summaryrefslogtreecommitdiff
path: root/Master/tlpkg/tlperl/lib/B/Concise.pm
blob: 284f797612cc3c7d4899d2a2170b6c9e56d24b35 (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
package B::Concise;
# Copyright (C) 2000-2003 Stephen McCamant. All rights reserved.
# This program is free software; you can redistribute and/or modify it
# under the same terms as Perl itself.

# Note: we need to keep track of how many use declarations/BEGIN
# blocks this module uses, so we can avoid printing them when user
# asks for the BEGIN blocks in her program. Update the comments and
# the count in concise_specials if you add or delete one. The
# -MO=Concise counts as use #1.

use strict; # use #2
use warnings; # uses #3 and #4, since warnings uses Carp

use Exporter (); # use #5

our $VERSION   = "0.76";
our @ISA       = qw(Exporter);
our @EXPORT_OK = qw( set_style set_style_standard add_callback
		     concise_subref concise_cv concise_main
		     add_style walk_output compile reset_sequence );
our %EXPORT_TAGS =
    ( io	=> [qw( walk_output compile reset_sequence )],
      style	=> [qw( add_style set_style_standard )],
      cb	=> [qw( add_callback )],
      mech	=> [qw( concise_subref concise_cv concise_main )],  );

# use #6
use B qw(class ppname main_start main_root main_cv cstring svref_2object
	 SVf_IOK SVf_NOK SVf_POK SVf_IVisUV SVf_FAKE OPf_KIDS OPf_SPECIAL
	 CVf_ANON PAD_FAKELEX_ANON PAD_FAKELEX_MULTI SVf_ROK);

my %style =
  ("terse" =>
   ["(?(#label =>\n)?)(*(    )*)#class (#addr) #name (?([#targ])?) "
    . "#svclass~(?((#svaddr))?)~#svval~(?(label \"#coplabel\")?)\n",
    "(*(    )*)goto #class (#addr)\n",
    "#class pp_#name"],
   "concise" =>
   ["#hyphseq2 (*(   (x( ;)x))*)<#classsym> #exname#arg(?([#targarglife])?)"
    . "~#flags(?(/#private)?)(?(:#hints)?)(x(;~->#next)x)\n"
    , "  (*(    )*)     goto #seq\n",
    "(?(<#seq>)?)#exname#arg(?([#targarglife])?)"],
   "linenoise" =>
   ["(x(;(*( )*))x)#noise#arg(?([#targarg])?)(x( ;\n)x)",
    "gt_#seq ",
    "(?(#seq)?)#noise#arg(?([#targarg])?)"],
   "debug" =>
   ["#class (#addr)\n\top_next\t\t#nextaddr\n\top_sibling\t#sibaddr\n\t"
    . "op_ppaddr\tPL_ppaddr[OP_#NAME]\n\top_type\t\t#typenum\n" .
    ($] > 5.009 ? '' : "\top_seq\t\t#seqnum\n")
    . "\top_flags\t#flagval\n\top_private\t#privval\t#hintsval\n"
    . "(?(\top_first\t#firstaddr\n)?)(?(\top_last\t\t#lastaddr\n)?)"
    . "(?(\top_sv\t\t#svaddr\n)?)",
    "    GOTO #addr\n",
    "#addr"],
   "env" => [$ENV{B_CONCISE_FORMAT}, $ENV{B_CONCISE_GOTO_FORMAT},
	     $ENV{B_CONCISE_TREE_FORMAT}],
  );

# Renderings, ie how Concise prints, is controlled by these vars
# primary:
our $stylename;		# selects current style from %style
my $order = "basic";	# how optree is walked & printed: basic, exec, tree

# rendering mechanics:
# these 'formats' are the line-rendering templates
# they're updated from %style when $stylename changes
my ($format, $gotofmt, $treefmt);

# lesser players:
my $base = 36;		# how <sequence#> is displayed
my $big_endian = 1;	# more <sequence#> display
my $tree_style = 0;	# tree-order details
my $banner = 1;		# print banner before optree is traversed
my $do_main = 0;	# force printing of main routine
my $show_src;		# show source code

