tal: add xor into child_parent pointer.
[ccan] / 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/alignof/alignof.h>
6 #include <assert.h>
7 #include <stdio.h>
8 #include <stddef.h>
9 #include <string.h>
10 #include <limits.h>
11 #include <stdint.h>
12 #include <errno.h>
13
14 //#define TAL_DEBUG 1
15
16 #define NOTIFY_IS_DESTRUCTOR 512
17 #define NOTIFY_EXTRA_ARG 1024
18
19 /* This makes our parent_child ptr stand out for to_tal_hdr checks */
20 #define TAL_PTR_OBFUSTICATOR ((intptr_t)0x1984200820142016ULL)
21
22 /* 32-bit type field, first byte 0 in either endianness. */
23 enum prop_type {
24         CHILDREN = 0x00c1d500,
25         NAME = 0x00111100,
26         NOTIFIER = 0x00071f00,
27         LENGTH = 0x00515300
28 };
29
30 struct tal_hdr {
31         struct list_node list;
32         struct prop_hdr *prop;
33         /* XOR with TAL_PTR_OBFUSTICATOR */
34         intptr_t parent_child;
35 };
36
37 struct prop_hdr {
38         enum prop_type type;
39         struct prop_hdr *next;
40 };
41
42 struct children {
43         struct prop_hdr hdr; /* CHILDREN */
44         struct tal_hdr *parent;
45         struct list_head children; /* Head of siblings. */
46 };
47
48 struct name {
49         struct prop_hdr hdr; /* NAME */
50         char name[];
51 };
52
53 struct length {
54         struct prop_hdr hdr; /* LENGTH */
55         size_t len;
56 };
57
58 struct notifier {
59         struct prop_hdr hdr; /* NOTIFIER */
60         enum tal_notify_type types;
61         union {
62                 void (*notifyfn)(tal_t *, enum tal_notify_type, void *);
63                 void (*destroy)(tal_t *); /* If NOTIFY_IS_DESTRUCTOR set */
64                 void (*destroy2)(tal_t *, void *); /* If NOTIFY_EXTRA_ARG */
65         } u;
66 };
67
68 /* Extra arg */
69 struct notifier_extra_arg {
70         struct notifier n;
71         void *arg;
72 };
73
74 #define EXTRA_ARG(n) (((struct notifier_extra_arg *)(n))->arg)
75
76 static struct {
77         struct tal_hdr hdr;
78         struct children c;
79 } null_parent = { { { &null_parent.hdr.list, &null_parent.hdr.list },
80                     &null_parent.c.hdr, TAL_PTR_OBFUSTICATOR },
81                   { { CHILDREN, NULL },
82                     &null_parent.hdr,
83                     { { &null_parent.c.children.n,
84                         &null_parent.c.children.n } }
85                   }
86 };
87
88
89 static void *(*allocfn)(size_t size) = malloc;
90 static void *(*resizefn)(void *, size_t size) = realloc;
91 static void (*freefn)(void *) = free;
92 static void (*errorfn)(const char *msg) = (void *)abort;
93 /* Count on non-destrutor notifiers; often stays zero. */
94 static size_t notifiers = 0;
95
96 static inline void COLD call_error(const char *msg)
97 {
98         errorfn(msg);
99 }
100
101 static bool get_destroying_bit(intptr_t parent_child)
102 {
103         return parent_child & 1;
104 }
105
106 static void set_destroying_bit(intptr_t *parent_child)
107 {
108         *parent_child |= 1;
109 }
110
111 static struct children *ignore_destroying_bit(intptr_t parent_child)
112 {
113         return (void *)((parent_child ^ TAL_PTR_OBFUSTICATOR) & ~(intptr_t)1);
114 }
115
116 /* This means valgrind can see leaks. */
117 void tal_cleanup(void)
118 {
119         struct tal_hdr *i;
120
121         while ((i = list_top(&null_parent.c.children, struct tal_hdr, list))) {
122                 list_del(&i->list);
123                 memset(i, 0, sizeof(*i));
124         }
125
126         /* Cleanup any taken pointers. */
127         take_cleanup();
128 }
129
130 /* We carefully start all real properties with a zero byte. */
131 static bool is_literal(const struct prop_hdr *prop)
132 {
133         return ((char *)prop)[0] != 0;
134 }
135
136 #ifndef NDEBUG
137 static const void *bounds_start, *bounds_end;
138
139 static void update_bounds(const void *new, size_t size)
140 {
141         if (unlikely(!bounds_start)) {
142                 bounds_start = new;
143                 bounds_end = (char *)new + size;
144         } else if (new < bounds_start)
145                 bounds_start = new;
146         else if ((char *)new + size > (char *)bounds_end)
147                 bounds_end = (char *)new + size;
148 }
149
150 static bool in_bounds(const void *p)
151 {
152         return !p
153                 || (p >= (void *)&null_parent && p <= (void *)(&null_parent + 1))
