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Overview
Comment: | 3604074,3606683 Rewrite of the fixempties() routine (and supporting routines) to completely eliminate the infinite loop hazard. Thanks to Tom Lane for the much improved solution. |
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Timelines: | family | ancestors | descendants | both | trunk |
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SHA1: |
4d7eba11ad2f9de4c5c41e7a1a29b96b |
User & Date: | dgp 2013-03-06 20:50:53 |
Context
2013-03-06
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21:55 | Cleaner error handling in fixempties(). check-in: c769b9bb91 user: dgp tags: trunk | |
20:54 | merge trunk check-in: 54d0ba332e user: dgp tags: dgp-refactor | |
20:50 | 3604074,3606683 Rewrite of the fixempties() routine (and supporting routines) to completely eliminat... check-in: 4d7eba11ad user: dgp tags: trunk | |
20:28 | 3604074,3606683 Rewrite of the fixempties() routine (and supporting routines) to completely eliminat... check-in: 71a42e2a9c user: dgp tags: core-8-5-branch | |
20:25 | merge trunk Closed-Leaf check-in: 83fa62555b user: dgp tags: bug-3606683 | |
12:26 | Tell fossil and Eclipse that the default eol-convention is LF. Tell fossil which files are binary a... check-in: da4c323ede user: jan.nijtmans tags: trunk | |
Changes
Changes to ChangeLog.
1 2 3 4 5 6 7 | 2013-02-28 Don Porter <[email protected]> * generic/tclLiteral.c: Revise TclReleaseLiteral() to tolerate a NULL interp argument. * generic/tclCompile.c: Update callers and revise mistaken comments. * generic/tclProc.c: | > > > > > > > | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | 2013-03-06 Don Porter <[email protected]> * generic/regc_nfa.c: [Bugs 3604074,3606683] Rewrite of the * generic/regcomp.c: fixempties() routine (and supporting routines) to completely eliminate the infinite loop hazard. Thanks to Tom Lane for the much improved solution. 2013-02-28 Don Porter <[email protected]> * generic/tclLiteral.c: Revise TclReleaseLiteral() to tolerate a NULL interp argument. * generic/tclCompile.c: Update callers and revise mistaken comments. * generic/tclProc.c: |
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Changes to generic/regc_nfa.c.
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491 492 493 494 495 496 497 498 499 500 501 502 503 504 | victim->from = NULL; /* precautions... */ victim->to = NULL; victim->inchain = NULL; victim->outchain = NULL; victim->freechain = from->free; from->free = victim; } /* - findarc - find arc, if any, from given source with given type and color * If there is more than one such arc, the result is random. ^ static struct arc *findarc(struct state *, int, pcolor); */ static struct arc * | > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 | victim->from = NULL; /* precautions... */ victim->to = NULL; victim->inchain = NULL; victim->outchain = NULL; victim->freechain = from->free; from->free = victim; } /* - hasnonemptyout - Does state have a non-EMPTY out arc? ^ static int hasnonemptyout(struct state *); */ static int hasnonemptyout( struct state *s) { struct arc *a; for (a = s->outs; a != NULL; a = a->outchain) { if (a->type != EMPTY) { return 1; } } return 0; } /* - nonemptyouts - count non-EMPTY out arcs of a state ^ static int nonemptyouts(struct state *); */ static int nonemptyouts( struct state *s) { int n = 0; struct arc *a; for (a = s->outs; a != NULL; a = a->outchain) { if (a->type != EMPTY) { n++; } } return n; } /* - nonemptyins - count non-EMPTY in arcs of a state ^ static int nonemptyins(struct state *); */ static int nonemptyins( struct state *s) { int n = 0; struct arc *a; for (a = s->ins; a != NULL; a = a->inchain) { if (a->type != EMPTY) { n++; } } return n; } /* - findarc - find arc, if any, from given source with given type and color * If there is more than one such arc, the result is random. ^ static struct arc *findarc(struct state *, int, pcolor); */ static struct arc * |
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555 556 557 558 559 560 561 | freearc(nfa, a); } assert(oldState->nins == 0); assert(oldState->ins == NULL); } /* | | > | | > > | > | 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 | freearc(nfa, a); } assert(oldState->nins == 0); assert(oldState->ins == NULL); } /* - copyins - copy in arcs of a state to another state * Either all arcs, or only non-empty ones as determined by all value. ^ static VOID copyins(struct nfa *, struct state *, struct state *, int); */ static void copyins( struct nfa *nfa, struct state *oldState, struct state *newState, int all) { struct arc *a; assert(oldState != newState); for (a=oldState->ins ; a!=NULL ; a=a->inchain) { if (all || a->type != EMPTY) { cparc(nfa, a, a->from, newState); } } } /* - moveouts - move all out arcs of a state to another state ^ static void moveouts(struct nfa *, struct state *, struct state *); */ |