# another factor: can affect all styles!
our @callbacks;		# allow external management

set_style_standard("concise");

my $curcv;
my $cop_seq_base;

sub set_style {
    ($format, $gotofmt, $treefmt) = @_;
    #warn "set_style: deprecated, use set_style_standard instead\n"; # someday
    die "expecting 3 style-format args\n" unless @_ == 3;
}

sub add_style {
    my ($newstyle,@args) = @_;
    die "style '$newstyle' already exists, choose a new name\n"
	if exists $style{$newstyle};
    die "expecting 3 style-format args\n" unless @args == 3;
    $style{$newstyle} = [@args];
    $stylename = $newstyle; # update rendering state
}

sub set_style_standard {
    ($stylename) = @_; # update rendering state
    die "err: style '$stylename' unknown\n" unless exists $style{$stylename};
    set_style(@{$style{$stylename}});
}

sub add_callback {
    push @callbacks, @_;
}

# output handle, used with all Concise-output printing
our $walkHandle;	# public for your convenience
BEGIN { $walkHandle = \*STDOUT }

sub walk_output { # updates $walkHandle
    my $handle = shift;
    return $walkHandle unless $handle; # allow use as accessor

    if (ref $handle eq 'SCALAR') {
	require Config;
	die "no perlio in this build, can't call walk_output (\\\$scalar)\n"
	    unless $Config::Config{useperlio};
	# in 5.8+, open(FILEHANDLE,MODE,REFERENCE) writes to string
	open my $tmp, '>', $handle;	# but cant re-set existing STDOUT
	$walkHandle = $tmp;		# so use my $tmp as intermediate var
	return $walkHandle;
    }
    my $iotype = ref $handle;
    die "expecting argument/object that can print\n"
	unless $iotype eq 'GLOB' or $iotype and $handle->can('print');
    $walkHandle = $handle;
}

sub concise_subref {
    my($order, $coderef, $name) = @_;
    my $codeobj = svref_2object($coderef);

    return concise_stashref(@_)
	unless ref $codeobj eq 'B::CV';
    concise_cv_obj($order, $codeobj, $name);
}

sub concise_stashref {
    my($order, $h) = @_;
    local *s;
    foreach my $k (sort keys %$h) {
	next unless defined $h->{$k};
	*s = $h->{$k};
	my $coderef = *s{CODE} or next;
	reset_sequence();
	print "FUNC: ", *s, "\n";
	my $codeobj = svref_2object($coderef);
	next unless ref $codeobj eq 'B::CV';
	eval { concise_cv_obj($order, $codeobj, $k) };
	warn "err $@ on $codeobj" if $@;
    }
}

# This should have been called concise_subref, but it was exported
# under this name in versions before 0.56
*concise_cv = \&concise_subref;

sub concise_cv_obj {
    my ($order, $cv, $name) = @_;
    # name is either a string, or a CODE ref (copy of $cv arg??)

    $curcv = $cv;

    if (ref($cv->XSUBANY) =~ /B::(\w+)/) {
	print $walkHandle "$name is a constant sub, optimized to a $1\n";
	return;
    }
    if ($cv->XSUB) {
	print $walkHandle "$name is XS code\n";
	return;
    }
    if (class($cv->START) eq "NULL") {
	no strict 'refs';
	if (ref $name eq 'CODE') {
	    print $walkHandle "coderef $name has no START\n";
	}
	elsif (exists &$name) {
	    print $walkHandle "$name exists in stash, but has no START\n";
	}
	else {
	    print $walkHandle "$name not in symbol table\n";
	}
	return;
    }
    sequence($cv->START);
    if ($order eq "exec") {
	walk_exec($cv->START);
    }
    elsif ($order eq "basic") {
	# walk_topdown($cv->ROOT, sub { $_[0]->concise($_[1]) }, 0);
	my $root = $cv->ROOT;
	unless (ref $root eq 'B::NULL') {
	    walk_topdown($root, sub { $_[0]->concise($_[1]) }, 0);
	} else {
	    print $walkHandle "B::NULL encountered doing ROOT on $cv. avoiding disaster\n";
	}
    } else {
	print $walkHandle tree($cv->ROOT, 0);
    }
}

sub concise_main {
    my($order) = @_;
    sequence(main_start);
    $curcv = main_cv;
    if ($order eq "exec") {
	return if class(main_start) eq "NULL";
	walk_exec(main_start);
    } elsif ($order eq "tree") {
	return if class(main_root) eq "NULL";
	print $walkHandle tree(main_root, 0);
    } elsif ($order eq "basic") {
	return if class(main_root) eq "NULL";
	walk_topdown(main_root,
		     sub { $_[0]->concise($_[1]) }, 0);
    }
}

sub concise_specials {
    my($name, $order, @cv_s) = @_;
    my $i = 1;
    if ($name eq "BEGIN") {
	splice(@cv_s, 0, 8); # skip 7 BEGIN blocks in this file. NOW 8 ??
    } elsif ($name eq "CHECK") {
	pop @cv_s; # skip the CHECK block that calls us
    }
    for my $cv (@cv_s) {
	print $walkHandle "$name $i:\n";
	$i++;
	concise_cv_obj($order, $cv, $name);
    }
}

