bisect.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "diff.h"
   4 #include "revision.h"
   5 #include "refs.h"
   6 #include "list-objects.h"
   7 #include "quote.h"
   8 #include "sha1-lookup.h"
   9 #include "run-command.h"
  10 #include "bisect.h"
  11
  12 struct sha1_array {
  13         unsigned char (*sha1)[20];
  14         int sha1_nr;
  15         int sha1_alloc;
  16 };
  17
  18 static struct sha1_array good_revs;
  19 static struct sha1_array skipped_revs;
  20
  21 static const unsigned char *current_bad_sha1;
  22
  23 struct argv_array {
  24         const char **argv;
  25         int argv_nr;
  26         int argv_alloc;
  27 };
  28
  29 struct argv_array rev_argv;
  30
  31 static const char *argv_diff_tree[] = {"diff-tree", "--pretty", NULL, NULL};
  32 static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
  33 static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
  34
  35 /* bits #0-15 in revision.h */
  36
  37 #define COUNTED         (1u<<16)
  38
  39 /*
  40  * This is a truly stupid algorithm, but it's only
  41  * used for bisection, and we just don't care enough.
  42  *
  43  * We care just barely enough to avoid recursing for
  44  * non-merge entries.
  45  */
  46 static int count_distance(struct commit_list *entry)
  47 {
  48         int nr = 0;
  49
  50         while (entry) {
  51                 struct commit *commit = entry->item;
  52                 struct commit_list *p;
  53
  54                 if (commit->object.flags & (UNINTERESTING | COUNTED))
  55                         break;
  56                 if (!(commit->object.flags & TREESAME))
  57                         nr++;
  58                 commit->object.flags |= COUNTED;
  59                 p = commit->parents;
  60                 entry = p;
  61                 if (p) {
  62                         p = p->next;
  63                         while (p) {
  64                                 nr += count_distance(p);
  65                                 p = p->next;
  66                         }
  67                 }
  68         }
  69
  70         return nr;
  71 }
  72
  73 static void clear_distance(struct commit_list *list)
  74 {
  75         while (list) {
  76                 struct commit *commit = list->item;
  77                 commit->object.flags &= ~COUNTED;
  78                 list = list->next;
  79         }
  80 }
  81
  82 #define DEBUG_BISECT 0
  83
  84 static inline int weight(struct commit_list *elem)
  85 {
  86         return *((int*)(elem->item->util));
  87 }
  88
  89 static inline void weight_set(struct commit_list *elem, int weight)
  90 {
  91         *((int*)(elem->item->util)) = weight;
  92 }
  93
  94 static int count_interesting_parents(struct commit *commit)
  95 {
  96         struct commit_list *p;
  97         int count;
  98
  99         for (count = 0, p = commit->parents; p; p = p->next) {
 100                 if (p->item->object.flags & UNINTERESTING)
 101                         continue;
 102                 count++;
 103         }
 104         return count;
 105 }
 106
 107 static inline int halfway(struct commit_list *p, int nr)
 108 {
 109         /*
 110          * Don't short-cut something we are not going to return!
 111          */
 112         if (p->item->object.flags & TREESAME)
 113                 return 0;
 114         if (DEBUG_BISECT)
 115                 return 0;
 116         /*
 117          * 2 and 3 are halfway of 5.
 118          * 3 is halfway of 6 but 2 and 4 are not.
