9fed477fe9595bd4e85d5243f1315c602915a830
[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/hash/hash.h>
5 #include <ccan/list/list.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
13 //#define TAL_DEBUG 1
14
15 /* How large should grouips get? */
16 #define GROUP_NODE_AVERAGE 32
17
18 /* 32-bit type field, first byte 0 in either endianness. */
19 enum prop_type {
20         CHILDREN = 0x00c1d500,
21         GROUP = 0x00600d00,
22         DESTRUCTOR = 0x00de5700,
23         NAME = 0x00111100,
24 };
25
26 struct tal_hdr {
27         struct tal_hdr *next;
28         struct prop_hdr *prop;
29 };
30
31 struct prop_hdr {
32         enum prop_type type;
33         struct prop_hdr *next;
34 };
35
36 /* Unlike other properties, this is owned by parent, not child! */
37 struct group {
38         struct prop_hdr hdr; /* GROUP */
39         struct list_head list; /* Head for child->group, node for others. */
40         /* We point to parent's children property, as it doesn't move! */
41         struct children *parent_child;
42         struct tal_hdr *first_child;
43 };
44
45 struct children {
46         struct prop_hdr hdr; /* CHILDREN */
47         struct tal_hdr *parent;
48         /* We always have one group.  Others may be added. */
49         struct group group;
50 };
51
52 struct destructor {
53         struct prop_hdr hdr; /* DESTRUCTOR */
54         void (*destroy)(void *me);
55 };
56
57 struct name {
58         struct prop_hdr hdr; /* NAME */
59         char name[];
60 };
61
62 static struct {
63         struct tal_hdr hdr;
64         struct children c;
65 } null_parent = { { NULL, &null_parent.c.hdr },
66                   { { CHILDREN, NULL },
67                     &null_parent.hdr,
68                     { { GROUP, NULL },
69                       { { &null_parent.c.group.list.n,
70                           &null_parent.c.group.list.n } },
71                       &null_parent.c, NULL } }
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
80 static inline void COLD call_error(const char *msg)
81 {
82         errorfn(msg);
83 }
84
85 static bool get_destroying_bit(struct tal_hdr *next)
86 {
87         return (size_t)next & 1;
88 }
89
90 static void set_destroying_bit(struct tal_hdr **next)
91 {
92         *next = (void *)((size_t)next | 1);
93 }
94
95 static struct tal_hdr *ignore_destroying_bit(struct tal_hdr *next)
96 {
97         return (void *)((size_t)next & ~(size_t)1);
98 }
99
100 static struct group *next_group(struct group *group)
101 {
102         return list_entry(group->list.n.next, struct group, list.n);
103 }
104
105 static bool atexit_set = false;
106 /* This means valgrind can see leaks. */
107 static void unlink_null(void)
108 {
109         struct group *i, *next;
110
111         for (i = next_group(&null_parent.c.group);
112              i != &null_parent.c.group;
113              i = next) {
114                 next = next_group(i);
115                 freefn(i);
116         }
117         null_parent.c.group.first_child = NULL;
118 }
119
120 #ifndef NDEBUG
121 static const void *bounds_start, *bounds_end;
122
123 static void update_bounds(const void *new)
124 {
125         if (unlikely(!bounds_start))
126                 bounds_start = bounds_end = new;
127         else if (new < bounds_start)
128                 bounds_start = new;
129         else if (new > bounds_end)
130                 bounds_end = new;
131 }
132
133 static bool in_bounds(const void *p)
134 {
135         return !p || (p >= bounds_start && p <= bounds_end);
136 }
137 #else
138 static void update_bounds(const void *new)
139 {
140 }
141
142 static bool in_bounds(const void *p)
143 {
144         return true;
145 }
146 #endif
147
148 static void check_bounds(const void *p)
149 {
150         if (!in_bounds(p))
151                 call_error("Not a valid header");
152 }
153
154 static struct tal_hdr *to_tal_hdr(const void *ctx)
155 {
156         struct tal_hdr *t;
157
158         t = (struct tal_hdr *)((char *)ctx - sizeof(struct tal_hdr));
159         check_bounds(t);
160         check_bounds(ignore_destroying_bit(t->next));
161         return t;
162 }
163
164 static struct tal_hdr *to_tal_hdr_or_null(const void *ctx)
165 {
166         if (!ctx)
167                 return &null_parent.hdr;
168         return to_tal_hdr(ctx);
169 }
170
171 static void *from_tal_hdr(struct tal_hdr *hdr)
172 {
173         return hdr + 1;
174 }
175
176 #ifdef TAL_DEBUG
177 static void *from_tal_hdr_or_null(struct tal_hdr *hdr)
178 {
179         if (hdr == &null_parent.hdr)
