Bug Summary

File:src/usr.bin/tsort/tsort.c
Warning:line 729, column 31
Access to field 'from' results in a dereference of a null pointer (loaded from variable 't')

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name tsort.c -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model pic -pic-level 1 -pic-is-pie -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-feature +retpoline-indirect-calls -target-feature +retpoline-indirect-branches -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/usr.bin/tsort/obj -resource-dir /usr/local/lib/clang/13.0.0 -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/usr/src/usr.bin/tsort/obj -ferror-limit 19 -fwrapv -D_RET_PROTECTOR -ret-protector -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c /usr/src/usr.bin/tsort/tsort.c
1/* $OpenBSD: tsort.c,v 1.37 2019/07/11 17:28:32 mestre Exp $ */
2/* ex:ts=8 sw=4:
3 *
4 * Copyright (c) 1999-2004 Marc Espie <espie@openbsd.org>
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18
19#include <assert.h>
20#include <ctype.h>
21#include <err.h>
22#include <limits.h>
23#include <stddef.h>
24#include <stdio.h>
25#include <stdint.h>
26#include <stdlib.h>
27#include <string.h>
28#include <unistd.h>
29#include <ohash.h>
30
31/* The complexity of topological sorting is O(e), where e is the
32 * size of input. While reading input, vertices have to be identified,
33 * thus add the complexity of e keys retrieval among v keys using
34 * an appropriate data structure. This program uses open double hashing
35 * for that purpose. See Knuth for the expected complexity of double
36 * hashing (Brent variation should probably be used if v << e, as a user
37 * option).
38 *
39 * The algorithm used for longest cycle reporting is accurate, but somewhat
40 * expensive. It may need to build all free paths of the graph (a free
41 * path is a path that never goes twice through the same node), whose
42 * number can be as high as O(2^e). Usually, the number of free paths is
43 * much smaller though. This program's author does not believe that a
44 * significantly better worst-case complexity algorithm exists.
45 *
46 * In case of a hints file, the set of minimal nodes is maintained as a
47 * heap. The resulting complexity is O(e+v log v) for the worst case.
48 * The average should actually be near O(e).
49 *
50 * If the hints file is incomplete, there is some extra complexity incurred
51 * by make_transparent, which does propagate order values to unmarked
52 * nodes. In the worst case, make_transparent is O(e u),
53 * where u is the number of originally unmarked nodes.
54 * In practice, it is much faster.
55 *
56 * The simple topological sort algorithm detects cycles. This program
57 * goes further, breaking cycles through the use of simple heuristics.
58 * Each cycle break checks the whole set of nodes, hence if c cycles break
59 * are needed, this is an extra cost of O(c v).
60 *
61 * Possible heuristics are as follows:
62 * - break cycle at node with lowest number of predecessors (default case),
63 * - break longest cycle at node with lowest number of predecessors,
64 * - break cycle at next node from the hints file.
65 *
66 * Except for the hints file case, which sets an explicit constraint on
67 * which cycle to break, those heuristics locally result in the smallest
68 * number of broken edges.
69 *
70 * Those are admittedly greedy strategies, as is the selection of the next
71 * node from the hints file amongst equivalent candidates that is used for
72 * `stable' topological sorting.
73 */
74
75#ifdef __GNUC__4
76#define UNUSED__attribute__((unused)) __attribute__((unused))
77#else
78#define UNUSED__attribute__((unused))
79#endif
80
81struct node;
82
83/* The set of arcs from a given node is stored as a linked list. */
84struct link {
85 struct link *next;
86 struct node *node;
87};
88
89#define NO_ORDER(2147483647 *2U +1U) UINT_MAX(2147483647 *2U +1U)
90
91struct node {
92 unsigned int refs; /* Number of arcs left, coming into this node.
