summaryrefslogtreecommitdiff
path: root/posix/regexec.c
blob: e2597dc47e9d80c11a06ef83d8919d0ba10fde5f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
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
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
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
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
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
644
645
646
647
648
649
650
651
652
653
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
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
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
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
/* Extended regular expression matching and search library.
   Copyright (C) 2002 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Isamu Hasegawa <isamu@yamato.ibm.com>.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <assert.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#if defined HAVE_WCHAR_H || defined _LIBC
# include <wchar.h>
#endif /* HAVE_WCHAR_H || _LIBC */
#if defined HAVE_WCTYPE_H || defined _LIBC
# include <wctype.h>
#endif /* HAVE_WCTYPE_H || _LIBC */

#ifdef _LIBC
# ifndef _RE_DEFINE_LOCALE_FUNCTIONS
#  define _RE_DEFINE_LOCALE_FUNCTIONS 1
#  include <locale/localeinfo.h>
#  include <locale/elem-hash.h>
#  include <locale/coll-lookup.h>
# endif
#endif

#include "regex.h"
#include "regex_internal.h"

static reg_errcode_t match_ctx_init (re_match_context_t *cache, int eflags,
				     re_string_t *input, int n);
static void match_ctx_free (re_match_context_t *cache);
static reg_errcode_t match_ctx_add_entry (re_match_context_t *cache, int node,
                                          int str_idx, int from, int to);
static void match_ctx_clear_flag (re_match_context_t *mctx);
static void sift_ctx_init (re_sift_context_t *sctx, re_dfastate_t **sifted_sts,
                           re_dfastate_t **limited_sts, int last_node,
                           int last_str_idx, int check_subexp);
static reg_errcode_t re_search_internal (const regex_t *preg,
                                         const char *string, int length,
                                         int start, int range, int stop,
                                         size_t nmatch, regmatch_t pmatch[],
                                         int eflags);
static int re_search_2_stub (struct re_pattern_buffer *bufp,
                             const char *string1, int length1,
                             const char *string2, int length2,
                             int start, int range, struct re_registers *regs,
                             int stop, int ret_len);
static int re_search_stub (struct re_pattern_buffer *bufp,
                           const char *string, int length, int start,
                           int range, int stop, struct re_registers *regs,
                           int ret_len);
static unsigned re_copy_regs (struct re_registers *regs, regmatch_t *pmatch,
                              int nregs, int regs_allocated);
static inline re_dfastate_t *acquire_init_state_context (reg_errcode_t *err,
                                                         const regex_t *preg,
                                                         const re_match_context_t *mctx,
                                                         int idx);
static int check_matching (const regex_t *preg, re_match_context_t *mctx,
                           int fl_search, int fl_longest_match);
static int check_halt_node_context (const re_dfa_t *dfa, int node,
                                    unsigned int context);
static int check_halt_state_context (const regex_t *preg,
                                     const re_dfastate_t *state,
                                     const re_match_context_t *mctx, int idx);
static void update_regs (re_dfa_t *dfa, regmatch_t *pmatch, int cur_node,
                         int cur_idx, int nmatch);
static int proceed_next_node (const regex_t *preg, regmatch_t *regs,
                              const re_match_context_t *mctx,
                              int *pidx, int node, re_node_set *eps_via_nodes);
static reg_errcode_t set_regs (const regex_t *preg,
                               const re_match_context_t *mctx,
                               size_t nmatch, regmatch_t *pmatch, int last);
#ifdef RE_ENABLE_I18N
static int sift_states_iter_mb (const regex_t *preg,
                                const re_match_context_t *mctx,
                                re_sift_context_t *sctx,
                                int node_idx, int str_idx, int max_str_idx);
#endif /* RE_ENABLE_I18N */
static reg_errcode_t sift_states_backward (const regex_t *preg,
                                           re_match_context_t *mctx,
                                           re_sift_context_t *sctx);
static reg_errcode_t update_cur_sifted_state (const regex_t *preg,
                                              re_match_context_t *mctx,
                                              re_sift_context_t *sctx,
                                              int str_idx,
                                              re_node_set *dest_nodes);
static reg_errcode_t add_epsilon_src_nodes (re_dfa_t *dfa,
                                            re_node_set *dest_nodes,
                                            const re_node_set *candidates);
static reg_errcode_t sub_epsilon_src_nodes (re_dfa_t *dfa, int node,
                                            re_node_set *dest_nodes,
                                            const re_node_set *and_nodes);
static reg_errcode_t check_subexp_limits (re_dfa_t *dfa,
                                          re_node_set *dest_nodes,
                                          const re_node_set *candidates,
                                          re_node_set *limits,
                                          struct re_backref_cache_entry *bkref_ents,
                                          int str_idx);
static reg_errcode_t search_subexp (const regex_t *preg,
                                    re_match_context_t *mctx,
                                    re_sift_context_t *sctx, int str_idx,
                                    re_node_set *dest_nodes);
static reg_errcode_t sift_states_bkref (const regex_t *preg,
                                        re_match_context_t *mctx,
                                        re_sift_context_t *sctx,
                                        int str_idx, re_node_set *dest_nodes);
static reg_errcode_t clean_state_log_if_need (re_match_context_t *mctx,
                                              int next_state_log_idx);
static reg_errcode_t merge_state_array (re_dfa_t *dfa, re_dfastate_t **dst,
                                        re_dfastate_t **src, int num);
static re_dfastate_t *transit_state (reg_errcode_t *err, const regex_t *preg,
                                     re_match_context_t *mctx,
                                     re_dfastate_t *state, int fl_search);
static re_dfastate_t *transit_state_sb (reg_errcode_t *err, const regex_t *preg,
                                        re_dfastate_t *pstate,
                                        int fl_search,
                                        re_match_context_t *mctx);
#ifdef RE_ENABLE_I18N
static reg_errcode_t transit_state_mb (const regex_t *preg,
                                       re_dfastate_t *pstate,
                                       re_match_context_t *mctx);
#endif /* RE_ENABLE_I18N */
static reg_errcode_t transit_state_bkref (const regex_t *preg,
                                          re_dfastate_t *pstate,
                                          re_match_context_t *mctx);
static reg_errcode_t transit_state_bkref_loop (const regex_t *preg,
                                               re_node_set *nodes,
                                               re_dfastate_t **work_state_log,
                                               re_match_context_t *mctx);
static re_dfastate_t **build_trtable (const regex_t *dfa,
                                      const re_dfastate_t *state,
                                      int fl_search);
#ifdef RE_ENABLE_I18N
static int check_node_accept_bytes (const regex_t *preg, int node_idx,
                                    const re_string_t *input, int idx);
# ifdef _LIBC
static unsigned int find_collation_sequence_value (const unsigned char *mbs,
                                                   size_t name_len);
# endif /* _LIBC */
#endif /* RE_ENABLE_I18N */
static int group_nodes_into_DFAstates (const regex_t *dfa,
                                       const re_dfastate_t *state,
                                       re_node_set *states_node,
                                       bitset *states_ch);
static int check_node_accept (const regex_t *preg, const re_token_t *node,
                              const re_match_context_t *mctx, int idx);
static reg_errcode_t extend_buffers (re_match_context_t *mctx);

/* Entry point for POSIX code.  */

/* regexec searches for a given pattern, specified by PREG, in the
   string STRING.

   If NMATCH is zero or REG_NOSUB was set in the cflags argument to
   `regcomp', we ignore PMATCH.  Otherwise, we assume PMATCH has at
   least NMATCH elements, and we set them to the offsets of the
   corresponding matched substrings.

   EFLAGS specifies `execution flags' which affect matching: if
   REG_NOTBOL is set, then ^ does not match at the beginning of the
   string; if REG_NOTEOL is set, then $ does not match at the end.

   We return 0 if we find a match and REG_NOMATCH if not.  */

int
regexec (preg, string, nmatch, pmatch, eflags)
    const regex_t *__restrict preg;
    const char *__restrict string;
    size_t nmatch;
    regmatch_t pmatch[];
    int eflags;
{
  reg_errcode_t err;
  int length = strlen (string);
  if (preg->no_sub)
    err = re_search_internal (preg, string, length, 0, length, length, 0,
                              NULL, eflags);
  else
    err = re_search_internal (preg, string, length, 0, length, length, nmatch,
                              pmatch, eflags);
  return err != REG_NOERROR;
}
#ifdef _LIBC
weak_alias (__regexec, regexec)
#endif

/* Entry points for GNU code.  */

/* re_match, re_search, re_match_2, re_search_2

   The former two functions operate on STRING with length LENGTH,
   while the later two operate on concatenation of STRING1 and STRING2
   with lengths LENGTH1 and LENGTH2, respectively.

   re_match() matches the compiled pattern in BUFP against the string,
   starting at index START.

   re_search() first tries matching at index START, then it tries to match
   starting from index START + 1, and so on.  The last start position tried
   is START + RANGE.  (Thus RANGE = 0 forces re_search to operate the same
   way as re_match().)

   The parameter STOP of re_{match,search}_2 specifies that no match exceeding
   the first STOP characters of the concatenation of the strings should be
   concerned.

   If REGS is not NULL, and BUFP->no_sub is not set, the offsets of the match
   and all groups is stroed in REGS.  (For the "_2" variants, the offsets are
   computed relative to the concatenation, not relative to the individual
   strings.)

   On success, re_match* functions return the length of the match, re_search*
   return the position of the start of the match.  Return value -1 means no
   match was found and -2 indicates an internal error.  */

int
re_match (bufp, string, length, start, regs)
    struct re_pattern_buffer *bufp;
    const char *string;
    int length, start;
    struct re_registers *regs;
{
  return re_search_stub (bufp, string, length, start, 0, length, regs, 1);
}
#ifdef _LIBC
weak_alias (__re_match, re_match)
#endif

int
re_search (bufp, string, length, start, range, regs)
    struct re_pattern_buffer *bufp;
    const char *string;
    int length, start, range;
    struct re_registers *regs;
{
  return re_search_stub (bufp, string, length, start, range, length, regs, 0);
}
#ifdef _LIBC
weak_alias (__re_search, re_search)
#endif

int
re_match_2 (bufp, string1, length1, string2, length2, start, regs, stop)
    struct re_pattern_buffer *bufp;
    const char *string1, *string2;
    int length1, length2, start, stop;
    struct re_registers *regs;
{
  return re_search_2_stub (bufp, string1, length1, string2, length2,
                           start, 0, regs, stop, 1);
}
#ifdef _LIBC
weak_alias (__re_match_2, re_match_2)
#endif

int
re_search_2 (bufp, string1, length1, string2, length2, start, range, regs, stop)
    struct re_pattern_buffer *bufp;
    const char *string1, *string2;
    int length1, length2, start, range, stop;
    struct re_registers *regs;
{
  return re_search_2_stub (bufp, string1, length1, string2, length2,
                           start, range, regs, stop, 0);
}
#ifdef _LIBC
weak_alias (__re_search_2, re_search_2)
#endif

static int
re_search_2_stub (bufp, string1, length1, string2, length2, start, range, regs,
                  stop, ret_len)
    struct re_pattern_buffer *bufp;
    const char *string1, *string2;
    int length1, length2, start, range, stop, ret_len;
    struct re_registers *regs;
{
  const char *str;
  int rval;
  int len = length1 + length2;
  int free_str = 0;

  if (BE (length1 < 0 || length2 < 0 || stop < 0, 0))
    return -2;

  /* Concatenate the strings.  */
  if (length2 > 0)
    if (length1 > 0)
      {
        char *s = re_malloc (char, len);

        if (BE (s == NULL, 0))
          return -2;
        memcpy (s, string1, length1);
        memcpy (s + length1, string2, length2);
        str = s;
        free_str = 1;
      }
    else
      str = string2;
  else
    str = string1;

  rval = re_search_stub (bufp, str, len, start, range, stop, regs,
                         ret_len);
  if (free_str)
      re_free ((char *) str);
  return rval;
}

/* The parameters have the same meaning as those of re_search.
   Additional parameters:
   If RET_LEN is nonzero the length of the match is returned (re_match style);
   otherwise the position of the match is returned.  */

static int
re_search_stub (bufp, string, length, start, range, stop, regs, ret_len)
    struct re_pattern_buffer *bufp;
    const char *string;
    int length, start, range, stop, ret_len;
    struct re_registers *regs;
{
  reg_errcode_t result;
  regmatch_t *pmatch;
  int nregs, rval;
  int eflags = 0;

  /* Check for out-of-range.  */
  if (BE (start < 0 || start > length || range < 0, 0))
    return -1;
  if (BE (start + range > length, 0))
    range = length - start;

  eflags |= (bufp->not_bol) ? REG_NOTBOL : 0;
  eflags |= (bufp->not_eol) ? REG_NOTEOL : 0;

