal_hdr_or_null(root);
 635         do {
 636                 struct group *next;
 637
 638                 /* Are we back to first child in group? */
 639                 group = find_property(t, GROUP);
 640                 if (!group)
 641                         return from_tal_hdr(t->next);
 642
 643                 /* Last group is one inside children property. */
 644                 next = next_group(group);
 645                 if (next != &group->parent_child->group)
 646                         return from_tal_hdr(next->first_child->next);
 647
 648                 /* OK, go back to parent. */
 649                 t = group->parent_child->parent;
 650         } while (t != top);
 651
 652         return NULL;
 653 }
 654
 655 tal_t *tal_parent(const tal_t *ctx)
 656 {
 657         struct group *group;
 658         struct tal_hdr *t;
 659
 660         if (!ctx)
 661                 return NULL;
 662
 663         t = debug_tal(to_tal_hdr(ctx));
 664
 665         while (!(group = find_property(t, GROUP)))
 666                 t = t->next;
 667
 668         if (group->parent_child->parent == &null_parent.hdr)
 669                 return NULL;
 670         return from_tal_hdr(group->parent_child->parent);
 671 }
 672
 673 bool tal_resize_(tal_t **ctxp, size_t size)
 674 {
 675         struct tal_hdr *old_t, *t, **prev;
 676         struct group *group;
 677         struct children *child;
 678
 679         old_t = debug_tal(to_tal_hdr(*ctxp));
 680
 681         /* Don't hand silly sizes to realloc. */
 682         if (size >> (CHAR_BIT*sizeof(size) - 1)) {
 683                 call_error("Reallocation size overflow");
 684                 return false;
 685         }
 686
 687         t = resizefn(old_t, size + sizeof(struct tal_hdr));
 688         if (!t) {
 689                 call_error("Reallocation failure");
 690                 return false;
 691         }
 692
 693         /* If it didn't move, we're done! */
 694         if (t == old_t)
 695                 return true;
 696         update_bounds(t);
 697
 698         /* Fix up linked list pointer. */
 699         for (prev = &t->next; *prev != old_t; prev = &(*prev)->next);
 700         *prev = t;
 701
 702         /* Fix up group pointer, if any. */
 703         group = find_property(t, GROUP);
 704         if (group) {
 705                 assert(group->first_child == old_t);
 706                 group->first_child = t;
 707         }
 708
 709         /* Fix up child propertie's parent pointer. */
 710         child = find_property(t, CHILDREN);
 711         if (child) {
 712                 assert(child->parent == old_t);
 713                 child->parent = t;
 714         }
 715         *ctxp = from_tal_hdr(debug_tal(t));
 716         return true;
 717 }
 718
 719 char *tal_strdup(const tal_t *ctx, const char *p)
 720 {
 721         return tal_dup(ctx, char, p, strlen(p)+1, 0);
 722 }
 723
 724 char *tal_strndup(const tal_t *ctx, const char *p, size_t n)
 725 {
 726         char *ret;
 727
 728         if (strlen(p) < n)
 729                 n = strlen(p);
 730         ret = tal_dup(ctx, char, p, n, 1);
 731         if (ret)
 732                 ret[n] = '\0';
 733         return ret;
 734 }
 735
 736 void *tal_dup_(const tal_t *ctx, const void *p, size_t n, size_t extra,
 737                const char *label)
 738 {
 739         void *ret;
 740
 741         /* Beware overflow! */
 742         if (n + extra < n || n + extra + sizeof(struct tal_hdr) < n) {
 743                 call_error("dup size overflow");
 744                 if (taken(p))
 745                         tal_free(p);
 746                 return NULL;
 747         }
 748
 749         if (taken(p)) {
 750                 if (unlikely(!p))
 751                         return NULL;
 752                 if (unlikely(!tal_resize_((void **)&p, n + extra))) {
 753                         tal_free(p);
 754                         return NULL;
 755                 }
 756                 if (unlikely(!tal_steal(ctx, p))) {
 757                         tal_free(p);
 758                         return NULL;
 759                 }
 760                 return (void *)p;
 761         }
 762         ret = tal_alloc_(ctx, n + extra, false, label);
 763         if (ret)
 764                 memcpy(ret, p, n);
 765         return ret;
 766 }
 767
 768 char *tal_asprintf(const tal_t *ctx, const char *fmt, ...)