my $start_sym = "\e(0"; # "\cN" sometimes also works
my $end_sym   = "\e(B"; # "\cO" respectively

my @tree_decorations =
  (["  ", "--", "+-", "|-", "| ", "`-", "-", 1],
   [" ", "-", "+", "+", "|", "`", "", 0],
   ["  ", map("$start_sym$_$end_sym", "qq", "wq", "tq", "x ", "mq", "q"), 1],
   [" ", map("$start_sym$_$end_sym", "q", "w", "t", "x", "m"), "", 0],
  );

my @render_packs; # collect -stash=<packages>

sub compileOpts {
    # set rendering state from options and args
    my (@options,@args);
    if (@_) {
	@options = grep(/^-/, @_);
	@args = grep(!/^-/, @_);
    }
    for my $o (@options) {
	# mode/order
	if ($o eq "-basic") {
	    $order = "basic";
	} elsif ($o eq "-exec") {
	    $order = "exec";
	} elsif ($o eq "-tree") {
	    $order = "tree";
	}
	# tree-specific
	elsif ($o eq "-compact") {
	    $tree_style |= 1;
	} elsif ($o eq "-loose") {
	    $tree_style &= ~1;
	} elsif ($o eq "-vt") {
	    $tree_style |= 2;
	} elsif ($o eq "-ascii") {
	    $tree_style &= ~2;
	}
	# sequence numbering
	elsif ($o =~ /^-base(\d+)$/) {
	    $base = $1;
	} elsif ($o eq "-bigendian") {
	    $big_endian = 1;
	} elsif ($o eq "-littleendian") {
	    $big_endian = 0;
	}
	# miscellaneous, presentation
	elsif ($o eq "-nobanner") {
	    $banner = 0;
	} elsif ($o eq "-banner") {
	    $banner = 1;
	}
	elsif ($o eq "-main") {
	    $do_main = 1;
	} elsif ($o eq "-nomain") {
	    $do_main = 0;
	} elsif ($o eq "-src") {
	    $show_src = 1;
	}
	elsif ($o =~ /^-stash=(.*)/) {
	    my $pkg = $1;
	    no strict 'refs';
	    if (!defined %{$pkg.'::'}) {
		eval "require $pkg";
	    } else {
		require Config;
		if (!$Config::Config{usedl}
		    && keys %{$pkg.'::'} == 1
		    && $pkg->can('bootstrap')) {
		    # It is something that we're staticly linked to, but hasn't
		    # yet been used.
		    eval "require $pkg";
		}
	    }
	    push @render_packs, $pkg;
	}
	# line-style options
	elsif (exists $style{substr($o, 1)}) {
	    $stylename = substr($o, 1);
	    set_style_standard($stylename);
	} else {
	    warn "Option $o unrecognized";
	}
    }
    return (@args);
}

sub compile {
    my (@args) = compileOpts(@_);
    return sub {
	my @newargs = compileOpts(@_); # accept new rendering options
	warn "disregarding non-options: @newargs\n" if @newargs;

	for my $objname (@args) {
	    next unless $objname; # skip null args to avoid noisy responses

	    if ($objname eq "BEGIN") {
		concise_specials("BEGIN", $order,
				 B::begin_av->isa("B::AV") ?
				 B::begin_av->ARRAY : ());
	    } elsif ($objname eq "INIT") {
		concise_specials("INIT", $order,
				 B::init_av->isa("B::AV") ?
				 B::init_av->ARRAY : ());
	    } elsif ($objname eq "CHECK") {
		concise_specials("CHECK", $order,
				 B::check_av->isa("B::AV") ?
				 B::check_av->ARRAY : ());
	    } elsif ($objname eq "UNITCHECK") {
		concise_specials("UNITCHECK", $order,
				 B::unitcheck_av->isa("B::AV") ?
				 B::unitcheck_av->ARRAY : ());
	    } elsif ($objname eq "END") {
		concise_specials("END", $order,
				 B::end_av->isa("B::AV") ?
				 B::end_av->ARRAY : ());
	    }
	    else {
		# convert function names to subrefs
		my $objref;
		if (ref $objname) {
		    print $walkHandle "B::Concise::compile($objname)\n"
			if $banner;
		    $objref = $objname;
		} else {
		    $objname = "main::" . $objname unless $objname =~ /::/;
		    print $walkHandle "$objname:\n";
		    no strict 'refs';
		    unless (exists &$objname) {
			print $walkHandle "err: unknown function ($objname)\n";
			return;
		    }
		    $objref = \&$objname;
		}
		concise_subref($order, $objref, $objname);
	    }
	}
	for my $pkg (@render_packs) {
	    no strict 'refs';
	    concise_stashref($order, \%{$pkg.'::'});
	}

