File: interp.c

package info (click to toggle)
ghostscript 8.71~dfsg2-9+squeeze1
  • links: PTS, VCS
  • area: main
  • in suites: squeeze
  • size: 79,896 kB
  • ctags: 80,654
  • sloc: ansic: 501,432; sh: 25,689; python: 4,853; cpp: 3,633; perl: 3,597; tcl: 1,480; makefile: 1,187; lisp: 407; asm: 284; xml: 263; awk: 66; csh: 17; yacc: 15
file content (1933 lines) | stat: -rw-r--r-- 58,518 bytes parent folder | download | duplicates (2)
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
/* Copyright (C) 2001-2006 Artifex Software, Inc.
   All Rights Reserved.
  
   This software is provided AS-IS with no warranty, either express or
   implied.

   This software is distributed under license and may not be copied, modified
   or distributed except as expressly authorized under the terms of that
   license.  Refer to licensing information at http://www.artifex.com/
   or contact Artifex Software, Inc.,  7 Mt. Lassen Drive - Suite A-134,
   San Rafael, CA  94903, U.S.A., +1(415)492-9861, for further information.
*/

/* $Id: interp.c 9536 2009-03-07 22:59:15Z alexcher $ */
/* Ghostscript language interpreter */
#include "memory_.h"
#include "string_.h"
#include "ghost.h"
#include "gsstruct.h"		/* for iastruct.h */
#include "gserrors.h"		/* for gpcheck.h */
#include "stream.h"
#include "ierrors.h"
#include "estack.h"
#include "ialloc.h"
#include "iastruct.h"
#include "icontext.h"
#include "icremap.h"
#include "idebug.h"
#include "igstate.h"		/* for handling e_RemapColor */
#include "inamedef.h"
#include "iname.h"		/* for the_name_table */
#include "interp.h"
#include "ipacked.h"
#include "ostack.h"		/* must precede iscan.h */
#include "strimpl.h"		/* for sfilter.h */
#include "sfilter.h"		/* for iscan.h */
#include "iscan.h"
#include "iddict.h"
#include "isave.h"
#include "istack.h"
#include "itoken.h"
#include "iutil.h"		/* for array_get */
#include "ivmspace.h"
#include "iinit.h"
#include "dstack.h"
#include "files.h"		/* for file_check_read */
#include "oper.h"
#include "store.h"
#include "gpcheck.h"

/*
 * We may or may not optimize the handling of the special fast operators
 * in packed arrays.  If we do this, they run much faster when packed, but
 * slightly slower when not packed.
 */
#define PACKED_SPECIAL_OPS 1

/*
 * Pseudo-operators (procedures of type t_oparray) record
 * the operand and dictionary stack pointers, and restore them if an error
 * occurs during the execution of the procedure and if the procedure hasn't
 * (net) decreased the depth of the stack.  While this obviously doesn't
 * do all the work of restoring the state if a pseudo-operator gets an
 * error, it's a big help.  The only downside is that pseudo-operators run
 * a little slower.
 */

/* GC descriptors for stacks */
extern_st(st_ref_stack);
public_st_dict_stack();
public_st_exec_stack();
public_st_op_stack();

/* 
 * The procedure to call if an operator requests rescheduling.
 * This causes an error unless the context machinery has been installed.
 */
static int
no_reschedule(i_ctx_t **pi_ctx_p)
{
    return_error(e_invalidcontext);
}
int (*gs_interp_reschedule_proc)(i_ctx_t **) = no_reschedule;

/*
 * The procedure to call for time-slicing.
 * This is a no-op unless the context machinery has been installed.
 */
int (*gs_interp_time_slice_proc)(i_ctx_t **) = 0;

/*
 * The number of interpreter "ticks" between calls on the time_slice_proc.
 * Currently, the clock ticks before each operator, and at each
 * procedure return.
 */
int gs_interp_time_slice_ticks = 0x7fff;

/*
 * Apply an operator.  When debugging, we route all operator calls
 * through a procedure.
 */
#ifdef DEBUG
static int
call_operator(op_proc_t op_proc, i_ctx_t *i_ctx_p)
{
    int code;

# ifdef DEBUG_TRACE_PS_OPERATORS
#   ifndef SHOW_STACK_DEPTHS
    if_debug1('!', "[!]operator %s\n", op_get_name_string(op_proc));
#   else
    if_debug3('!', "[!][es=%d os=%d]operator %s\n",
	    esp-i_ctx_p->exec_stack.stack.bot,
	    osp-i_ctx_p->op_stack.stack.bot,
	    op_get_name_string(op_proc));
#   endif
# endif
    code = op_proc(i_ctx_p);
# if defined(DEBUG_TRACE_PS_OPERATORS) && !defined(SHOW_STACK_DEPTHS)
    if_debug2('!', "[!][es=%d os=%d]\n",
	    esp-i_ctx_p->exec_stack.stack.bot,
	    osp-i_ctx_p->op_stack.stack.bot);
# endif
    return code; /* A good place for a conditional breakpoint. */
}
#else
#  define call_operator(proc, p) ((*(proc))(p))
#endif

/* Define debugging statistics. */
#ifdef DEBUG
struct stats_interp_s {
    long top;
    long lit, lit_array, exec_array, exec_operator, exec_name;
    long x_add, x_def, x_dup, x_exch, x_if, x_ifelse,
	x_index, x_pop, x_roll, x_sub;
    long find_name, name_lit, name_proc, name_oparray, name_operator;
    long p_full, p_exec_operator, p_exec_oparray, p_exec_non_x_operator,
	p_integer, p_lit_name, p_exec_name;
    long p_find_name, p_name_lit, p_name_proc;
} stats_interp;
# define INCR(v) (++(stats_interp.v))
#else
# define INCR(v) DO_NOTHING
#endif

/* Forward references */
static int estack_underflow(i_ctx_t *);
static int interp(i_ctx_t **, const ref *, ref *);
static int interp_exit(i_ctx_t *);
static void set_gc_signal(i_ctx_t *, int *, int);
static int copy_stack(i_ctx_t *, const ref_stack_t *, int skip, ref *);
static int oparray_pop(i_ctx_t *);
static int oparray_cleanup(i_ctx_t *);
static int zerrorexec(i_ctx_t *);
static int zfinderrorobject(i_ctx_t *);
static int errorexec_find(i_ctx_t *, ref *);
static int errorexec_pop(i_ctx_t *);
static int errorexec_cleanup(i_ctx_t *);
static int zsetstackprotect(i_ctx_t *);
static int zcurrentstackprotect(i_ctx_t *);

/* Stack sizes */

/* The maximum stack sizes may all be set in the makefile. */

/*
 * Define the initial maximum size of the operand stack (MaxOpStack
 * user parameter).
 */
#ifndef MAX_OSTACK
#  define MAX_OSTACK 800
#endif
/*
 * The minimum block size for extending the operand stack is the larger of:
 *      - the maximum number of parameters to an operator
 *      (currently setcolorscreen, with 12 parameters);
 *      - the maximum number of values pushed by an operator
 *      (currently setcolortransfer, which calls zcolor_remap_one 4 times
 *      and therefore pushes 16 values).
 */
#define MIN_BLOCK_OSTACK 16
const int gs_interp_max_op_num_args = MIN_BLOCK_OSTACK;		/* for iinit.c */

/*
 * Define the initial maximum size of the execution stack (MaxExecStack
 * user parameter).
 */
#ifndef MAX_ESTACK
#  define MAX_ESTACK 5000
#endif
/*
 * The minimum block size for extending the execution stack is the largest
 * size of a contiguous block surrounding an e-stack mark.  (At least,
 * that's what the minimum value would be if we supported multi-block
 * estacks, which we currently don't.)  Currently, the largest such block is
 * the one created for text processing, which is 8 (snumpush) slots.
 */
#define MIN_BLOCK_ESTACK 8
/*
 * If we get an e-stack overflow, we need to cut it back far enough to
 * have some headroom for executing the error procedure.
 */
#define ES_HEADROOM 20

/*
 * Define the initial maximum size of the dictionary stack (MaxDictStack
 * user parameter).  Again, this is also currently the block size for
 * extending the d-stack.
 */
#ifndef MAX_DSTACK
#  define MAX_DSTACK 20
#endif
/*
 * The minimum block size for extending the dictionary stack is the number
 * of permanent entries on the dictionary stack, currently 3.
 */
#define MIN_BLOCK_DSTACK 3

/* See estack.h for a description of the execution stack. */

/* The logic for managing icount and iref below assumes that */
/* there are no control operators which pop and then push */
/* information on the execution stack. */