 119          */
 120         switch (2 * weight(p) - nr) {
 121         case -1: case 0: case 1:
 122                 return 1;
 123         default:
 124                 return 0;
 125         }
 126 }
 127
 128 #if !DEBUG_BISECT
 129 #define show_list(a,b,c,d) do { ; } while (0)
 130 #else
 131 static void show_list(const char *debug, int counted, int nr,
 132                       struct commit_list *list)
 133 {
 134         struct commit_list *p;
 135
 136         fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
 137
 138         for (p = list; p; p = p->next) {
 139                 struct commit_list *pp;
 140                 struct commit *commit = p->item;
 141                 unsigned flags = commit->object.flags;
 142                 enum object_type type;
 143                 unsigned long size;
 144                 char *buf = read_sha1_file(commit->object.sha1, &type, &size);
 145                 char *ep, *sp;
 146
 147                 fprintf(stderr, "%c%c%c ",
 148                         (flags & TREESAME) ? ' ' : 'T',
 149                         (flags & UNINTERESTING) ? 'U' : ' ',
 150                         (flags & COUNTED) ? 'C' : ' ');
 151                 if (commit->util)
 152                         fprintf(stderr, "%3d", weight(p));
 153                 else
 154                         fprintf(stderr, "---");
 155                 fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
 156                 for (pp = commit->parents; pp; pp = pp->next)
 157                         fprintf(stderr, " %.*s", 8,
 158                                 sha1_to_hex(pp->item->object.sha1));
 159
 160                 sp = strstr(buf, "\n\n");
 161                 if (sp) {
 162                         sp += 2;
 163                         for (ep = sp; *ep && *ep != '\n'; ep++)
 164                                 ;
 165                         fprintf(stderr, " %.*s", (int)(ep - sp), sp);
 166                 }
 167                 fprintf(stderr, "\n");
 168         }
 169 }
 170 #endif /* DEBUG_BISECT */
 171
 172 static struct commit_list *best_bisection(struct commit_list *list, int nr)
 173 {
 174         struct commit_list *p, *best;
 175         int best_distance = -1;
 176
 177         best = list;
 178         for (p = list; p; p = p->next) {
 179                 int distance;
 180                 unsigned flags = p->item->object.flags;
 181
 182                 if (flags & TREESAME)
 183                         continue;
 184                 distance = weight(p);
 185                 if (nr - distance < distance)
 186                         distance = nr - distance;
 187                 if (distance > best_distance) {
 188                         best = p;
 189                         best_distance = distance;
 190                 }
 191         }
 192
 193         return best;
 194 }
 195
 196 struct commit_dist {
 197         struct commit *commit;
 198         int distance;
 199 };
 200
 201 static int compare_commit_dist(const void *a_, const void *b_)
 202 {
 203         struct commit_dist *a, *b;
 204
 205         a = (struct commit_dist *)a_;
 206         b = (struct commit_dist *)b_;
 207         if (a->distance != b->distance)
 208                 return b->distance - a->distance; /* desc sort */
 209         return hashcmp(a->commit->object.sha1, b->commit->object.sha1);
 210 }
 211
 212 static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
 213 {
 214         struct commit_list *p;
 215         struct commit_dist *array = xcalloc(nr, sizeof(*array));
 216         int cnt, i;
 217
 218         for (p = list, cnt = 0; p; p = p->next) {
 219                 int distance;
 220                 unsigned flags = p->item->object.flags;
 221
 222                 if (flags & TREESAME)
 223                         continue;
 224                 distance = weight(p);
 225                 if (nr - distance < distance)
 226                         distance = nr - distance;
 227                 array[cnt].commit = p->item;
 228                 array[cnt].distance = distance;
 229                 cnt++;
 230         }
 231         qsort(array, cnt, sizeof(*array), compare_commit_dist);
 232         for (p = list, i = 0; i < cnt; i++) {
 233                 struct name_decoration *r = xmalloc(sizeof(*r) + 100);
 234                 struct object *obj = &(array[i].commit->object);
 235
 236                 sprintf(r->name, "dist=%d", array[i].distance);
 237                 r->next = add_decoration(&name_decoration, obj, r);
 238                 p->item = array[i].commit;
 239                 p = p->next;
 240         }
 241         if (p)
 242                 p->next = NULL;
 243         free(array);
 244         return list;
 245 }
 246
 247 /*
 248  * zero or positive weight is the number of interesting commits it can
 249  * reach, including itself.  Especially, weight = 0 means it does not
 250  * reach any tree-changing commits (e.g. just above uninteresting one
 251  * but traversal is with pathspec).
 252  *
 253  * weight = -1 means it has one parent and its distance is yet to
 254  * be computed.
 255  *
 256  * weight = -2 means it has more than one parent and its distance is
 257  * unknown.  After running count_distance() first, they will get zero
 258  * or positive distance.
 259  */
 260 static struct commit_list *do_find_bisection(struct commit_list *list,
 261                                              int nr, int *weights,
 262                                              int find_all)
 263 {
 264         int n, counted;
 265         struct commit_list *p;
 266
 267         counted = 0;
 268
 269         for (n = 0, p = list; p; p = p->next) {
 270                 struct commit *commit = p->item;
 271                 unsigned flags = commit->object.flags;
 272
 273                 p->item->util = &weights[n++];
 274                 switch (count_interesting_parents(commit)) {
 275                 case 0:
 276                         if (!(flags & TREESAME)) {
 277                                 weight_set(p, 1);
 278                                 counted++;
 279                                 show_list("bisection 2 count one",
 280                                           counted, nr, list);
 281                         }
 282                         /*
 283                          * otherwise, it is known not to reach any
 284                          * tree-changing commit and gets weight 0.