  /* Compile fastmap if we haven't yet.  */
  if (range > 0 && bufp->fastmap != NULL && !bufp->fastmap_accurate)
    re_compile_fastmap (bufp);

  if (BE (bufp->no_sub, 0))
    regs = NULL;

  /* We need at least 1 register.  */
  if (regs == NULL)
    nregs = 1;
  else if (BE (bufp->regs_allocated == REGS_FIXED &&
               regs->num_regs < bufp->re_nsub + 1, 0))
    {
      nregs = regs->num_regs;
      if (BE (nregs < 1, 0))
        {
          /* Nothing can be copied to regs.  */
          regs = NULL;
          nregs = 1;
        }
    }
  else
    nregs = bufp->re_nsub + 1;
  pmatch = re_malloc (regmatch_t, nregs);
  if (BE (pmatch == NULL, 0))
    return -2;

  result = re_search_internal (bufp, string, length, start, range, stop,
                               nregs, pmatch, eflags);

  rval = 0;

  /* I hope we needn't fill ther regs with -1's when no match was found.  */
  if (result != REG_NOERROR)
    rval = -1;
  else if (regs != NULL)
    {
      /* If caller wants register contents data back, copy them.  */
      bufp->regs_allocated = re_copy_regs (regs, pmatch, nregs,
                                           bufp->regs_allocated);
      if (BE (bufp->regs_allocated == REGS_UNALLOCATED, 0))
        rval = -2;
    }

  if (BE (rval == 0, 1))
    {
      if (ret_len)
        {
          assert (pmatch[0].rm_so == start);
          rval = pmatch[0].rm_eo - start;
        }
      else
        rval = pmatch[0].rm_so;
    }
  re_free (pmatch);
  return rval;
}

static unsigned
re_copy_regs (regs, pmatch, nregs, regs_allocated)
    struct re_registers *regs;
    regmatch_t *pmatch;
    int nregs, regs_allocated;
{
  int rval = REGS_REALLOCATE;
  int i;
  int need_regs = nregs + 1;
  /* We need one extra element beyond `num_regs' for the `-1' marker GNU code
     uses.  */

  /* Have the register data arrays been allocated?  */
  if (regs_allocated == REGS_UNALLOCATED)
    { /* No.  So allocate them with malloc.  */
      regs->start = re_malloc (regoff_t, need_regs);
      if (BE (regs->start == NULL, 0))
        return REGS_UNALLOCATED;
      regs->end = re_malloc (regoff_t, need_regs);
      if (BE (regs->end == NULL, 0))
        {
          re_free (regs->start);
          return REGS_UNALLOCATED;
        }
      regs->num_regs = need_regs;
    }
  else if (regs_allocated == REGS_REALLOCATE)
    { /* Yes.  If we need more elements than were already
         allocated, reallocate them.  If we need fewer, just
         leave it alone.  */
      if (need_regs > regs->num_regs)
        {
          regs->start = re_realloc (regs->start, regoff_t, need_regs);
          if (BE (regs->start == NULL, 0))
            {
              if (regs->end != NULL)
                re_free (regs->end);
              return REGS_UNALLOCATED;
            }
          regs->end = re_realloc (regs->end, regoff_t, need_regs);
          if (BE (regs->end == NULL, 0))
            {
              re_free (regs->start);
              return REGS_UNALLOCATED;
            }
          regs->num_regs = need_regs;
        }
    }
  else
    {
      assert (regs_allocated == REGS_FIXED);
      /* This function may not be called with REGS_FIXED and nregs too big.  */
      assert (regs->num_regs >= nregs);
      rval = REGS_FIXED;
    }

  /* Copy the regs.  */
  for (i = 0; i < nregs; ++i)
    {
      regs->start[i] = pmatch[i].rm_so;
      regs->end[i] = pmatch[i].rm_eo;
    }
  for ( ; i < regs->num_regs; ++i)
    regs->start[i] = regs->end[i] = -1;

  return rval;
}

/* Set REGS to hold NUM_REGS registers, storing them in STARTS and
   ENDS.  Subsequent matches using PATTERN_BUFFER and REGS will use
   this memory for recording register information.  STARTS and ENDS
   must be allocated using the malloc library routine, and must each
   be at least NUM_REGS * sizeof (regoff_t) bytes long.

   If NUM_REGS == 0, then subsequent matches should allocate their own
   register data.

   Unless this function is called, the first search or match using
   PATTERN_BUFFER will allocate its own register data, without
   freeing the old data.  */

void
re_set_registers (bufp, regs, num_regs, starts, ends)
    struct re_pattern_buffer *bufp;
    struct re_registers *regs;
    unsigned num_regs;
    regoff_t *starts, *ends;
{
  if (num_regs)
    {
      bufp->regs_allocated = REGS_REALLOCATE;
      regs->num_regs = num_regs;
      regs->start = starts;
      regs->end = ends;
    }
  else
    {
      bufp->regs_allocated = REGS_UNALLOCATED;
      regs->num_regs = 0;
      regs->start = regs->end = (regoff_t *) 0;
    }
}
#ifdef _LIBC
weak_alias (__re_set_registers, re_set_registers)
#endif

/* Entry points compatible with 4.2 BSD regex library.  We don't define
   them unless specifically requested.  */

#if defined _REGEX_RE_COMP || defined _LIBC
int
# ifdef _LIBC
weak_function
# endif
re_exec (s)
     const char *s;
{
  return 0 == regexec (&re_comp_buf, s, 0, NULL, 0);
}
#endif /* _REGEX_RE_COMP */

static re_node_set empty_set;

/* Internal entry point.  */

/* Searches for a compiled pattern PREG in the string STRING, whose
   length is LENGTH.  NMATCH, PMATCH, and EFLAGS have the same
   mingings with regexec.  START, and RANGE have the same meanings
   with re_search.
   Return REG_NOERROR if we find a match, and REG_NOMATCH if not,
   otherwise return the error code.
   Note: We assume front end functions already check ranges.
   (START + RANGE >= 0 && START + RANGE <= LENGTH)  */

static reg_errcode_t
re_search_internal (preg, string, length, start, range, stop, nmatch, pmatch,
                    eflags)
    const regex_t *preg;
    const char *string;
    int length, start, range, stop, eflags;
    size_t nmatch;
    regmatch_t pmatch[];
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
  re_string_t input;
  int left_lim, right_lim, incr;
  int fl_longest_match, match_first, match_last = -1;
  re_match_context_t mctx;
  char *fastmap = ((preg->fastmap != NULL && preg->fastmap_accurate)
                   ? preg->fastmap : NULL);

  /* Check if the DFA haven't been compiled.  */
  if (BE (preg->used == 0 || dfa->init_state == NULL
          || dfa->init_state_word == NULL || dfa->init_state_nl == NULL
          || dfa->init_state_begbuf == NULL, 0))
    return REG_NOMATCH;

  re_node_set_init_empty (&empty_set);

  /* We must check the longest matching, if nmatch > 0.  */
  fl_longest_match = (nmatch != 0);

  err = re_string_allocate (&input, string, length, dfa->nodes_len + 1,
                            preg->translate, preg->syntax & RE_ICASE);
  if (BE (err != REG_NOERROR, 0))
    return err;
  input.stop = stop;

  err = match_ctx_init (&mctx, eflags, &input, dfa->nbackref * 2);
  if (BE (err != REG_NOERROR, 0))
    return err;

  /* We will log all the DFA states through which the dfa pass,
     if nmatch > 1, or this dfa has "multibyte node", which is a
     back-reference or a node which can accept multibyte character or
     multi character collating element.  */
  if (nmatch > 1 || dfa->has_mb_node)
    {
      mctx.state_log = re_malloc (re_dfastate_t *, dfa->nodes_len + 1);
      if (BE (mctx.state_log == NULL, 0))
        return REG_ESPACE;
    }
  else
    mctx.state_log = NULL;

#ifdef DEBUG
  /* We assume front-end functions already check them.  */
  assert (start + range >= 0 && start + range <= length);
#endif

  match_first = start;
  input.tip_context = ((eflags & REG_NOTBOL) ? CONTEXT_BEGBUF
                       : CONTEXT_NEWLINE | CONTEXT_BEGBUF);

  /* Check incrementally whether of not the input string match.  */
  incr = (range < 0) ? -1 : 1;
  left_lim = (range < 0) ? start + range : start;
  right_lim = (range < 0) ? start : start + range;

  for (;;)
    {
      /* At first get the current byte from input string.  */
      int ch;
      if (MB_CUR_MAX > 1 && (preg->syntax & RE_ICASE || preg->translate))
        {
          /* In this case, we can't determin easily the current byte,
             since it might be a component byte of a multibyte character.
             Then we use the constructed buffer instead.  */
          /* If MATCH_FIRST is out of the valid range, reconstruct the
             buffers.  */
          if (input.raw_mbs_idx + input.valid_len <= match_first)
            re_string_reconstruct (&input, match_first, eflags,
                                   preg->newline_anchor);
          /* If MATCH_FIRST is out of the buffer, leave it as '\0'.
             Note that MATCH_FIRST must not be smaller than 0.  */
          ch = ((match_first >= length) ? 0
                : re_string_byte_at (&input, match_first - input.raw_mbs_idx));
        }
      else
        {
          /* We apply translate/conversion manually, since it is trivial
             in this case.  */
          /* If MATCH_FIRST is out of the buffer, leave it as '\0'.
             Note that MATCH_FIRST must not be smaller than 0.  */
          ch = (match_first < length) ? (unsigned char)string[match_first] : 0;
          /* Apply translation if we need.  */
          ch = preg->translate ? preg->translate[ch] : ch;
          /* In case of case insensitive mode, convert to upper case.  */
          ch = ((preg->syntax & RE_ICASE) && islower (ch)) ? toupper (ch) : ch;
        }

      /* Eliminate inappropriate one by fastmap.  */
      if (preg->can_be_null || fastmap == NULL || fastmap[ch])
        {
          /* Reconstruct the buffers so that the matcher can assume that
             the matching starts from the begining of the buffer.  */
          re_string_reconstruct (&input, match_first, eflags,
                                 preg->newline_anchor);
#ifdef RE_ENABLE_I18N
          /* Eliminate it when it is a component of a multibyte character
             and isn't the head of a multibyte character.  */
          if (MB_CUR_MAX == 1 || re_string_first_byte (&input, 0))
#endif
            {
              /* It seems to be appropriate one, then use the matcher.  */
              /* We assume that the matching starts from 0.  */
              mctx.state_log_top = mctx.nbkref_ents = mctx.max_mb_elem_len = 0;
              match_last = check_matching (preg, &mctx, 0, fl_longest_match);
              if (match_last != -1)
                {
                  if (BE (match_last == -2, 0))
                    return REG_ESPACE;
                  else
                    break; /* We found a matching.  */
                }
            }
        }
      /* Update counter.  */
      match_first += incr;
      if (match_first < left_lim || right_lim < match_first)
        break;
    }

  /* Set pmatch[] if we need.  */
  if (match_last != -1 && nmatch > 0)
    {
      int reg_idx;

      /* Initialize registers.  */
      for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
        pmatch[reg_idx].rm_so = pmatch[reg_idx].rm_eo = -1;

      /* Set the points where matching start/end.  */
      pmatch[0].rm_so = 0;
      mctx.match_last = pmatch[0].rm_eo = match_last;

      if (!preg->no_sub && nmatch > 1)
        {
          /* We need the ranges of all the subexpressions.  */
          int halt_node;
          re_dfastate_t **sifted_states;
          re_dfastate_t **lim_states = NULL;
          re_dfastate_t *pstate = mctx.state_log[match_last];
          re_sift_context_t sctx;
#ifdef DEBUG
          assert (mctx.state_log != NULL);
#endif
          halt_node = check_halt_state_context (preg, pstate, &mctx,
                                                match_last);
          if (dfa->has_plural_match)
            {
              match_ctx_clear_flag (&mctx);
              sifted_states = re_malloc (re_dfastate_t *, match_last + 1);
              if (BE (sifted_states == NULL, 0))
                return REG_ESPACE;
              if (dfa->nbackref)
                {
                  lim_states = calloc (sizeof (re_dfastate_t *),
                                       match_last + 1);
                  if (BE (lim_states == NULL, 0))
                    return REG_ESPACE;
                }
              sift_ctx_init (&sctx, sifted_states, lim_states, halt_node,
                             mctx.match_last, 0);
              err = sift_states_backward (preg, &mctx, &sctx);
              if (BE (err != REG_NOERROR, 0))
                return err;
              if (lim_states != NULL)
                {
                  err = merge_state_array (dfa, sifted_states, lim_states,
                                           match_last + 1);
                  if (BE (err != REG_NOERROR, 0))
                    return err;
                  re_free (lim_states);
                }
              re_node_set_free (&sctx.limits);
              re_free (mctx.state_log);
              mctx.state_log = sifted_states;
            }
          err = set_regs (preg, &mctx, nmatch, pmatch, halt_node);
          if (BE (err != REG_NOERROR, 0))
            return err;
        }