/* Stacks */
extern_st(st_ref_stack);
#define OS_GUARD_UNDER 10
#define OS_GUARD_OVER 10
#define OS_REFS_SIZE(body_size)\
  (stack_block_refs + OS_GUARD_UNDER + (body_size) + OS_GUARD_OVER)

#define ES_GUARD_UNDER 1
#define ES_GUARD_OVER 10
#define ES_REFS_SIZE(body_size)\
  (stack_block_refs + ES_GUARD_UNDER + (body_size) + ES_GUARD_OVER)

#define DS_REFS_SIZE(body_size)\
  (stack_block_refs + (body_size))

/* Extended types.  The interpreter may replace the type of operators */
/* in procedures with these, to speed up the interpretation loop. */
/****** NOTE: If you add or change entries in this list, */
/****** you must change the three dispatches in the interpreter loop. */
/* The operator procedures are declared in opextern.h. */
#define tx_op t_next_index
typedef enum {
    tx_op_add = tx_op,
    tx_op_def,
    tx_op_dup,
    tx_op_exch,
    tx_op_if,
    tx_op_ifelse,
    tx_op_index,
    tx_op_pop,
    tx_op_roll,
    tx_op_sub,
    tx_next_op
} special_op_types;

#define num_special_ops ((int)tx_next_op - tx_op)
const int gs_interp_num_special_ops = num_special_ops;	/* for iinit.c */
const int tx_next_index = tx_next_op;

/*
 * NOTE: if the size of either table below ever exceeds 15 real entries, it
 * will have to be split.
 */
/* Define the extended-type operators per the list above. */
const op_def interp1_op_defs[] = {
    /*
     * The very first entry, which corresponds to operator index 0,
     * must not contain an actual operator.
     */
    op_def_begin_dict("systemdict"),
    {"2add", zadd},
    {"2def", zdef},
    {"1dup", zdup},
    {"2exch", zexch},
    {"2if", zif},
    {"3ifelse", zifelse},
    {"1index", zindex},
    {"1pop", zpop},
    {"2roll", zroll},
    {"2sub", zsub},
    op_def_end(0)
};
/* Define the internal interpreter operators. */
const op_def interp2_op_defs[] = {
    {"0.currentstackprotect", zcurrentstackprotect},
    {"1.setstackprotect", zsetstackprotect},
    {"2.errorexec", zerrorexec},
    {"0.finderrorobject", zfinderrorobject},
    {"0%interp_exit", interp_exit},
    {"0%oparray_pop", oparray_pop},
    {"0%errorexec_pop", errorexec_pop},
    op_def_end(0)
};

#define make_null_proc(pref)\
  make_empty_const_array(pref, a_executable + a_readonly)

/* Initialize the interpreter. */
int
gs_interp_init(i_ctx_t **pi_ctx_p, const ref *psystem_dict,
	       gs_dual_memory_t *dmem)
{
    /* Create and initialize a context state. */
    gs_context_state_t *pcst = 0;
    int code = context_state_alloc(&pcst, psystem_dict, dmem);

    if (code >= 0)
	code = context_state_load(pcst);
    if (code < 0)
	lprintf1("Fatal error %d in gs_interp_init!", code);
    *pi_ctx_p = pcst;
    return code;
}
/*
 * Create initial stacks for the interpreter.
 * We export this for creating new contexts.
 */
int
gs_interp_alloc_stacks(gs_ref_memory_t *mem, gs_context_state_t * pcst)
{
    gs_ref_memory_t *smem =
	(gs_ref_memory_t *)gs_memory_stable((gs_memory_t *)mem);
    ref stk;

#define REFS_SIZE_OSTACK OS_REFS_SIZE(MAX_OSTACK)
#define REFS_SIZE_ESTACK ES_REFS_SIZE(MAX_ESTACK)
#define REFS_SIZE_DSTACK DS_REFS_SIZE(MAX_DSTACK)
    gs_alloc_ref_array(smem, &stk, 0,
		       REFS_SIZE_OSTACK + REFS_SIZE_ESTACK +
		       REFS_SIZE_DSTACK, "gs_interp_alloc_stacks");

    {
	ref_stack_t *pos = &pcst->op_stack.stack;

	r_set_size(&stk, REFS_SIZE_OSTACK);
	ref_stack_init(pos, &stk, OS_GUARD_UNDER, OS_GUARD_OVER, NULL,
		       smem, NULL);
	ref_stack_set_error_codes(pos, e_stackunderflow, e_stackoverflow);
	ref_stack_set_max_count(pos, MAX_OSTACK);
	stk.value.refs += REFS_SIZE_OSTACK;
    }

    {
	ref_stack_t *pes = &pcst->exec_stack.stack;
	ref euop;

	r_set_size(&stk, REFS_SIZE_ESTACK);
	make_oper(&euop, 0, estack_underflow);
	ref_stack_init(pes, &stk, ES_GUARD_UNDER, ES_GUARD_OVER, &euop,
		       smem, NULL);
	ref_stack_set_error_codes(pes, e_ExecStackUnderflow,
				  e_execstackoverflow);
	/**************** E-STACK EXPANSION IS NYI. ****************/
	ref_stack_allow_expansion(pes, false);
	ref_stack_set_max_count(pes, MAX_ESTACK);
	stk.value.refs += REFS_SIZE_ESTACK;
    }

    {
	ref_stack_t *pds = &pcst->dict_stack.stack;

	r_set_size(&stk, REFS_SIZE_DSTACK);
	ref_stack_init(pds, &stk, 0, 0, NULL, smem, NULL);
	ref_stack_set_error_codes(pds, e_dictstackunderflow,
				  e_dictstackoverflow);
	ref_stack_set_max_count(pds, MAX_DSTACK);
    }

#undef REFS_SIZE_OSTACK
#undef REFS_SIZE_ESTACK
#undef REFS_SIZE_DSTACK
    return 0;
}
/*
 * Free the stacks when destroying a context.  This is the inverse of
 * create_stacks.
 */
void
gs_interp_free_stacks(gs_ref_memory_t * smem, gs_context_state_t * pcst)
{
    /* Free the stacks in inverse order of allocation. */
    ref_stack_release(&pcst->dict_stack.stack);
    ref_stack_release(&pcst->exec_stack.stack);
    ref_stack_release(&pcst->op_stack.stack);
}
void
gs_interp_reset(i_ctx_t *i_ctx_p)
{   /* Reset the stacks. */
    ref_stack_clear(&o_stack);
    ref_stack_clear(&e_stack);
    esp++;
    make_oper(esp, 0, interp_exit);
    ref_stack_pop_to(&d_stack, min_dstack_size);
    dict_set_top();
}
/* Report an e-stack block underflow.  The bottom guard slots of */
/* e-stack blocks contain a pointer to this procedure. */
static int
estack_underflow(i_ctx_t *i_ctx_p)
{
    return e_ExecStackUnderflow;
}

/*
 * Create an operator during initialization.
 * If operator is hard-coded into the interpreter,
 * assign it a special type and index.
 */
void
gs_interp_make_oper(ref * opref, op_proc_t proc, int idx)
{
    int i;

    for (i = num_special_ops; i > 0 && proc != interp1_op_defs[i].proc; --i)
	DO_NOTHING;
    if (i > 0)
	make_tasv(opref, tx_op + (i - 1), a_executable, i, opproc, proc);
    else
	make_tasv(opref, t_operator, a_executable, idx, opproc, proc);
}

/*
 * Call the garbage collector, updating the context pointer properly.
 */
int
interp_reclaim(i_ctx_t **pi_ctx_p, int space)
{
    i_ctx_t *i_ctx_p = *pi_ctx_p;
    gs_gc_root_t ctx_root;
    int code;

    gs_register_struct_root(imemory_system, &ctx_root,
			    (void **)pi_ctx_p, "interp_reclaim(pi_ctx_p)");
    code = (*idmemory->reclaim)(idmemory, space);
    i_ctx_p = *pi_ctx_p;	/* may have moved */
    gs_unregister_root(imemory_system, &ctx_root, "interp_reclaim(pi_ctx_p)");
    return code;
}