 285                          */
 286                         break;
 287                 case 1:
 288                         weight_set(p, -1);
 289                         break;
 290                 default:
 291                         weight_set(p, -2);
 292                         break;
 293                 }
 294         }
 295
 296         show_list("bisection 2 initialize", counted, nr, list);
 297
 298         /*
 299          * If you have only one parent in the resulting set
 300          * then you can reach one commit more than that parent
 301          * can reach.  So we do not have to run the expensive
 302          * count_distance() for single strand of pearls.
 303          *
 304          * However, if you have more than one parents, you cannot
 305          * just add their distance and one for yourself, since
 306          * they usually reach the same ancestor and you would
 307          * end up counting them twice that way.
 308          *
 309          * So we will first count distance of merges the usual
 310          * way, and then fill the blanks using cheaper algorithm.
 311          */
 312         for (p = list; p; p = p->next) {
 313                 if (p->item->object.flags & UNINTERESTING)
 314                         continue;
 315                 if (weight(p) != -2)
 316                         continue;
 317                 weight_set(p, count_distance(p));
 318                 clear_distance(list);
 319
 320                 /* Does it happen to be at exactly half-way? */
 321                 if (!find_all && halfway(p, nr))
 322                         return p;
 323                 counted++;
 324         }
 325
 326         show_list("bisection 2 count_distance", counted, nr, list);
 327
 328         while (counted < nr) {
 329                 for (p = list; p; p = p->next) {
 330                         struct commit_list *q;
 331                         unsigned flags = p->item->object.flags;
 332
 333                         if (0 <= weight(p))
 334                                 continue;
 335                         for (q = p->item->parents; q; q = q->next) {
 336                                 if (q->item->object.flags & UNINTERESTING)
 337                                         continue;
 338                                 if (0 <= weight(q))
 339                                         break;
 340                         }
 341                         if (!q)
 342                                 continue;
 343
 344                         /*
 345                          * weight for p is unknown but q is known.
 346                          * add one for p itself if p is to be counted,
 347                          * otherwise inherit it from q directly.
 348                          */
 349                         if (!(flags & TREESAME)) {
 350                                 weight_set(p, weight(q)+1);
 351                                 counted++;
 352                                 show_list("bisection 2 count one",
 353                                           counted, nr, list);
 354                         }
 355                         else
 356                                 weight_set(p, weight(q));
 357
 358                         /* Does it happen to be at exactly half-way? */
 359                         if (!find_all && halfway(p, nr))
 360                                 return p;
 361                 }
 362         }
 363
 364         show_list("bisection 2 counted all", counted, nr, list);
 365
 366         if (!find_all)
 367                 return best_bisection(list, nr);
 368         else
 369                 return best_bisection_sorted(list, nr);
 370 }
 371
 372 struct commit_list *find_bisection(struct commit_list *list,
 373                                           int *reaches, int *all,
 374                                           int find_all)
 375 {
 376         int nr, on_list;
 377         struct commit_list *p, *best, *next, *last;
 378         int *weights;
 379
 380         show_list("bisection 2 entry", 0, 0, list);
 381
 382         /*
 383          * Count the number of total and tree-changing items on the
 384          * list, while reversing the list.