 769 {
 770         va_list ap;
 771         char *ret;
 772
 773         va_start(ap, fmt);
 774         ret = tal_vasprintf(ctx, fmt, ap);
 775         va_end(ap);
 776
 777         return ret;
 778 }
 779
 780 char *tal_vasprintf(const tal_t *ctx, const char *fmt, va_list ap)
 781 {
 782         size_t max = strlen(fmt) * 2;
 783         char *buf;
 784         int ret;
 785
 786         buf = tal_arr(ctx, char, max);
 787         while (buf) {
 788                 va_list ap2;
 789
 790                 va_copy(ap2, ap);
 791                 ret = vsnprintf(buf, max, fmt, ap2);
 792                 va_end(ap2);
 793
 794                 if (ret < max)
 795                         break;
 796                 if (!tal_resize(&buf, max *= 2)) {
 797                         tal_free(buf);
 798                         buf = NULL;
 799                 }
 800         }
 801         if (taken(fmt))
 802                 tal_free(fmt);
 803         return buf;
 804 }
 805
 806 void tal_set_backend(void *(*alloc_fn)(size_t size),
 807                      void *(*resize_fn)(void *, size_t size),
 808                      void (*free_fn)(void *),
 809                      void (*error_fn)(const char *msg))
 810 {
 811         if (alloc_fn)
 812                 allocfn = alloc_fn;
 813         if (resize_fn)
 814                 resizefn = resize_fn;
 815         if (free_fn)
 816                 freefn = free_fn;
 817         if (error_fn)
 818                 errorfn = error_fn;
 819 }
 820
 821 #ifdef CCAN_TAL_DEBUG
 822 static void dump_node(unsigned int indent, const struct tal_hdr *t)
 823 {
 824         unsigned int i;
 825         const struct prop_hdr *p;
 826
 827         for (i = 0; i < indent; i++)
 828                 printf("  ");
 829         printf("%p", t);
 830         for (p = t->prop; p; p = p->next) {
 831                 struct group *g;
 832                 struct children *c;
 833                 struct destructor *d;
 834                 struct name *n;
 835                 if (is_literal(p)) {
 836                         printf(" \"%s\"", (const char *)p);
 837                         break;
 838                 }
 839                 switch (p->type) {
 840                 case CHILDREN:
 841                         c = (struct children *)p;
 842                         printf(" CHILDREN(%p):parent=%p,group=%p\n",
 843                                p, c->parent, &c->group);
 844                         g = &c->group;
 845                         printf("  GROUP(%p):list={%p,%p},parent_ch=%p,first=%p",
 846                                g, g->list.n.next, g->list.n.next,
 847                                g->parent_child, g->first_child);
 848                         break;
 849                 case GROUP:
 850                         g = (struct group *)p;
 851                         printf(" GROUP(%p):list={%p,%p},,parent_ch=%p,first=%p",
 852                                p, g->list.n.next, g->list.n.next,
 853                                g->parent_child, g->first_child);
 854                         break;
 855                 case DESTRUCTOR:
 856                         d = (struct destructor *)p;
 857                         printf(" DESTRUCTOR(%p):fn=%p", p, d->destroy);
 858                         break;
 859                 case NAME:
 860                         n = (struct name *)p;
 861                         printf(" NAME(%p):%s", p, n->name);
 862                         break;
 863                 default:
 864                         printf(" **UNKNOWN(%p):%i**", p, p->type);
 865                 }
 866         }
 867         printf("\n");
 868 }
 869
 870 static void tal_dump_(unsigned int level, const struct tal_hdr *t)
 871 {
 872         struct children *children;
 873         struct group *group;
 874
 875         dump_node(level, t);
 876
 877         children = find_property(t, CHILDREN);
 878         if (!children)
 879                 return;
 880
 881         group = &children->group;
 882         do {
 883                 struct tal_hdr *i;
 884
 885                 i = group->first_child;
 886                 if (i) {
 887                         do {
 888                                 tal_dump_(level+1, i);
 889                                 i = i->next;
 890                         } while (i != group->first_child);
 891                 }
 892                 group = next_group(group);
 893         } while (group != &children->group);
 894 }
 895
 896 void tal_dump(void)
 897 {
 898         tal_dump_(0, &null_parent.hdr);
 899 }
 900 #endif /* CCAN_TAL_DEBUG */
 901