/*
 * Invoke the interpreter.  If execution completes normally, return 0.
 * If an error occurs, the action depends on user_errors as follows:
 *    user_errors < 0: always return an error code.
 *    user_errors >= 0: let the PostScript machinery handle all errors.
 *      (This will eventually result in a fatal error if no 'stopped'
 *      is active.)
 * In case of a quit or a fatal error, also store the exit code.
 * Set *perror_object to null or the error object.
 */
static int gs_call_interp(i_ctx_t **, ref *, int, int *, ref *);
int
gs_interpret(i_ctx_t **pi_ctx_p, ref * pref, int user_errors, int *pexit_code,
	     ref * perror_object)
{
    i_ctx_t *i_ctx_p = *pi_ctx_p;
    gs_gc_root_t error_root;
    int code;

    gs_register_ref_root(imemory_system, &error_root,
			 (void **)&perror_object, "gs_interpret");
    code = gs_call_interp(pi_ctx_p, pref, user_errors, pexit_code,
			  perror_object);
    i_ctx_p = *pi_ctx_p;
    gs_unregister_root(imemory_system, &error_root, "gs_interpret");
    /* Avoid a dangling reference to a stack-allocated GC signal. */
    set_gc_signal(i_ctx_p, NULL, 0);
    return code;
}
static int
gs_call_interp(i_ctx_t **pi_ctx_p, ref * pref, int user_errors,
	       int *pexit_code, ref * perror_object)
{
    ref *epref = pref;
    ref doref;
    ref *perrordict;
    ref error_name;
    int code, ccode;
    ref saref;
    int gc_signal = 0;
    i_ctx_t *i_ctx_p = *pi_ctx_p;

    *pexit_code = 0;
    ialloc_reset_requested(idmemory);
again:
    /* Avoid a dangling error object that might get traced by a future GC. */
    make_null(perror_object);
    o_stack.requested = e_stack.requested = d_stack.requested = 0;
    while (gc_signal) {		/* Some routine below triggered a GC. */
	gs_gc_root_t epref_root;

	gc_signal = 0;
	/* Make sure that doref will get relocated properly if */
	/* a garbage collection happens with epref == &doref. */
	gs_register_ref_root(imemory_system, &epref_root,
			     (void **)&epref, "gs_call_interp(epref)");
	code = interp_reclaim(pi_ctx_p, -1);
	i_ctx_p = *pi_ctx_p;
	gs_unregister_root(imemory_system, &epref_root,
			   "gs_call_interp(epref)");
	if (code < 0)
	    return code;
    }
    code = interp(pi_ctx_p, epref, perror_object);
    i_ctx_p = *pi_ctx_p;
    if (!r_has_type(&i_ctx_p->error_object, t__invalid)) {
	*perror_object = i_ctx_p->error_object;
	make_t(&i_ctx_p->error_object, t__invalid);
    }
    /* Prevent a dangling reference to the GC signal in ticks_left */
    /* in the frame of interp, but be prepared to do a GC if */
    /* an allocation in this routine asks for it. */
    set_gc_signal(i_ctx_p, &gc_signal, 1);
    if (esp < esbot)		/* popped guard entry */
	esp = esbot;
    switch (code) {
	case e_Fatal:
	    *pexit_code = 255;
	    return code;
	case e_Quit:
	    *perror_object = osp[-1];
	    *pexit_code = code = osp->value.intval;
	    osp -= 2;
	    return
		(code == 0 ? e_Quit :
		 code < 0 && code > -100 ? code : e_Fatal);
	case e_InterpreterExit:
	    return 0;
	case e_ExecStackUnderflow:
/****** WRONG -- must keep mark blocks intact ******/
	    ref_stack_pop_block(&e_stack);
	    doref = *perror_object;
	    epref = &doref;
	    goto again;
	case e_VMreclaim:
	    /* Do the GC and continue. */
	    code = interp_reclaim(pi_ctx_p,
				  (osp->value.intval == 2 ?
				   avm_global : avm_local));
	    i_ctx_p = *pi_ctx_p;
	    /****** What if code < 0? ******/
	    make_oper(&doref, 0, zpop);
	    epref = &doref;
	    goto again;
	case e_NeedInput:
	case e_interrupt:
	    return code;
    }
    /* Adjust osp in case of operand stack underflow */
    if (osp < osbot - 1)
	osp = osbot - 1;
    /* We have to handle stack over/underflow specially, because */
    /* we might be able to recover by adding or removing a block. */
    switch (code) {
	case e_dictstackoverflow:
	    /* We don't have to handle this specially: */
	    /* The only places that could generate it */
	    /* use check_dstack, which does a ref_stack_extend, */
	    /* so if` we get this error, it's a real one. */
	    if (osp >= ostop) {
		if ((ccode = ref_stack_extend(&o_stack, 1)) < 0)
		    return ccode;
	    }
            /* Skip system dictionaries for CET 20-02-02 */
	    ccode = copy_stack(i_ctx_p, &d_stack, min_dstack_size, &saref);
	    if (ccode < 0)
		return ccode;
	    ref_stack_pop_to(&d_stack, min_dstack_size);
	    dict_set_top();
	    *++osp = saref;
	    break;
	case e_dictstackunderflow:
	    if (ref_stack_pop_block(&d_stack) >= 0) {
		dict_set_top();
		doref = *perror_object;
		epref = &doref;
		goto again;
	    }
	    break;
	case e_execstackoverflow:
	    /* We don't have to handle this specially: */
	    /* The only places that could generate it */
	    /* use check_estack, which does a ref_stack_extend, */
	    /* so if we get this error, it's a real one. */
	    if (osp >= ostop) {
		if ((ccode = ref_stack_extend(&o_stack, 1)) < 0)
		    return ccode;
	    }
	    ccode = copy_stack(i_ctx_p, &e_stack, 0, &saref);
	    if (ccode < 0)
		return ccode;
	    {
		uint count = ref_stack_count(&e_stack);
		uint limit = ref_stack_max_count(&e_stack) - ES_HEADROOM;

		if (count > limit) {
		    /*
		     * If there is an e-stack mark within MIN_BLOCK_ESTACK of
		     * the new top, cut the stack back to remove the mark.
		     */
		    int skip = count - limit;
		    int i;

		    for (i = skip; i < skip + MIN_BLOCK_ESTACK; ++i) {
			const ref *ep = ref_stack_index(&e_stack, i);

			if (r_has_type_attrs(ep, t_null, a_executable)) {
			    skip = i + 1;
			    break;
			}
		    }
		    pop_estack(i_ctx_p, skip);
		}
	    }
	    *++osp = saref;
	    break;
	case e_stackoverflow:
	    if (ref_stack_extend(&o_stack, o_stack.requested) >= 0) {	/* We can't just re-execute the object, because */
		/* it might be a procedure being pushed as a */
		/* literal.  We check for this case specially. */
		doref = *perror_object;
		if (r_is_proc(&doref)) {
		    *++osp = doref;
		    make_null_proc(&doref);
		}
		epref = &doref;
		goto again;
	    }
	    ccode = copy_stack(i_ctx_p, &o_stack, 0, &saref);
	    if (ccode < 0)
		return ccode;
	    ref_stack_clear(&o_stack);
	    *++osp = saref;
	    break;
	case e_stackunderflow:
	    if (ref_stack_pop_block(&o_stack) >= 0) {
		doref = *perror_object;
		epref = &doref;
		goto again;
	    }
	    break;
    }
    if (user_errors < 0)
	return code;
    if (gs_errorname(i_ctx_p, code, &error_name) < 0)
	return code;		/* out-of-range error code! */
    /*
     * For greater Adobe compatibility, only the standard PostScript errors
     * are defined in errordict; the rest are in gserrordict.
     */
    if (dict_find_string(systemdict, "errordict", &perrordict) <= 0 ||
	(dict_find(perrordict, &error_name, &epref) <= 0 &&
	 (dict_find_string(systemdict, "gserrordict", &perrordict) <= 0 ||
	  dict_find(perrordict, &error_name, &epref) <= 0))
	)
	return code;		/* error name not in errordict??? */
    doref = *epref;
    epref = &doref;
    /* Push the error object on the operand stack if appropriate. */
    if (!ERROR_IS_INTERRUPT(code)) {
	/* Replace the error object if within an oparray or .errorexec. */
	*++osp = *perror_object;
	errorexec_find(i_ctx_p, osp);
    }
    goto again;
}
static int
interp_exit(i_ctx_t *i_ctx_p)
{
    return e_InterpreterExit;
}

/* Set the GC signal for all VMs. */
static void
set_gc_signal(i_ctx_t *i_ctx_p, int *psignal, int value)
{
    gs_memory_gc_status_t stat;
    int i;

    for (i = 0; i < countof(idmemory->spaces_indexed); i++) {
	gs_ref_memory_t *mem = idmemory->spaces_indexed[i];
	gs_ref_memory_t *mem_stable;

	if (mem == 0)
	    continue;
	for (;; mem = mem_stable) {
	    mem_stable = (gs_ref_memory_t *)
		gs_memory_stable((gs_memory_t *)mem);
	    gs_memory_gc_status(mem, &stat);
	    stat.psignal = psignal;
	    stat.signal_value = value;
	    gs_memory_set_gc_status(mem, &stat);
	    if (mem_stable == mem)
		break;
	}
    }
}