      /* At last, add the offset to the each registers, since we slided
         the buffers so that We can assume that the matching starts from 0.  */
      for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
        if (pmatch[reg_idx].rm_so != -1)
          {
            pmatch[reg_idx].rm_so += match_first;
            pmatch[reg_idx].rm_eo += match_first;
          }
    }

  re_free (mctx.state_log);
  if (dfa->nbackref)
    match_ctx_free (&mctx);
  re_string_destruct (&input);

  return (match_last == -1) ? REG_NOMATCH : REG_NOERROR;
}

/* Acquire an initial state and return it.
   We must select appropriate initial state depending on the context,
   since initial states may have constraints like "\<", "^", etc..  */

static inline re_dfastate_t *
acquire_init_state_context (err, preg, mctx, idx)
     reg_errcode_t *err;
     const regex_t *preg;
     const re_match_context_t *mctx;
     int idx;
{
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;

  *err = REG_NOERROR;
  if (dfa->init_state->has_constraint)
    {
      unsigned int context;
      context =  re_string_context_at (mctx->input, idx - 1, mctx->eflags,
                                       preg->newline_anchor);
      if (IS_WORD_CONTEXT (context))
        return dfa->init_state_word;
      else if (IS_ORDINARY_CONTEXT (context))
        return dfa->init_state;
      else if (IS_BEGBUF_CONTEXT (context) && IS_NEWLINE_CONTEXT (context))
        return dfa->init_state_begbuf;
      else if (IS_NEWLINE_CONTEXT (context))
        return dfa->init_state_nl;
      else if (IS_BEGBUF_CONTEXT (context))
        {
          /* It is relatively rare case, then calculate on demand.  */
          return  re_acquire_state_context (err, dfa,
                                            dfa->init_state->entrance_nodes,
                                            context);
        }
      else
        /* Must not happen?  */
        return dfa->init_state;
    }
  else
    return dfa->init_state;
}

/* Check whether the regular expression match input string INPUT or not,
   and return the index where the matching end, return -1 if not match,
   or return -2 in case of an error.
   FL_SEARCH means we must search where the matching starts,
   FL_LONGEST_MATCH means we want the POSIX longest matching.
   Note that the matcher assume that the maching starts from the current
   index of the buffer.  */

static int
check_matching (preg, mctx, fl_search, fl_longest_match)
    const regex_t *preg;
    re_match_context_t *mctx;
    int fl_search, fl_longest_match;
{
  reg_errcode_t err;
  int match = 0;
  int match_last = -1;
  int cur_str_idx = re_string_cur_idx (mctx->input);
  re_dfastate_t *cur_state;

  cur_state = acquire_init_state_context (&err, preg, mctx, cur_str_idx);
  /* An initial state must not be NULL(invalid state).  */
  if (BE (cur_state == NULL, 0))
    return -2;
  if (mctx->state_log != NULL)
    mctx->state_log[cur_str_idx] = cur_state;

  if (cur_state->has_backref)
    {
      int i;
      re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
      for (i = 0; i < cur_state->nodes.nelem; ++i)
        {
          re_token_type_t type;
          int node = cur_state->nodes.elems[i];
          int entity = (dfa->nodes[node].type != OP_CONTEXT_NODE ? node
                        : dfa->nodes[node].opr.ctx_info->entity);
          type = dfa->nodes[entity].type;
          if (type == OP_BACK_REF)
            {
              int clexp_idx;
              for (clexp_idx = 0; clexp_idx < cur_state->nodes.nelem;
                   ++clexp_idx)
                {
                  re_token_t *clexp_node;
                  clexp_node = dfa->nodes + cur_state->nodes.elems[clexp_idx];
                  if (clexp_node->type == OP_CLOSE_SUBEXP
                      && clexp_node->opr.idx + 1== dfa->nodes[entity].opr.idx)
                    {
                      err = match_ctx_add_entry (mctx, node, 0, 0, 0);
                      if (BE (err != REG_NOERROR, 0))
                        return -2;
                      break;
                    }
                }
            }
        }
    }

  /* If the RE accepts NULL string.  */
  if (cur_state->halt)
    {
      if (!cur_state->has_constraint
          || check_halt_state_context (preg, cur_state, mctx, cur_str_idx))
        {
          if (!fl_longest_match)
            return cur_str_idx;
          else
            {
              match_last = cur_str_idx;
              match = 1;
            }
        }
    }

  while (!re_string_eoi (mctx->input))
    {
      cur_state = transit_state (&err, preg, mctx, cur_state,
                                 fl_search && !match);
      if (cur_state == NULL) /* Reached at the invalid state or an error.  */
        {
          cur_str_idx = re_string_cur_idx (mctx->input);
          if (BE (err != REG_NOERROR, 0))
            return -2;
          if (fl_search && !match)
            {
              /* Restart from initial state, since we are searching
                 the point from where matching start.  */
#ifdef RE_ENABLE_I18N
              if (MB_CUR_MAX == 1
                  || re_string_first_byte (mctx->input, cur_str_idx))
#endif /* RE_ENABLE_I18N */
                cur_state = acquire_init_state_context (&err, preg, mctx,
                                                        cur_str_idx);
              if (BE (cur_state == NULL && err != REG_NOERROR, 0))
                return -2;
              if (mctx->state_log != NULL)
                mctx->state_log[cur_str_idx] = cur_state;
            }
          else if (!fl_longest_match && match)
            break;
          else /* (fl_longest_match && match) || (!fl_search && !match)  */
            {
              if (mctx->state_log == NULL)
                break;
              else
                {
                  int max = mctx->state_log_top;
                  for (; cur_str_idx <= max; ++cur_str_idx)
                    if (mctx->state_log[cur_str_idx] != NULL)
                      break;
                  if (cur_str_idx > max)
                    break;
                }
            }
        }

      if (cur_state != NULL && cur_state->halt)
        {
          /* Reached at a halt state.
             Check the halt state can satisfy the current context.  */
          if (!cur_state->has_constraint
              || check_halt_state_context (preg, cur_state, mctx,
                                           re_string_cur_idx (mctx->input)))
            {
              /* We found an appropriate halt state.  */
              match_last = re_string_cur_idx (mctx->input);
              match = 1;
              if (!fl_longest_match)
                break;
            }
        }
   }
  return match_last;
}

/* Check NODE match the current context.  */

static int check_halt_node_context (dfa, node, context)
    const re_dfa_t *dfa;
    int node;
    unsigned int context;
{
  int entity;
  re_token_type_t type = dfa->nodes[node].type;
  if (type == END_OF_RE)
    return 1;
  if (type != OP_CONTEXT_NODE)
    return 0;
  entity = dfa->nodes[node].opr.ctx_info->entity;
  if (dfa->nodes[entity].type != END_OF_RE
      || NOT_SATISFY_NEXT_CONSTRAINT (dfa->nodes[node].constraint, context))
    return 0;
  return 1;
}

/* Check the halt state STATE match the current context.
   Return 0 if not match, if the node, STATE has, is a halt node and
   match the context, return the node.  */

static int
check_halt_state_context (preg, state, mctx, idx)
    const regex_t *preg;
    const re_dfastate_t *state;
    const re_match_context_t *mctx;
    int idx;
{
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  int i;
  unsigned int context;
#ifdef DEBUG
  assert (state->halt);
#endif
  context = re_string_context_at (mctx->input, idx, mctx->eflags,
                                  preg->newline_anchor);
  for (i = 0; i < state->nodes.nelem; ++i)
    if (check_halt_node_context (dfa, state->nodes.elems[i], context))
      return state->nodes.elems[i];
  return 0;
}

/* Compute the next node to which "NFA" transit from NODE("NFA" is a NFA
   corresponding to the DFA).
   Return the destination node, and update EPS_VIA_NODES, return -1 in case
   of errors.  */

static int
proceed_next_node (preg, regs, mctx, pidx, node, eps_via_nodes)
    const regex_t *preg;
    regmatch_t *regs;
    const re_match_context_t *mctx;
    int *pidx, node;
    re_node_set *eps_via_nodes;
{
  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
  int i, err, dest_node, cur_entity;
  dest_node = -1;
  cur_entity = ((dfa->nodes[node].type == OP_CONTEXT_NODE)
                ? dfa->nodes[node].opr.ctx_info->entity : node);
  if (IS_EPSILON_NODE (dfa->nodes[node].type))
    {
      int dest_entity = INT_MAX;
      err = re_node_set_insert (eps_via_nodes, node);
      if (BE (err < 0, 0))
        return -1;
      for (i = 0; i < mctx->state_log[*pidx]->nodes.nelem; ++i)
        {
          int candidate, candidate_entity;
          candidate = mctx->state_log[*pidx]->nodes.elems[i];
          candidate_entity = ((dfa->nodes[candidate].type == OP_CONTEXT_NODE)
                              ? dfa->nodes[candidate].opr.ctx_info->entity
                              : candidate);
          if (!re_node_set_contains (dfa->edests + node, candidate))
            if (candidate == candidate_entity
                || !re_node_set_contains (dfa->edests + node, candidate_entity))
              continue;

          /* In order to avoid infinite loop like "(a*)*".  */
          if (cur_entity > candidate_entity
              && re_node_set_contains (eps_via_nodes, candidate))
            continue;

          if (dest_entity > candidate_entity)
            {
              dest_node = candidate;
              dest_entity = candidate_entity;
            }
        }
#ifdef DEBUG
      assert (dest_node != -1);
#endif
      return dest_node;
    }
  else
    {
      int naccepted = 0, entity = node;
      re_token_type_t type = dfa->nodes[node].type;
      if (type == OP_CONTEXT_NODE)
        {
          entity = dfa->nodes[node].opr.ctx_info->entity;
          type = dfa->nodes[entity].type;
        }

#ifdef RE_ENABLE_I18N
      if (ACCEPT_MB_NODE (type))
        naccepted = check_node_accept_bytes (preg, entity, mctx->input, *pidx);
      else
#endif /* RE_ENABLE_I18N */
      if (type == OP_BACK_REF)
        {
          int subexp_idx = dfa->nodes[entity].opr.idx;
          naccepted = regs[subexp_idx].rm_eo - regs[subexp_idx].rm_so;

          if (naccepted == 0)
            {
              err = re_node_set_insert (eps_via_nodes, node);
              if (BE (err < 0, 0))
                return -1;
              dest_node = dfa->nexts[node];
              if (re_node_set_contains (&mctx->state_log[*pidx]->nodes,
                                        dest_node))
                return dest_node;
              for (i = 0; i < mctx->state_log[*pidx]->nodes.nelem; ++i)
                {
                  dest_node = mctx->state_log[*pidx]->nodes.elems[i];
                  if ((dfa->nodes[dest_node].type == OP_CONTEXT_NODE
                       && (dfa->nexts[node]
                           == dfa->nodes[dest_node].opr.ctx_info->entity)))
                    return dest_node;
                }
            }
        }

      if (naccepted != 0
          || check_node_accept (preg, dfa->nodes + node, mctx, *pidx))
        {
          dest_node = dfa->nexts[node];
          *pidx = (naccepted == 0) ? *pidx + 1 : *pidx + naccepted;
#ifdef DEBUG
          assert (mctx->state_log[*pidx] != NULL);
#endif
          re_node_set_empty (eps_via_nodes);
          return dest_node;
        }
    }
  /* Must not reach here.  */
#ifdef DEBUG
  assert (0);
#endif
  return 0;
}

/* Set the positions where the subexpressions are starts/ends to registers
   PMATCH.
   Note: We assume that pmatch[0] is already set, and
   pmatch[i].rm_so == pmatch[i].rm_eo == -1 (i > 1).  */

static reg_errcode_t
set_regs (preg, mctx, nmatch, pmatch, last_node)
    const regex_t *preg;
    const re_match_context_t *mctx;
    size_t nmatch;
    regmatch_t *pmatch;
    int last_node;
{
  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
  int idx, cur_node, real_nmatch;
  re_node_set eps_via_nodes;
#ifdef DEBUG
  assert (nmatch > 1);
  assert (mctx->state_log != NULL);
#endif
  cur_node = dfa->init_node;
  real_nmatch = (nmatch <= preg->re_nsub) ? nmatch : preg->re_nsub + 1;
  re_node_set_init_empty (&eps_via_nodes);
  for (idx = pmatch[0].rm_so; idx <= pmatch[0].rm_eo ;)
    {
      update_regs (dfa, pmatch, cur_node, idx, real_nmatch);
      if (idx == pmatch[0].rm_eo && cur_node == last_node)
        break;

      /* Proceed to next node.  */
      cur_node = proceed_next_node (preg, pmatch, mctx, &idx, cur_node,
                                    &eps_via_nodes);
      if (BE (cur_node < 0, 0))
        return REG_ESPACE;
    }
  re_node_set_free (&eps_via_nodes);
  return REG_NOERROR;
}

static void
update_regs (dfa, pmatch, cur_node, cur_idx, nmatch)
     re_dfa_t *dfa;
     regmatch_t *pmatch;
     int cur_node, cur_idx, nmatch;
{
  int type = dfa->nodes[cur_node].type;
  int reg_num;
  if (type != OP_OPEN_SUBEXP && type != OP_CLOSE_SUBEXP)
    return;
  reg_num = dfa->nodes[cur_node].opr.idx + 1;
  if (reg_num >= nmatch)
    return;
  if (type == OP_OPEN_SUBEXP)
    {
      /* We are at the first node of this sub expression.  */
      pmatch[reg_num].rm_so = cur_idx;
      pmatch[reg_num].rm_eo = -1;
    }
  else if (type == OP_CLOSE_SUBEXP)
    /* We are at the first node of this sub expression.  */
    pmatch[reg_num].rm_eo = cur_idx;
}

#define NUMBER_OF_STATE 1

/* This function checks the STATE_LOG from the SCTX->last_str_idx to 0
   and sift the nodes in each states according to the following rules.
   Updated state_log will be wrote to STATE_LOG.