	if (!@args or $do_main or @render_packs) {
	    print $walkHandle "main program:\n" if $do_main;
	    concise_main($order);
	}
	return @args;	# something
    }
}

my %labels;
my $lastnext;	# remembers op-chain, used to insert gotos

my %opclass = ('OP' => "0", 'UNOP' => "1", 'BINOP' => "2", 'LOGOP' => "|",
	       'LISTOP' => "@", 'PMOP' => "/", 'SVOP' => "\$", 'GVOP' => "*",
	       'PVOP' => '"', 'LOOP' => "{", 'COP' => ";", 'PADOP' => "#");

no warnings 'qw'; # "Possible attempt to put comments..."; use #7
my @linenoise =
  qw'#  () sc (  @? 1  $* gv *{ m$ m@ m% m? p/ *$ $  $# & a& pt \\ s\\ rf bl
     `  *? <> ?? ?/ r/ c/ // qr s/ /c y/ =  @= C  sC Cp sp df un BM po +1 +I
     -1 -I 1+ I+ 1- I- ** *  i* /  i/ %$ i% x  +  i+ -  i- .  "  << >> <  i<
     >  i> <= i, >= i. == i= != i! <? i? s< s> s, s. s= s! s? b& b^ b| -0 -i
     !  ~  a2 si cs rd sr e^ lg sq in %x %o ab le ss ve ix ri sf FL od ch cy
     uf lf uc lc qm @  [f [  @[ eh vl ky dl ex %  ${ @{ uk pk st jn )  )[ a@
     a% sl +] -] [- [+ so rv GS GW MS MW .. f. .f && || ^^ ?: &= |= -> s{ s}
     v} ca wa di rs ;; ;  ;d }{ {  }  {} f{ it {l l} rt }l }n }r dm }g }e ^o
     ^c ^| ^# um bm t~ u~ ~d DB db ^s se ^g ^r {w }w pf pr ^O ^K ^R ^W ^d ^v
     ^e ^t ^k t. fc ic fl .s .p .b .c .l .a .h g1 s1 g2 s2 ?. l? -R -W -X -r
     -w -x -e -o -O -z -s -M -A -C -S -c -b -f -d -p -l -u -g -k -t -T -B cd
     co cr u. cm ut r. l@ s@ r@ mD uD oD rD tD sD wD cD f$ w$ p$ sh e$ k$ g3
     g4 s4 g5 s5 T@ C@ L@ G@ A@ S@ Hg Hc Hr Hw Mg Mc Ms Mr Sg Sc So rq do {e
     e} {t t} g6 G6 6e g7 G7 7e g8 G8 8e g9 G9 9e 6s 7s 8s 9s 6E 7E 8E 9E Pn
     Pu GP SP EP Gn Gg GG SG EG g0 c$ lk t$ ;s n> // /= CO';

my $chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

sub op_flags { # common flags (see BASOP.op_flags in op.h)
    my($x) = @_;
    my(@v);
    push @v, "v" if ($x & 3) == 1;
    push @v, "s" if ($x & 3) == 2;
    push @v, "l" if ($x & 3) == 3;
    push @v, "K" if $x & 4;
    push @v, "P" if $x & 8;
    push @v, "R" if $x & 16;
    push @v, "M" if $x & 32;
    push @v, "S" if $x & 64;
    push @v, "*" if $x & 128;
    return join("", @v);
}

sub base_n {
    my $x = shift;
    return "-" . base_n(-$x) if $x < 0;
    my $str = "";
    do { $str .= substr($chars, $x % $base, 1) } while $x = int($x / $base);
    $str = reverse $str if $big_endian;
    return $str;
}

my %sequence_num;
my $seq_max = 1;

sub reset_sequence {
    # reset the sequence
    %sequence_num = ();
    $seq_max = 1;
    $lastnext = 0;
}

sub seq {
    my($op) = @_;
    return "-" if not exists $sequence_num{$$op};
    return base_n($sequence_num{$$op});
}

sub walk_topdown {
    my($op, $sub, $level) = @_;
    $sub->($op, $level);
    if ($op->flags & OPf_KIDS) {
	for (my $kid = $op->first; $$kid; $kid = $kid->sibling) {
	    walk_topdown($kid, $sub, $level + 1);
	}
    }
    elsif (class($op) eq "PMOP") {
	my $maybe_root = $op->pmreplroot;
	if (ref($maybe_root) and $maybe_root->isa("B::OP")) {
	    # It really is the root of the replacement, not something
	    # else stored here for lack of space elsewhere
	    walk_topdown($maybe_root, $sub, $level + 1);
	}
    }
}