/* Copy top elements of an overflowed stack into a (local) array. */
/* Adobe copies only 500 top elements, we copy up to 65535 top elements */
/* for better debugging, PLRM compliance, and backward compatibility. */
static int
copy_stack(i_ctx_t *i_ctx_p, const ref_stack_t * pstack, int skip, ref * arr)
{
    uint size = ref_stack_count(pstack) - skip;
    uint save_space = ialloc_space(idmemory);
    int code;

    if (size > 65535)
        size = 65535;
    ialloc_set_space(idmemory, avm_local);
    code = ialloc_ref_array(arr, a_all, size, "copy_stack");
    if (code >= 0)
	code = ref_stack_store(pstack, arr, size, 0, 1, true, idmemory,
			       "copy_stack");
    ialloc_set_space(idmemory, save_space);
    return code;
}

/* Get the name corresponding to an error number. */
int
gs_errorname(i_ctx_t *i_ctx_p, int code, ref * perror_name)
{
    ref *perrordict, *pErrorNames;

    if (dict_find_string(systemdict, "errordict", &perrordict) <= 0 ||
	dict_find_string(systemdict, "ErrorNames", &pErrorNames) <= 0
	)
	return_error(e_undefined);	/* errordict or ErrorNames not found?! */
    return array_get(imemory, pErrorNames, (long)(-code - 1), perror_name);
}

/* Store an error string in $error.errorinfo. */
/* This routine is here because of the proximity to the error handler. */
int
gs_errorinfo_put_string(i_ctx_t *i_ctx_p, const char *str)
{
    ref rstr;
    ref *pderror;
    int code = string_to_ref(str, &rstr, iimemory, "gs_errorinfo_put_string");

    if (code < 0)
	return code;
    if (dict_find_string(systemdict, "$error", &pderror) <= 0 ||
	!r_has_type(pderror, t_dictionary) ||
	idict_put_string(pderror, "errorinfo", &rstr) < 0
	)
	return_error(e_Fatal);
    return 0;
}

/* Main interpreter. */
/* If execution terminates normally, return e_InterpreterExit. */
/* If an error occurs, leave the current object in *perror_object */
/* and return a (negative) error code. */
static int
interp(i_ctx_t **pi_ctx_p /* context for execution, updated if resched */,
       const ref * pref /* object to interpret */,
       ref * perror_object)
{
    i_ctx_t *i_ctx_p = *pi_ctx_p;
    /*
     * Note that iref may actually be either a ref * or a ref_packed *.
     * Certain DEC compilers assume that a ref * is ref-aligned even if it
     * is cast to a short *, and generate code on this assumption, leading
     * to "unaligned access" errors.  For this reason, we declare
     * iref_packed, and use a macro to cast it to the more aligned type
     * where necessary (which is almost everywhere it is used).  This may
     * lead to compiler warnings about "cast increases alignment
     * requirements", but this is less harmful than expensive traps at run
     * time.
     */
    register const ref_packed *iref_packed = (const ref_packed *)pref;
    /*
     * To make matters worse, some versions of gcc/egcs have a bug that
     * leads them to assume that if iref_packed is EVER cast to a ref *,
     * it is ALWAYS ref-aligned.  We detect this in stdpre.h and provide
     * the following workaround:
     */
#ifdef ALIGNMENT_ALIASING_BUG
    const ref *iref_temp;
#  define IREF (iref_temp = (const ref *)iref_packed, iref_temp)
#else
#  define IREF ((const ref *)iref_packed)
#endif
#define SET_IREF(rp) (iref_packed = (const ref_packed *)(rp))
    register int icount = 0;	/* # of consecutive tokens at iref */
    register os_ptr iosp = osp;	/* private copy of osp */
    register es_ptr iesp = esp;	/* private copy of esp */
    int code;
    ref token;			/* token read from file or string, */
				/* must be declared in this scope */
    register const ref *pvalue = 0;
    uint opindex;		/* needed for oparrays */
    os_ptr whichp;

    /*
     * We have to make the error information into a struct;
     * otherwise, the Watcom compiler will assign it to registers
     * strictly on the basis of textual frequency.
     * We also have to use ref_assign_inline everywhere, and
     * avoid direct assignments of refs, so that esi and edi
     * will remain available on Intel processors.
     */
    struct interp_error_s {
	int code;
	int line;
	const ref *obj;
	ref full;
    } ierror;

    /*
     * Get a pointer to the name table so that we can use the
     * inline version of name_index_ref.
     */
    const name_table *const int_nt = imemory->gs_lib_ctx->gs_name_table;

#define set_error(ecode)\
  { ierror.code = ecode; ierror.line = __LINE__; }
#define return_with_error(ecode, objp)\
  { set_error(ecode); ierror.obj = objp; goto rwe; }
#define return_with_error_iref(ecode)\
  { set_error(ecode); goto rwei; }
#define return_with_code_iref()\
  { ierror.line = __LINE__; goto rweci; }
#define return_with_stackoverflow(objp)\
  { o_stack.requested = 1; return_with_error(e_stackoverflow, objp); }
#define return_with_stackoverflow_iref()\
  { o_stack.requested = 1; return_with_error_iref(e_stackoverflow); }
/*
 * If control reaches the special operators (x_add, etc.) as a result of
 * interpreting an executable name, iref points to the name, not the
 * operator, so the name rather than the operator becomes the error object,
 * which is wrong.  We detect and handle this case explicitly when an error
 * occurs, so as not to slow down the non-error case.
 */
#define return_with_error_tx_op(err_code)\
  { if (r_has_type(IREF, t_name)) {\
        return_with_error(err_code, pvalue);\
    } else {\
        return_with_error_iref(err_code);\
    }\
  }

    int ticks_left = gs_interp_time_slice_ticks;

    /*
     * If we exceed the VMThreshold, set ticks_left to -100
     * to alert the interpreter that we need to garbage collect.
     */
    set_gc_signal(i_ctx_p, &ticks_left, -100);

    esfile_clear_cache();
    /*
     * From here on, if icount > 0, iref and icount correspond
     * to the top entry on the execution stack: icount is the count
     * of sequential entries remaining AFTER the current one.
     */
#define IREF_NEXT(ip)\
  ((const ref_packed *)((const ref *)(ip) + 1))
#define IREF_NEXT_EITHER(ip)\
  ( r_is_packed(ip) ? (ip) + 1 : IREF_NEXT(ip) )
#define store_state(ep)\
  ( icount > 0 ? (ep->value.const_refs = IREF + 1, r_set_size(ep, icount)) : 0 )
#define store_state_short(ep)\
  ( icount > 0 ? (ep->value.packed = iref_packed + 1, r_set_size(ep, icount)) : 0 )
#define store_state_either(ep)\
  ( icount > 0 ? (ep->value.packed = IREF_NEXT_EITHER(iref_packed), r_set_size(ep, icount)) : 0 )
#define next()\
  if ( --icount > 0 ) { iref_packed = IREF_NEXT(iref_packed); goto top; } else goto out
#define next_short()\
  if ( --icount <= 0 ) { if ( icount < 0 ) goto up; iesp--; }\
  ++iref_packed; goto top
#define next_either()\
  if ( --icount <= 0 ) { if ( icount < 0 ) goto up; iesp--; }\
  iref_packed = IREF_NEXT_EITHER(iref_packed); goto top

#if !PACKED_SPECIAL_OPS
#  undef next_either
#  define next_either() next()
#  undef store_state_either
#  define store_state_either(ep) store_state(ep)
#endif