180                 return NULL;
181         return from_tal_hdr(hdr);
182 }
183
184 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
185 {
186         tal_check(from_tal_hdr_or_null(tal), "TAL_DEBUG ");
187         return tal;
188 }
189 #else
190 static struct tal_hdr *debug_tal(struct tal_hdr *tal)
191 {
192         return tal;
193 }
194 #endif
195
196 static void *allocate(size_t size)
197 {
198         void *ret;
199
200         /* Don't hand silly sizes to malloc. */
201         if (size >> (CHAR_BIT*sizeof(size) - 1)) {
202                 call_error("allocation size overflow");
203                 return NULL;
204         }
205
206         ret = allocfn(size);
207         if (!ret)
208                 call_error("allocation failed");
209         else
210                 update_bounds(ret);
211         return ret;
212 }
213
214 /* We carefully start all real properties with a zero byte. */
215 static bool is_literal(const struct prop_hdr *prop)
216 {
217         return ((char *)prop)[0] != 0;
218 }
219
220 static struct prop_hdr **find_property_ptr(const struct tal_hdr *t,
221                                            enum prop_type type)
222 {
223         struct prop_hdr **p;
224
225         for (p = (struct prop_hdr **)&t->prop; *p; p = &(*p)->next) {
226                 if (is_literal(*p)) {
227                         if (type == NAME)
228                                 return p;
229                         break;
230                 }
231                 if ((*p)->type == type)
232                         return p;
233         }
234         return NULL;
235 }
236
237 static void *find_property(const struct tal_hdr *parent, enum prop_type type)
238 {
239         struct prop_hdr **p = find_property_ptr(parent, type);
240
241         if (p)
242                 return *p;
243         return NULL;
244 }
245
246 static void init_property(struct prop_hdr *hdr,
247                           struct tal_hdr *parent,
248                           enum prop_type type)
249 {
250         hdr->type = type;
251         hdr->next = parent->prop;
252         parent->prop = hdr;
253 }
254
255 static struct destructor *add_destructor_property(struct tal_hdr *t,
256                                                   void (*destroy)(void *))
257 {
258         struct destructor *prop = allocate(sizeof(*prop));
259         if (prop) {
260                 init_property(&prop->hdr, t, DESTRUCTOR);
261                 prop->destroy = destroy;
262         }
263         return prop;
264 }
265
266 static struct name *add_name_property(struct tal_hdr *t, const char *name)
267 {
268         struct name *prop;
269
270         prop = allocate(sizeof(*prop) + strlen(name) + 1);
271         if (prop) {
272                 init_property(&prop->hdr, t, NAME);
273                 strcpy(prop->name, name);
274         }
275         return prop;
276 }
277
278 static void init_group_property(struct group *group,
279                                 struct children *parent_child,
280                                 struct tal_hdr *child)
281 {
282         init_property(&group->hdr, child, GROUP);
283         group->parent_child = parent_child;
284         group->first_child = child;
285 }
286
287 static struct children *add_child_property(struct tal_hdr *parent,
288                                            struct tal_hdr *child)
289 {
290         struct children *prop = allocate(sizeof(*prop));
291         if (prop) {
292                 init_property(&prop->hdr, parent, CHILDREN);
293                 prop->parent = parent;
294
295                 init_group_property(&prop->group, prop, child);
296                 list_head_init(&prop->group.list);
297                 update_bounds(&prop->group);
298         }
299         return prop;
300 }
301
302 static struct group *add_group_property(struct tal_hdr *child,
303                                         struct children *parent_child)
304 {
305         struct group *prop = allocate(sizeof(*prop));
306         if (prop)
307                 init_group_property(prop, parent_child, child);
308         return prop;
309 }
310
311 static bool add_child(struct tal_hdr *parent, struct tal_hdr *child)
312 {
313         struct group *group;
314         struct children *children = find_property(parent, CHILDREN);
315
316         if (!children) {
317                 children = add_child_property(parent, child);
318                 if (!children)
319                         return false;
320                 list_head_init(&children->group.list);