sub walklines {
    my($ar, $level) = @_;
    for my $l (@$ar) {
	if (ref($l) eq "ARRAY") {
	    walklines($l, $level + 1);
	} else {
	    $l->concise($level);
	}
    }
}

sub walk_exec {
    my($top, $level) = @_;
    my %opsseen;
    my @lines;
    my @todo = ([$top, \@lines]);
    while (@todo and my($op, $targ) = @{shift @todo}) {
	for (; $$op; $op = $op->next) {
	    last if $opsseen{$$op}++;
	    push @$targ, $op;
	    my $name = $op->name;
	    if (class($op) eq "LOGOP") {
		my $ar = [];
		push @$targ, $ar;
		push @todo, [$op->other, $ar];
	    } elsif ($name eq "subst" and $ {$op->pmreplstart}) {
		my $ar = [];
		push @$targ, $ar;
		push @todo, [$op->pmreplstart, $ar];
	    } elsif ($name =~ /^enter(loop|iter)$/) {
		if ($] > 5.009) {
		    $labels{${$op->nextop}} = "NEXT";
		    $labels{${$op->lastop}} = "LAST";
		    $labels{${$op->redoop}} = "REDO";
		} else {
		    $labels{$op->nextop->seq} = "NEXT";
		    $labels{$op->lastop->seq} = "LAST";
		    $labels{$op->redoop->seq} = "REDO";		
		}
	    }
	}
    }
    walklines(\@lines, 0);
}

# The structure of this routine is purposely modeled after op.c's peep()
sub sequence {
    my($op) = @_;
    my $oldop = 0;
    return if class($op) eq "NULL" or exists $sequence_num{$$op};
    for (; $$op; $op = $op->next) {
	last if exists $sequence_num{$$op};
	my $name = $op->name;
	if ($name =~ /^(null|scalar|lineseq|scope)$/) {
	    next if $oldop and $ {$op->next};
	} else {
	    $sequence_num{$$op} = $seq_max++;
	    if (class($op) eq "LOGOP") {
		my $other = $op->other;
		$other = $other->next while $other->name eq "null";
		sequence($other);
	    } elsif (class($op) eq "LOOP") {
		my $redoop = $op->redoop;
		$redoop = $redoop->next while $redoop->name eq "null";
		sequence($redoop);
		my $nextop = $op->nextop;
		$nextop = $nextop->next while $nextop->name eq "null";
		sequence($nextop);
		my $lastop = $op->lastop;
		$lastop = $lastop->next while $lastop->name eq "null";
		sequence($lastop);
	    } elsif ($name eq "subst" and $ {$op->pmreplstart}) {
		my $replstart = $op->pmreplstart;
		$replstart = $replstart->next while $replstart->name eq "null";
		sequence($replstart);
	    }
	}
	$oldop = $op;
    }
}

sub fmt_line {    # generate text-line for op.
    my($hr, $op, $text, $level) = @_;

    $_->($hr, $op, \$text, \$level, $stylename) for @callbacks;

    return '' if $hr->{SKIP};	# suppress line if a callback said so
    return '' if $hr->{goto} and $hr->{goto} eq '-';	# no goto nowhere

    # spec: (?(text1#varText2)?)
    $text =~ s/\(\?\(([^\#]*?)\#(\w+)([^\#]*?)\)\?\)/
	$hr->{$2} ? $1.$hr->{$2}.$3 : ""/eg;

    # spec: (x(exec_text;basic_text)x)
    $text =~ s/\(x\((.*?);(.*?)\)x\)/$order eq "exec" ? $1 : $2/egs;

    # spec: (*(text)*)
    $text =~ s/\(\*\(([^;]*?)\)\*\)/$1 x $level/egs;

    # spec: (*(text1;text2)*)
    $text =~ s/\(\*\((.*?);(.*?)\)\*\)/$1 x ($level - 1) . $2 x ($level>0)/egs;

    # convert #Var to tag=>val form: Var\t#var
    $text =~ s/\#([A-Z][a-z]+)(\d+)?/\t\u$1\t\L#$1$2/gs;

    # spec: #varN
    $text =~ s/\#([a-zA-Z]+)(\d+)/sprintf("%-$2s", $hr->{$1})/eg;

    $text =~ s/\#([a-zA-Z]+)/$hr->{$1}/eg;	# populate #var's
    $text =~ s/[ \t]*~+[ \t]*/ /g;		# squeeze tildes