    /* We want to recognize executable arrays here, */
    /* so we push the argument on the estack and enter */
    /* the loop at the bottom. */
    if (iesp >= estop)
	return_with_error(e_execstackoverflow, pref);
    ++iesp;
    ref_assign_inline(iesp, pref);
    goto bot;
  top:
	/*
	 * This is the top of the interpreter loop.
	 * iref points to the ref being interpreted.
	 * Note that this might be an element of a packed array,
	 * not a real ref: we carefully arranged the first 16 bits of
	 * a ref and of a packed array element so they could be distinguished
	 * from each other.  (See ghost.h and packed.h for more detail.)
	 */
    INCR(top);
#ifdef DEBUG
    /* Do a little validation on the top o-stack entry. */
    if (iosp >= osbot &&
	(r_type(iosp) == t__invalid || r_type(iosp) >= tx_next_op)
	) {
	lprintf("Invalid value on o-stack!\n");
	return_with_error_iref(e_Fatal);
    }
    if (gs_debug['I'] ||
	(gs_debug['i'] &&
	 (r_is_packed(iref_packed) ?
	  r_packed_is_name(iref_packed) :
	  r_has_type(IREF, t_name)))
	) {
	os_ptr save_osp = osp;	/* avoid side-effects */
	es_ptr save_esp = esp;

	osp = iosp;
	esp = iesp;
	dlprintf5("d%u,e%u<%u>0x%lx(%d): ",
		  ref_stack_count(&d_stack), ref_stack_count(&e_stack),
		  ref_stack_count(&o_stack), (ulong)IREF, icount);
	debug_print_ref(imemory, IREF);
	if (iosp >= osbot) {
	    dputs(" // ");
	    debug_print_ref(imemory, iosp);
	}
	dputc('\n');
	osp = save_osp;
	esp = save_esp;
	dflush();
    }
#endif
/* Objects that have attributes (arrays, dictionaries, files, and strings) */
/* use lit and exec; other objects use plain and plain_exec. */
#define lit(t) type_xe_value(t, a_execute)
#define exec(t) type_xe_value(t, a_execute + a_executable)
#define nox(t) type_xe_value(t, 0)
#define nox_exec(t) type_xe_value(t, a_executable)
#define plain(t) type_xe_value(t, 0)
#define plain_exec(t) type_xe_value(t, a_executable)
    /*
     * We have to populate enough cases of the switch statement to force
     * some compilers to use a dispatch rather than a testing loop.
     * What a nuisance!
     */
    switch (r_type_xe(iref_packed)) {
	    /* Access errors. */
#define cases_invalid()\
  case plain(t__invalid): case plain_exec(t__invalid)
	  cases_invalid():
	    return_with_error_iref(e_Fatal);
#define cases_nox()\
  case nox_exec(t_array): case nox_exec(t_dictionary):\
  case nox_exec(t_file): case nox_exec(t_string):\
  case nox_exec(t_mixedarray): case nox_exec(t_shortarray)
	  cases_nox():
	    return_with_error_iref(e_invalidaccess);
	    /*
	     * Literal objects.  We have to enumerate all the types.
	     * In fact, we have to include some extra plain_exec entries
	     * just to populate the switch.  We break them up into groups
	     * to avoid overflowing some preprocessors.
	     */
#define cases_lit_1()\
  case lit(t_array): case nox(t_array):\
  case plain(t_boolean): case plain_exec(t_boolean):\
  case lit(t_dictionary): case nox(t_dictionary)
#define cases_lit_2()\
  case lit(t_file): case nox(t_file):\
  case plain(t_fontID): case plain_exec(t_fontID):\
  case plain(t_integer): case plain_exec(t_integer):\
  case plain(t_mark): case plain_exec(t_mark)
#define cases_lit_3()\
  case plain(t_name):\
  case plain(t_null):\
  case plain(t_oparray):\
  case plain(t_operator)
#define cases_lit_4()\
  case plain(t_real): case plain_exec(t_real):\
  case plain(t_save): case plain_exec(t_save):\
  case lit(t_string): case nox(t_string)
#define cases_lit_5()\
  case lit(t_mixedarray): case nox(t_mixedarray):\
  case lit(t_shortarray): case nox(t_shortarray):\
  case plain(t_device): case plain_exec(t_device):\
  case plain(t_struct): case plain_exec(t_struct):\
  case plain(t_astruct): case plain_exec(t_astruct)
	    /* Executable arrays are treated as literals in direct execution. */
#define cases_lit_array()\
  case exec(t_array): case exec(t_mixedarray): case exec(t_shortarray)
	  cases_lit_1():
	  cases_lit_2():
	  cases_lit_3():
	  cases_lit_4():
	  cases_lit_5():
	    INCR(lit);
	    break;
	  cases_lit_array():
	    INCR(lit_array);
	    break;
	    /* Special operators. */
	case plain_exec(tx_op_add):
x_add:	    INCR(x_add);
	    if ((code = zop_add(iosp)) < 0)
		return_with_error_tx_op(code);
	    iosp--;
	    next_either();
	case plain_exec(tx_op_def):
x_def:	    INCR(x_def);
	    osp = iosp;	/* sync o_stack */
	    if ((code = zop_def(i_ctx_p)) < 0)
		return_with_error_tx_op(code);
	    iosp -= 2;
	    next_either();
	case plain_exec(tx_op_dup):
x_dup:	    INCR(x_dup);
	    if (iosp < osbot)
		return_with_error_tx_op(e_stackunderflow);
	    if (iosp >= ostop) {
		o_stack.requested = 1;
                return_with_error_tx_op(e_stackoverflow);
            }
	    iosp++;
	    ref_assign_inline(iosp, iosp - 1);
	    next_either();
	case plain_exec(tx_op_exch):
x_exch:	    INCR(x_exch);
	    if (iosp <= osbot)
		return_with_error_tx_op(e_stackunderflow);
	    ref_assign_inline(&token, iosp);
	    ref_assign_inline(iosp, iosp - 1);
	    ref_assign_inline(iosp - 1, &token);
	    next_either();
	case plain_exec(tx_op_if):
x_if:	    INCR(x_if);
	    if (!r_is_proc(iosp))
		return_with_error_tx_op(check_proc_failed(iosp));
	    if (!r_has_type(iosp - 1, t_boolean))
		return_with_error_tx_op((iosp <= osbot ?
					e_stackunderflow : e_typecheck));
	    if (!iosp[-1].value.boolval) {
		iosp -= 2;
		next_either();
	    }
	    if (iesp >= estop)
		return_with_error_tx_op(e_execstackoverflow);
	    store_state_either(iesp);
	    whichp = iosp;
	    iosp -= 2;
	    goto ifup;
	case plain_exec(tx_op_ifelse):
x_ifelse:   INCR(x_ifelse);
	    if (!r_is_proc(iosp))
		return_with_error_tx_op(check_proc_failed(iosp));
	    if (!r_is_proc(iosp - 1))
		return_with_error_tx_op(check_proc_failed(iosp - 1));
	    if (!r_has_type(iosp - 2, t_boolean))
		return_with_error_tx_op((iosp < osbot + 2 ?
					e_stackunderflow : e_typecheck));
	    if (iesp >= estop)
		return_with_error_tx_op(e_execstackoverflow);
	    store_state_either(iesp);
	    whichp = (iosp[-2].value.boolval ? iosp - 1 : iosp);
	    iosp -= 3;
	    /* Open code "up" for the array case(s) */
	  ifup:if ((icount = r_size(whichp) - 1) <= 0) {
		if (icount < 0)
		    goto up;	/* 0-element proc */
		SET_IREF(whichp->value.refs);	/* 1-element proc */
		if (--ticks_left > 0)
		    goto top;
	    }
	    ++iesp;
	    /* Do a ref_assign, but also set iref. */
	    iesp->tas = whichp->tas;
	    SET_IREF(iesp->value.refs = whichp->value.refs);
	    if (--ticks_left > 0)
		goto top;
	    goto slice;
	case plain_exec(tx_op_index):
x_index:    INCR(x_index);
	    osp = iosp;	/* zindex references o_stack */
	    if ((code = zindex(i_ctx_p)) < 0)
		return_with_error_tx_op(code);
	    next_either();
	case plain_exec(tx_op_pop):
x_pop:	    INCR(x_pop);
	    if (iosp < osbot)
		return_with_error_tx_op(e_stackunderflow);
	    iosp--;
	    next_either();
	case plain_exec(tx_op_roll):
x_roll:	    INCR(x_roll);
	    osp = iosp;	/* zroll references o_stack */
	    if ((code = zroll(i_ctx_p)) < 0)
		return_with_error_tx_op(code);
	    iosp -= 2;
	    next_either();
	case plain_exec(tx_op_sub):
x_sub:	    INCR(x_sub);
	    if ((code = zop_sub(iosp)) < 0)
		return_with_error_tx_op(code);
	    iosp--;
	    next_either();
	    /* Executable types. */
	case plain_exec(t_null):
	    goto bot;
	case plain_exec(t_oparray):
	    /* Replace with the definition and go again. */
	    INCR(exec_array);
	    opindex = op_index(IREF);
	    pvalue = IREF->value.const_refs;
	  opst:		/* Prepare to call a t_oparray procedure in *pvalue. */
	    store_state(iesp);
	  oppr:		/* Record the stack depths in case of failure. */
	    if (iesp >= estop - 4)
		return_with_error_iref(e_execstackoverflow);
	    iesp += 5;
	    osp = iosp;		/* ref_stack_count_inline needs this */
	    make_mark_estack(iesp - 4, es_other, oparray_cleanup);
	    make_int(iesp - 3, opindex); /* for .errorexec effect */
	    make_int(iesp - 2, ref_stack_count_inline(&o_stack));
	    make_int(iesp - 1, ref_stack_count_inline(&d_stack));
	    make_op_estack(iesp, oparray_pop);
	    goto pr;
	  prst:		/* Prepare to call the procedure (array) in *pvalue. */
	    store_state(iesp);
	  pr:			/* Call the array in *pvalue.  State has been stored. */
	    if ((icount = r_size(pvalue) - 1) <= 0) {
		if (icount < 0)
		    goto up;	/* 0-element proc */
		SET_IREF(pvalue->value.refs);	/* 1-element proc */
		if (--ticks_left > 0)
		    goto top;
	    }
	    if (iesp >= estop)
		return_with_error_iref(e_execstackoverflow);
	    ++iesp;
	    /* Do a ref_assign, but also set iref. */
	    iesp->tas = pvalue->tas;
	    SET_IREF(iesp->value.refs = pvalue->value.refs);
	    if (--ticks_left > 0)
		goto top;
	    goto slice;
	case plain_exec(t_operator):
	    INCR(exec_operator);
	    if (--ticks_left <= 0) {	/* The following doesn't work, */
		/* and I can't figure out why. */
/****** goto sst; ******/
	    }
	    esp = iesp;		/* save for operator */
	    osp = iosp;		/* ditto */
	    /* Operator routines take osp as an argument. */
	    /* This is just a convenience, since they adjust */
	    /* osp themselves to reflect the results. */
	    /* Operators that (net) push information on the */
	    /* operand stack must check for overflow: */
	    /* this normally happens automatically through */
	    /* the push macro (in oper.h). */
	    /* Operators that do not typecheck their operands, */
	    /* or take a variable number of arguments, */
	    /* must check explicitly for stack underflow. */
	    /* (See oper.h for more detail.) */
	    /* Note that each case must set iosp = osp: */
	    /* this is so we can switch on code without having to */
	    /* store it and reload it (for dumb compilers). */
	    switch (code = call_operator(real_opproc(IREF), i_ctx_p)) {
		case 0:	/* normal case */
		case 1:	/* alternative success case */
		    iosp = osp;
		    next();
		case o_push_estack:	/* store the state and go to up */
		    store_state(iesp);
		  opush:iosp = osp;
		    iesp = esp;
		    if (--ticks_left > 0)
			goto up;
		    goto slice;
		case o_pop_estack:	/* just go to up */
		  opop:iosp = osp;
		    if (esp == iesp)
			goto bot;
		    iesp = esp;
		    goto up;
		case o_reschedule:
		    store_state(iesp);
		    goto res;
		case e_RemapColor:
oe_remap:	    store_state(iesp);
remap:		    if (iesp + 2 >= estop) {
			esp = iesp;
			code = ref_stack_extend(&e_stack, 2);
			if (code < 0)
			    return_with_error_iref(code);
			iesp = esp;
		    }
		    packed_get(imemory, iref_packed, iesp + 1);
		    make_oper(iesp + 2, 0,
			      r_ptr(&istate->remap_color_info,
				    int_remap_color_info_t)->proc);
		    iesp += 2;
		    goto up;
	    }
	    iosp = osp;
	    iesp = esp;
	    return_with_code_iref();
	case plain_exec(t_name):
	    INCR(exec_name);
	    pvalue = IREF->value.pname->pvalue;
	    if (!pv_valid(pvalue)) {
		uint nidx = names_index(int_nt, IREF);
		uint htemp;