   Rules: We throw away the Node `a' in the STATE_LOG[STR_IDX] if...
     1. When STR_IDX == MATCH_LAST(the last index in the state_log):
        If `a' isn't the LAST_NODE and `a' can't epsilon transit to
        the LAST_NODE, we throw away the node `a'.
     2. When 0 <= STR_IDX < MATCH_LAST and `a' accepts
        string `s' and transit to `b':
        i. If 'b' isn't in the STATE_LOG[STR_IDX+strlen('s')], we throw
           away the node `a'.
        ii. If 'b' is in the STATE_LOG[STR_IDX+strlen('s')] but 'b' is
            throwed away, we throw away the node `a'.
     3. When 0 <= STR_IDX < n and 'a' epsilon transit to 'b':
        i. If 'b' isn't in the STATE_LOG[STR_IDX], we throw away the
           node `a'.
        ii. If 'b' is in the STATE_LOG[STR_IDX] but 'b' is throwed away,
            we throw away the node `a'.  */

#define STATE_NODE_CONTAINS(state,node) \
  ((state) != NULL && re_node_set_contains (&(state)->nodes, node))

static reg_errcode_t
sift_states_backward (preg, mctx, sctx)
     const regex_t *preg;
     re_match_context_t *mctx;
     re_sift_context_t *sctx;
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
  int null_cnt = 0;
  int str_idx = sctx->last_str_idx;
  re_node_set cur_dest;
  re_node_set *cur_src; /* Points the state_log[str_idx]->nodes  */

#ifdef DEBUG
  assert (mctx->state_log != NULL && mctx->state_log[str_idx] != NULL);
#endif
  cur_src = &mctx->state_log[str_idx]->nodes;

  /* Build sifted state_log[str_idx].  It has the nodes which can epsilon
     transit to the last_node and the last_node itself.  */
  err = re_node_set_init_1 (&cur_dest, sctx->last_node);
  if (BE (err != REG_NOERROR, 0))
    return err;
  err = update_cur_sifted_state (preg, mctx, sctx, str_idx, &cur_dest);
  if (BE (err != REG_NOERROR, 0))
    return err;

  /* Then check each states in the state_log.  */
  while (str_idx > 0)
    {
      int i, ret;
      /* Update counters.  */
      null_cnt = (sctx->sifted_states[str_idx] == NULL) ? null_cnt + 1 : 0;
      if (null_cnt > mctx->max_mb_elem_len)
        {
          memset (sctx->sifted_states, '\0',
                  sizeof (re_dfastate_t *) * str_idx);
          return REG_NOERROR;
        }
      re_node_set_empty (&cur_dest);
      --str_idx;
      cur_src = ((mctx->state_log[str_idx] == NULL) ? &empty_set
                 : &mctx->state_log[str_idx]->nodes);

      /* Then build the next sifted state.
         We build the next sifted state on `cur_dest', and update
         `sifted_states[str_idx]' with `cur_dest'.
         Note:
         `cur_dest' is the sifted state from `state_log[str_idx + 1]'.
         `cur_src' points the node_set of the old `state_log[str_idx]'.  */
      for (i = 0; i < cur_src->nelem; i++)
        {
          int prev_node = cur_src->elems[i];
          int entity = prev_node;
          int naccepted = 0;
          re_token_type_t type = dfa->nodes[prev_node].type;

          if (IS_EPSILON_NODE(type))
            continue;
          if (type == OP_CONTEXT_NODE)
            {
              entity = dfa->nodes[prev_node].opr.ctx_info->entity;
              type = dfa->nodes[entity].type;
            }
#ifdef RE_ENABLE_I18N
          /* If the node may accept `multi byte'.  */
          if (ACCEPT_MB_NODE (type))
            naccepted = sift_states_iter_mb (preg, mctx, sctx, entity, str_idx,
                                             sctx->last_str_idx);

#endif /* RE_ENABLE_I18N */
          /* We don't check backreferences here.
             See update_cur_sifted_state().  */

          if (!naccepted
              && check_node_accept (preg, dfa->nodes + prev_node, mctx,
                                    str_idx)
              && STATE_NODE_CONTAINS (sctx->sifted_states[str_idx + 1],
                                      dfa->nexts[prev_node]))
            naccepted = 1;

          if (naccepted == 0)
            continue;

          ret = re_node_set_insert (&cur_dest, prev_node);
          if (BE (ret == -1, 0))
            return err;
        }

      /* Add all the nodes which satisfy the following conditions:
         - It can epsilon transit to a node in CUR_DEST.
         - It is in CUR_SRC.
         And update state_log.  */
      err = update_cur_sifted_state (preg, mctx, sctx, str_idx, &cur_dest);
      if (BE (err != REG_NOERROR, 0))
        return err;
    }

  re_node_set_free (&cur_dest);
  return REG_NOERROR;
}

/* Helper functions.  */

static inline reg_errcode_t
clean_state_log_if_need (mctx, next_state_log_idx)
    re_match_context_t *mctx;
    int next_state_log_idx;
{
  int top = mctx->state_log_top;

  if (next_state_log_idx >= mctx->input->bufs_len
      || (next_state_log_idx >= mctx->input->valid_len
          && mctx->input->valid_len < mctx->input->len))
    {
      reg_errcode_t err;
      err = extend_buffers (mctx);
      if (BE (err != REG_NOERROR, 0))
        return err;
    }

  if (top < next_state_log_idx)
    {
      memset (mctx->state_log + top + 1, '\0',
              sizeof (re_dfastate_t *) * (next_state_log_idx - top));
      mctx->state_log_top = next_state_log_idx;
    }
  return REG_NOERROR;
}

static reg_errcode_t merge_state_array (dfa, dst, src, num)
     re_dfa_t *dfa;
     re_dfastate_t **dst;
     re_dfastate_t **src;
     int num;
{
  int st_idx;
  reg_errcode_t err;
  for (st_idx = 0; st_idx < num; ++st_idx)
    {
      if (dst[st_idx] == NULL)
        dst[st_idx] = src[st_idx];
      else if (src[st_idx] != NULL)
        {
          re_node_set merged_set;
          err = re_node_set_init_union (&merged_set, &dst[st_idx]->nodes,
                                        &src[st_idx]->nodes);
          if (BE (err != REG_NOERROR, 0))
            return err;
          dst[st_idx] = re_acquire_state (&err, dfa, &merged_set);
          if (BE (err != REG_NOERROR, 0))
            return err;
          re_node_set_free (&merged_set);
        }
    }
  return REG_NOERROR;
}

static reg_errcode_t
update_cur_sifted_state (preg, mctx, sctx, str_idx, dest_nodes)
     const regex_t *preg;
     re_match_context_t *mctx;
     re_sift_context_t *sctx;
     int str_idx;
     re_node_set *dest_nodes;
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
  const re_node_set *candidates;
  candidates = ((mctx->state_log[str_idx] == NULL) ? &empty_set
                : &mctx->state_log[str_idx]->nodes);

  /* At first, add the nodes which can epsilon transit to a node in
     DEST_NODE.  */
  err = add_epsilon_src_nodes (dfa, dest_nodes, candidates);
  if (BE (err != REG_NOERROR, 0))
    return err;

  /* Then, check the limitations in the current sift_context.  */
  if (sctx->limits.nelem)
    {
      err = check_subexp_limits (dfa, dest_nodes, candidates, &sctx->limits,
                                 mctx->bkref_ents, str_idx);
      if (BE (err != REG_NOERROR, 0))
        return err;
    }

  /* Update state_log.  */
  sctx->sifted_states[str_idx] = re_acquire_state (&err, dfa, dest_nodes);
  if (BE (sctx->sifted_states[str_idx] == NULL && err != REG_NOERROR, 0))
    return err;

  /* If we are searching for the subexpression candidates.
     Note that we were from transit_state_bkref_loop() in this case.  */
  if (sctx->check_subexp)
    {
      err = search_subexp (preg, mctx, sctx, str_idx, dest_nodes);
      if (BE (err != REG_NOERROR, 0))
        return err;
    }

  if ((mctx->state_log[str_idx] != NULL
       && mctx->state_log[str_idx]->has_backref))
    {
      err = sift_states_bkref (preg, mctx, sctx, str_idx, dest_nodes);
      if (BE (err != REG_NOERROR, 0))
        return err;
    }
  return REG_NOERROR;
}

static reg_errcode_t
add_epsilon_src_nodes (dfa, dest_nodes, candidates)
     re_dfa_t *dfa;
     re_node_set *dest_nodes;
     const re_node_set *candidates;
{
  reg_errcode_t err;
  int src_idx;
  re_node_set src_copy;

  err = re_node_set_init_copy (&src_copy, dest_nodes);
  if (BE (err != REG_NOERROR, 0))
    return err;
  for (src_idx = 0; src_idx < src_copy.nelem; ++src_idx)
    {
      err = re_node_set_add_intersect (dest_nodes, candidates,
                                       dfa->inveclosures
                                       + src_copy.elems[src_idx]);
      if (BE (err != REG_NOERROR, 0))
        return err;
    }
  re_node_set_free (&src_copy);
  return REG_NOERROR;
}

static reg_errcode_t
sub_epsilon_src_nodes (dfa, node, dest_nodes, candidates)
     re_dfa_t *dfa;
     int node;
     re_node_set *dest_nodes;
     const re_node_set *candidates;
{
    int ecl_idx;
    reg_errcode_t err;
    re_node_set *inv_eclosure = dfa->inveclosures + node;
    re_node_set except_nodes;
    re_node_set_init_empty (&except_nodes);
    for (ecl_idx = 0; ecl_idx < inv_eclosure->nelem; ++ecl_idx)
      {
        int cur_node = inv_eclosure->elems[ecl_idx];
        if (cur_node == node)
          continue;
        if (dfa->edests[cur_node].nelem)
          {
            int edst1 = dfa->edests[cur_node].elems[0];
            int edst2 = ((dfa->edests[cur_node].nelem > 1)
                         ? dfa->edests[cur_node].elems[1] : -1);
            if ((!re_node_set_contains (inv_eclosure, edst1)
                 && re_node_set_contains (dest_nodes, edst1))
                || (edst2 > 0
                    && !re_node_set_contains (inv_eclosure, edst2)
                    && re_node_set_contains (dest_nodes, edst2)))
              {
                err = re_node_set_add_intersect (&except_nodes, candidates,
                                                 dfa->inveclosures + cur_node);
                if (BE (err != REG_NOERROR, 0))
                  return err;
              }
          }
      }
    for (ecl_idx = 0; ecl_idx < inv_eclosure->nelem; ++ecl_idx)
      {
        int cur_node = inv_eclosure->elems[ecl_idx];
        if (!re_node_set_contains (&except_nodes, cur_node))
          {
            int idx = re_node_set_contains (dest_nodes, cur_node) - 1;
            re_node_set_remove_at (dest_nodes, idx);
          }
      }
    re_node_set_free (&except_nodes);
    return REG_NOERROR;
}