    $text = "# $hr->{src}\n$text" if $show_src and $hr->{src};

    chomp $text;
    return "$text\n" if $text ne "";
    return $text; # suppress empty lines
}

our %priv; # used to display each opcode's BASEOP.op_private values

$priv{$_}{128} = "LVINTRO"
  for ("pos", "substr", "vec", "threadsv", "gvsv", "rv2sv", "rv2hv", "rv2gv",
       "rv2av", "rv2arylen", "aelem", "helem", "aslice", "hslice", "padsv",
       "padav", "padhv", "enteriter");
$priv{$_}{64} = "REFC" for ("leave", "leavesub", "leavesublv", "leavewrite");
$priv{"aassign"}{64} = "COMMON";
$priv{"aassign"}{32} = $] < 5.009 ? "PHASH" : "STATE";
$priv{"sassign"}{32} = "STATE";
$priv{"sassign"}{64} = "BKWARD";
$priv{$_}{64} = "RTIME" for ("match", "subst", "substcont", "qr");
@{$priv{"trans"}}{1,2,4,8,16,64} = ("<UTF", ">UTF", "IDENT", "SQUASH", "DEL",
				    "COMPL", "GROWS");
$priv{"repeat"}{64} = "DOLIST";
$priv{"leaveloop"}{64} = "CONT";
@{$priv{$_}}{32,64,96} = ("DREFAV", "DREFHV", "DREFSV")
  for (qw(rv2gv rv2sv padsv aelem helem));
$priv{$_}{16} = "STATE" for ("padav", "padhv", "padsv");
@{$priv{"entersub"}}{16,32,64} = ("DBG","TARG","NOMOD");
@{$priv{$_}}{4,8,128} = ("INARGS","AMPER","NO()") for ("entersub", "rv2cv");
$priv{"gv"}{32} = "EARLYCV";
$priv{"aelem"}{16} = $priv{"helem"}{16} = "LVDEFER";
$priv{$_}{16} = "OURINTR" for ("gvsv", "rv2sv", "rv2av", "rv2hv", "r2gv",
	"enteriter");
$priv{$_}{16} = "TARGMY"
  for (map(($_,"s$_"),"chop", "chomp"),
       map(($_,"i_$_"), "postinc", "postdec", "multiply", "divide", "modulo",
	   "add", "subtract", "negate"), "pow", "concat", "stringify",
       "left_shift", "right_shift", "bit_and", "bit_xor", "bit_or",
       "complement", "atan2", "sin", "cos", "rand", "exp", "log", "sqrt",
       "int", "hex", "oct", "abs", "length", "index", "rindex", "sprintf",
       "ord", "chr", "crypt", "quotemeta", "join", "push", "unshift", "flock",
       "chdir", "chown", "chroot", "unlink", "chmod", "utime", "rename",
       "link", "symlink", "mkdir", "rmdir", "wait", "waitpid", "system",
       "exec", "kill", "getppid", "getpgrp", "setpgrp", "getpriority",
       "setpriority", "time", "sleep");
$priv{$_}{4} = "REVERSED" for ("enteriter", "iter");
@{$priv{"const"}}{4,8,16,32,64,128} = ("SHORT","STRICT","ENTERED",'$[',"BARE","WARN");
$priv{"flip"}{64} = $priv{"flop"}{64} = "LINENUM";
$priv{"list"}{64} = "GUESSED";
$priv{"delete"}{64} = "SLICE";
$priv{"exists"}{64} = "SUB";
@{$priv{"sort"}}{1,2,4,8,16,32,64} = ("NUM", "INT", "REV", "INPLACE","DESC","QSORT","STABLE");
$priv{"threadsv"}{64} = "SVREFd";
@{$priv{$_}}{16,32,64,128} = ("INBIN","INCR","OUTBIN","OUTCR")
  for ("open", "backtick");
$priv{"exit"}{128} = "VMS";
$priv{$_}{2} = "FTACCESS"
  for ("ftrread", "ftrwrite", "ftrexec", "fteread", "ftewrite", "fteexec");
$priv{"entereval"}{2} = "HAS_HH";
if ($] >= 5.009) {
  # Stacked filetests are post 5.8.x
  $priv{$_}{4} = "FTSTACKED"
    for ("ftrread", "ftrwrite", "ftrexec", "fteread", "ftewrite", "fteexec",
         "ftis", "fteowned", "ftrowned", "ftzero", "ftsize", "ftmtime",
	 "ftatime", "ftctime", "ftsock", "ftchr", "ftblk", "ftfile", "ftdir",
	 "ftpipe", "ftlink", "ftsuid", "ftsgid", "ftsvtx", "fttty", "fttext",
	 "ftbinary");
  # Lexical $_ is post 5.8.x
  $priv{$_}{2} = "GREPLEX"
    for ("mapwhile", "mapstart", "grepwhile", "grepstart");
}