		INCR(find_name);
		if ((pvalue = dict_find_name_by_index_inline(nidx, htemp)) == 0)
		    return_with_error_iref(e_undefined);
	    }
	    /* Dispatch on the type of the value. */
	    /* Again, we have to over-populate the switch. */
	    switch (r_type_xe(pvalue)) {
		  cases_invalid():
		    return_with_error_iref(e_Fatal);
		  cases_nox():	/* access errors */
		    return_with_error_iref(e_invalidaccess);
		  cases_lit_1():
		  cases_lit_2():
		  cases_lit_3():
		  cases_lit_4():
		  cases_lit_5():
		      INCR(name_lit);
		    /* Just push the value */
		    if (iosp >= ostop)
			return_with_stackoverflow(pvalue);
		    ++iosp;
		    ref_assign_inline(iosp, pvalue);
		    next();
		case exec(t_array):
		case exec(t_mixedarray):
		case exec(t_shortarray):
		    INCR(name_proc);
		    /* This is an executable procedure, execute it. */
		    goto prst;
		case plain_exec(tx_op_add):
		    goto x_add;
		case plain_exec(tx_op_def):
		    goto x_def;
		case plain_exec(tx_op_dup):
		    goto x_dup;
		case plain_exec(tx_op_exch):
		    goto x_exch;
		case plain_exec(tx_op_if):
		    goto x_if;
		case plain_exec(tx_op_ifelse):
		    goto x_ifelse;
		case plain_exec(tx_op_index):
		    goto x_index;
		case plain_exec(tx_op_pop):
		    goto x_pop;
		case plain_exec(tx_op_roll):
		    goto x_roll;
		case plain_exec(tx_op_sub):
		    goto x_sub;
		case plain_exec(t_null):
		    goto bot;
		case plain_exec(t_oparray):
		    INCR(name_oparray);
		    opindex = op_index(pvalue);
		    pvalue = (const ref *)pvalue->value.const_refs;
		    goto opst;
		case plain_exec(t_operator):
		    INCR(name_operator);
		    {		/* Shortcut for operators. */
			/* See above for the logic. */
			if (--ticks_left <= 0) {	/* The following doesn't work, */
			    /* and I can't figure out why. */
/****** goto sst; ******/
			}
			esp = iesp;
			osp = iosp;
			switch (code = call_operator(real_opproc(pvalue),
						     i_ctx_p)
				) {
			    case 0:	/* normal case */
			    case 1:	/* alternative success case */
				iosp = osp;
				next();
			    case o_push_estack:
				store_state(iesp);
				goto opush;
			    case o_pop_estack:
				goto opop;
			    case o_reschedule:
				store_state(iesp);
				goto res;
			    case e_RemapColor:
				goto oe_remap;
			}
			iosp = osp;
			iesp = esp;
			return_with_error(code, pvalue);
		    }
		case plain_exec(t_name):
		case exec(t_file):
		case exec(t_string):
		default:
		    /* Not a procedure, reinterpret it. */
		    store_state(iesp);
		    icount = 0;
		    SET_IREF(pvalue);
		    goto top;
	    }
	case exec(t_file):
	    {	/* Executable file.  Read the next token and interpret it. */
		stream *s;
		scanner_state sstate;

		check_read_known_file(s, IREF, return_with_error_iref);
	    rt:
		if (iosp >= ostop)	/* check early */
		    return_with_stackoverflow_iref();
		osp = iosp;	/* scan_token uses ostack */
		scanner_init_options(&sstate, IREF, i_ctx_p->scanner_options);
	    again:
		code = scan_token(i_ctx_p, &token, &sstate);
		iosp = osp;	/* ditto */
		switch (code) {
		    case 0:	/* read a token */
			/* It's worth checking for literals, which make up */
			/* the majority of input tokens, before storing the */
			/* state on the e-stack.  Note that because of //, */
			/* the token may have *any* type and attributes. */
			/* Note also that executable arrays aren't executed */
			/* at the top level -- they're treated as literals. */
			if (!r_has_attr(&token, a_executable) ||
			    r_is_array(&token)
			    ) {	/* If scan_token used the o-stack, */
			    /* we know we can do a push now; if not, */
			    /* the pre-check is still valid. */
			    iosp++;
			    ref_assign_inline(iosp, &token);
			    goto rt;
			}
			store_state(iesp);
			/* Push the file on the e-stack */
			if (iesp >= estop)
			    return_with_error_iref(e_execstackoverflow);
			esfile_set_cache(++iesp);
			ref_assign_inline(iesp, IREF);
			SET_IREF(&token);
			icount = 0;
			goto top;
		    case e_undefined:	/* //name undefined */
			scanner_error_object(i_ctx_p, &sstate, &token);
			return_with_error(code, &token);
		    case scan_EOF:	/* end of file */
			esfile_clear_cache();
			goto bot;
		    case scan_BOS:
			/* Binary object sequences */
			/* ARE executed at the top level. */
			store_state(iesp);
			/* Push the file on the e-stack */
			if (iesp >= estop)
			    return_with_error_iref(e_execstackoverflow);
			esfile_set_cache(++iesp);
			ref_assign_inline(iesp, IREF);
			pvalue = &token;
			goto pr;
		    case scan_Refill:
			store_state(iesp);
			/* iref may point into the exec stack; */
			/* save its referent now. */
			ref_assign_inline(&token, IREF);
			/* Push the file on the e-stack */
			if (iesp >= estop)
			    return_with_error_iref(e_execstackoverflow);
			++iesp;
			ref_assign_inline(iesp, &token);
			esp = iesp;
			osp = iosp;
			code = scan_handle_refill(i_ctx_p, &sstate, true,
						  ztokenexec_continue);
		scan_cont:
			iosp = osp;
			iesp = esp;
			switch (code) {
			    case 0:
				iesp--;		/* don't push the file */
				goto again;	/* stacks are unchanged */
			    case o_push_estack:
				esfile_clear_cache();
				if (--ticks_left > 0)
				    goto up;
				goto slice;
			}
			/* must be an error */
			iesp--;	/* don't push the file */
			return_with_code_iref();
		    case scan_Comment:
		    case scan_DSC_Comment: {
			/* See scan_Refill above for comments. */
			ref file_token;