321
322                 /* Child links to itself. */
323                 child->next = child;
324                 return true;
325         }
326
327         /* Last one (may be children->group itself). */
328         group = next_group(&children->group);
329
330         /* Empty group can happen: null_parent, or all children freed. */
331         if (unlikely(!group->first_child)) {
332                 assert(group == &children->group);
333                 /* This hits on first child appended to null parent. */
334                 if (unlikely(!atexit_set)) {
335                         atexit(unlink_null);
336                         atexit_set = true;
337                 }
338                 /* Link group into this child, make it the first one. */
339                 group->hdr.next = child->prop;
340                 child->prop = &group->hdr;
341                 group->first_child = child;
342
343                 /* Child links to itself. */
344                 child->next = child;
345                 return true;
346         }
347
348         if (unlikely(hash_pointer(child, 0) % GROUP_NODE_AVERAGE == 0)) {
349                 struct group *newgroup;
350
351                 newgroup = add_group_property(child, children);
352                 if (likely(newgroup)) {
353                         list_add(&children->group.list, &newgroup->list.n);
354
355                         /* Child links to itself. */
356                         child->next = child;
357                         return true;
358                 }
359                 /* Fall through: on allocation failure reuse old group. */
360         }
361
362         /* We insert after head, otherwise we'd need to find end. */
363         child->next = group->first_child->next;
364         group->first_child->next = child;
365         return true;
366 }
367
368 static void del_tree(struct tal_hdr *t)
369 {
370         struct prop_hdr **prop, *p, *next;
371
372         /* Already being destroyed?  Don't loop. */
373         if (unlikely(get_destroying_bit(t->next)))
374                 return;
375
376         set_destroying_bit(&t->next);
377
378         /* Carefully call destructors, removing as we go. */
379         while ((prop = find_property_ptr(t, DESTRUCTOR))) {
380                 struct destructor *d = (struct destructor *)*prop;
381                 d->destroy(from_tal_hdr(t));
382                 *prop = d->hdr.next;
383                 freefn(d);
384         }
385
386         /* Now free children and groups. */
387         prop = find_property_ptr(t, CHILDREN);
388         if (prop) {
389                 struct children *c = (struct children *)*prop;
390                 struct group *group, *next;
391
392                 group = &c->group;
393                 do {
394                         next = next_group(group);
395                         if (group->first_child) {
396                                 struct tal_hdr *i, *nextc;
397
398                                 i = group->first_child;
399                                 do {
400                                         nextc = i->next;
401                                         del_tree(i);
402                                         i = nextc;
403                                 } while (i != group->first_child);
404                         }
405                         if (group != &c->group)
406                                 freefn(group);
407                         group = next;
408                 } while (group != &c->group);
409         }
410
411         /* Finally free our properties (groups are freed by parent). */
412         for (p = t->prop; p && !is_literal(p); p = next) {
413                 next = p->next;
414                 if (p->type != GROUP)
415                         freefn(p);
416         }
417         freefn(t);
418 }
419
420 void *tal_alloc_(const tal_t *ctx, size_t size, bool clear, const char *label)
421 {
422         struct tal_hdr *child, *parent = debug_tal(to_tal_hdr_or_null(ctx));
423
424         child = allocate(sizeof(struct tal_hdr) + size);
425         if (!child)
426                 return NULL;
427         if (clear)
428                 memset(from_tal_hdr(child), 0, size);
429         child->prop = (void *)label;
430         if (!add_child(parent, child)) {
431                 freefn(child);
432                 return NULL;
433         }
434         debug_tal(parent);
435         return from_tal_hdr(debug_tal(child));
436 }
437
438 /* Update back ptrs, etc, as required.