our %hints; # used to display each COP's op_hints values

# strict refs, subs, vars
@hints{2,512,1024} = ('$', '&', '*');
# integers, locale, bytes, arybase
@hints{1,4,8,16,32} = ('i', 'l', 'b', '[');
# block scope, localise %^H, $^OPEN (in), $^OPEN (out)
@hints{256,131072,262144,524288} = ('{','%','<','>');
# overload new integer, float, binary, string, re
@hints{4096,8192,16384,32768,65536} = ('I', 'F', 'B', 'S', 'R');
# taint and eval
@hints{1048576,2097152} = ('T', 'E');
# filetest access, UTF-8
@hints{4194304,8388608} = ('X', 'U');

sub _flags {
    my($hash, $x) = @_;
    my @s;
    for my $flag (sort {$b <=> $a} keys %$hash) {
	if ($hash->{$flag} and $x & $flag and $x >= $flag) {
	    $x -= $flag;
	    push @s, $hash->{$flag};
	}
    }
    push @s, $x if $x;
    return join(",", @s);
}

sub private_flags {
    my($name, $x) = @_;
    _flags($priv{$name}, $x);
}

sub hints_flags {
    my($x) = @_;
    _flags(\%hints, $x);
}

sub concise_sv {
    my($sv, $hr, $preferpv) = @_;
    $hr->{svclass} = class($sv);
    $hr->{svclass} = "UV"
      if $hr->{svclass} eq "IV" and $sv->FLAGS & SVf_IVisUV;
    Carp::cluck("bad concise_sv: $sv") unless $sv and $$sv;
    $hr->{svaddr} = sprintf("%#x", $$sv);
    if ($hr->{svclass} eq "GV" && $sv->isGV_with_GP()) {
	my $gv = $sv;
	my $stash = $gv->STASH->NAME; if ($stash eq "main") {
	    $stash = "";
	} else {
	    $stash = $stash . "::";
	}
	$hr->{svval} = "*$stash" . $gv->SAFENAME;
	return "*$stash" . $gv->SAFENAME;
    } else {
	if ($] >= 5.011) {
	    while (class($sv) eq "IV" && $sv->FLAGS & SVf_ROK) {
		$hr->{svval} .= "\\";
		$sv = $sv->RV;
	    }
	} else {
	    while (class($sv) eq "RV") {
		$hr->{svval} .= "\\";
		$sv = $sv->RV;
	    }
	}
	if (class($sv) eq "SPECIAL") {
	    $hr->{svval} .= ["Null", "sv_undef", "sv_yes", "sv_no"]->[$$sv];
	} elsif ($preferpv && $sv->FLAGS & SVf_POK) {
	    $hr->{svval} .= cstring($sv->PV);
	} elsif ($sv->FLAGS & SVf_NOK) {
	    $hr->{svval} .= $sv->NV;
	} elsif ($sv->FLAGS & SVf_IOK) {
	    $hr->{svval} .= $sv->int_value;
	} elsif ($sv->FLAGS & SVf_POK) {
	    $hr->{svval} .= cstring($sv->PV);
	} elsif (class($sv) eq "HV") {
	    $hr->{svval} .= 'HASH';
	}

	$hr->{svval} = 'undef' unless defined $hr->{svval};
	my $out = $hr->{svclass};
	return $out .= " $hr->{svval}" ; 
    }
}

my %srclines;

sub fill_srclines {
    my $fullnm = shift;
    if ($fullnm eq '-e') {
	$srclines{$fullnm} = [ $fullnm, "-src not supported for -e" ];
	return;
    }
    open (my $fh, '<', $fullnm)
	or warn "# $fullnm: $!, (chdirs not supported by this feature yet)\n"
	and return;
    my @l = <$fh>;
    chomp @l;
    unshift @l, $fullnm; # like @{_<$fullnm} in debug, array starts at 1
    $srclines{$fullnm} = \@l;
}