			store_state(iesp);
			ref_assign_inline(&file_token, IREF);
			if (iesp >= estop)
			    return_with_error_iref(e_execstackoverflow);
			++iesp;
			ref_assign_inline(iesp, &file_token);
			esp = iesp;
			osp = iosp;
			code = ztoken_handle_comment(i_ctx_p,
						     &sstate, &token,
						     code, true, true,
						     ztokenexec_continue);
		    }
			goto scan_cont;
		    default:	/* error */
			ref_assign_inline(&token, IREF);
			scanner_error_object(i_ctx_p, &sstate, &token);
			return_with_error(code, &token);
		}
	    }
	case exec(t_string):
	    {			/* Executable string.  Read a token and interpret it. */
		stream ss;
		scanner_state sstate;

		s_init(&ss, NULL);
		sread_string(&ss, IREF->value.bytes, r_size(IREF));
		scanner_init_stream_options(&sstate, &ss, SCAN_FROM_STRING);
		osp = iosp;	/* scan_token uses ostack */
		code = scan_token(i_ctx_p, &token, &sstate);
		iosp = osp;	/* ditto */
		switch (code) {
		    case 0:	/* read a token */
		    case scan_BOS:	/* binary object sequence */
			store_state(iesp);
			/* If the updated string isn't empty, push it back */
			/* on the e-stack. */
			{
			    uint size = sbufavailable(&ss);

			    if (size) {
				if (iesp >= estop)
				    return_with_error_iref(e_execstackoverflow);
				++iesp;
				iesp->tas.type_attrs = IREF->tas.type_attrs;
				iesp->value.const_bytes = sbufptr(&ss);
				r_set_size(iesp, size);
			    }
			}
			if (code == 0) {
			    SET_IREF(&token);
			    icount = 0;
			    goto top;
			}
			/* Handle BOS specially */
			pvalue = &token;
			goto pr;
		    case scan_EOF:	/* end of string */
			goto bot;
		    case scan_Refill:	/* error */
			code = gs_note_error(e_syntaxerror);
		    default:	/* error */
			ref_assign_inline(&token, IREF);
			scanner_error_object(i_ctx_p, &sstate, &token);
			return_with_error(code, &token);
		}
	    }
	    /* Handle packed arrays here by re-dispatching. */
	    /* This also picks up some anomalous cases of non-packed arrays. */
	default:
	    {
		uint index;

		switch (*iref_packed >> r_packed_type_shift) {
		    case pt_full_ref:
		    case pt_full_ref + 1:
			INCR(p_full);
			if (iosp >= ostop)
			    return_with_stackoverflow_iref();
			/* We know this can't be an executable object */
			/* requiring special handling, so we just push it. */
			++iosp;
			/* We know that refs are properly aligned: */
			/* see packed.h for details. */
			ref_assign_inline(iosp, IREF);
			next();
		    case pt_executable_operator:
			index = *iref_packed & packed_value_mask;
			if (--ticks_left <= 0) {	/* The following doesn't work, */
			    /* and I can't figure out why. */
/****** goto sst_short; ******/
			}
			if (!op_index_is_operator(index)) {
			    INCR(p_exec_oparray);
			    store_state_short(iesp);
			    opindex = index;
			    /* Call the operator procedure. */
			    index -= op_def_count;
			    pvalue = (const ref *)
				(index < r_size(&op_array_table_global.table) ?
			      op_array_table_global.table.value.const_refs +
				 index :
			       op_array_table_local.table.value.const_refs +
			    (index - r_size(&op_array_table_global.table)));
			    goto oppr;
			}
			INCR(p_exec_operator);
			/* See the main plain_exec(t_operator) case */
			/* for details of what happens here. */
#if PACKED_SPECIAL_OPS
			/*
			 * We arranged in iinit.c that the special ops
			 * have operator indices starting at 1.
			 *
			 * The (int) cast in the next line is required
			 * because some compilers don't allow arithmetic
			 * involving two different enumerated types.
			 */
#  define case_xop(xop) case xop - (int)tx_op + 1
			switch (index) {
			      case_xop(tx_op_add):goto x_add;
			      case_xop(tx_op_def):goto x_def;
			      case_xop(tx_op_dup):goto x_dup;
			      case_xop(tx_op_exch):goto x_exch;
			      case_xop(tx_op_if):goto x_if;
			      case_xop(tx_op_ifelse):goto x_ifelse;
			      case_xop(tx_op_index):goto x_index;
			      case_xop(tx_op_pop):goto x_pop;
			      case_xop(tx_op_roll):goto x_roll;
			      case_xop(tx_op_sub):goto x_sub;
			    case 0:	/* for dumb compilers */
			    default:
				;
			}
#  undef case_xop
#endif
			INCR(p_exec_non_x_operator);
			esp = iesp;
			osp = iosp;
			switch (code = call_operator(op_index_proc(index), i_ctx_p)) {
			    case 0:
			    case 1:
				iosp = osp;
				next_short();
			    case o_push_estack:
				store_state_short(iesp);
				goto opush;
			    case o_pop_estack:
				iosp = osp;
				if (esp == iesp) {
				    next_short();
				}
				iesp = esp;
				goto up;
			    case o_reschedule:
				store_state_short(iesp);
				goto res;
			    case e_RemapColor:
				store_state_short(iesp);
				goto remap;
			}
			iosp = osp;
			iesp = esp;
			return_with_code_iref();
		    case pt_integer:
			INCR(p_integer);
			if (iosp >= ostop)
			    return_with_stackoverflow_iref();
			++iosp;
			make_int(iosp,
				 ((int)*iref_packed & packed_int_mask) +
				 packed_min_intval);
			next_short();
		    case pt_literal_name:
			INCR(p_lit_name);
			{
			    uint nidx = *iref_packed & packed_value_mask;

			    if (iosp >= ostop)
				return_with_stackoverflow_iref();
			    ++iosp;
			    name_index_ref_inline(int_nt, nidx, iosp);
			    next_short();
			}
		    case pt_executable_name:
			INCR(p_exec_name);
			{
			    uint nidx = *iref_packed & packed_value_mask;

			    pvalue = name_index_ptr_inline(int_nt, nidx)->pvalue;
			    if (!pv_valid(pvalue)) {
				uint htemp;