93 * Note that nodes with a null count can't
94 * be part of cycles. */
95 unsigned int order; /* Order of nodes according to a hint file. */
96
97 struct link *arcs; /* List of forward arcs. */
98
99 /* Cycle detection algorithms build a free path of nodes. */
100 struct node *from; /* Previous node in the current path. */
101 struct link *traverse; /* Next link to traverse when backtracking. */
102 unsigned int mark; /* Mark processed nodes in cycle discovery. */
103
104 char k[1]; /* Name of this node. */
105};
106
107#define HASH_START9 9
108
109struct array {
110 unsigned int entries;
111 struct node **t;
112};
113
114static void nodes_init(struct ohash *);
115static struct node *node_lookup(struct ohash *, const char *, const char *);
116static __dead__attribute__((__noreturn__)) void usage(void);
117static struct node *new_node(const char *, const char *);
118
119static unsigned int read_pairs(FILE *, struct ohash *, int,
120 const char *, unsigned int, int);
121static void split_nodes(struct ohash *, struct array *, struct array *);
122static void make_transparent(struct ohash *);
123static void insert_arc(struct node *, struct node *);
124
125#ifdef DEBUG
126static void dump_node(struct node *);
127static void dump_array(struct array *);
128static void dump_hash(struct ohash *);
129#endif
130static unsigned int read_hints(FILE *, struct ohash *, int,
131 const char *, unsigned int);
132static struct node *find_smallest_node(struct array *);
133static struct node *find_good_cycle_break(struct array *);
134static void print_cycle(struct array *);
135static struct node *find_cycle_from(struct node *, struct array *);
136static struct node *find_predecessor(struct array *, struct node *);
137static unsigned int traverse_node(struct node *, unsigned int, struct array *);
138static struct node *find_longest_cycle(struct array *, struct array *);
139static struct node *find_normal_cycle(struct array *, struct array *);
140
141static void heap_down(struct array *, unsigned int);
142static void heapify(struct array *, int);
143static struct node *dequeue(struct array *);
144static void enqueue(struct array *, struct node *);
145
146
147
148static void *hash_calloc(size_t, size_t, void *);
149static void hash_free(void *, void *);
150static void* entry_alloc(size_t, void *);
151static void *ereallocarray(void *, size_t, size_t);
152static void *emem(void *);
153#define DEBUG_TRAVERSE0 0
154static struct ohash_info node_info = {
155 offsetof(struct node, k)__builtin_offsetof(struct node, k), NULL((void*)0), hash_calloc, hash_free, entry_alloc };
156static void parse_args(int, char *[], struct ohash *);
157static int tsort(struct ohash *);
158
159static int quiet_flag, long_flag,
160 warn_flag, hints_flag, verbose_flag;
161
162
163int main(int, char *[]);
164
165/***
166 *** Memory handling.
167 ***/
168
169static void *
170emem(void *p)
171{
172 if (p)
173 return p;
174 else
175 errx(1, "Memory exhausted");
176}
177
178static void *
179hash_calloc(size_t n, size_t s, void *u UNUSED__attribute__((unused)))
180{
181 return emem(calloc(n, s));
182}
183
184static void
185hash_free(void *p, void *u UNUSED__attribute__((unused)))
186{
187 free(p);
188}
189
190static void *
191entry_alloc(size_t s, void *u UNUSED__attribute__((unused)))
192{
193 return ereallocarray(NULL((void*)0), 1, s);
194}
195
196static void *
197ereallocarray(void *p, size_t n, size_t s)
198{
199 return emem(reallocarray(p, n, s));
200}
201
202
203/***
204 *** Hash table.
205 ***/
206
207/* Inserting and finding nodes in the hash structure.