 902 #ifndef NDEBUG
 903 static bool check_err(struct tal_hdr *t, const char *errorstr,
 904                       const char *errmsg)
 905 {
 906         if (errorstr) {
 907                 /* Try not to malloc: it may be corrupted. */
 908                 char msg[strlen(errorstr) + 20 + strlen(errmsg) + 1];
 909                 sprintf(msg, "%s:%p %s", errorstr, from_tal_hdr(t), errmsg);
 910                 call_error(msg);
 911         }
 912         return false;
 913 }
 914
 915 static bool check_group(struct group *group,
 916                         struct tal_hdr *t, const char *errorstr);
 917
 918 static bool check_node(struct group *group,
 919                        struct tal_hdr *t, const char *errorstr)
 920 {
 921         struct prop_hdr *p;
 922         struct name *name = NULL;
 923         struct children *children = NULL;
 924         struct group *gr = NULL;
 925
 926         if (t != &null_parent.hdr && !in_bounds(t))
 927                 return check_err(t, errorstr, "invalid pointer");
 928
 929         for (p = t->prop; p; p = p->next) {
 930                 if (is_literal(p)) {
 931                         if (name)
 932                                 return check_err(t, errorstr,
 933                                                  "has extra literal");
 934                         name = (struct name *)p;
 935                         break;
 936                 }
 937                 if (p != &null_parent.c.hdr && p != &null_parent.c.group.hdr
 938                     && !in_bounds(p))
 939                         return check_err(t, errorstr,
 940                                          "has bad property pointer");
 941
 942                 switch (p->type) {
 943                 case GROUP:
 944                         if (gr)
 945                                 return check_err(t, errorstr,
 946                                                  "has two groups");
 947                         gr = (struct group *)p;
 948                         break;
 949                 case CHILDREN:
 950                         if (children)
 951                                 return check_err(t, errorstr,
 952                                                  "has two child nodes");
 953                         children = (struct children *)p;
 954                         break;
 955                 case DESTRUCTOR:
 956                         break;
 957                 case NAME:
 958                         if (name)
 959                                 return check_err(t, errorstr,
 960                                                  "has two names");
 961                         name = (struct name *)p;
 962                         break;
 963                 default:
 964                         return check_err(t, errorstr, "has unknown property");
 965                 }
 966         }
 967         if (group && gr != group)
 968                 return check_err(t, errorstr, "has bad group");
 969
 970         if (children) {
 971                 if (!list_check(&children->group.list, errorstr))
 972                         return false;
 973                 gr = &children->group;
 974                 do {
 975                         if (gr->first_child) {
 976                                 if (!check_group(gr, gr->first_child, errorstr))
 977                                         return false;
 978                         } else if (gr != &children->group) {
 979                                 /* Empty groups should be deleted! */
 980                                 return check_err(t, errorstr,
 981                                                  "has empty group");
 982                         }
 983                         gr = next_group(gr);
 984                 } while (gr != &children->group);
 985         }
 986         return true;
 987 }
 988
 989 static bool check_group(struct group *group,
 990                         struct tal_hdr *t, const char *errorstr)
 991 {
 992         struct tal_hdr *i;
 993
 994         i = t;
 995         do {
 996                 if (!check_node(group, i, errorstr))
 997                         return false;
 998                 group = NULL;
 999                 i = i->next;
1000         } while (i != t);
1001         return true;
1002 }
1003
1004 bool tal_check(const tal_t *ctx, const char *errorstr)
1005 {
1006         struct tal_hdr *t = to_tal_hdr_or_null(ctx);
1007
1008         return check_node(NULL, t, errorstr);
1009 }
1010 #else /* NDEBUG */
1011 bool tal_check(const tal_t *ctx, const char *errorstr)
1012 {
1013         return true;
1014 }
1015 #endif