154                 || (p >= bounds_start && p <= bounds_end);
155 }
156 #else
157 static void update_bounds(const void *new, size_t size)
158 {
159 }
160
161 static bool in_bounds(const void *p)
162 {
163         return true;
164 }
165 #endif
166
167 static void check_bounds(const void *p)
168 {
169         if (!in_bounds(p))
170                 call_error("Not a valid header");
171 }
172
173 static struct tal_hdr *to_tal_hdr(const void *ctx)
174 {
175         struct tal_hdr *t;
176
177         t = (struct tal_hdr *)((char *)ctx - sizeof(struct tal_hdr));
178         check_bounds(t);
179         check_bounds(ignore_destroying_bit(t->parent_child));
180         check_bounds(t->list.next);
181         check_bounds(t->list.prev);
182         if (t->prop && !is_literal(t->prop))
183                 check_bounds(t->prop);
184         return t;
185 }
186
187 static struct tal_hdr *to_tal_hdr_or_null(const void *ctx)
188 {
189         if (!ctx)
190                 return &null_parent.hdr;
191         return to_tal_hdr(ctx);
192 }
193
194 static void *from_tal_hdr(const struct tal_hdr *hdr)
195 {
196         return (void *)(hdr + 1);
197 }
198
199 #ifdef TAL_DEBUG
200 static void *from_tal_hdr_or_null(struct tal_hdr *hdr)
201 {
202         if (hdr == &null_parent.hdr)
203                 return NULL;
204         return from_tal_hdr(hdr);
205 }
206
207 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
208 {
209         tal_check(from_tal_hdr_or_null(tal), "TAL_DEBUG ");
210         return tal;
211 }
212 #else
213 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
214 {
215         return tal;
216 }
217 #endif
218
219 static void notify(const struct tal_hdr *ctx,
220                    enum tal_notify_type type, const void *info,
221                    int saved_errno)
222 {
223         const struct prop_hdr *p;
224
225         for (p = ctx->prop; p; p = p->next) {
226                 struct notifier *n;
227
228                 if (is_literal(p))
229                         break;
230                 if (p->type != NOTIFIER)
231                         continue;
232                 n = (struct notifier *)p;
233                 if (n->types & type) {
234                         errno = saved_errno;
235                         if (n->types & NOTIFY_IS_DESTRUCTOR) {
236                                 if (n->types & NOTIFY_EXTRA_ARG)
237                                         n->u.destroy2(from_tal_hdr(ctx),
238                                                       EXTRA_ARG(n));
239                                 else
240                                         n->u.destroy(from_tal_hdr(ctx));
241                         } else
242                                 n->u.notifyfn(from_tal_hdr(ctx), type,
243                                               (void *)info);
244                 }
245         }
246 }
247
248 static void *allocate(size_t size)
249 {
250         void *ret = allocfn(size);
251         if (!ret)
252                 call_error("allocation failed");
253         else
254                 update_bounds(ret, size);
255         return ret;
256 }
257
258 static struct prop_hdr **find_property_ptr(const struct tal_hdr *t,
259                                            enum prop_type type)
260 {
261         struct prop_hdr **p;
262
263         for (p = (struct prop_hdr **)&t->prop; *p; p = &(*p)->next) {
264                 if (is_literal(*p)) {
265                         if (type == NAME)
266                                 return p;
267                         break;
268                 }
269                 if ((*p)->type == type)
270                         return p;
271         }
272         return NULL;
273 }
274
275 static void *find_property(const struct tal_hdr *parent, enum prop_type type)
276 {
277         struct prop_hdr **p = find_property_ptr(parent, type);
278
279         if (p)
280                 return *p;
281         return NULL;
282 }
283
284 static void init_property(struct prop_hdr *hdr,
285                           struct tal_hdr *parent,
286                           enum prop_type type)
287 {
288         hdr->type = type;
289         hdr->next = parent->prop;
290         parent->prop = hdr;
291 }
292
293 static struct notifier *add_notifier_property(struct tal_hdr *t,
294                                               enum tal_notify_type types,