208 * We handle interval strings for efficiency wrt fgetln. */
209static struct node *
210new_node(const char *start, const char *end)
211{
212 struct node *n;
213
214 n = ohash_create_entry(&node_info, start, &end);
215 n->from = NULL((void*)0);
216 n->arcs = NULL((void*)0);
217 n->refs = 0;
218 n->mark = 0;
219 n->order = NO_ORDER(2147483647 *2U +1U);
220 n->traverse = NULL((void*)0);
221 return n;
222}
223
224
225static void
226nodes_init(struct ohash *h)
227{
228 ohash_init(h, HASH_START9, &node_info);
229}
230
231static struct node *
232node_lookup(struct ohash *h, const char *start, const char *end)
233{
234 unsigned int i;
235 struct node * n;
236
237 i = ohash_qlookupi(h, start, &end);
238
239 n = ohash_find(h, i);
240 if (n == NULL((void*)0))
241 n = ohash_insert(h, i, new_node(start, end));
242 return n;
243}
244
245#ifdef DEBUG
246static void
247dump_node(struct node *n)
248{
249 struct link *l;
250
251 if (n->refs == 0)
252 return;
253 printf("%s (%u/%u): ", n->k, n->order, n->refs);
254 for (l = n->arcs; l != NULL((void*)0); l = l->next)
255 if (n->refs != 0)
256 printf("%s(%u/%u) ", l->node->k, l->node->order, l->node->refs);
257 putchar('\n')(!__isthreaded ? __sputc('\n', (&__sF[1])) : (putc)('\n',
(&__sF[1])));
258}
259
260static void
261dump_array(struct array *a)
262{
263 unsigned int i;
264
265 for (i = 0; i < a->entries; i++)
266 dump_node(a->t[i]);
267}
268
269static void
270dump_hash(struct ohash *h)
271{
272 unsigned int i;
273 struct node *n;
274
275 for (n = ohash_first(h, &i); n != NULL((void*)0); n = ohash_next(h, &i))
276 dump_node(n);
277}
278#endif
279
280/***
281 *** Reading data.
282 ***/
283
284static void
285insert_arc(struct node *a, struct node *b)
286{
287 struct link *l;
288
289 /* Check that this arc is not already present. */
290 for (l = a->arcs; l != NULL((void*)0); l = l->next) {
291 if (l->node == b)
292 return;
293 }
294 b->refs++;
295 l = ereallocarray(NULL((void*)0), 1, sizeof(struct link));
296 l->node = b;
297 l->next = a->arcs;
298 a->arcs = l;
299}
300
301static unsigned int
302read_pairs(FILE *f, struct ohash *h, int reverse, const char *name,
303 unsigned int order, int hint)
304{
305 int toggle;
306 struct node *a;
307 size_t size;
308 char *str;
309
310 toggle = 1;
311 a = NULL((void*)0);
312
313 while ((str = fgetln(f, &size)) != NULL((void*)0)) {
314 char *sentinel;
315
316 sentinel = str + size;
317 for (;;) {
318 char *e;
319
320 while (str < sentinel &&
321 isspace((unsigned char)*str))
322 str++;
323 if (str == sentinel)
324 break;
325 for (e = str;
326 e < sentinel && !isspace((unsigned char)*e); e++)
327 continue;
328 if (toggle) {
329 a = node_lookup(h, str, e);
330 if (a->order == NO_ORDER(2147483647 *2U +1U) && hint)
331 a->order = order++;
332 } else {
333 struct node *b;
334
335 b = node_lookup(h, str, e);
336 assert(a != NULL)((a != ((void*)0)) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 336, __func__, "a != NULL"));
337 if (b != a) {
338 if (reverse)
339 insert_arc(b, a);
340 else
341 insert_arc(a, b);
342 }
343 }
344 toggle = !toggle;
345 str = e;
346 }
347 }
348 if (toggle == 0)
349 errx(1, "odd number of node names in %s", name);
350 if (!feof(f)(!__isthreaded ? (((f)->_flags & 0x0020) != 0) : (feof
)(f)))
351 err(1, "error reading %s", name);
352 return order;
353}
354
355static unsigned int
356read_hints(FILE *f, struct ohash *h, int quiet, const char *name,
357 unsigned int order)
358{
359 char *str;
360 size_t size;
361
362 while ((str = fgetln(f, &size)) != NULL((void*)0)) {
363 char *sentinel;
364
365 sentinel = str + size;
366 for (;;) {
367 char *e;
368 struct node *a;
369
370 while (str < sentinel && isspace((unsigned char)*str))
371 str++;
372 if (str == sentinel)
373 break;
374 for (e = str;
375 e < sentinel && !isspace((unsigned char)*e); e++)
376 continue;
377 a = node_lookup(h, str, e);
378 if (a->order != NO_ORDER(2147483647 *2U +1U)) {
379 if (!quiet)
380 warnx(
381 "duplicate node %s in hints file %s",
382 a->k, name);
383 } else
384 a->order = order++;
385 str = e;
386 }
387 }
388 if (!feof(f)(!__isthreaded ? (((f)->_flags & 0x0020) != 0) : (feof
)(f)))
389 err(1, "error reading %s", name);
390 return order;
391}
392
393
394/***
395 *** Standard heap handling routines.