/* Check the limitations of sub expressions LIMITS, and remove the nodes
   which are against limitations from DEST_NODES. */

static reg_errcode_t
check_subexp_limits (dfa, dest_nodes, candidates, limits, bkref_ents, str_idx)
     re_dfa_t *dfa;
     re_node_set *dest_nodes;
     const re_node_set *candidates;
     re_node_set *limits;
     struct re_backref_cache_entry *bkref_ents;
     int str_idx;
{
  reg_errcode_t err;
  int node_idx, lim_idx;

  for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
    {
      int bkref, subexp_idx;
      struct re_backref_cache_entry *ent;
      ent = bkref_ents + limits->elems[lim_idx];

      if (str_idx <= ent->subexp_from || ent->str_idx < str_idx)
        continue; /* This is unrelated limitation.  */

      bkref = (dfa->nodes[ent->node].type == OP_CONTEXT_NODE
               ? dfa->nodes[ent->node].opr.ctx_info->entity : ent->node);
      subexp_idx = dfa->nodes[bkref].opr.idx - 1;

      if (ent->subexp_to == str_idx)
        {
          int ops_node = -1;
          int cls_node = -1;
          for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
            {
              int node = dest_nodes->elems[node_idx];
              re_token_type_t type= dfa->nodes[node].type;
              if (type == OP_OPEN_SUBEXP
                  && subexp_idx == dfa->nodes[node].opr.idx)
                ops_node = node;
              else if (type == OP_CLOSE_SUBEXP
                       && subexp_idx == dfa->nodes[node].opr.idx)
                cls_node = node;
            }

          /* Check the limitation of the open subexpression.  */
          /* Note that (ent->subexp_to = str_idx != ent->subexp_from).  */
          if (ops_node >= 0)
            {
              err = sub_epsilon_src_nodes(dfa, ops_node, dest_nodes,
                                          candidates);
              if (BE (err != REG_NOERROR, 0))
                return err;
            }
          /* Check the limitation of the close subexpression.  */
          for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
            {
              int node = dest_nodes->elems[node_idx];
              if (!re_node_set_contains (dfa->inveclosures + node, cls_node)
                  && !re_node_set_contains (dfa->eclosures + node, cls_node))
                {
                  /* It is against this limitation.
                     Remove it form the current sifted state.  */
                  err = sub_epsilon_src_nodes(dfa, node, dest_nodes,
                                              candidates);
                  if (BE (err != REG_NOERROR, 0))
                    return err;
                  --node_idx;
                }
            }
        }
      else /* (ent->subexp_to != str_idx)  */
        {
          for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
            {
              int node = dest_nodes->elems[node_idx];
              re_token_type_t type= dfa->nodes[node].type;
              if (type == OP_CLOSE_SUBEXP || type == OP_OPEN_SUBEXP)
                {
                  if (subexp_idx != dfa->nodes[node].opr.idx)
                    continue;
                  if ((type == OP_CLOSE_SUBEXP && ent->subexp_to != str_idx)
                      || (type == OP_OPEN_SUBEXP))
                    {
                      /* It is against this limitation.
                         Remove it form the current sifted state.  */
                      err = sub_epsilon_src_nodes(dfa, node, dest_nodes,
                                                  candidates);
                      if (BE (err != REG_NOERROR, 0))
                        return err;
                    }
                }
            }
        }
    }
  return REG_NOERROR;
}

/* Search for the top (in case of sctx->check_subexp < 0) or the
   bottom (in case of sctx->check_subexp > 0) of the subexpressions
   which the backreference sctx->cur_bkref can match.  */

static reg_errcode_t
search_subexp (preg, mctx, sctx, str_idx, dest_nodes)
     const regex_t *preg;
     re_match_context_t *mctx;
     re_sift_context_t *sctx;
     int str_idx;
     re_node_set *dest_nodes;
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
  re_sift_context_t local_sctx;
  int node_idx, node;
  const re_node_set *candidates;
  candidates = ((mctx->state_log[str_idx] == NULL) ? &empty_set
                : &mctx->state_log[str_idx]->nodes);
  local_sctx.sifted_states = NULL; /* Mark that it hasn't been initialized.  */

  for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
    {
      re_token_type_t type;
      int entity;
      node = dest_nodes->elems[node_idx];
      type = dfa->nodes[node].type;
      entity = (type != OP_CONTEXT_NODE ? node
                : dfa->nodes[node].opr.ctx_info->entity);
      type = (type != OP_CONTEXT_NODE ? type : dfa->nodes[entity].type);

      if (type == OP_CLOSE_SUBEXP
          && sctx->check_subexp == dfa->nodes[node].opr.idx + 1)
        {
          /* Found the bottom of the subexpression, then search for the
             top of it.  */
          if (local_sctx.sifted_states == NULL)
            {
              /* It hasn't been initialized yet, initialize it now.  */
              local_sctx = *sctx;
              err = re_node_set_init_copy (&local_sctx.limits, &sctx->limits);
              if (BE (err != REG_NOERROR, 0))
                return err;
            }
          local_sctx.check_subexp = -sctx->check_subexp;
          local_sctx.last_node = node;
          local_sctx.last_str_idx = local_sctx.cls_subexp_idx = str_idx;
          err = sift_states_backward (preg, mctx, &local_sctx);
          if (BE (err != REG_NOERROR, 0))
            return err;
          /* There must not 2 same node in a node set.  */
          break;
        }
      else if (type == OP_OPEN_SUBEXP
               && -sctx->check_subexp == dfa->nodes[node].opr.idx + 1)
        {
          /* Found the top of the subexpression, check that the
             backreference can match the input string.  */
          char *buf;
          int dest_str_idx;
          int bkref_str_idx = re_string_cur_idx (mctx->input);
          int subexp_len = sctx->cls_subexp_idx - str_idx;
          if (subexp_len < 0 || bkref_str_idx + subexp_len > mctx->input->len)
            break;

          if (bkref_str_idx + subexp_len > mctx->input->valid_len
              && mctx->input->valid_len < mctx->input->len)
            {
              reg_errcode_t err;
              err = extend_buffers (mctx);
              if (BE (err != REG_NOERROR, 0))
                return err;
            }
          buf = (char *) re_string_get_buffer (mctx->input);
          if (strncmp (buf + str_idx, buf + bkref_str_idx, subexp_len) != 0)
            break;
          /* Successfully matched, add a new cache entry.  */
          dest_str_idx = bkref_str_idx + subexp_len;
          err = match_ctx_add_entry (mctx, sctx->cur_bkref, bkref_str_idx,
                                     str_idx, sctx->cls_subexp_idx);
          if (BE (err != REG_NOERROR, 0))
            return err;
          err = clean_state_log_if_need (mctx, dest_str_idx);
          if (BE (err != REG_NOERROR, 0))
            return err;
          break;
        }
    }

  /* Remove the top/bottom of the sub expression we processed.  */
  if (node_idx < dest_nodes->nelem)
    {
      err = sub_epsilon_src_nodes(dfa, node, dest_nodes, candidates);
      if (BE (err != REG_NOERROR, 0))
        return err;
      /* Update state_log.  */
      sctx->sifted_states[str_idx] = re_acquire_state (&err, dfa, dest_nodes);
      if (BE (err != REG_NOERROR, 0))
        return err;
    }

  if (local_sctx.sifted_states != NULL)
    re_node_set_free (&local_sctx.limits);
  return REG_NOERROR;
}

static reg_errcode_t
sift_states_bkref (preg, mctx, sctx, str_idx, dest_nodes)
     const regex_t *preg;
     re_match_context_t *mctx;
     re_sift_context_t *sctx;
     int str_idx;
     re_node_set *dest_nodes;
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
  int node_idx, node;
  re_sift_context_t local_sctx;
  const re_node_set *candidates;
  candidates = ((mctx->state_log[str_idx] == NULL) ? &empty_set
                : &mctx->state_log[str_idx]->nodes);
  local_sctx.sifted_states = NULL; /* Mark that it hasn't been initialized.  */

  for (node_idx = 0; node_idx < candidates->nelem; ++node_idx)
    {
      int entity;
      int cur_bkref_idx = re_string_cur_idx (mctx->input);
      re_token_type_t type;
      node = candidates->elems[node_idx];
      type = dfa->nodes[node].type;
      entity = (type != OP_CONTEXT_NODE ? node
                : dfa->nodes[node].opr.ctx_info->entity);
      type = (type != OP_CONTEXT_NODE ? type : dfa->nodes[entity].type);
      if (node == sctx->cur_bkref && str_idx == cur_bkref_idx)
        continue;
      /* Avoid infinite loop for the REs like "()\1+".  */
      if (node == sctx->last_node && str_idx == sctx->last_str_idx)
        continue;
      if (type == OP_BACK_REF)
        {
          int enabled_idx;
          for (enabled_idx = 0; enabled_idx < mctx->nbkref_ents; ++enabled_idx)
            {
              int disabled_idx, subexp_len, to_idx;
              struct re_backref_cache_entry *entry;
              entry = mctx->bkref_ents + enabled_idx;
              subexp_len = entry->subexp_to - entry->subexp_from;
              to_idx = str_idx + subexp_len;

              if (entry->node != node || entry->str_idx != str_idx
                  || to_idx > sctx->last_str_idx
                  || sctx->sifted_states[to_idx] == NULL)
                continue;
              if (!STATE_NODE_CONTAINS (sctx->sifted_states[to_idx],
                                        dfa->nexts[node]))
                {
                  int dst_idx;
                  re_node_set *dsts = &sctx->sifted_states[to_idx]->nodes;
                  for (dst_idx = 0; dst_idx < dsts->nelem; ++dst_idx)
                    {
                      int dst_node = dsts->elems[dst_idx];
                      if (dfa->nodes[dst_node].type == OP_CONTEXT_NODE
                          && (dfa->nodes[dst_node].opr.ctx_info->entity
                              == dfa->nexts[node]))
                        break;
                    }
                  if (dst_idx == dsts->nelem)
                    continue;
                }

              if (sctx->check_subexp == dfa->nodes[entity].opr.idx)
                {
                  char *buf;
                  buf = (char *) re_string_get_buffer (mctx->input);
                  if (strncmp (buf + entry->subexp_from,
                               buf + cur_bkref_idx, subexp_len) != 0)
                    continue;
                  err = match_ctx_add_entry (mctx, sctx->cur_bkref,
                                             cur_bkref_idx, entry->subexp_from,
                                             entry->subexp_to);
                  if (BE (err != REG_NOERROR, 0))
                    return err;
                  err = clean_state_log_if_need (mctx, cur_bkref_idx
                                                 + subexp_len);
                  if (BE (err != REG_NOERROR, 0))
                    return err;
                }
              else
                {
                  entry->flag = 0;
                  for (disabled_idx = enabled_idx + 1;
                       disabled_idx < mctx->nbkref_ents; ++disabled_idx)
                    {
                      struct re_backref_cache_entry *entry2;
                      entry2 = mctx->bkref_ents + enabled_idx;
                      if (entry2->node != node || entry2->str_idx != str_idx)
                        continue;
                      entry2->flag = 1;
                    }

                  if (local_sctx.sifted_states == NULL)
                    {
                      local_sctx = *sctx;
                      local_sctx.sifted_states = re_malloc (re_dfastate_t *,
                                                            str_idx + 1);
                      if (BE (local_sctx.sifted_states == NULL, 0))
                        return REG_ESPACE;
                      err = re_node_set_init_copy (&local_sctx.limits,
                                                   &sctx->limits);
                      if (BE (err != REG_NOERROR, 0))
                        return err;
                    }
                  local_sctx.last_node = node;
                  local_sctx.last_str_idx = str_idx;
                  err = re_node_set_insert (&local_sctx.limits, enabled_idx);
                  if (BE (err < 0, 0))
                    return REG_ESPACE;
                  err = sift_states_backward (preg, mctx, &local_sctx);
                  if (BE (err != REG_NOERROR, 0))
                    return err;
                  if (sctx->limited_states != NULL)
                    {
                      err = merge_state_array (dfa, sctx->limited_states,
                                               local_sctx.sifted_states,
                                               str_idx + 1);
                      if (BE (err != REG_NOERROR, 0))
                        return err;
                    }
                  re_node_set_remove_at (&local_sctx.limits,
                                         local_sctx.limits.nelem - 1);
                  entry->flag = 1;
                }
            }
          for (enabled_idx = 0; enabled_idx < mctx->nbkref_ents; ++enabled_idx)
            {
              struct re_backref_cache_entry *entry;
              entry = mctx->bkref_ents + enabled_idx;
              if (entry->node == node && entry->str_idx == str_idx)
                entry->flag = 0;
            }
        }
    }
  if (local_sctx.sifted_states != NULL)
    {
      free (local_sctx.sifted_states);
      re_node_set_free (&local_sctx.limits);
    }

  return REG_NOERROR;
}


#ifdef RE_ENABLE_I18N
static int
sift_states_iter_mb (preg, mctx, sctx, node_idx, str_idx, max_str_idx)
    const regex_t *preg;
    const re_match_context_t *mctx;
    re_sift_context_t *sctx;
    int node_idx, str_idx, max_str_idx;
{
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  int naccepted;
  /* Check the node can accept `multi byte'.  */
  naccepted = check_node_accept_bytes (preg, node_idx, mctx->input, str_idx);
  if (naccepted > 0 && str_idx + naccepted <= max_str_idx &&
      !STATE_NODE_CONTAINS (sctx->sifted_states[str_idx + naccepted],
                            dfa->nexts[node_idx]))
    /* The node can't accept the `multi byte', or the
       destination was already throwed away, then the node
       could't accept the current input `multi byte'.   */
    naccepted = 0;
  /* Otherwise, it is sure that the node could accept
     `naccepted' bytes input.  */
  return naccepted;
}
#endif /* RE_ENABLE_I18N */