439  * May return pointer to parent. */
440 static struct tal_hdr *remove_node(struct tal_hdr *t)
441 {
442         struct prop_hdr **prop;
443         struct tal_hdr *prev;
444
445         /* Loop around to find previous node. */
446         for (prev = t->next; prev->next != t; prev = prev->next);
447
448         /* Unlink ourselves. */
449         prev->next = t->next;
450
451         /* Are we the node with the group property? */
452         prop = find_property_ptr(t, GROUP);
453         if (prop) {
454                 struct group *group = (struct group *)*prop;
455
456                 /* Are we the only one? */
457                 if (prev == t) {
458                         struct children *c = group->parent_child;
459                         /* Is this the group embedded in the child property? */
460                         if (group == &c->group) {
461                                 group->first_child = NULL;
462                         } else {
463                                 /* Empty group, so free it. */
464                                 list_del_from(&c->group.list, &group->list.n);
465                                 *prop = group->hdr.next;
466                                 freefn(group);
467                         }
468                         return c->parent;
469                 } else {
470                         /* Move property to next node. */
471                         group->first_child = t->next;
472
473                         *prop = group->hdr.next;
474                         group->hdr.next = t->next->prop;
475                         t->next->prop = &group->hdr;
476                 }
477         }
478         return NULL;
479 }
480
481 void tal_free(const tal_t *ctx)
482 {
483         struct tal_hdr *t;
484
485         if (!ctx)
486                 return;
487
488         t = debug_tal(to_tal_hdr(ctx));
489         remove_node(t);
490         del_tree(t);
491 }
492
493 void *tal_steal_(const tal_t *new_parent, const tal_t *ctx)
494 {
495         if (ctx) {
496                 struct tal_hdr *newpar, *t, *old_next, *old_parent;
497
498                 newpar = debug_tal(to_tal_hdr_or_null(new_parent));
499                 t = debug_tal(to_tal_hdr(ctx));
500
501                 /* Save enough data to get us back if we fail! */
502                 old_next = t->next;
503
504                 /* Unlink it from old parent. */
505                 old_parent = remove_node(t);
506                 if (unlikely(!add_child(newpar, t))) {
507                         /* If we were last child, parent returned by
508                          * remove_node, otherwise search old siblings
509                          * for it. */
510                         if (!old_parent) {
511                                 struct group *g;
512                                 while (!(g = find_property(old_next, GROUP)))
513                                         old_next = old_next->next;
514                                 old_parent = g->parent_child->parent;
515                         }
516                         /* We can always add to old parent, becuase it has one
517                          * group already. */
518                         if (!add_child(old_parent, t))
519                                 abort();
520                         return NULL;
521                 }
522                 debug_tal(newpar);
523         }
524         return (void *)ctx;
525 }
526
527 bool tal_add_destructor_(tal_t *ctx, void (*destroy)(void *me))
528 {
529         return add_destructor_property(debug_tal(to_tal_hdr(ctx)), destroy);
530 }
531
532 bool tal_set_name_(tal_t *ctx, const char *name, bool literal)
533 {
534         struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
535         struct prop_hdr **prop = find_property_ptr(t, NAME);
536
537         /* Get rid of any old name */
538         if (prop) {
539                 struct name *name = (struct name *)*prop;
540                 if (is_literal(&name->hdr))
541                         *prop = NULL;
542                 else {
543                         *prop = name->hdr.next;
544                         freefn(name);
545                 }
546         }
547
548         if (literal && name[0]) {
549                 struct prop_hdr **p;
550
551                 /* Append literal. */
552                 for (p = &t->prop; *p && !is_literal(*p); p = &(*p)->next);
553                 *p = (struct prop_hdr *)name;
554                 return true;
555         }
556         if (!add_name_property(t, name))
557                 return false;
558         debug_tal(t);
559         return true;
560 }
561
562 const char *tal_name(const tal_t *t)
563 {
564         struct name *n;