396 ***/
397
398static void
399heap_down(struct array *h, unsigned int i)
400{
401 unsigned int j;
402 struct node *swap;
403
404 for (; (j=2*i+1) < h->entries; i = j) {
405 if (j+1 < h->entries && h->t[j+1]->order < h->t[j]->order)
406 j++;
407 if (h->t[i]->order <= h->t[j]->order)
408 break;
409 swap = h->t[i];
410 h->t[i] = h->t[j];
411 h->t[j] = swap;
412 }
413}
414
415static void
416heapify(struct array *h, int verbose)
417{
418 unsigned int i;
419
420 for (i = h->entries; i != 0;) {
421 if (h->t[--i]->order == NO_ORDER(2147483647 *2U +1U) && verbose)
422 warnx("node %s absent from hints file", h->t[i]->k);
423 heap_down(h, i);
424 }
425}
426
427#define DEQUEUE(h)( hints_flag ? dequeue(h) : (h)->t[--(h)->entries] ) ( hints_flag ? dequeue(h) : (h)->t[--(h)->entries] )
428
429static struct node *
430dequeue(struct array *h)
431{
432 struct node *n;
433
434 if (h->entries == 0)
435 n = NULL((void*)0);
436 else {
437 n = h->t[0];
438 if (--h->entries != 0) {
439 h->t[0] = h->t[h->entries];
440 heap_down(h, 0);
441 }
442 }
443 return n;
444}
445
446#define ENQUEUE(h, n)do { if (hints_flag) enqueue((h), (n)); else (h)->t[(h)->
entries++] = (n); } while(0); do { \
447 if (hints_flag) \
448 enqueue((h), (n)); \
449 else \
450 (h)->t[(h)->entries++] = (n); \
451 } while(0);
452
453static void
454enqueue(struct array *h, struct node *n)
455{
456 unsigned int i, j;
457 struct node *swap;
458
459 h->t[h->entries++] = n;
460 for (i = h->entries-1; i > 0; i = j) {
461 j = (i-1)/2;
462 if (h->t[j]->order < h->t[i]->order)
463 break;
464 swap = h->t[j];
465 h->t[j] = h->t[i];
466 h->t[i] = swap;
467 }
468}
469
470/* Nodes without order should not hinder direct dependencies.
471 * Iterate until no nodes are left.
472 */
473static void
474make_transparent(struct ohash *hash)
475{
476 struct node *n;
477 unsigned int i;
478 struct link *l;
479 int adjusted;
480 int bad;
481 unsigned int min;
482
483 /* first try to solve complete nodes */
484 do {
485 adjusted = 0;
486 bad = 0;
487 for (n = ohash_first(hash, &i); n != NULL((void*)0);
488 n = ohash_next(hash, &i)) {
489 if (n->order == NO_ORDER(2147483647 *2U +1U)) {
490 min = NO_ORDER(2147483647 *2U +1U);
491
492 for (l = n->arcs; l != NULL((void*)0); l = l->next) {
493 /* unsolved node -> delay resolution */
494 if (l->node->order == NO_ORDER(2147483647 *2U +1U)) {
495 bad = 1;
496 break;
497 } else if (l->node->order < min)
498 min = l->node->order;
499 }
500 if (min < NO_ORDER(2147483647 *2U +1U) && l == NULL((void*)0)) {
501 n->order = min;
502 adjusted = 1;
503 }
504 }
505 }
506
507 } while (adjusted);
508
509 /* then, if incomplete nodes are left, do them */
510 if (bad) do {
511 adjusted = 0;
512 for (n = ohash_first(hash, &i); n != NULL((void*)0);
513 n = ohash_next(hash, &i))
514 if (n->order == NO_ORDER(2147483647 *2U +1U))
515 for (l = n->arcs; l != NULL((void*)0); l = l->next)
516 if (l->node->order < n->order) {
517 n->order = l->node->order;
518 adjusted = 1;
519 }
520 } while (adjusted);
521}
522
523
524/***
525 *** Search through hash array for nodes.