 385          */
 386         for (nr = on_list = 0, last = NULL, p = list;
 387              p;
 388              p = next) {
 389                 unsigned flags = p->item->object.flags;
 390
 391                 next = p->next;
 392                 if (flags & UNINTERESTING)
 393                         continue;
 394                 p->next = last;
 395                 last = p;
 396                 if (!(flags & TREESAME))
 397                         nr++;
 398                 on_list++;
 399         }
 400         list = last;
 401         show_list("bisection 2 sorted", 0, nr, list);
 402
 403         *all = nr;
 404         weights = xcalloc(on_list, sizeof(*weights));
 405
 406         /* Do the real work of finding bisection commit. */
 407         best = do_find_bisection(list, nr, weights, find_all);
 408         if (best) {
 409                 if (!find_all)
 410                         best->next = NULL;
 411                 *reaches = weight(best);
 412         }
 413         free(weights);
 414         return best;
 415 }
 416
 417 static void argv_array_push(struct argv_array *array, const char *string)
 418 {
 419         ALLOC_GROW(array->argv, array->argv_nr + 1, array->argv_alloc);
 420         array->argv[array->argv_nr++] = string;
 421 }
 422
 423 static void argv_array_push_sha1(struct argv_array *array,
 424                                  const unsigned char *sha1,
 425                                  const char *format)
 426 {
 427         struct strbuf buf = STRBUF_INIT;
 428         strbuf_addf(&buf, format, sha1_to_hex(sha1));
 429         argv_array_push(array, strbuf_detach(&buf, NULL));
 430 }
 431
 432 static void sha1_array_push(struct sha1_array *array,
 433                             const unsigned char *sha1)
 434 {
 435         ALLOC_GROW(array->sha1, array->sha1_nr + 1, array->sha1_alloc);
 436         hashcpy(array->sha1[array->sha1_nr++], sha1);
 437 }
 438
 439 static int register_ref(const char *refname, const unsigned char *sha1,
 440                         int flags, void *cb_data)
 441 {
 442         if (!strcmp(refname, "bad")) {
 443                 current_bad_sha1 = sha1;
 444         } else if (!prefixcmp(refname, "good-")) {
 445                 sha1_array_push(&good_revs, sha1);
 446         } else if (!prefixcmp(refname, "skip-")) {
 447                 sha1_array_push(&skipped_revs, sha1);
 448         }
 449
 450         return 0;
 451 }
 452
 453 static int read_bisect_refs(void)
 454 {
 455         return for_each_ref_in("refs/bisect/", register_ref, NULL);
 456 }
 457
 458 void read_bisect_paths(struct argv_array *array)
 459 {
 460         struct strbuf str = STRBUF_INIT;
 461         const char *filename = git_path("BISECT_NAMES");
 462         FILE *fp = fopen(filename, "r");
 463
 464         if (!fp)
 465                 die("Could not open file '%s': %s", filename, strerror(errno));
 466
 467         while (strbuf_getline(&str, fp, '\n') != EOF) {
 468                 char *quoted;
 469                 int res;
 470
 471                 strbuf_trim(&str);
 472                 quoted = strbuf_detach(&str, NULL);
 473                 res = sq_dequote_to_argv(quoted, &array->argv,
 474                                          &array->argv_nr, &array->argv_alloc);
 475                 if (res)
 476                         die("Badly quoted content in file '%s': %s",
 477                             filename, quoted);
 478         }
 479
 480         strbuf_release(&str);
 481         fclose(fp);
 482 }
 483
 484 static int skipcmp(const void *a, const void *b)
 485 {
 486         return hashcmp(a, b);
 487 }
 488
 489 static void prepare_skipped(void)
 490 {
 491         qsort(skipped_revs.sha1, skipped_revs.sha1_nr,
 492               sizeof(*skipped_revs.sha1), skipcmp);
 493 }
 494
 495 static const unsigned char *skipped_sha1_access(size_t index, void *table)
 496 {
 497         unsigned char (*skipped)[20] = table;
 498         return skipped[index];
 499 }
 500
 501 static int lookup_skipped(unsigned char *sha1)
 502 {
 503         return sha1_pos(sha1, skipped_revs.sha1, skipped_revs.sha1_nr,
 504                         skipped_sha1_access);
 505 }
 506
 507 struct commit_list *filter_skipped(struct commit_list *list,
 508                                    struct commit_list **tried,
 509                                    int show_all)
 510 {
 511         struct commit_list *filtered = NULL, **f = &filtered;
 512
 513         *tried = NULL;
 514
 515         if (!skipped_revs.sha1_nr)
 516                 return list;
 517
 518         prepare_skipped();
 519
 520         while (list) {
 521                 struct commit_list *next = list->next;
 522                 list->next = NULL;
 523                 if (0 <= lookup_skipped(list->item->object.sha1)) {
 524                         /* Move current to tried list */
 525                         *tried = list;
 526                         tried = &list->next;
 527                 } else {
 528                         if (!show_all)
 529                                 return list;
 530                         /* Move current to filtered list */
 531                         *f = list;