295                                               void (*fn)(void *,
296                                                          enum tal_notify_type,
297                                                          void *),
298                                               void *extra_arg)
299 {
300         struct notifier *prop;
301
302         if (types & NOTIFY_EXTRA_ARG)
303                 prop = allocate(sizeof(struct notifier_extra_arg));
304         else
305                 prop = allocate(sizeof(struct notifier));
306
307         if (prop) {
308                 init_property(&prop->hdr, t, NOTIFIER);
309                 prop->types = types;
310                 prop->u.notifyfn = fn;
311                 if (types & NOTIFY_EXTRA_ARG)
312                         EXTRA_ARG(prop) = extra_arg;
313         }
314         return prop;
315 }
316
317 static enum tal_notify_type del_notifier_property(struct tal_hdr *t,
318                                                   void (*fn)(tal_t *,
319                                                              enum tal_notify_type,
320                                                              void *),
321                                                   bool match_extra_arg,
322                                                   void *extra_arg)
323 {
324         struct prop_hdr **p;
325
326         for (p = (struct prop_hdr **)&t->prop; *p; p = &(*p)->next) {
327                 struct notifier *n;
328                 enum tal_notify_type types;
329
330                 if (is_literal(*p))
331                         break;
332                 if ((*p)->type != NOTIFIER)
333                         continue;
334                 n = (struct notifier *)*p;
335                 if (n->u.notifyfn != fn)
336                         continue;
337
338                 types = n->types;
339                 if ((types & NOTIFY_EXTRA_ARG)
340                     && match_extra_arg
341                     && extra_arg != EXTRA_ARG(n))
342                         continue;
343
344                 *p = (*p)->next;
345                 freefn(n);
346                 return types & ~(NOTIFY_IS_DESTRUCTOR|NOTIFY_EXTRA_ARG);
347         }
348         return 0;
349 }
350
351 static struct name *add_name_property(struct tal_hdr *t, const char *name)
352 {
353         struct name *prop;
354
355         prop = allocate(sizeof(*prop) + strlen(name) + 1);
356         if (prop) {
357                 init_property(&prop->hdr, t, NAME);
358                 strcpy(prop->name, name);
359         }
360         return prop;
361 }
362
363 static struct children *add_child_property(struct tal_hdr *parent,
364                                            struct tal_hdr *child UNNEEDED)
365 {
366         struct children *prop = allocate(sizeof(*prop));
367         if (prop) {
368                 init_property(&prop->hdr, parent, CHILDREN);
369                 prop->parent = parent;
370                 list_head_init(&prop->children);
371         }
372         return prop;
373 }
374
375 static bool add_child(struct tal_hdr *parent, struct tal_hdr *child)
376 {
377         struct children *children = find_property(parent, CHILDREN);
378
379         if (!children) {
380                 children = add_child_property(parent, child);
381                 if (!children)
382                         return false;
383         }
384         list_add(&children->children, &child->list);
385         child->parent_child = (intptr_t)children ^ TAL_PTR_OBFUSTICATOR;
386         return true;
387 }
388
389 static void del_tree(struct tal_hdr *t, const tal_t *orig, int saved_errno)
390 {
391         struct prop_hdr **prop, *p, *next;
392
393         /* Already being destroyed?  Don't loop. */
394         if (unlikely(get_destroying_bit(t->parent_child)))
395                 return;
396
397         set_destroying_bit(&t->parent_child);
398
399         /* Call free notifiers. */
400         notify(t, TAL_NOTIFY_FREE, (tal_t *)orig, saved_errno);
401
402         /* Now free children and groups. */
403         prop = find_property_ptr(t, CHILDREN);
404         if (prop) {
405                 struct tal_hdr *i;
406                 struct children *c = (struct children *)*prop;
407
408                 while ((i = list_top(&c->children, struct tal_hdr, list))) {