526 ***/
527
528/* Split nodes into unrefed nodes/live nodes. */
529static void
530split_nodes(struct ohash *hash, struct array *heap, struct array *remaining)
531{
532
533 struct node *n;
534 unsigned int i;
535
536 heap->t = ereallocarray(NULL((void*)0), ohash_entries(hash),
537 sizeof(struct node *));
538 remaining->t = ereallocarray(NULL((void*)0), ohash_entries(hash),
539 sizeof(struct node *));
540 heap->entries = 0;
541 remaining->entries = 0;
542
543 for (n = ohash_first(hash, &i); n != NULL((void*)0); n = ohash_next(hash, &i)) {
544 if (n->refs == 0)
545 heap->t[heap->entries++] = n;
546 else
547 remaining->t[remaining->entries++] = n;
548 }
549}
550
551/* Good point to break a cycle: live node with as few refs as possible. */
552static struct node *
553find_good_cycle_break(struct array *h)
554{
555 unsigned int i;
556 unsigned int best;
557 struct node *u;
558
559 best = UINT_MAX(2147483647 *2U +1U);
560 u = NULL((void*)0);
561
562 assert(h->entries != 0)((h->entries != 0) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 562, __func__, "h->entries != 0"));
563 for (i = 0; i < h->entries; i++) {
564 struct node *n = h->t[i];
565 /* No need to look further. */
566 if (n->refs == 1)
567 return n;
568 if (n->refs != 0 && n->refs < best) {
569 best = n->refs;
570 u = n;
571 }
572 }
573 assert(u != NULL)((u != ((void*)0)) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 573, __func__, "u != NULL"));
574 return u;
575}
576
577/* Retrieve the node with the smallest order. */
578static struct node *
579find_smallest_node(struct array *h)
580{
581 unsigned int i;
582 unsigned int best;
583 struct node *u;
584
585 best = UINT_MAX(2147483647 *2U +1U);
586 u = NULL((void*)0);
587
588 assert(h->entries != 0)((h->entries != 0) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 588, __func__, "h->entries != 0"));
589 for (i = 0; i < h->entries; i++) {
590 struct node *n = h->t[i];
591 if (n->refs != 0 && n->order < best) {
592 best = n->order;
593 u = n;
594 }
595 }
596 assert(u != NULL)((u != ((void*)0)) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 596, __func__, "u != NULL"));
597 return u;
598}
599
600
601/***
602 *** Graph algorithms.
603 ***/
604
605/* Explore the nodes reachable from i to find a cycle, store it in c.
606 * This may fail. */
607static struct node *
608find_cycle_from(struct node *i, struct array *c)
609{
610 struct node *n;
611
612 n = i;
613 /* XXX Previous cycle findings may have left this pointer non-null. */
614 i->from = NULL((void*)0);
615
616 for (;;) {
617 /* Note that all marks are reversed before this code exits. */
618 n->mark = 1;
619 if (n->traverse)
620 n->traverse = n->traverse->next;
621 else
622 n->traverse = n->arcs;
623 /* Skip over dead nodes. */
624 while (n->traverse && n->traverse->node->refs == 0)
625 n->traverse = n->traverse->next;
626 if (n->traverse) {
627 struct node *go = n->traverse->node;
628
629 if (go->mark) {
630 c->entries = 0;
631 for (; n != NULL((void*)0) && n != go; n = n->from) {
632 c->t[c->entries++] = n;
633 n->mark = 0;
634 }
635 for (; n != NULL((void*)0); n = n->from)
636 n->mark = 0;
637 c->t[c->entries++] = go;
638 return go;
639 } else {
640 go->from = n;
641 n = go;
642 }
643 } else {
644 n->mark = 0;
645 n = n->from;
646 if (n == NULL((void*)0))
647 return NULL((void*)0);
648 }
649 }
650}
651
652/* Find a live predecessor of node n. This is a slow routine, as it needs
653 * to go through the whole array, but it is not needed often.