565
566         n = find_property(debug_tal(to_tal_hdr(t)), NAME);
567         if (!n)
568                 return NULL;
569
570         if (is_literal(&n->hdr))
571                 return (const char *)n;
572         return n->name;
573 }
574
575 /* Start one past first child: make stopping natural in circ. list. */
576 static struct tal_hdr *first_child(struct tal_hdr *parent)
577 {
578         struct children *child;
579         struct group *group;
580
581         child = find_property(parent, CHILDREN);
582         if (!child)
583                 return NULL;
584
585         /* Careful of empty group embedded in child property. */
586         if (child->group.first_child)
587                 return child->group.first_child->next;
588
589         /* There could still be another group! */
590         group = next_group(&child->group);
591         if (group == &child->group)
592                 return NULL;
593
594         return group->first_child->next;
595 }
596
597 tal_t *tal_first(const tal_t *root)
598 {
599         struct tal_hdr *c, *t = debug_tal(to_tal_hdr_or_null(root));
600
601         c = first_child(t);
602         if (!c)
603                 return NULL;
604         return from_tal_hdr(c);
605 }
606
607 tal_t *tal_next(const tal_t *root, const tal_t *prev)
608 {
609         struct tal_hdr *c, *t = debug_tal(to_tal_hdr(prev)), *top;
610         struct group *group;
611
612         /* Children? */
613         c = first_child(t);
614         if (c)
615                 return from_tal_hdr(c);
616
617         top = to_tal_hdr_or_null(root);
618         do {
619                 struct group *next;
620
621                 /* Are we back to first child in group? */
622                 group = find_property(t, GROUP);
623                 if (!group)
624                         return from_tal_hdr(t->next);
625
626                 /* Last group is one inside children property. */
627                 next = next_group(group);
628                 if (next != &group->parent_child->group)
629                         return from_tal_hdr(next->first_child->next);
630
631                 /* OK, go back to parent. */
632                 t = group->parent_child->parent;
633         } while (t != top);
634
635         return NULL;
636 }
637
638 tal_t *tal_parent(const tal_t *ctx)
639 {
640         struct group *group;
641         struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
642
643         while (!(group = find_property(t, GROUP)))
644                 t = t->next;
645
646         if (group->parent_child->parent == &null_parent.hdr)
647                 return NULL;
648         return from_tal_hdr(group->parent_child->parent);
649 }
650
651 void *tal_realloc_(tal_t *ctx, size_t size)
652 {
653         struct tal_hdr *old_t, *t, **prev;
654         struct group *group;
655         struct children *child;
656
657         old_t = debug_tal(to_tal_hdr(ctx));
658
659         t = resizefn(old_t, size + sizeof(struct tal_hdr));
660         if (!t) {
661                 call_error("Reallocation failure");
662                 tal_free(old_t);
663                 return NULL;
664         }
665         if (t == old_t)
666                 return ctx;
667         update_bounds(t);
668
669         /* Fix up linked list pointer. */
670         for (prev = &t->next; *prev != old_t; prev = &(*prev)->next);
671         *prev = t;
672
673         /* Fix up group pointer, if any. */
674         group = find_property(t, GROUP);
675         if (group) {
676                 assert(group->first_child == old_t);
677                 group->first_child = t;
678         }
679
680         /* Fix up child propertie's parent pointer. */
681         child = find_property(t, CHILDREN);
682         if (child) {
683                 assert(child->parent == old_t);
684                 child->parent = t;
685         }
686
687         return from_tal_hdr(debug_tal(t));
688 }
689
690 char *tal_strdup(const tal_t *ctx, const char *p)
691 {
692         return tal_memdup(ctx, p, strlen(p)+1);
693 }
694
695 char *tal_strndup(const tal_t *ctx, const char *p, size_t n)
696 {
697         char *ret;
698
699         if (strlen(p) < n)
700                 n = strlen(p);
701         ret = tal_memdup(ctx, p, n+1);
702         if (ret)
703                 ret[n] = '\0';
704         return ret;
705 }
706
707 void *tal_memdup(const tal_t *ctx, const void *p, size_t n)
708 {
709         void *ret;
710
711         if (ctx == TAL_TAKE)
712                 return (void *)p;
713
714         ret = tal_arr(ctx, char, n);
715         if (ret)
716                 memcpy(ret, p, n);
717         return ret;
718 }
719
720 char *tal_asprintf(const tal_t *ctx, const char *fmt, ...)