				INCR(p_find_name);
				if ((pvalue = dict_find_name_by_index_inline(nidx, htemp)) == 0) {
				    names_index_ref(int_nt, nidx, &token);
				    return_with_error(e_undefined, &token);
				}
			    }
			    if (r_has_masked_attrs(pvalue, a_execute, a_execute + a_executable)) {	/* Literal, push it. */
				INCR(p_name_lit);
				if (iosp >= ostop)
				    return_with_stackoverflow_iref();
				++iosp;
				ref_assign_inline(iosp, pvalue);
				next_short();
			    }
			    if (r_is_proc(pvalue)) {	/* This is an executable procedure, */
				/* execute it. */
				INCR(p_name_proc);
				store_state_short(iesp);
				goto pr;
			    }
			    /* Not a literal or procedure, reinterpret it. */
			    store_state_short(iesp);
			    icount = 0;
			    SET_IREF(pvalue);
			    goto top;
			}
			/* default can't happen here */
		}
	    }
    }
    /* Literal type, just push it. */
    if (iosp >= ostop)
	return_with_stackoverflow_iref();
    ++iosp;
    ref_assign_inline(iosp, IREF);
  bot:next();
  out:				/* At most 1 more token in the current procedure. */
    /* (We already decremented icount.) */
    if (!icount) {
	/* Pop the execution stack for tail recursion. */
	iesp--;
	iref_packed = IREF_NEXT(iref_packed);
	goto top;
    }
  up:if (--ticks_left < 0)
	goto slice;
    /* See if there is anything left on the execution stack. */
    if (!r_is_proc(iesp)) {
	SET_IREF(iesp--);
	icount = 0;
	goto top;
    }
    SET_IREF(iesp->value.refs);	/* next element of array */
    icount = r_size(iesp) - 1;
    if (icount <= 0) {		/* <= 1 more elements */
	iesp--;			/* pop, or tail recursion */
	if (icount < 0)
	    goto up;
    }
    goto top;
res:
    /* Some operator has asked for context rescheduling. */
    /* We've done a store_state. */
    *pi_ctx_p = i_ctx_p;
    code = (*gs_interp_reschedule_proc)(pi_ctx_p);
    i_ctx_p = *pi_ctx_p;
  sched:			/* We've just called a scheduling procedure. */
    /* The interpreter state is in memory; iref is not current. */
    if (code < 0) {
	set_error(code);
	/*
	 * We need a real object to return as the error object.
	 * (It only has to last long enough to store in
	 * *perror_object.)
	 */
	make_null_proc(&ierror.full);
	SET_IREF(ierror.obj = &ierror.full);
	goto error_exit;
    }
    /* Reload state information from memory. */
    iosp = osp;
    iesp = esp;
    goto up;
#if 0				/****** ****** ***** */
  sst:				/* Time-slice, but push the current object first. */
    store_state(iesp);
    if (iesp >= estop)
	return_with_error_iref(e_execstackoverflow);
    iesp++;
    ref_assign_inline(iesp, iref);
#endif /****** ****** ***** */
  slice:			/* It's time to time-slice or garbage collect. */
    /* iref is not live, so we don't need to do a store_state. */
    osp = iosp;
    esp = iesp;
    /* If ticks_left <= -100, we need to GC now. */
    if (ticks_left <= -100) {	/* We need to garbage collect now. */
	*pi_ctx_p = i_ctx_p;
	code = interp_reclaim(pi_ctx_p, -1);
	i_ctx_p = *pi_ctx_p;
    } else if (gs_interp_time_slice_proc) {
	*pi_ctx_p = i_ctx_p;
	code = (*gs_interp_time_slice_proc)(pi_ctx_p);
	i_ctx_p = *pi_ctx_p;
    } else
	code = 0;
    ticks_left = gs_interp_time_slice_ticks;
    set_code_on_interrupt(imemory, &code);
    goto sched;

    /* Error exits. */

  rweci:
    ierror.code = code;
  rwei:
    ierror.obj = IREF;
  rwe:
    if (!r_is_packed(iref_packed))
	store_state(iesp);
    else {
	/*
	 * We need a real object to return as the error object.
	 * (It only has to last long enough to store in *perror_object.)
	 */
	packed_get(imemory, (const ref_packed *)ierror.obj, &ierror.full);
	store_state_short(iesp);
	if (IREF == ierror.obj)
	    SET_IREF(&ierror.full);
	ierror.obj = &ierror.full;
    }
  error_exit:
    if (ERROR_IS_INTERRUPT(ierror.code)) {	/* We must push the current object being interpreted */
	/* back on the e-stack so it will be re-executed. */
	/* Currently, this is always an executable operator, */
	/* but it might be something else someday if we check */
	/* for interrupts in the interpreter loop itself. */
	if (iesp >= estop)
	    code = e_execstackoverflow;
	else {
	    iesp++;
	    ref_assign_inline(iesp, IREF);
	}
    }
    esp = iesp;
    osp = iosp;
    ref_assign_inline(perror_object, ierror.obj);
#ifdef DEBUG
    if (ierror.code == e_InterpreterExit) {
	/* Do not call gs_log_error to reduce the noise. */
	return e_InterpreterExit;
    }
#endif
    return gs_log_error(ierror.code, __FILE__, ierror.line);
}

/* Pop the bookkeeping information for a normal exit from a t_oparray. */
static int
oparray_pop(i_ctx_t *i_ctx_p)
{
    esp -= 4;
    return o_pop_estack;
}

/* Restore the stack pointers after an error inside a t_oparray procedure. */
/* This procedure is called only from pop_estack. */
static int
oparray_cleanup(i_ctx_t *i_ctx_p)
{				/* esp points just below the cleanup procedure. */
    es_ptr ep = esp;
    uint ocount_old = (uint) ep[3].value.intval;
    uint dcount_old = (uint) ep[4].value.intval;
    uint ocount = ref_stack_count(&o_stack);
    uint dcount = ref_stack_count(&d_stack);

    if (ocount > ocount_old)
	ref_stack_pop(&o_stack, ocount - ocount_old);
    if (dcount > dcount_old) {
	ref_stack_pop(&d_stack, dcount - dcount_old);
	dict_set_top();
    }
    return 0;
}

/* Don't restore the stack pointers. */
static int
oparray_no_cleanup(i_ctx_t *i_ctx_p)
{
    return 0;
}

/* Find the innermost oparray. */
static ref *
oparray_find(i_ctx_t *i_ctx_p)
{
    long i;
    ref *ep;

    for (i = 0; (ep = ref_stack_index(&e_stack, i)) != 0; ++i) {
	if (r_is_estack_mark(ep) &&
	    (ep->value.opproc == oparray_cleanup ||
	     ep->value.opproc == oparray_no_cleanup)
	    )
	    return ep;
    }
    return 0;
}

/* <errorobj> <obj> .errorexec ... */
/* Execute an object, substituting errorobj for the 'command' if an error */
/* occurs during the execution.  Cf .execfile (in zfile.c). */
static int
zerrorexec(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    int code;

    check_op(2);
    check_estack(4);		/* mark/cleanup, errobj, pop, obj */
    push_mark_estack(es_other, errorexec_cleanup);
    *++esp = op[-1];
    push_op_estack(errorexec_pop);
    code = zexec(i_ctx_p);
    if (code >= 0)
	pop(1);
    else
	esp -= 3;		/* undo our additions to estack */
    return code;
}

/* - .finderrorobject <errorobj> true */
/* - .finderrorobject false */
/* If we are within an .errorexec or oparray, return the error object */
/* and true, otherwise return false. */
static int
zfinderrorobject(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    ref errobj;

    if (errorexec_find(i_ctx_p, &errobj)) {
	push(2);
	op[-1] = errobj;
	make_true(op);
    } else {
	push(1);
	make_false(op);
    }
    return 0;
}

/*
 * Find the innermost .errorexec or oparray.  If there is an oparray, or a
 * .errorexec with errobj != null, store it in *perror_object and return 1,
 * otherwise return 0;
 */
static int
errorexec_find(i_ctx_t *i_ctx_p, ref *perror_object)
{
    long i;
    const ref *ep;

    for (i = 0; (ep = ref_stack_index(&e_stack, i)) != 0; ++i) {
	if (r_is_estack_mark(ep)) {
	    if (ep->value.opproc == oparray_cleanup) {
		/* See oppr: above. */
		uint opindex = (uint)ep[1].value.intval;
		if (opindex == 0) /* internal operator, ignore */
		    continue;
		op_index_ref(opindex, perror_object);
		return 1;
	    }
	    if (ep->value.opproc == oparray_no_cleanup)
		return 0;	/* protection disabled */
	    if (ep->value.opproc == errorexec_cleanup) {
		if (r_has_type(ep + 1, t_null))
		    return 0;
		*perror_object = ep[1];	/* see .errorexec above */
		return 1;
	    }
	}
    }
    return 0;
}

/* Pop the bookkeeping information on a normal exit from .errorexec. */
static int
errorexec_pop(i_ctx_t *i_ctx_p)
{
    esp -= 2;
    return o_pop_estack;
}

/* Clean up when unwinding the stack on an error.  (No action needed.) */
static int
errorexec_cleanup(i_ctx_t *i_ctx_p)
{
    return 0;
}

/* <bool> .setstackprotect - */
/* Set whether to protect the stack for the innermost oparray. */
static int
zsetstackprotect(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    ref *ep = oparray_find(i_ctx_p);

    check_type(*op, t_boolean);
    if (ep == 0)
	return_error(e_rangecheck);
    ep->value.opproc =
	(op->value.boolval ? oparray_cleanup : oparray_no_cleanup);
    pop(1);
    return 0;
}

/* - .currentstackprotect <bool> */
/* Return the stack protection status. */
static int
zcurrentstackprotect(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    ref *ep = oparray_find(i_ctx_p);

    if (ep == 0)
	return_error(e_rangecheck);
    push(1);
    make_bool(op, ep->value.opproc == oparray_cleanup);
    return 0;
}