/* Functions for state transition.  */

/* Return the next state to which the current state STATE will transit by
   accepting the current input byte, and update STATE_LOG if necessary.
   If STATE can accept a multibyte char/collating element/back reference
   update the destination of STATE_LOG.  */

static re_dfastate_t *
transit_state (err, preg, mctx, state, fl_search)
     reg_errcode_t *err;
     const regex_t *preg;
     re_match_context_t *mctx;
     re_dfastate_t *state;
     int fl_search;
{
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  re_dfastate_t **trtable, *next_state;
  unsigned char ch;

  if (re_string_cur_idx (mctx->input) + 1 >= mctx->input->bufs_len
      || (re_string_cur_idx (mctx->input) + 1 >= mctx->input->valid_len
          && mctx->input->valid_len < mctx->input->len))
    {
      *err = extend_buffers (mctx);
      if (BE (*err != REG_NOERROR, 0))
        return NULL;
    }

  *err = REG_NOERROR;
  if (state == NULL)
    {
      next_state = state;
      re_string_skip_bytes (mctx->input, 1);
    }
  else
    {
#ifdef RE_ENABLE_I18N
      /* If the current state can accept multibyte.  */
      if (state->accept_mb)
        {
          *err = transit_state_mb (preg, state, mctx);
          if (BE (*err != REG_NOERROR, 0))
            return NULL;
        }
#endif /* RE_ENABLE_I18N */

      /* Then decide the next state with the single byte.  */
      if (1)
        {
          /* Use transition table  */
          ch = re_string_fetch_byte (mctx->input);
          trtable = fl_search ? state->trtable_search : state->trtable;
          if (trtable == NULL)
            {
              trtable = build_trtable (preg, state, fl_search);
              if (fl_search)
                state->trtable_search = trtable;
              else
                state->trtable = trtable;
            }
          next_state = trtable[ch];
        }
      else
        {
          /* don't use transition table  */
          next_state = transit_state_sb (err, preg, state, fl_search, mctx);
          if (BE (next_state == NULL && err != REG_NOERROR, 0))
            return NULL;
        }
    }

  /* Update the state_log if we need.  */
  if (mctx->state_log != NULL)
    {
      int cur_idx = re_string_cur_idx (mctx->input);
      if (cur_idx > mctx->state_log_top)
        {
          mctx->state_log[cur_idx] = next_state;
          mctx->state_log_top = cur_idx;
        }
      else if (mctx->state_log[cur_idx] == 0)
        {
          mctx->state_log[cur_idx] = next_state;
        }
      else
        {
          re_dfastate_t *pstate;
          unsigned int context;
          re_node_set next_nodes, *log_nodes, *table_nodes = NULL;
          /* If (state_log[cur_idx] != 0), it implies that cur_idx is
             the destination of a multibyte char/collating element/
             back reference.  Then the next state is the union set of
             these destinations and the results of the transition table.  */
          pstate = mctx->state_log[cur_idx];
          log_nodes = pstate->entrance_nodes;
          if (next_state != NULL)
            {
              table_nodes = next_state->entrance_nodes;
              *err = re_node_set_init_union (&next_nodes, table_nodes,
                                             log_nodes);
              if (BE (*err != REG_NOERROR, 0))
                return NULL;
            }
          else
            next_nodes = *log_nodes;
          /* Note: We already add the nodes of the initial state,
                   then we don't need to add them here.  */

          context = re_string_context_at (mctx->input,
                                          re_string_cur_idx (mctx->input) - 1,
                                          mctx->eflags, preg->newline_anchor);
          next_state = mctx->state_log[cur_idx]
            = re_acquire_state_context (err, dfa, &next_nodes, context);
          /* We don't need to check errors here, since the return value of
             this function is next_state and ERR is already set.  */

          if (table_nodes != NULL)
            re_node_set_free (&next_nodes);
        }
      /* If the next state has back references.  */
      if (next_state != NULL && next_state->has_backref)
        {
          *err = transit_state_bkref (preg, next_state, mctx);
          if (BE (*err != REG_NOERROR, 0))
            return NULL;
          next_state = mctx->state_log[cur_idx];
        }
    }
  return next_state;
}

/* Helper functions for transit_state.  */

/* Return the next state to which the current state STATE will transit by
   accepting the current input byte.  */

static re_dfastate_t *
transit_state_sb (err, preg, state, fl_search, mctx)
     reg_errcode_t *err;
     const regex_t *preg;
     re_dfastate_t *state;
     int fl_search;
     re_match_context_t *mctx;
{
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  re_node_set next_nodes;
  re_dfastate_t *next_state;
  int node_cnt, cur_str_idx = re_string_cur_idx (mctx->input);
  unsigned int context;

  *err = re_node_set_alloc (&next_nodes, state->nodes.nelem + 1);
  if (BE (*err != REG_NOERROR, 0))
    return NULL;
  for (node_cnt = 0; node_cnt < state->nodes.nelem; ++node_cnt)
    {
      int cur_node = state->nodes.elems[node_cnt];
      if (check_node_accept (preg, dfa->nodes + cur_node, mctx, cur_str_idx))
        {
          *err = re_node_set_merge (&next_nodes,
                                    dfa->eclosures + dfa->nexts[cur_node]);
          if (BE (*err != REG_NOERROR, 0))
            return NULL;
        }
    }
  if (fl_search)
    {
#ifdef RE_ENABLE_I18N
      int not_initial = 0;
      if (MB_CUR_MAX > 1)
        for (node_cnt = 0; node_cnt < next_nodes.nelem; ++node_cnt)
          if (dfa->nodes[next_nodes.elems[node_cnt]].type == CHARACTER)
            {
              not_initial = dfa->nodes[next_nodes.elems[node_cnt]].mb_partial;
              break;
            }
      if (!not_initial)
#endif
        {
          *err = re_node_set_merge (&next_nodes,
                                    dfa->init_state->entrance_nodes);
          if (BE (*err != REG_NOERROR, 0))
            return NULL;
        }
    }
  context = re_string_context_at (mctx->input, cur_str_idx, mctx->eflags,
                                  preg->newline_anchor);
  next_state = re_acquire_state_context (err, dfa, &next_nodes, context);
  /* We don't need to check errors here, since the return value of
     this function is next_state and ERR is already set.  */

  re_node_set_free (&next_nodes);
  re_string_skip_bytes (mctx->input, 1);
  return next_state;
}

#ifdef RE_ENABLE_I18N
static reg_errcode_t
transit_state_mb (preg, pstate, mctx)
    const regex_t *preg;
    re_dfastate_t *pstate;
    re_match_context_t *mctx;
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  int i;

  for (i = 0; i < pstate->nodes.nelem; ++i)
    {
      re_node_set dest_nodes, *new_nodes;
      int cur_node_idx = pstate->nodes.elems[i];
      int naccepted = 0, dest_idx;
      unsigned int context;
      re_dfastate_t *dest_state;

      if (dfa->nodes[cur_node_idx].type == OP_CONTEXT_NODE)
        {
          context = re_string_context_at (mctx->input,
                                          re_string_cur_idx (mctx->input),
                                          mctx->eflags, preg->newline_anchor);
          if (NOT_SATISFY_NEXT_CONSTRAINT (dfa->nodes[cur_node_idx].constraint,
                                        context))
            continue;
          cur_node_idx = dfa->nodes[cur_node_idx].opr.ctx_info->entity;
        }

      /* How many bytes the node can accepts?  */
      if (ACCEPT_MB_NODE (dfa->nodes[cur_node_idx].type))
        naccepted = check_node_accept_bytes (preg, cur_node_idx, mctx->input,
                                             re_string_cur_idx (mctx->input));
      if (naccepted == 0)
        continue;

      /* The node can accepts `naccepted' bytes.  */
      dest_idx = re_string_cur_idx (mctx->input) + naccepted;
      mctx->max_mb_elem_len = ((mctx->max_mb_elem_len < naccepted) ? naccepted
                               : mctx->max_mb_elem_len);
      err = clean_state_log_if_need (mctx, dest_idx);
      if (BE (err != REG_NOERROR, 0))
        return err;
#ifdef DEBUG
      assert (dfa->nexts[cur_node_idx] != -1);
#endif
      /* `cur_node_idx' may point the entity of the OP_CONTEXT_NODE,
         then we use pstate->nodes.elems[i] instead.  */
      new_nodes = dfa->eclosures + dfa->nexts[pstate->nodes.elems[i]];

      dest_state = mctx->state_log[dest_idx];
      if (dest_state == NULL)
        dest_nodes = *new_nodes;
      else
        {
          err = re_node_set_init_union (&dest_nodes,
                                        dest_state->entrance_nodes, new_nodes);
          if (BE (err != REG_NOERROR, 0))
            return err;
        }
      context = re_string_context_at (mctx->input, dest_idx - 1, mctx->eflags,
                                      preg->newline_anchor);
      mctx->state_log[dest_idx]
        = re_acquire_state_context (&err, dfa, &dest_nodes, context);
      if (BE (mctx->state_log[dest_idx] == NULL && err != REG_NOERROR, 0))
        return err;
      if (dest_state != NULL)
        re_node_set_free (&dest_nodes);
    }
  return REG_NOERROR;
}
#endif /* RE_ENABLE_I18N */

static reg_errcode_t
transit_state_bkref (preg, pstate, mctx)
    const regex_t *preg;
    re_dfastate_t *pstate;
    re_match_context_t *mctx;
{
  reg_errcode_t err;
  re_dfastate_t **work_state_log;

  work_state_log = re_malloc (re_dfastate_t *,
                              re_string_cur_idx (mctx->input) + 1);
  if (BE (work_state_log == NULL, 0))
    return REG_ESPACE;

  err = transit_state_bkref_loop (preg, &pstate->nodes, work_state_log, mctx);
  re_free (work_state_log);
  return err;
}

/* Caller must allocate `work_state_log'.  */

static reg_errcode_t
transit_state_bkref_loop (preg, nodes, work_state_log, mctx)
    const regex_t *preg;
    re_node_set *nodes;
    re_dfastate_t **work_state_log;
    re_match_context_t *mctx;
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  int i;
  regmatch_t *cur_regs = re_malloc (regmatch_t, preg->re_nsub + 1);
  int cur_str_idx = re_string_cur_idx (mctx->input);
  if (BE (cur_regs == NULL, 0))
    return REG_ESPACE;

  for (i = 0; i < nodes->nelem; ++i)
    {
      int dest_str_idx, subexp_idx, prev_nelem, bkc_idx;
      int node_idx = nodes->elems[i];
      unsigned int context;
      re_token_t *node = dfa->nodes + node_idx;
      re_node_set *new_dest_nodes;
      re_sift_context_t sctx;

      /* Check whether `node' is a backreference or not.  */
      if (node->type == OP_BACK_REF)
        subexp_idx = node->opr.idx;
      else if (node->type == OP_CONTEXT_NODE &&
               dfa->nodes[node->opr.ctx_info->entity].type == OP_BACK_REF)
        {
          context = re_string_context_at (mctx->input, cur_str_idx,
                                          mctx->eflags, preg->newline_anchor);
          if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
            continue;
          subexp_idx = dfa->nodes[node->opr.ctx_info->entity].opr.idx;
        }
      else
        continue;

      /* `node' is a backreference.
         Check the substring which the substring matched.  */
      sift_ctx_init (&sctx, work_state_log, NULL, node_idx, cur_str_idx,
                     subexp_idx);
      sctx.cur_bkref = node_idx;
      match_ctx_clear_flag (mctx);
      err = sift_states_backward (preg, mctx, &sctx);
      if (BE (err != REG_NOERROR, 0))
        return err;