654 */
655static struct node *
656find_predecessor(struct array *a, struct node *n)
657{
658 unsigned int i;
659
660 for (i = 0; i < a->entries; i++) {
661 struct node *m;
662
663 m = a->t[i];
664 if (m->refs != 0) {
665 struct link *l;
666
667 for (l = m->arcs; l != NULL((void*)0); l = l->next)
668 if (l->node == n)
669 return m;
670 }
671 }
672 assert(1 == 0)((1 == 0) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 672, __func__, "1 == 0"));
673 return NULL((void*)0);
674}
675
676/* Traverse all strongly connected components reachable from node n.
677 Start numbering them at o. Return the maximum order reached.
678 Update the largest cycle found so far.
679 */
680static unsigned int
681traverse_node(struct node *n, unsigned int o, struct array *c)
682{
683 unsigned int min, max;
684
685 n->from = NULL((void*)0);
9
←
Null pointer value stored to field 'from'
→
686 min = o;
687 max = ++o;
688
689 for (;;) {
10
←
Loop condition is true. Entering loop body
→
690 n->mark = o;
691 if (DEBUG_TRAVERSE0)
11
←
Taking false branch
→
692 printf("%s(%u) ", n->k, n->mark);
693 /* Find next arc to explore. */
694 if (n->traverse)
12
←
Assuming field 'traverse' is null
→
13
←
Taking false branch
→
695 n->traverse = n->traverse->next;
696 else
697 n->traverse = n->arcs;
698 /* Skip over dead nodes. */
699 while (n->traverse && n->traverse->node->refs == 0)
14
←
Assuming field 'traverse' is non-null
→
15
←
Assuming field 'refs' is not equal to 0
→
16
←
Loop condition is false. Execution continues on line 702
→
700 n->traverse = n->traverse->next;
701 /* If arc left. */
702 if (n->traverse
16.1
Field 'traverse' is non-null
) {
17
←
Taking true branch
→
703 struct node *go;
704
705 go = n->traverse->node;
706 /* Optimisation: if go->mark < min, we already
707 * visited this strongly-connected component in
708 * a previous pass. Hence, this can yield no new
709 * cycle. */
710
711 /* Not part of the current path: go for it. */
712 if (go->mark == 0 || go->mark == min) {
18
←
Assuming field 'mark' is not equal to 0
→
19
←
Assuming 'min' is not equal to field 'mark'
→
20
←
Taking false branch
→
713 go->from = n;
714 n = go;
715 o++;
716 if (o > max)
717 max = o;
718 /* Part of the current path: check cycle length. */
719 } else if (go->mark > min
20.1
'min' is < field 'mark'
) {
21
←
Taking true branch
→
720 if (DEBUG_TRAVERSE0)
22
←
Taking false branch
→
721 printf("%d\n", o - go->mark + 1);
722 if (o - go->mark + 1 > c->entries) {
23
←
Assuming the condition is true
→
24
←
Taking true branch
→
723 struct node *t;
724 unsigned int i;
725
726 c->entries = o - go->mark + 1;
727 i = 0;
728 c->t[i++] = go;
729 for (t = n; t
27.1
't' is not equal to 'go'
 != go; t = t->from)
25
←
Assuming 't' is not equal to 'go'
→
26
←
Loop condition is true. Entering loop body
→
27
←
Null pointer value stored to 't'
→
28
←
Loop condition is true. Entering loop body
→
29
←
Access to field 'from' results in a dereference of a null pointer (loaded from variable 't')
730 c->t[i++] = t;
731 }
732 }
733
734 /* No arc left: backtrack. */
735 } else {
736 n->mark = min;
737 n = n->from;
738 if (!n)
739 return max;
740 o--;
741 }
742 }
743}
744
745static void
746print_cycle(struct array *c)
747{
748 unsigned int i;
749
750 /* Printing in reverse order, since cycle discoveries finds reverse