409                         list_del(&i->list);
410                         del_tree(i, orig, saved_errno);
411                 }
412         }
413
414         /* Finally free our properties. */
415         for (p = t->prop; p && !is_literal(p); p = next) {
416                 next = p->next;
417                 /* LENGTH is appended, so don't free separately! */
418                 if (p->type != LENGTH)
419                         freefn(p);
420         }
421         freefn(t);
422 }
423
424 static size_t extra_for_length(size_t size)
425 {
426         size_t extra;
427         const size_t align = ALIGNOF(struct length);
428
429         /* Round up size, and add tailer. */
430         extra = ((size + align-1) & ~(align-1)) - size;
431         extra += sizeof(struct length);
432         return extra;
433 }
434
435 void *tal_alloc_(const tal_t *ctx, size_t size,
436                  bool clear, bool add_length, const char *label)
437 {
438         size_t req_size = size;
439         struct tal_hdr *child, *parent = debug_tal(to_tal_hdr_or_null(ctx));
440
441 #ifdef CCAN_TAL_DEBUG
442         /* Always record length if debugging. */
443         add_length = true;
444 #endif
445         if (add_length)
446                 size += extra_for_length(size);
447
448         child = allocate(sizeof(struct tal_hdr) + size);
449         if (!child)
450                 return NULL;
451         if (clear)
452                 memset(from_tal_hdr(child), 0, req_size);
453         child->prop = (void *)label;
454
455         if (add_length) {
456                 struct length *lprop;
457                 lprop = (struct length *)((char *)(child+1) + size) - 1;
458                 init_property(&lprop->hdr, child, LENGTH);
459                 lprop->len = req_size;
460         }
461         if (!add_child(parent, child)) {
462                 freefn(child);
463                 return NULL;
464         }
465         debug_tal(parent);
466         if (notifiers)
467                 notify(parent, TAL_NOTIFY_ADD_CHILD, from_tal_hdr(child), 0);
468         return from_tal_hdr(debug_tal(child));
469 }
470
471 static bool adjust_size(size_t *size, size_t count)
472 {
473         const size_t extra = sizeof(struct tal_hdr) + sizeof(struct length)*2;
474
475         /* Multiplication wrap */
476         if (count && unlikely(*size * count / *size != count))
477                 goto overflow;
478
479         *size *= count;
480
481         /* Make sure we don't wrap adding header/tailer. */
482         if (*size + extra < extra)
483                 goto overflow;
484         return true;
485 overflow:
486         call_error("allocation size overflow");
487         return false;
488 }
489
490 void *tal_alloc_arr_(const tal_t *ctx, size_t size, size_t count, bool clear,
491                      bool add_length, const char *label)
492 {
493         if (!adjust_size(&size, count))
494                 return NULL;
495
496         return tal_alloc_(ctx, size, clear, add_length, label);
497 }
498
499 void *tal_free(const tal_t *ctx)
500 {
501         if (ctx) {
502                 struct tal_hdr *t;
503                 int saved_errno = errno;
504                 t = debug_tal(to_tal_hdr(ctx));
505                 if (notifiers)
506                         notify(ignore_destroying_bit(t->parent_child)->parent,
507                                TAL_NOTIFY_DEL_CHILD, ctx, saved_errno);
508                 list_del(&t->list);
509                 del_tree(t, ctx, saved_errno);
510                 errno = saved_errno;
511         }
512         return NULL;
513 }
514
515 void *tal_steal_(const tal_t *new_parent, const tal_t *ctx)
516 {
517         if (ctx) {
518                 struct tal_hdr *newpar, *t, *old_parent;
519
520                 newpar = debug_tal(to_tal_hdr_or_null(new_parent));
521                 t = debug_tal(to_tal_hdr(ctx));
522
523                 /* Unlink it from old parent. */
524                 list_del(&t->list);
525                 old_parent = ignore_destroying_bit(t->parent_child)->parent;
526
527                 if (unlikely(!add_child(newpar, t))) {
528                         /* We can always add to old parent, becuase it has a
529                          * children property already. */
530                         if (!add_child(old_parent, t))
531                                 abort();