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594 595 596 597 598 599 600 | while ((a = oldState->outs) != NULL) { cparc(nfa, a, newState, a->to); freearc(nfa, a); } } /* | | > | | > > | > | 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 | while ((a = oldState->outs) != NULL) { cparc(nfa, a, newState, a->to); freearc(nfa, a); } } /* - copyouts - copy out arcs of a state to another state * Either all arcs, or only non-empty ones as determined by all value. ^ static VOID copyouts(struct nfa *, struct state *, struct state *, int); */ static void copyouts( struct nfa *nfa, struct state *oldState, struct state *newState, int all) { struct arc *a; assert(oldState != newState); for (a=oldState->outs ; a!=NULL ; a=a->outchain) { if (all || a->type != EMPTY) { cparc(nfa, a, newState, a->to); } } } /* - cloneouts - copy out arcs of a state to another state pair, modifying type ^ static void cloneouts(struct nfa *, struct state *, struct state *, ^ struct state *, int); |
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966 967 968 969 970 971 972 | */ if (from->nouts > 1) { s = newstate(nfa); if (NISERR()) { return 0; } | | | | | 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 | */ if (from->nouts > 1) { s = newstate(nfa); if (NISERR()) { return 0; } assert(to != from); /* con is not an inarc */ copyins(nfa, from, s, 1); /* duplicate inarcs */ cparc(nfa, con, s, to); /* move constraint arc */ freearc(nfa, con); from = s; con = from->outs; } assert(from->nouts == 1); /* |
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1126 1127 1128 1129 1130 1131 1132 | */ if (to->nins > 1) { s = newstate(nfa); if (NISERR()) { return 0; } | | | 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 | */ if (to->nins > 1) { s = newstate(nfa); if (NISERR()) { return 0; } copyouts(nfa, to, s, 1); /* duplicate outarcs */ cparc(nfa, con, from, s); /* move constraint */ freearc(nfa, con); to = s; con = to->ins; } assert(to->nins == 1); |
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1243 1244 1245 1246 1247 1248 1249 | */ static void fixempties( struct nfa *nfa, FILE *f) /* for debug output; NULL none */ { struct state *s; | | | < > | > > < < < | | > > > | > | > > > > > > | > | < | > | > > > > > > | > > > > > > | | > | | < < < < < > > > | < < < | | | | | | | < > | > > > > > | < < < > > > > > > | < | | < | > > > | > | | > > > > | > > | | < | > > > > > > > > > > > > | > > > > > > > | | < > > > > > | | | | | < | > > > | < > | < < > | | > > > > > > > > | < < < | | > | < | | | | < < | > > > > > > > > > > > > > > > > > > > > > > > > > > | < | > > > > | | | < | 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 | */ static void fixempties( struct nfa *nfa, FILE *f) /* for debug output; NULL none */ { struct state *s; struct state *s2; struct state *nexts; struct arc *a; struct arc *nexta; /* * First, get rid of any states whose sole out-arc is an EMPTY, * since they're basically just aliases for their successor. The * parsing algorithm creates enough of these that it's worth * special-casing this. */ for (s = nfa->states; s != NULL && !NISERR(); s = nexts) { nexts = s->next; if (s->flag || s->nouts != 1) { continue; } a = s->outs; assert(a != NULL && a->outchain == NULL); if (a->type != EMPTY) { continue; } if (s != a->to) { moveins(nfa, s, a->to); } dropstate(nfa, s); } /* * Similarly, get rid of any state with a single EMPTY in-arc, by * folding it into its predecessor. */ for (s = nfa->states; s != NULL && !NISERR(); s = nexts) { nexts = s->next; /* Ensure tmp fields are clear for next step */ assert(s->tmp = NULL); if (s->flag || s->nins != 1) { continue; } a = s->ins; assert(a != NULL && a->inchain == NULL); if (a->type != EMPTY) { continue; } if (s != a->from) { moveouts(nfa, s, a->from); } dropstate(nfa, s); } /* * For each remaining NFA state, find all other states that are * reachable from it by a chain of one or more EMPTY arcs. Then * generate new arcs that eliminate the need for each such chain. * * If we just do this straightforwardly, the algorithm gets slow in * complex graphs, because the same arcs get copied to all * intermediate states of an EMPTY chain, and then uselessly pushed * repeatedly to the chain's final state; we waste a lot of time in * newarc's duplicate checking. To improve matters, we decree that * any state with only EMPTY out-arcs is "doomed" and will not be * part of the final NFA. That can be ensured by not adding any new * out-arcs to such a state. Having ensured that, we need not update * the state's in-arcs list either; all arcs that might have gotten * pushed forward to it will just get pushed directly to successor * states. This eliminates most of the useless duplicate arcs. */ for (s = nfa->states; s != NULL && !NISERR(); s = s->next) { for (s2 = emptyreachable(s, s); s2 != s && !NISERR(); s2 = nexts) { /* * If s2 is doomed, we decide that (1) we will always push * arcs forward to it, not pull them back to s; and (2) we * can optimize away the push-forward, per comment above. * So do nothing. */ if (s2->flag || hasnonemptyout(s2)) { replaceempty(nfa, s, s2); } /* Reset the tmp fields as we walk back */ nexts = s2->tmp; s2->tmp = NULL; } s->tmp = NULL; } /* * Remove all the EMPTY arcs, since we don't need them anymore. */ for (s = nfa->states; s != NULL; s = s->next) { for (a = s->outs; a != NULL; a = nexta) { nexta = a->outchain; if (a->type == EMPTY) { freearc(nfa, a); } } } /* * And remove any states that have become useless. (This cleanup is * not very thorough, and would be even less so if we tried to * combine it with the previous step; but cleanup() will take care * of anything we miss.) */ for (s = nfa->states; s != NULL && !NISERR(); s = nexts) { nexts = s->next; if ((s->nins == 0 || s->nouts == 0) && !s->flag) { dropstate(nfa, s); } } if (f != NULL && !NISERR()) { dumpnfa(nfa, f); } } /* - emptyreachable - recursively find all states reachable from s by EMPTY arcs * The return value is the last such state found. Its tmp field links back * to the next-to-last such state, and so on back to s, so that all these * states can be located without searching the whole NFA. * The maximum recursion depth here is equal to the length of the longest * loop-free chain of EMPTY arcs, which is surely no more than the size of * the NFA, and in practice will be a lot less than that. ^ static struct state *emptyreachable(struct state *, struct state *); */ static struct state * emptyreachable( struct state *s, struct state *lastfound) { struct arc *a; s->tmp = lastfound; lastfound = s; for (a = s->outs; a != NULL; a = a->outchain) { if (a->type == EMPTY && a->to->tmp == NULL) { lastfound = emptyreachable(a->to, lastfound); } } return lastfound; } /* - replaceempty - replace an EMPTY arc chain with some non-empty arcs * The EMPTY arc(s) should be deleted later, but we can't do it here because * they may still be needed to identify other arc chains during fixempties(). ^ static void replaceempty(struct nfa *, struct state *, struct state *); */ static void replaceempty( struct nfa *nfa, struct state *from, struct state *to) { int fromouts; int toins; assert(from != to); /* * Create replacement arcs that bypass the need for the EMPTY chain. We * can do this either by pushing arcs forward (linking directly from * "from"'s predecessors to "to") or by pulling them back (linking * directly from "from" to "to"'s successors). In general, we choose * whichever way creates greater fan-out or fan-in, so as to improve the * odds of reducing the other state to zero in-arcs or out-arcs and * thereby being able to delete it. However, if "from" is doomed (has no * non-EMPTY out-arcs), we must keep it so, so always push forward in that * case. * * The fan-out/fan-in comparison should count only non-EMPTY arcs. If * "from" is doomed, we can skip counting "to"'s arcs, since we want to * force taking the copynonemptyins path in that case. */ fromouts = nonemptyouts(from); toins = (fromouts == 0) ? 1 : nonemptyins(to); if (fromouts > toins) { copyouts(nfa, to, from, 0); return; } if (fromouts < toins) { copyins(nfa, from, to, 0); return; } /* * fromouts == toins. Decide on secondary issue: copy fewest arcs. * * Doesn't seem to be worth the trouble to exclude empties from these * comparisons; that takes extra time and doesn't seem to improve the * resulting graph much. */ if (from->nins > to->nouts) { copyouts(nfa, to, from, 0); return; } copyins(nfa, from, to, 0); } /* - cleanup - clean up NFA after optimizations ^ static void cleanup(struct nfa *); */ static void |
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Changes to generic/regcomp.c.