751 * edges. */
752 for (i = c->entries; i != 0;) {
753 i--;
754 warnx("%s", c->t[i]->k);
755 }
756}
757
758static struct node *
759find_longest_cycle(struct array *h, struct array *c)
760{
761 unsigned int i;
762 unsigned int o;
763 unsigned int best;
764 struct node *n;
765 static int notfirst = 0;
766
767 assert(h->entries != 0)((h->entries != 0) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 767, __func__, "h->entries != 0"));
1
Assuming field 'entries' is not equal to 0
→
2
←
'?' condition is true
→
768
769 /* No cycle found yet. */
770 c->entries = 0;
771
772 /* Reset the set of marks, except the first time around. */
773 if (notfirst
2.1
'notfirst' is 0
) {
3
←
Taking false branch
→
774 for (i = 0; i < h->entries; i++)
775 h->t[i]->mark = 0;
776 } else
777 notfirst = 1;
778
779 o = 0;
780
781 /* Traverse the array. Each unmarked, live node heralds a
782 * new set of strongly connected components. */
783 for (i = 0; i
3.1
'i' is < field 'entries'
 < h->entries; i++) {
4
←
Loop condition is true. Entering loop body
→
784 n = h->t[i];
785 if (n->refs != 0 && n->mark == 0) {
5
←
Assuming field 'refs' is not equal to 0
→
6
←
Assuming field 'mark' is equal to 0
→
7
←
Taking true branch
→
786 /* Each call to traverse_node uses a separate
787 * interval of numbers to mark nodes. */
788 o++;
789 o = traverse_node(n, o, c);
8
←
Calling 'traverse_node'
→
790 }
791 }
792
793 assert(c->entries != 0)((c->entries != 0) ? (void)0 : __assert2("/usr/src/usr.bin/tsort/tsort.c"
, 793, __func__, "c->entries != 0"));
794 n = c->t[0];
795 best = n->refs;
796 for (i = 0; i < c->entries; i++) {
797 if (c->t[i]->refs < best) {
798 n = c->t[i];
799 best = n->refs;
800 }
801 }
802 return n;
803}
804
805static struct node *
806find_normal_cycle(struct array *h, struct array *c)
807{
808 struct node *b, *n;
809
810 if (hints_flag)
811 n = find_smallest_node(h);
812 else
813 n = find_good_cycle_break(h);
814 while ((b = find_cycle_from(n, c)) == NULL((void*)0))
815 n = find_predecessor(h, n);
816 return b;
817}
818
819
820#define plural(n)((n) > 1 ? "s" : "") ((n) > 1 ? "s" : "")
821
822static void
823parse_args(int argc, char *argv[], struct ohash *pairs)
824{
825 int c;
826 unsigned int order;
827 int reverse_flag;
828 const char **files;
829 int i, j;
830
831 i = 0;
832
833 reverse_flag = quiet_flag = long_flag =
834 warn_flag = hints_flag = verbose_flag = 0;
835 /* argc is good enough, as we start at argv[1] */
836 files = ereallocarray(NULL((void*)0), argc, sizeof (char *));
837 while ((c = getopt(argc, argv, "h:flqrvw")) != -1) {
838 switch(c) {
839 case 'h':
840 files[i++] = optarg;
841 hints_flag = 1;
842 break;
843 /*FALLTHRU*/
844 case 'f':
845 hints_flag = 2;
846 break;
847 case 'l':
848 long_flag = 1;
849 break;
850 case 'q':
851 quiet_flag = 1;
852 break;
853 case 'r':
854 reverse_flag = 1;
855 break;
856 case 'v':
857 verbose_flag = 1;
858 break;
859 case 'w':
860 warn_flag = 1;
861 break;
862 default:
863 usage();
864 }
865 }
866
867 argc -= optind;
868 argv += optind;
869
870 switch(argc) {
871 case 1:
872 files[i++] = argv[0];
873 break;
874 case 0:
875 break;
876 default:
877 usage();
878 }
879
880 files[i] = NULL((void*)0);
881
882 nodes_init(pairs);
883 order = 0;
884
885 for (j = 0; j != i-argc; j++) {
886 FILE *f;
887
888 f = fopen(files[j], "r");