532                         return NULL;
533                 }
534                 debug_tal(newpar);
535                 if (notifiers)
536                         notify(t, TAL_NOTIFY_STEAL, new_parent, 0);
537         }
538         return (void *)ctx;
539 }
540
541 bool tal_add_destructor_(const tal_t *ctx, void (*destroy)(void *me))
542 {
543         tal_t *t = debug_tal(to_tal_hdr(ctx));
544         return add_notifier_property(t, TAL_NOTIFY_FREE|NOTIFY_IS_DESTRUCTOR,
545                                      (void *)destroy, NULL);
546 }
547
548 bool tal_add_destructor2_(const tal_t *ctx, void (*destroy)(void *me, void *arg),
549                           void *arg)
550 {
551         tal_t *t = debug_tal(to_tal_hdr(ctx));
552         return add_notifier_property(t, TAL_NOTIFY_FREE|NOTIFY_IS_DESTRUCTOR
553                                      |NOTIFY_EXTRA_ARG,
554                                      (void *)destroy, arg);
555 }
556
557 /* We could support notifiers with an extra arg, but we didn't add to API */
558 bool tal_add_notifier_(const tal_t *ctx, enum tal_notify_type types,
559                        void (*callback)(tal_t *, enum tal_notify_type, void *))
560 {
561         tal_t *t = debug_tal(to_tal_hdr(ctx));
562         struct notifier *n;
563
564         assert(types);
565         assert((types & ~(TAL_NOTIFY_FREE | TAL_NOTIFY_STEAL | TAL_NOTIFY_MOVE
566                           | TAL_NOTIFY_RESIZE | TAL_NOTIFY_RENAME
567                           | TAL_NOTIFY_ADD_CHILD | TAL_NOTIFY_DEL_CHILD
568                           | TAL_NOTIFY_ADD_NOTIFIER
569                           | TAL_NOTIFY_DEL_NOTIFIER)) == 0);
570
571         /* Don't call notifier about itself: set types after! */
572         n = add_notifier_property(t, 0, callback, NULL);
573         if (unlikely(!n))
574                 return false;
575
576         if (notifiers)
577                 notify(t, TAL_NOTIFY_ADD_NOTIFIER, callback, 0);
578
579         n->types = types;
580         if (types != TAL_NOTIFY_FREE)
581                 notifiers++;
582         return true;
583 }
584
585 bool tal_del_notifier_(const tal_t *ctx,
586                        void (*callback)(tal_t *, enum tal_notify_type, void *),
587                        bool match_extra_arg, void *extra_arg)
588 {
589         struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
590         enum tal_notify_type types;
591
592         types = del_notifier_property(t, callback, match_extra_arg, extra_arg);
593         if (types) {
594                 notify(t, TAL_NOTIFY_DEL_NOTIFIER, callback, 0);
595                 if (types != TAL_NOTIFY_FREE)
596                         notifiers--;
597                 return true;
598         }
599         return false;
600 }
601
602 bool tal_del_destructor_(const tal_t *ctx, void (*destroy)(void *me))
603 {
604         return tal_del_notifier_(ctx, (void *)destroy, false, NULL);
605 }
606
607 bool tal_del_destructor2_(const tal_t *ctx, void (*destroy)(void *me, void *arg),
608                           void *arg)
609 {
610         return tal_del_notifier_(ctx, (void *)destroy, true, arg);
611 }
612
613 bool tal_set_name_(tal_t *ctx, const char *name, bool literal)
614 {
615         struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
616         struct prop_hdr **prop = find_property_ptr(t, NAME);
617
618         /* Get rid of any old name */
619         if (prop) {
620                 struct name *name = (struct name *)*prop;
621                 if (is_literal(&name->hdr))
622                         *prop = NULL;
623                 else {
624                         *prop = name->hdr.next;
625                         freefn(name);
626                 }
627         }
628
629         if (literal && name[0]) {
630                 struct prop_hdr **p;
631
632                 /* Append literal. */
633                 for (p = &t->prop; *p && !is_literal(*p); p = &(*p)->next);
634                 *p = (struct prop_hdr *)name;
635         } else if (!add_name_property(t, name))
636                 return false;
637
638         debug_tal(t);
639         if (notifiers)
640                 notify(t, TAL_NOTIFY_RENAME, name, 0);
641         return true;
642 }
643
644 const char *tal_name(const tal_t *t)
645 {
646         struct name *n;
647
648         n = find_property(debug_tal(to_tal_hdr(t)), NAME);