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117 118 119 120 121 122 123 124 125 126 | static struct state *newfstate(struct nfa *, int flag); static void dropstate(struct nfa *, struct state *); static void freestate(struct nfa *, struct state *); static void destroystate(struct nfa *, struct state *); static void newarc(struct nfa *, int, pcolor, struct state *, struct state *); static struct arc *allocarc(struct nfa *, struct state *); static void freearc(struct nfa *, struct arc *); static struct arc *findarc(struct state *, int, pcolor); static void cparc(struct nfa *, struct arc *, struct state *, struct state *); static void moveins(struct nfa *, struct state *, struct state *); | > > > | | > | | 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 | static struct state *newfstate(struct nfa *, int flag); static void dropstate(struct nfa *, struct state *); static void freestate(struct nfa *, struct state *); static void destroystate(struct nfa *, struct state *); static void newarc(struct nfa *, int, pcolor, struct state *, struct state *); static struct arc *allocarc(struct nfa *, struct state *); static void freearc(struct nfa *, struct arc *); static int hasnonemptyout(struct state *); static int nonemptyouts(struct state *); static int nonemptyins(struct state *); static struct arc *findarc(struct state *, int, pcolor); static void cparc(struct nfa *, struct arc *, struct state *, struct state *); static void moveins(struct nfa *, struct state *, struct state *); static void copyins(struct nfa *, struct state *, struct state *, int); static void moveouts(struct nfa *, struct state *, struct state *); static void copyouts(struct nfa *, struct state *, struct state *, int); static void cloneouts(struct nfa *, struct state *, struct state *, struct state *, int); static void delsub(struct nfa *, struct state *, struct state *); static void deltraverse(struct nfa *, struct state *, struct state *); static void dupnfa(struct nfa *, struct state *, struct state *, struct state *, struct state *); static void duptraverse(struct nfa *, struct state *, struct state *, int); static void cleartraverse(struct nfa *, struct state *); static void specialcolors(struct nfa *); static long optimize(struct nfa *, FILE *); static void pullback(struct nfa *, FILE *); static int pull(struct nfa *, struct arc *); static void pushfwd(struct nfa *, FILE *); static int push(struct nfa *, struct arc *); #define INCOMPATIBLE 1 /* destroys arc */ #define SATISFIED 2 /* constraint satisfied */ #define COMPATIBLE 3 /* compatible but not satisfied yet */ static int combine(struct arc *, struct arc *); static void fixempties(struct nfa *, FILE *); static struct state *emptyreachable(struct state *, struct state *); static void replaceempty(struct nfa *, struct state *, struct state *); static void cleanup(struct nfa *); static void markreachable(struct nfa *, struct state *, struct state *, struct state *); static void markcanreach(struct nfa *, struct state *, struct state *, struct state *); static long analyze(struct nfa *); static void compact(struct nfa *, struct cnfa *); static void carcsort(struct carc *, struct carc *); static void freecnfa(struct cnfa *); |
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603 604 605 606 607 608 609 | /* * Do the splits. */ for (s=slist ; s!=NULL ; s=s2) { s2 = newstate(nfa); | | | 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 | /* * Do the splits. */ for (s=slist ; s!=NULL ; s=s2) { s2 = newstate(nfa); copyouts(nfa, s, s2, 1); for (a=s->ins ; a!=NULL ; a=b) { b = a->inchain; if (a->from != pre) { cparc(nfa, a, a->from, s2); freearc(nfa, a); } |
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