      /* And add the epsilon closures (which is `new_dest_nodes') of
         the backreference to appropriate state_log.  */
#ifdef DEBUG
      assert (dfa->nexts[node_idx] != -1);
#endif
      for (bkc_idx = 0; bkc_idx < mctx->nbkref_ents; ++bkc_idx)
        {
          int subexp_len;
          re_dfastate_t *dest_state;
          struct re_backref_cache_entry *bkref_ent;
          bkref_ent = mctx->bkref_ents + bkc_idx;
          if (bkref_ent->node != node_idx || bkref_ent->str_idx != cur_str_idx)
            continue;
          subexp_len = bkref_ent->subexp_to - bkref_ent->subexp_from;
          new_dest_nodes = ((node->type == OP_CONTEXT_NODE && subexp_len == 0)
                            ? dfa->nodes[node_idx].opr.ctx_info->bkref_eclosure
                            : dfa->eclosures + dfa->nexts[node_idx]);
          dest_str_idx = (cur_str_idx + bkref_ent->subexp_to
                          - bkref_ent->subexp_from);
          context = (IS_WORD_CHAR (re_string_byte_at (mctx->input,
                                                      dest_str_idx - 1))
                     ? CONTEXT_WORD : 0);
          dest_state = mctx->state_log[dest_str_idx];
          prev_nelem = ((mctx->state_log[cur_str_idx] == NULL) ? 0
                        : mctx->state_log[cur_str_idx]->nodes.nelem);
          /* Add `new_dest_node' to state_log.  */
          if (dest_state == NULL)
            {
              mctx->state_log[dest_str_idx]
                = re_acquire_state_context (&err, dfa, new_dest_nodes,
                                            context);
              if (BE (mctx->state_log[dest_str_idx] == NULL
                      && err != REG_NOERROR, 0))
                return err;
            }
          else
            {
              re_node_set dest_nodes;
              err = re_node_set_init_union (&dest_nodes,
                                            dest_state->entrance_nodes,
                                            new_dest_nodes);
              if (BE (err != REG_NOERROR, 0))
                return err;
              mctx->state_log[dest_str_idx]
                = re_acquire_state_context (&err, dfa, &dest_nodes, context);
              if (BE (mctx->state_log[dest_str_idx] == NULL
                      && err != REG_NOERROR, 0))
                return err;
              re_node_set_free (&dest_nodes);
            }
          /* We need to check recursively if the backreference can epsilon
             transit.  */
          if (subexp_len == 0
              && mctx->state_log[cur_str_idx]->nodes.nelem > prev_nelem)
            {
              err = transit_state_bkref_loop (preg, new_dest_nodes,
                                              work_state_log, mctx);
              if (BE (err != REG_NOERROR, 0))
                return err;
            }
        }
    }
  re_free (cur_regs);
  return REG_NOERROR;
}

/* Build transition table for the state.
   Return the new table if succeeded, otherwise return NULL.  */

static re_dfastate_t **
build_trtable (preg, state, fl_search)
    const regex_t *preg;
    const re_dfastate_t *state;
    int fl_search;
{
  reg_errcode_t err;
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  int i, j, k, ch;
  int ndests; /* Number of the destination states from `state'.  */
  re_dfastate_t **trtable, **dest_states, **dest_states_word, **dest_states_nl;
  re_node_set follows, *dests_node;
  bitset *dests_ch;
  bitset acceptable;

  /* We build DFA states which corresponds to the destination nodes
     from `state'.  `dests_node[i]' represents the nodes which i-th
     destination state contains, and `dests_ch[i]' represents the
     characters which i-th destination state accepts.  */
  dests_node = re_malloc (re_node_set, SBC_MAX);
  dests_ch = re_malloc (bitset, SBC_MAX);

  /* Initialize transiton table.  */
  trtable = (re_dfastate_t **) calloc (sizeof (re_dfastate_t *), SBC_MAX);
  if (BE (dests_node == NULL || dests_ch == NULL || trtable == NULL, 0))
    return NULL;

  /* At first, group all nodes belonging to `state' into several
     destinations.  */
  ndests = group_nodes_into_DFAstates (preg, state, dests_node, dests_ch);
  if (BE (ndests <= 0, 0))
    {
      re_free (dests_node);
      re_free (dests_ch);
      /* Return NULL in case of an error, trtable otherwise.  */
      return (ndests < 0) ? NULL : trtable;
    }

  dest_states = re_malloc (re_dfastate_t *, ndests);
  dest_states_word = re_malloc (re_dfastate_t *, ndests);
  dest_states_nl = re_malloc (re_dfastate_t *, ndests);
  bitset_empty (acceptable);

  err = re_node_set_alloc (&follows, ndests + 1);
  if (BE (dest_states == NULL || dest_states_word == NULL
          || dest_states_nl == NULL || err != REG_NOERROR, 0))
    return NULL;

  /* Then build the states for all destinations.  */
  for (i = 0; i < ndests; ++i)
    {
      int next_node;
      re_node_set_empty (&follows);
      /* Merge the follows of this destination states.  */
      for (j = 0; j < dests_node[i].nelem; ++j)
        {
          next_node = dfa->nexts[dests_node[i].elems[j]];
          if (next_node != -1)
            {
              err = re_node_set_merge (&follows, dfa->eclosures + next_node);
              if (BE (err != REG_NOERROR, 0))
                return NULL;
            }
        }
      /* If search flag is set, merge the initial state.  */
      if (fl_search)
        {
#ifdef RE_ENABLE_I18N
          int not_initial = 0;
          for (j = 0; j < follows.nelem; ++j)
            if (dfa->nodes[follows.elems[j]].type == CHARACTER)
              {
                not_initial = dfa->nodes[follows.elems[j]].mb_partial;
                break;
              }
          if (!not_initial)
#endif
            {
              err = re_node_set_merge (&follows,
                                       dfa->init_state->entrance_nodes);
              if (BE (err != REG_NOERROR, 0))
                return NULL;
            }
        }
      dest_states[i] = re_acquire_state_context (&err, dfa, &follows, 0);
      if (BE (dest_states[i] == NULL && err != REG_NOERROR, 0))
        return NULL;
      /* If the new state has context constraint,
         build appropriate states for these contexts.  */
      if (dest_states[i]->has_constraint)
        {
          dest_states_word[i] = re_acquire_state_context (&err, dfa, &follows,
                                                          CONTEXT_WORD);
          if (BE (dest_states_word[i] == NULL && err != REG_NOERROR, 0))
            return NULL;
          dest_states_nl[i] = re_acquire_state_context (&err, dfa, &follows,
                                                        CONTEXT_NEWLINE);
          if (BE (dest_states_nl[i] == NULL && err != REG_NOERROR, 0))
            return NULL;
        }
      else
        {
          dest_states_word[i] = dest_states[i];
          dest_states_nl[i] = dest_states[i];
        }
      bitset_merge (acceptable, dests_ch[i]);
    }

  /* Update the transition table.  */
  /* For all characters ch...:  */
  for (i = 0, ch = 0; i < BITSET_UINTS; ++i)
    for (j = 0; j < UINT_BITS; ++j, ++ch)
      if ((acceptable[i] >> j) & 1)
        {
          /* The current state accepts the character ch.  */
          if (IS_WORD_CHAR (ch))
            {
              for (k = 0; k < ndests; ++k)
                if ((dests_ch[k][i] >> j) & 1)
                  {
                    /* k-th destination accepts the word character ch.  */
                    trtable[ch] = dest_states_word[k];
                    /* There must be only one destination which accepts
                       character ch.  See group_nodes_into_DFAstates.  */
                    break;
                  }
            }
          else /* not WORD_CHAR */
            {
              for (k = 0; k < ndests; ++k)
                if ((dests_ch[k][i] >> j) & 1)
                  {
                    /* k-th destination accepts the non-word character ch.  */
                    trtable[ch] = dest_states[k];
                    /* There must be only one destination which accepts
                       character ch.  See group_nodes_into_DFAstates.  */
                    break;
                  }
            }
        }
  /* new line */
  if (bitset_contain (acceptable, NEWLINE_CHAR))
    {
      /* The current state accepts newline character.  */
      for (k = 0; k < ndests; ++k)
        if (bitset_contain (dests_ch[k], NEWLINE_CHAR))
          {
            /* k-th destination accepts newline character.  */
            trtable[NEWLINE_CHAR] = dest_states_nl[k];
            /* There must be only one destination which accepts
               newline.  See group_nodes_into_DFAstates.  */
            break;
          }
    }

  re_free (dest_states_nl);
  re_free (dest_states_word);
  re_free (dest_states);

  re_node_set_free (&follows);
  for (i = 0; i < ndests; ++i)
    re_node_set_free (dests_node + i);

  re_free (dests_ch);
  re_free (dests_node);

  return trtable;
}

/* Group all nodes belonging to STATE into several destinations.
   Then for all destinations, set the nodes belonging to the destination
   to DESTS_NODE[i] and set the characters accepted by the destination
   to DEST_CH[i].  This function return the number of destinations.  */

static int
group_nodes_into_DFAstates (preg, state, dests_node, dests_ch)
    const regex_t *preg;
    const re_dfastate_t *state;
    re_node_set *dests_node;
    bitset *dests_ch;
{
  reg_errcode_t err;
  const re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  int i, j, k;
  int ndests; /* Number of the destinations from `state'.  */
  bitset accepts; /* Characters a node can accept.  */
  const re_node_set *cur_nodes = &state->nodes;
  bitset_empty (accepts);
  ndests = 0;

  /* For all the nodes belonging to `state',  */
  for (i = 0; i < cur_nodes->nelem; ++i)
    {
      unsigned int constraint = 0;
      re_token_t *node = &dfa->nodes[cur_nodes->elems[i]];
      re_token_type_t type = node->type;

      if (type == OP_CONTEXT_NODE)
        {
          constraint = node->constraint;
          node = dfa->nodes + node->opr.ctx_info->entity;
          type = node->type;
        }

      /* Enumerate all single byte character this node can accept.  */
      if (type == CHARACTER)
        bitset_set (accepts, node->opr.c);
      else if (type == SIMPLE_BRACKET)
        {
          bitset_merge (accepts, node->opr.sbcset);
        }
      else if (type == OP_PERIOD)
        {
          bitset_set_all (accepts);
          if (!(preg->syntax & RE_DOT_NEWLINE))
            bitset_clear (accepts, '\n');
          if (preg->syntax & RE_DOT_NOT_NULL)
            bitset_clear (accepts, '\0');
        }
      else
        continue;

      /* Check the `accepts' and sift the characters which are not
         match it the context.  */
      if (constraint)
        {
          if (constraint & NEXT_WORD_CONSTRAINT)
            for (j = 0; j < BITSET_UINTS; ++j)
              accepts[j] &= dfa->word_char[j];
          else if (constraint & NEXT_NOTWORD_CONSTRAINT)
            for (j = 0; j < BITSET_UINTS; ++j)
              accepts[j] &= ~dfa->word_char[j];
          else if (constraint & NEXT_NEWLINE_CONSTRAINT)
            {
              int accepts_newline = bitset_contain (accepts, NEWLINE_CHAR);
              bitset_empty (accepts);
              if (accepts_newline)
                bitset_set (accepts, NEWLINE_CHAR);
              else
                continue;
            }
        }

      /* Then divide `accepts' into DFA states, or create a new
         state.  */
      for (j = 0; j < ndests; ++j)
        {
          bitset intersec; /* Intersection sets, see below.  */
          bitset remains;
          /* Flags, see below.  */
          int has_intersec, not_subset, not_consumed;

          /* Optimization, skip if this state doesn't accept the character.  */
          if (type == CHARACTER && !bitset_contain (dests_ch[j], node->opr.c))
            continue;

          /* Enumerate the intersection set of this state and `accepts'.  */
          has_intersec = 0;
          for (k = 0; k < BITSET_UINTS; ++k)
            has_intersec |= intersec[k] = accepts[k] & dests_ch[j][k];
          /* And skip if the intersection set is empty.  */
          if (!has_intersec)
            continue;

          /* Then check if this state is a subset of `accepts'.  */
          not_subset = not_consumed = 0;
          for (k = 0; k < BITSET_UINTS; ++k)
            {
              not_subset |= remains[k] = ~accepts[k] & dests_ch[j][k];
              not_consumed |= accepts[k] = accepts[k] & ~dests_ch[j][k];
            }

          /* If this state isn't a subset of `accepts', create a
             new group state, which has the `remains'. */
          if (not_subset)
            {
              bitset_copy (dests_ch[ndests], remains);
              bitset_copy (dests_ch[j], intersec);
              err = re_node_set_init_copy (dests_node + ndests, &dests_node[j]);
              if (BE (err != REG_NOERROR, 0))
                return -1;
              ++ndests;
            }

          /* Put the position in the current group. */
          err = re_node_set_insert (&dests_node[j], cur_nodes->elems[i]);
          if (BE (err < 0, 0))
            return -1;

          /* If all characters are consumed, go to next node. */
          if (!not_consumed)
            break;
        }
      /* Some characters remain, create a new group. */
      if (j == ndests)
        {
          bitset_copy (dests_ch[ndests], accepts);
          err = re_node_set_init_1 (dests_node + ndests, cur_nodes->elems[i]);
          if (BE (err != REG_NOERROR, 0))
            return -1;
          ++ndests;
          bitset_empty (accepts);
        }
    }
  return ndests;
}

#ifdef RE_ENABLE_I18N
/* Check how many bytes the node `dfa->nodes[node_idx]' accepts.
   Return the number of the bytes the node accepts.
   STR_IDX is the current index of the input string.