649         if (!n)
650                 return NULL;
651
652         if (is_literal(&n->hdr))
653                 return (const char *)n;
654         return n->name;
655 }
656
657 size_t tal_len(const tal_t *ptr)
658 {
659         struct length *l;
660
661         if (!ptr)
662                 return 0;
663
664         l = find_property(debug_tal(to_tal_hdr(ptr)), LENGTH);
665         if (!l)
666                 return 0;
667         return l->len;
668 }
669
670 /* Start one past first child: make stopping natural in circ. list. */
671 static struct tal_hdr *first_child(struct tal_hdr *parent)
672 {
673         struct children *child;
674
675         child = find_property(parent, CHILDREN);
676         if (!child)
677                 return NULL;
678
679         return list_top(&child->children, struct tal_hdr, list);
680 }
681
682 tal_t *tal_first(const tal_t *root)
683 {
684         struct tal_hdr *c, *t = debug_tal(to_tal_hdr_or_null(root));
685
686         c = first_child(t);
687         if (!c)
688                 return NULL;
689         return from_tal_hdr(c);
690 }
691
692 tal_t *tal_next(const tal_t *prev)
693 {
694         struct tal_hdr *next, *prevhdr = debug_tal(to_tal_hdr(prev));
695         struct list_head *head;
696
697         head = &ignore_destroying_bit(prevhdr->parent_child)->children;
698         next = list_next(head, prevhdr, list);
699         if (!next)
700                 return NULL;
701         return from_tal_hdr(next);
702 }
703
704 tal_t *tal_parent(const tal_t *ctx)
705 {
706         struct tal_hdr *t;
707
708         if (!ctx)
709                 return NULL;
710
711         t = debug_tal(to_tal_hdr(ctx));
712         if (ignore_destroying_bit(t->parent_child)->parent == &null_parent.hdr)
713                 return NULL;
714         return from_tal_hdr(ignore_destroying_bit(t->parent_child)->parent);
715 }
716
717 bool tal_resize_(tal_t **ctxp, size_t size, size_t count, bool clear)
718 {
719         struct tal_hdr *old_t, *t;
720         struct children *child;
721         struct prop_hdr **lenp;
722         struct length len;
723         size_t extra = 0;
724
725         old_t = debug_tal(to_tal_hdr(*ctxp));
726
727         if (!adjust_size(&size, count))
728                 return false;
729
730         lenp = find_property_ptr(old_t, LENGTH);
731         if (lenp) {
732                 /* Copy here, in case we're shrinking! */
733                 len = *(struct length *)*lenp;
734                 extra = extra_for_length(size);
735         } else /* If we don't have an old length, we can't clear! */
736                 assert(!clear);
737
738         t = resizefn(old_t, sizeof(struct tal_hdr) + size + extra);
739         if (!t) {
740                 call_error("Reallocation failure");
741                 return false;
742         }
743
744         /* Copy length to end. */
745         if (lenp) {
746                 struct length *new_len;
747
748                 /* Clear between old end and new end. */
749                 if (clear && size > len.len) {
750                         char *old_end = (char *)(t + 1) + len.len;
751                         memset(old_end, 0, size - len.len);
752                 }
753
754                 new_len = (struct length *)((char *)(t + 1) + size
755                                             + extra - sizeof(len));
756                 len.len = size;
757                 *new_len = len;
758
759                 /* Be careful replacing next ptr; could be old hdr. */
760                 if (lenp == &old_t->prop)
761                         t->prop = &new_len->hdr;
762                 else
763                         *lenp = &new_len->hdr;
764         }
765
766         update_bounds(t, sizeof(struct tal_hdr) + size + extra);
767
768         /* If it didn't move, we're done! */
769         if (t != old_t) {
770                 /* Fix up linked list pointers. */
771                 t->list.next->prev = t->list.prev->next = &t->list;
772
773                 /* Fix up child property's parent pointer. */
774                 child = find_property(t, CHILDREN);
775                 if (child) {
776                         assert(child->parent == old_t);
777                         child->parent = t;
778                 }
779                 *ctxp = from_tal_hdr(debug_tal(t));
780                 if (notifiers)