721 {
722         va_list ap;
723         char *ret;
724
725         va_start(ap, fmt);
726         ret = tal_vasprintf(ctx, fmt, ap);
727         va_end(ap);
728
729         return ret;
730 }
731
732 char *tal_vasprintf(const tal_t *ctx, const char *fmt, va_list ap)
733 {
734         size_t max = strlen(fmt) * 2;
735         char *buf;
736         int ret;
737
738         if (ctx == TAL_TAKE)
739                 buf = tal_arr(tal_parent(fmt), char, max);
740         else
741                 buf = tal_arr(ctx, char, max);
742
743         while (buf) {
744                 va_list ap2;
745
746                 va_copy(ap2, ap);
747                 ret = vsnprintf(buf, max, fmt, ap2);
748                 va_end(ap2);
749
750                 if (ret < max)
751                         break;
752                 buf = tal_resize(buf, max *= 2);
753         }
754         if (ctx == TAL_TAKE)
755                 tal_free(fmt);
756         return buf;
757 }
758
759 void tal_set_backend(void *(*alloc_fn)(size_t size),
760                      void *(*resize_fn)(void *, size_t size),
761                      void (*free_fn)(void *),
762                      void (*error_fn)(const char *msg))
763 {
764         if (alloc_fn)
765                 allocfn = alloc_fn;
766         if (resize_fn)
767                 resizefn = resize_fn;
768         if (free_fn)
769                 freefn = free_fn;
770         if (error_fn)
771                 errorfn = error_fn;
772 }
773
774 #ifdef CCAN_TAL_DEBUG
775 static void dump_node(unsigned int indent, const struct tal_hdr *t)
776 {
777         unsigned int i;
778         const struct prop_hdr *p;
779
780         for (i = 0; i < indent; i++)
781                 printf("  ");
782         printf("%p", t);
783         for (p = t->prop; p; p = p->next) {
784                 struct group *g;
785                 struct children *c;
786                 struct destructor *d;
787                 struct name *n;
788                 if (is_literal(p)) {
789                         printf(" \"%s\"", (const char *)p);
790                         break;
791                 }
792                 switch (p->type) {
793                 case CHILDREN:
794                         c = (struct children *)p;
795                         printf(" CHILDREN(%p):parent=%p,group=%p\n",
796                                p, c->parent, &c->group);
797                         g = &c->group;
798                         printf("  GROUP(%p):list={%p,%p},parent_ch=%p,first=%p",
799                                g, g->list.n.next, g->list.n.next,
800                                g->parent_child, g->first_child);
801                         break;
802                 case GROUP:
803                         g = (struct group *)p;
804                         printf(" GROUP(%p):list={%p,%p},,parent_ch=%p,first=%p",
805                                p, g->list.n.next, g->list.n.next,
806                                g->parent_child, g->first_child);
807                         break;
808                 case DESTRUCTOR:
809                         d = (struct destructor *)p;
810                         printf(" DESTRUCTOR(%p):fn=%p", p, d->destroy);
811                         break;
812                 case NAME:
813                         n = (struct name *)p;
814                         printf(" NAME(%p):%s", p, n->name);
815                         break;
816                 default:
817                         printf(" **UNKNOWN(%p):%i**", p, p->type);
818                 }
819         }
820         printf("\n");
821 }
822
823 static void tal_dump_(unsigned int level, const struct tal_hdr *t)
824 {
825         struct children *children;
826         struct group *group;
827
828         dump_node(level, t);
829
830         children = find_property(t, CHILDREN);
831         if (!children)
832                 return;
833
834         group = &children->group;
835         do {
836                 struct tal_hdr *i;
837
838                 i = group->first_child;
839                 if (i) {
840                         do {
841                                 tal_dump_(level+1, i);
842                                 i = i->next;
843                         } while (i != group->first_child);
844                 }
845                 group = next_group(group);
846         } while (group != &children->group);
847 }
848
849 void tal_dump(void)
850 {
851         tal_dump_(0, &null_parent.hdr);
852 }
853 #endif /* CCAN_TAL_DEBUG */
854