   This function handles the nodes which can accept one character, or
   one collating element like '.', '[a-z]', opposite to the other nodes
   can only accept one byte.  */

static int
check_node_accept_bytes (preg, node_idx, input, str_idx)
    const regex_t *preg;
    int node_idx, str_idx;
    const re_string_t *input;
{
  const re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  const re_token_t *node = dfa->nodes + node_idx;
  int elem_len = re_string_elem_size_at (input, str_idx);
  int char_len = re_string_char_size_at (input, str_idx);
  int i;
# ifdef _LIBC
  int j;
  uint32_t nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
# endif /* _LIBC */
  if (elem_len <= 1 && char_len <= 1)
    return 0;
  if (node->type == OP_PERIOD)
    {
      /* '.' accepts any one character except the following two cases.  */
      if ((!(preg->syntax & RE_DOT_NEWLINE) &&
           re_string_byte_at (input, str_idx) == '\n') ||
          ((preg->syntax & RE_DOT_NOT_NULL) &&
           re_string_byte_at (input, str_idx) == '\0'))
        return 0;
      return char_len;
    }
  else if (node->type == COMPLEX_BRACKET)
    {
      const re_charset_t *cset = node->opr.mbcset;
# ifdef _LIBC
      const unsigned char *pin = re_string_get_buffer (input) + str_idx;
# endif /* _LIBC */
      int match_len = 0;
      wchar_t wc = ((cset->nranges || cset->nchar_classes || cset->nmbchars)
                    ? re_string_wchar_at (input, str_idx) : 0);

      /* match with multibyte character?  */
      for (i = 0; i < cset->nmbchars; ++i)
        if (wc == cset->mbchars[i])
          {
            match_len = char_len;
            goto check_node_accept_bytes_match;
          }
      /* match with character_class?  */
      for (i = 0; i < cset->nchar_classes; ++i)
        {
          wctype_t wt = cset->char_classes[i];
          if (__iswctype (wc, wt))
            {
              match_len = char_len;
              goto check_node_accept_bytes_match;
            }
        }

# ifdef _LIBC
      if (nrules != 0)
        {
          unsigned int in_collseq = 0;
          const int32_t *table, *indirect;
          const unsigned char *weights, *extra;
          const char *collseqwc;
          int32_t idx;
          /* This #include defines a local function!  */
#  include <locale/weight.h>

          /* match with collating_symbol?  */
          if (cset->ncoll_syms)
            extra = (const unsigned char *)
              _NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB);
          for (i = 0; i < cset->ncoll_syms; ++i)
            {
              const unsigned char *coll_sym = extra + cset->coll_syms[i];
              /* Compare the length of input collating element and
                 the length of current collating element.  */
              if (*coll_sym != elem_len)
                continue;
              /* Compare each bytes.  */
              for (j = 0; j < *coll_sym; j++)
                if (pin[j] != coll_sym[1 + j])
                  break;
              if (j == *coll_sym)
                {
                  /* Match if every bytes is equal.  */
                  match_len = j;
                  goto check_node_accept_bytes_match;
                }
            }

          if (cset->nranges)
            {
              if (elem_len <= char_len)
                {
                  collseqwc = _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQWC);
                  in_collseq = collseq_table_lookup (collseqwc, wc);
                }
              else
                in_collseq = find_collation_sequence_value (pin, elem_len);
            }
          /* match with range expression?  */
          for (i = 0; i < cset->nranges; ++i)
            if (cset->range_starts[i] <= in_collseq
                && in_collseq <= cset->range_ends[i])
              {
                match_len = elem_len;
                goto check_node_accept_bytes_match;
              }

          /* match with equivalence_class?  */
          if (cset->nequiv_classes)
            {
              const unsigned char *cp = pin;
              table = (const int32_t *)
                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_TABLEMB);
              weights = (const unsigned char *)
                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_WEIGHTMB);
              extra = (const unsigned char *)
                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_EXTRAMB);
              indirect = (const int32_t *)
                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_INDIRECTMB);
              idx = findidx (&cp);
              if (idx > 0)
                for (i = 0; i < cset->nequiv_classes; ++i)
                  {
                    int32_t equiv_class_idx = cset->equiv_classes[i];
                    size_t weight_len = weights[idx];
                    if (weight_len == weights[equiv_class_idx])
                      {
                        int cnt = 0;
                        while (cnt <= weight_len
                               && (weights[equiv_class_idx + 1 + cnt]
                                   == weights[idx + 1 + cnt]))
                          ++cnt;
                        if (cnt > weight_len)
                          {
                            match_len = elem_len;
                            goto check_node_accept_bytes_match;
                          }
                      }
                  }
            }
        }
      else
# endif /* _LIBC */
        {
          /* match with range expression?  */
#if __GNUC__ >= 2
          wchar_t cmp_buf[] = {L'\0', L'\0', wc, L'\0', L'\0', L'\0'};
#else
          wchar_t cmp_buf[] = {L'\0', L'\0', L'\0', L'\0', L'\0', L'\0'};
          cmp_buf[2] = wc;
#endif
          for (i = 0; i < cset->nranges; ++i)
            {
              cmp_buf[0] = cset->range_starts[i];
              cmp_buf[4] = cset->range_ends[i];
              if (wcscoll (cmp_buf, cmp_buf + 2) <= 0
                  && wcscoll (cmp_buf + 2, cmp_buf + 4) <= 0)
                {
                  match_len = char_len;
                  goto check_node_accept_bytes_match;
                }
            }
        }
    check_node_accept_bytes_match:
      if (!cset->non_match)
        return match_len;
      else
        {
          if (match_len > 0)
            return 0;
          else
            return (elem_len > char_len) ? elem_len : char_len;
        }
    }
  return 0;
}

# ifdef _LIBC
static unsigned int
find_collation_sequence_value (mbs, mbs_len)
    const unsigned char *mbs;
    size_t mbs_len;
{
  uint32_t nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
  if (nrules == 0)
    {
      if (mbs_len == 1)
        {
          /* No valid character.  Match it as a single byte character.  */
          const unsigned char *collseq = (const unsigned char *)
            _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQMB);
          return collseq[mbs[0]];
        }
      return UINT_MAX;
    }
  else
    {
      int32_t idx;
      const unsigned char *extra = (const unsigned char *)
        _NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB);

      for (idx = 0; ;)
        {
          int mbs_cnt, found = 0;
          int32_t elem_mbs_len;
          /* Skip the name of collating element name.  */
          idx = idx + extra[idx] + 1;
          elem_mbs_len = extra[idx++];
          if (mbs_len == elem_mbs_len)
            {
              for (mbs_cnt = 0; mbs_cnt < elem_mbs_len; ++mbs_cnt)
                if (extra[idx + mbs_cnt] != mbs[mbs_cnt])
                  break;
              if (mbs_cnt == elem_mbs_len)
                /* Found the entry.  */
                found = 1;
            }
          /* Skip the byte sequence of the collating element.  */
          idx += elem_mbs_len;
          /* Adjust for the alignment.  */
          idx = (idx + 3) & ~3;
          /* Skip the collation sequence value.  */
          idx += sizeof (uint32_t);
          /* Skip the wide char sequence of the collating element.  */
          idx = idx + sizeof (uint32_t) * (extra[idx] + 1);
          /* If we found the entry, return the sequence value.  */
          if (found)
            return *(uint32_t *) (extra + idx);
          /* Skip the collation sequence value.  */
          idx += sizeof (uint32_t);
        }
    }
}
# endif /* _LIBC */
#endif /* RE_ENABLE_I18N */

/* Check whether the node accepts the byte which is IDX-th
   byte of the INPUT.  */

static int
check_node_accept (preg, node, mctx, idx)
    const regex_t *preg;
    const re_token_t *node;
    const re_match_context_t *mctx;
    int idx;
{
  const re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  const re_token_t *cur_node;
  unsigned char ch;
  if (node->type == OP_CONTEXT_NODE)
    {
      /* The node has constraints.  Check whether the current context
         satisfies the constraints.  */
      unsigned int context = re_string_context_at (mctx->input, idx,
                                                   mctx->eflags,
                                                   preg->newline_anchor);
      if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
        return 0;
      cur_node = dfa->nodes + node->opr.ctx_info->entity;
    }
  else
    cur_node = node;

  ch = re_string_byte_at (mctx->input, idx);
  if (cur_node->type == CHARACTER)
    return cur_node->opr.c == ch;
  else if (cur_node->type == SIMPLE_BRACKET)
    return bitset_contain (cur_node->opr.sbcset, ch);
  else if (cur_node->type == OP_PERIOD)
    return !((ch == '\n' && !(preg->syntax & RE_DOT_NEWLINE))
             || (ch == '\0' && (preg->syntax & RE_DOT_NOT_NULL)));
  else
    return 0;
}

/* Extend the buffers, if the buffers have run out.  */

static reg_errcode_t
extend_buffers (mctx)
     re_match_context_t *mctx;
{
  reg_errcode_t ret;
  re_string_t *pstr = mctx->input;

  /* Double the lengthes of the buffers.  */
  ret = re_string_realloc_buffers (pstr, pstr->bufs_len * 2);
  if (BE (ret != REG_NOERROR, 0))
    return ret;

  if (mctx->state_log != NULL)
    {
      /* And double the length of state_log.  */
      mctx->state_log = re_realloc (mctx->state_log, re_dfastate_t *,
                                    pstr->bufs_len * 2);
      if (BE (mctx->state_log == NULL, 0))
        return REG_ESPACE;
    }

  /* Then reconstruct the buffers.  */
  if (pstr->icase)
    {
#ifdef RE_ENABLE_I18N
      if (MB_CUR_MAX > 1)
        build_wcs_upper_buffer (pstr);
      else
#endif /* RE_ENABLE_I18N  */
        build_upper_buffer (pstr);
    }
  else
    {
#ifdef RE_ENABLE_I18N
      if (MB_CUR_MAX > 1)
        build_wcs_buffer (pstr);
      else
#endif /* RE_ENABLE_I18N  */
        {
          if (pstr->trans != NULL)
            re_string_translate_buffer (pstr);
          else
            pstr->valid_len = pstr->bufs_len;
        }
    }
  return REG_NOERROR;
}


/* Functions for matching context.  */

static reg_errcode_t
match_ctx_init (mctx, eflags, input, n)
    re_match_context_t *mctx;
    int eflags, n;
    re_string_t *input;
{
  mctx->eflags = eflags;
  mctx->input = input;
  mctx->match_last = -1;
  if (n > 0)
    {
      mctx->bkref_ents = re_malloc (struct re_backref_cache_entry, n);
      if (BE (mctx->bkref_ents == NULL, 0))
        return REG_ESPACE;
    }
  else
    mctx->bkref_ents = NULL;
  mctx->nbkref_ents = 0;
  mctx->abkref_ents = n;
  mctx->max_mb_elem_len = 0;
  return REG_NOERROR;
}

static void
match_ctx_free (mctx)
    re_match_context_t *mctx;
{
  re_free (mctx->bkref_ents);
}

/* Add a new backreference entry to the cache.  */

static reg_errcode_t
match_ctx_add_entry (mctx, node, str_idx, from, to)
    re_match_context_t *mctx;
    int node, str_idx, from, to;
{
  if (mctx->nbkref_ents >= mctx->abkref_ents)
    {
      mctx->bkref_ents = re_realloc (mctx->bkref_ents,
                                     struct re_backref_cache_entry,
                                     mctx->abkref_ents * 2);
      if (BE (mctx->bkref_ents == NULL, 0))
        return REG_ESPACE;
      memset (mctx->bkref_ents + mctx->nbkref_ents, '\0',
             sizeof (struct re_backref_cache_entry) * mctx->abkref_ents);
      mctx->abkref_ents *= 2;
    }
  mctx->bkref_ents[mctx->nbkref_ents].node = node;
  mctx->bkref_ents[mctx->nbkref_ents].str_idx = str_idx;
  mctx->bkref_ents[mctx->nbkref_ents].subexp_from = from;
  mctx->bkref_ents[mctx->nbkref_ents].subexp_to = to;
  mctx->bkref_ents[mctx->nbkref_ents++].flag = 0;
  if (mctx->max_mb_elem_len < to - from)
    mctx->max_mb_elem_len = to - from;
  return REG_NOERROR;
}

static void
match_ctx_clear_flag (mctx)
     re_match_context_t *mctx;
{
  int i;
  for (i = 0; i < mctx->nbkref_ents; ++i)
    {
      mctx->bkref_ents[i].flag = 0;
    }
}

static void
sift_ctx_init (sctx, sifted_sts, limited_sts, last_node, last_str_idx,
               check_subexp)
    re_sift_context_t *sctx;
    re_dfastate_t **sifted_sts, **limited_sts;
    int last_node, last_str_idx, check_subexp;
{
  sctx->sifted_states = sifted_sts;
  sctx->limited_states = limited_sts;
  sctx->last_node = last_node;
  sctx->last_str_idx = last_str_idx;
  sctx->check_subexp = check_subexp;
  re_node_set_init_empty (&sctx->limits);
}