781                         notify(t, TAL_NOTIFY_MOVE, from_tal_hdr(old_t), 0);
782         }
783         if (notifiers)
784                 notify(t, TAL_NOTIFY_RESIZE, (void *)size, 0);
785
786         return true;
787 }
788
789 bool tal_expand_(tal_t **ctxp, const void *src, size_t size, size_t count)
790 {
791         struct length *l;
792         size_t old_len;
793         bool ret = false;
794
795         l = find_property(debug_tal(to_tal_hdr(*ctxp)), LENGTH);
796         old_len = l->len;
797
798         /* Check for additive overflow */
799         if (old_len + count * size < old_len) {
800                 call_error("dup size overflow");
801                 goto out;
802         }
803
804         /* Don't point src inside thing we're expanding! */
805         assert(src < *ctxp
806                || (char *)src >= (char *)(*ctxp) + old_len);
807
808         if (!tal_resize_(ctxp, size, old_len/size + count, false))
809                 goto out;
810
811         memcpy((char *)*ctxp + old_len, src, count * size);
812         ret = true;
813
814 out:
815         if (taken(src))
816                 tal_free(src);
817         return ret;
818 }
819
820 void *tal_dup_(const tal_t *ctx, const void *p, size_t size,
821                size_t n, size_t extra, bool add_length,
822                const char *label)
823 {
824         void *ret;
825         size_t nbytes = size;
826
827         if (!adjust_size(&nbytes, n)) {
828                 if (taken(p))
829                         tal_free(p);
830                 return NULL;
831         }
832
833         /* Beware addition overflow! */
834         if (n + extra < n) {
835                 call_error("dup size overflow");
836                 if (taken(p))
837                         tal_free(p);
838                 return NULL;
839         }
840
841         if (taken(p)) {
842                 if (unlikely(!p))
843                         return NULL;
844                 if (unlikely(!tal_resize_((void **)&p, size, n + extra, false)))
845                         return tal_free(p);
846                 if (unlikely(!tal_steal(ctx, p)))
847                         return tal_free(p);
848                 return (void *)p;
849         }
850
851         ret = tal_alloc_arr_(ctx, size, n + extra, false, add_length, label);
852         if (ret)
853                 memcpy(ret, p, nbytes);
854         return ret;
855 }
856
857 void tal_set_backend(void *(*alloc_fn)(size_t size),
858                      void *(*resize_fn)(void *, size_t size),
859                      void (*free_fn)(void *),
860                      void (*error_fn)(const char *msg))
861 {
862         if (alloc_fn)
863                 allocfn = alloc_fn;
864         if (resize_fn)
865                 resizefn = resize_fn;
866         if (free_fn)
867                 freefn = free_fn;
868         if (error_fn)
869                 errorfn = error_fn;
870 }
871
872 #ifdef CCAN_TAL_DEBUG
873 static void dump_node(unsigned int indent, const struct tal_hdr *t)
874 {
875         unsigned int i;
876         const struct prop_hdr *p;
877
878         for (i = 0; i < indent; i++)
879                 printf("  ");
880         printf("%p", t);
881         for (p = t->prop; p; p = p->next) {
882                 struct children *c;
883                 struct name *n;
884                 struct notifier *no;
885                 struct length *l;
886                 if (is_literal(p)) {
887                         printf(" \"%s\"", (const char *)p);
888                         break;
889                 }
890                 switch (p->type) {
891                 case CHILDREN:
892                         c = (struct children *)p;
893                         printf(" CHILDREN(%p):parent=%p,children={%p,%p}\n",
894                                p, c->parent,
895                                c->children.n.prev, c->children.n.next);
896                         break;
897                 case NAME:
898                         n = (struct name *)p;
899                         printf(" NAME(%p):%s", p, n->name);
900                         break;
901                 case NOTIFIER:
902                         no = (struct notifier *)p;
903                         printf(" NOTIFIER(%p):fn=%p", p, no->u.notifyfn);
904                         break;
905                 case LENGTH:
906                         l = (struct length *)p;
907                         printf(" LENGTH(%p):len=%zu", p, l->len);
908                         break;
909                 default:
910                         printf(" **UNKNOWN(%p):%i**", p, p->type);
911                 }
912         }
913         printf("\n");
914 }
915
916 static void tal_dump_(unsigned int level, const struct tal_hdr *t)
917 {
918         struct children *children;
919
920         dump_node(level, t);
921
922         children = find_property(t, CHILDREN);
923         if (children) {
924                 struct tal_hdr *i;
925
926                 list_for_each(&children->children, i, list)
927                         tal_dump_(level + 1, i);
928         }
929 }
930
931 void tal_dump(void)
932 {
933         tal_dump_(0, &null_parent.hdr);
934 }
935 #endif /* CCAN_TAL_DEBUG */
936
937 #ifndef NDEBUG
938 static bool check_err(struct tal_hdr *t, const char *errorstr,
939                       const char *errmsg)
940 {
941         if (errorstr) {
942                 /* Try not to malloc: it may be corrupted. */
943                 char msg[strlen(errorstr) + 20 + strlen(errmsg) + 1];
944                 sprintf(msg, "%s:%p %s", errorstr, from_tal_hdr(t), errmsg);
945                 call_error(msg);
946         }
947         return false;
948 }
949
950 static bool check_node(struct children *parent_child,
951                        struct tal_hdr *t, const char *errorstr)
952 {
953         struct prop_hdr *p;
954         struct name *name = NULL;
955         struct children *children = NULL;
956         struct length *length = NULL;
957
958         if (!in_bounds(t))
959                 return check_err(t, errorstr, "invalid pointer");
960
961         if (ignore_destroying_bit(t->parent_child) != parent_child)
962                 return check_err(t, errorstr, "incorrect parent");
963
964         for (p = t->prop; p; p = p->next) {
965                 if (is_literal(p)) {
966                         if (name)
967                                 return check_err(t, errorstr,
968                                                  "has extra literal");
969                         break;
970                 }
971                 if (!in_bounds(p))
972                         return check_err(t, errorstr,
973                                          "has bad property pointer");
974
975                 switch (p->type) {
976                 case CHILDREN:
977                         if (children)
978                                 return check_err(t, errorstr,
979                                                  "has two child nodes");
980                         children = (struct children *)p;
981                         break;
982                 case LENGTH:
983                         if (length)
984                                 return check_err(t, errorstr,
985                                                  "has two lengths");
986                         length = (struct length *)p;
987                         break;
988                 case NOTIFIER:
989                         break;
990                 case NAME:
991                         if (name)
992                                 return check_err(t, errorstr,
993                                                  "has two names");
994                         name = (struct name *)p;
995                         break;
996                 default:
997                         return check_err(t, errorstr, "has unknown property");
998                 }
999         }
1000         if (children) {
1001                 struct tal_hdr *i;
1002
1003                 if (!list_check(&children->children, errorstr))
1004                         return false;
1005                 list_for_each(&children->children, i, list) {
1006                         if (!check_node(children, i, errorstr))
1007                                 return false;
1008                 }
1009         }
1010         return true;
1011 }
1012
1013 bool tal_check(const tal_t *ctx, const char *errorstr)
1014 {
1015         struct tal_hdr *t = to_tal_hdr_or_null(ctx);
1016
1017         return check_node(ignore_destroying_bit(t->parent_child), t, errorstr);
1018 }
1019 #else /* NDEBUG */
1020 bool tal_check(const tal_t *ctx, const char *errorstr)
1021 {
1022         return true;
1023 }
1024 #endif