889 if (f == NULL((void*)0))
890 err(1, "Can't open hint file %s", files[i]);
891 order = read_hints(f, pairs, quiet_flag, files[i], order);
892 fclose(f);
893 }
894 free(files);
895
896 if (argc == 1) {
897 FILE *f;
898
899 f = fopen(argv[0], "r");
900 if (f == NULL((void*)0))
901 err(1, "Can't open file %s", argv[0]);
902 order = read_pairs(f, pairs, reverse_flag, argv[0], order,
903 hints_flag == 2);
904 fclose(f);
905 } else {
906 order = read_pairs(stdin(&__sF[0]), pairs, reverse_flag, "stdin",
907 order, hints_flag == 2);
908 }
909}
910
911static int
912tsort(struct ohash *pairs)
913{
914 struct array aux; /* Unrefed nodes/cycle reporting. */
915 struct array remaining;
916 unsigned int broken_arcs, broken_cycles;
917 unsigned int left;
918
919 broken_arcs = 0;
920 broken_cycles = 0;
921
922 if (hints_flag)
923 make_transparent(pairs);
924 split_nodes(pairs, &aux, &remaining);
925 ohash_delete(pairs);
926
927 if (hints_flag)
928 heapify(&aux, verbose_flag);
929
930 left = remaining.entries + aux.entries;
931 while (left != 0) {
932
933 /* Standard topological sort. */
934 while (aux.entries) {
935 struct link *l;
936 struct node *n;
937
938 n = DEQUEUE(&aux)( hints_flag ? dequeue(&aux) : (&aux)->t[--(&aux
)->entries] );
939 printf("%s\n", n->k);
940 left--;
941 /* We can't free nodes, as we don't know which
942 * entry we can remove in the hash table. We
943 * rely on refs == 0 to recognize live nodes.
944 * Decrease ref count of live nodes, enter new
945 * candidates into the unrefed list. */
946 for (l = n->arcs; l != NULL((void*)0); l = l->next)
947 if (l->node->refs != 0 &&
948 --l->node->refs == 0) {
949 ENQUEUE(&aux, l->node)do { if (hints_flag) enqueue((&aux), (l->node)); else (
&aux)->t[(&aux)->entries++] = (l->node); } while
(0);;
950 }
951 }
952 /* There are still cycles to break. */
953 if (left != 0) {
954 struct node *n;
955
956 broken_cycles++;
957 /* XXX Simple cycle detection and long cycle
958 * detection are mutually exclusive. */
959
960 if (long_flag)
961 n = find_longest_cycle(&remaining, &aux);
962 else
963 n = find_normal_cycle(&remaining, &aux);
964
965 if (!quiet_flag) {
966 warnx("cycle in data");
967 print_cycle(&aux);
968 }
969
970 if (verbose_flag)
971 warnx("%u edge%s broken", n->refs,
972 plural(n->refs)((n->refs) > 1 ? "s" : ""));
973 broken_arcs += n->refs;
974 n->refs = 0;
975 /* Reinitialization, cycle reporting uses aux. */
976 aux.t[0] = n;
977 aux.entries = 1;
978 }
979 }
980 if (verbose_flag && broken_cycles != 0)
981 warnx("%u cycle%s broken, for a total of %u edge%s",
982 broken_cycles, plural(broken_cycles)((broken_cycles) > 1 ? "s" : ""),
983 broken_arcs, plural(broken_arcs)((broken_arcs) > 1 ? "s" : ""));
984 if (warn_flag)
985 return (broken_cycles < 256 ? broken_cycles : 255);
986 else
987 return (0);
988}
989
990int
991main(int argc, char *argv[])
992{
993 struct ohash pairs;
994
995 if (pledge("stdio rpath", NULL((void*)0)) == -1)
996 err(1, "pledge");
997
998 parse_args(argc, argv, &pairs);
999
1000 if (pledge("stdio", NULL((void*)0)) == -1)
1001 err(1, "pledge");
1002
1003 return tsort(&pairs);
1004}
1005
1006
1007extern char *__progname;
1008
1009static void
1010usage(void)
1011{
1012 fprintf(stderr(&__sF[2]), "Usage: %s [-flqrvw] [-h file] [file]\n", __progname);
1013 exit(1);
1014}