855 #ifndef NDEBUG
856 static bool check_err(struct tal_hdr *t, const char *errorstr,
857                       const char *errmsg)
858 {
859         if (errorstr) {
860                 /* Try not to malloc: it may be corrupted. */
861                 char msg[strlen(errorstr) + 20 + strlen(errmsg) + 1];
862                 sprintf(msg, "%s:%p %s", errorstr, from_tal_hdr(t), errmsg);
863                 call_error(msg);
864         }
865         return false;
866 }
867
868 static bool check_group(struct group *group,
869                         struct tal_hdr *t, const char *errorstr);
870
871 static bool check_node(struct group *group,
872                        struct tal_hdr *t, const char *errorstr)
873 {
874         struct prop_hdr *p;
875         struct name *name = NULL;
876         struct children *children = NULL;
877         struct group *gr = NULL;
878
879         if (t != &null_parent.hdr && !in_bounds(t))
880                 return check_err(t, errorstr, "invalid pointer");
881
882         for (p = t->prop; p; p = p->next) {
883                 if (is_literal(p)) {
884                         if (name)
885                                 return check_err(t, errorstr,
886                                                  "has extra literal");
887                         name = (struct name *)p;
888                         break;
889                 }
890                 if (p != &null_parent.c.hdr && p != &null_parent.c.group.hdr
891                     && !in_bounds(p))
892                         return check_err(t, errorstr,
893                                          "has bad property pointer");
894
895                 switch (p->type) {
896                 case GROUP:
897                         if (gr)
898                                 return check_err(t, errorstr,
899                                                  "has two groups");
900                         gr = (struct group *)p;
901                         break;
902                 case CHILDREN:
903                         if (children)
904                                 return check_err(t, errorstr,
905                                                  "has two child nodes");
906                         children = (struct children *)p;
907                         break;
908                 case DESTRUCTOR:
909                         break;
910                 case NAME:
911                         if (name)
912                                 return check_err(t, errorstr,
913                                                  "has two names");
914                         name = (struct name *)p;
915                         break;
916                 default:
917                         return check_err(t, errorstr, "has unknown property");
918                 }
919         }
920         if (group && gr != group)
921                 return check_err(t, errorstr, "has bad group");
922
923         if (children) {
924                 if (!list_check(&children->group.list, errorstr))
925                         return false;
926                 gr = &children->group;
927                 do {
928                         if (gr->first_child) {
929                                 if (!check_group(gr, gr->first_child, errorstr))
930                                         return false;
931                         } else if (gr != &children->group) {
932                                 /* Empty groups should be deleted! */
933                                 return check_err(t, errorstr,
934                                                  "has empty group");
935                         }
936                         gr = next_group(gr);
937                 } while (gr != &children->group);
938         }
939         return true;
940 }
941
942 static bool check_group(struct group *group,
943                         struct tal_hdr *t, const char *errorstr)
944 {
945         struct tal_hdr *i;
946
947         i = t;
948         do {
949                 if (!check_node(group, i, errorstr))
950                         return false;
951                 group = NULL;
952                 i = i->next;
953         } while (i != t);
954         return true;
955 }
956
957 bool tal_check(const tal_t *ctx, const char *errorstr)
958 {
959         struct tal_hdr *t = to_tal_hdr_or_null(ctx);
960
961         return check_node(NULL, t, errorstr);
962 }
963 #else /* NDEBUG */
964 bool tal_check(const tal_t *ctx, const char *errorstr)
965 {
966         return true;
967 }
968 #endif