 532                         f = &list->next;
 533                 }
 534                 list = next;
 535         }
 536
 537         return filtered;
 538 }
 539
 540 static void bisect_rev_setup(struct rev_info *revs, const char *prefix)
 541 {
 542         int i;
 543
 544         init_revisions(revs, prefix);
 545         revs->abbrev = 0;
 546         revs->commit_format = CMIT_FMT_UNSPECIFIED;
 547
 548         if (read_bisect_refs())
 549                 die("reading bisect refs failed");
 550
 551         /* rev_argv.argv[0] will be ignored by setup_revisions */
 552         argv_array_push(&rev_argv, xstrdup("bisect_rev_setup"));
 553         argv_array_push_sha1(&rev_argv, current_bad_sha1, "%s");
 554         for (i = 0; i < good_revs.sha1_nr; i++)
 555                 argv_array_push_sha1(&rev_argv, good_revs.sha1[i], "^%s");
 556         argv_array_push(&rev_argv, xstrdup("--"));
 557         read_bisect_paths(&rev_argv);
 558         argv_array_push(&rev_argv, NULL);
 559
 560         setup_revisions(rev_argv.argv_nr, rev_argv.argv, revs, NULL);
 561         revs->limited = 1;
 562 }
 563
 564 static void bisect_common(struct rev_info *revs, const char *prefix,
 565                           int *reaches, int *all)
 566 {
 567         bisect_rev_setup(revs, prefix);
 568
 569         if (prepare_revision_walk(revs))
 570                 die("revision walk setup failed");
 571         if (revs->tree_objects)
 572                 mark_edges_uninteresting(revs->commits, revs, NULL);
 573
 574         revs->commits = find_bisection(revs->commits, reaches, all,
 575                                        !!skipped_revs.sha1_nr);
 576 }
 577
 578 static void exit_if_skipped_commits(struct commit_list *tried,
 579                                     const unsigned char *bad)
 580 {
 581         if (!tried)
 582                 return;
 583
 584         printf("There are only 'skip'ped commits left to test.\n"
 585                "The first bad commit could be any of:\n");
 586         print_commit_list(tried, "%s\n", "%s\n");
 587         if (bad)
 588                 printf("%s\n", sha1_to_hex(bad));
 589         printf("We cannot bisect more!\n");
 590         exit(2);
 591 }
 592
 593 static void mark_expected_rev(char *bisect_rev_hex)
 594 {
 595         int len = strlen(bisect_rev_hex);
 596         const char *filename = git_path("BISECT_EXPECTED_REV");
 597         int fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
 598
 599         if (fd < 0)
 600                 die("could not create file '%s': %s",
 601                     filename, strerror(errno));
 602
 603         bisect_rev_hex[len] = '\n';
 604         write_or_die(fd, bisect_rev_hex, len + 1);
 605         bisect_rev_hex[len] = '\0';
 606
 607         if (close(fd) < 0)
 608                 die("closing file %s: %s", filename, strerror(errno));
 609 }
 610
 611 static int bisect_checkout(char *bisect_rev_hex)
 612 {
 613         int res;
 614
 615         mark_expected_rev(bisect_rev_hex);
 616
 617         argv_checkout[2] = bisect_rev_hex;
 618         res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
 619         if (res)
 620                 exit(res);
 621
 622         argv_show_branch[1] = bisect_rev_hex;
 623         return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
 624 }
 625
 626 /*
 627  * We use the convention that exiting with an exit code 10 means that
 628  * the bisection process finished successfully.
 629  * In this case the calling shell script should exit 0.
 630  */
 631 int bisect_next_exit(const char *prefix)
 632 {
 633         struct rev_info revs;
 634         struct commit_list *tried;
 635         int reaches = 0, all = 0, nr;
 636         const unsigned char *bisect_rev;
 637         char bisect_rev_hex[41];
 638
 639         bisect_common(&revs, prefix, &reaches, &all);
 640
 641         revs.commits = filter_skipped(revs.commits, &tried, 0);
 642
 643         if (!revs.commits) {
 644                 /*
 645                  * We should exit here only if the "bad"
 646                  * commit is also a "skip" commit.
 647                  */
 648                 exit_if_skipped_commits(tried, NULL);
 649
 650                 printf("%s was both good and bad\n",
 651                        sha1_to_hex(current_bad_sha1));
 652                 exit(1);
 653         }
 654
 655         bisect_rev = revs.commits->item->object.sha1;
 656         memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), 41);
 657
 658         if (!hashcmp(bisect_rev, current_bad_sha1)) {
 659                 exit_if_skipped_commits(tried, current_bad_sha1);
 660                 printf("%s is first bad commit\n", bisect_rev_hex);
 661                 argv_diff_tree[2] = bisect_rev_hex;
 662                 run_command_v_opt(argv_diff_tree, RUN_GIT_CMD);
 663                 /* This means the bisection process succeeded. */
 664                 exit(10);
 665         }
 666
 667         nr = all - reaches - 1;
 668         printf("Bisecting: %d revisions left to test after this "
 669                "(roughly %d steps)\n", nr, estimate_bisect_steps(all));
 670
 671         return bisect_checkout(bisect_rev_hex);
 672 }
 673