sub concise_op {
    my ($op, $level, $format) = @_;
    my %h;
    $h{exname} = $h{name} = $op->name;
    $h{NAME} = uc $h{name};
    $h{class} = class($op);
    $h{extarg} = $h{targ} = $op->targ;
    $h{extarg} = "" unless $h{extarg};
    if ($h{name} eq "null" and $h{targ}) {
	# targ holds the old type
	$h{exname} = "ex-" . substr(ppname($h{targ}), 3);
	$h{extarg} = "";
    } elsif ($op->name =~ /^leave(sub(lv)?|write)?$/) {
	# targ potentially holds a reference count
	if ($op->private & 64) {
	    my $refs = "ref" . ($h{targ} != 1 ? "s" : "");
	    $h{targarglife} = $h{targarg} = "$h{targ} $refs";
	}
    } elsif ($h{targ}) {
	my $padname = (($curcv->PADLIST->ARRAY)[0]->ARRAY)[$h{targ}];
	if (defined $padname and class($padname) ne "SPECIAL") {
	    $h{targarg}  = $padname->PVX;
	    if ($padname->FLAGS & SVf_FAKE) {
		if ($] < 5.009) {
		    $h{targarglife} = "$h{targarg}:FAKE";
		} else {
		    # These changes relate to the jumbo closure fix.
		    # See changes 19939 and 20005
		    my $fake = '';
		    $fake .= 'a'
		   	if $padname->PARENT_FAKELEX_FLAGS & PAD_FAKELEX_ANON;
		    $fake .= 'm'
		   	if $padname->PARENT_FAKELEX_FLAGS & PAD_FAKELEX_MULTI;
		    $fake .= ':' . $padname->PARENT_PAD_INDEX
			if $curcv->CvFLAGS & CVf_ANON;
		    $h{targarglife} = "$h{targarg}:FAKE:$fake";
		}
	    }
	    else {
		my $intro = $padname->COP_SEQ_RANGE_LOW - $cop_seq_base;
		my $finish = int($padname->COP_SEQ_RANGE_HIGH) - $cop_seq_base;
		$finish = "end" if $finish == 999999999 - $cop_seq_base;
		$h{targarglife} = "$h{targarg}:$intro,$finish";
	    }
	} else {
	    $h{targarglife} = $h{targarg} = "t" . $h{targ};
	}
    }
    $h{arg} = "";
    $h{svclass} = $h{svaddr} = $h{svval} = "";
    if ($h{class} eq "PMOP") {
	my $precomp = $op->precomp;
	if (defined $precomp) {
	    $precomp = cstring($precomp); # Escape literal control sequences
 	    $precomp = "/$precomp/";
	} else {
	    $precomp = "";
	}
	my $pmreplroot = $op->pmreplroot;
	my $pmreplstart;
	if (ref($pmreplroot) eq "B::GV") {
	    # with C<@stash_array = split(/pat/, str);>,
	    #  *stash_array is stored in /pat/'s pmreplroot.
	    $h{arg} = "($precomp => \@" . $pmreplroot->NAME . ")";
	} elsif (!ref($pmreplroot) and $pmreplroot) {
	    # same as the last case, except the value is actually a
	    # pad offset for where the GV is kept (this happens under
	    # ithreads)
	    my $gv = (($curcv->PADLIST->ARRAY)[1]->ARRAY)[$pmreplroot];
	    $h{arg} = "($precomp => \@" . $gv->NAME . ")";
	} elsif ($ {$op->pmreplstart}) {
	    undef $lastnext;
	    $pmreplstart = "replstart->" . seq($op->pmreplstart);
	    $h{arg} = "(" . join(" ", $precomp, $pmreplstart) . ")";
	} else {
	    $h{arg} = "($precomp)";
	}
    } elsif ($h{class} eq "PVOP" and $h{name} ne "trans") {
	$h{arg} = '("' . $op->pv . '")';
	$h{svval} = '"' . $op->pv . '"';
    } elsif ($h{class} eq "COP") {
	my $label = $op->label;
	$h{coplabel} = $label;
	$label = $label ? "$label: " : "";
	my $loc = $op->file;
	my $pathnm = $loc;
	$loc =~ s[.*/][];
	my $ln = $op->line;
	$loc .= ":$ln";
	my($stash, $cseq) = ($op->stash->NAME, $op->cop_seq - $cop_seq_base);
	my $arybase = $op->arybase;
	$arybase = $arybase ? ' $[=' . $arybase : "";
	$h{arg} = "($label$stash $cseq $loc$arybase)";
	if ($show_src) {
	    fill_srclines($pathnm) unless exists $srclines{$pathnm};
	    # Would love to retain Jim's use of // but this code needs to be
	    # portable to 5.8.x
	    my $line = $srclines{$pathnm}[$ln];
	    $line = "-src unavailable under -e" unless defined $line;
	    $h{src} = "$ln: $line";
	}
    } elsif ($h{class} eq "LOOP") {
	$h{arg} = "(next->" . seq($op->nextop) . " last->" . seq($op->lastop)
	  . " redo->" . seq($op->redoop) . ")";
    } elsif ($h{class} eq "LOGOP") {
	undef $lastnext;
	$h{arg} = "(other->" . seq($op->other) . ")";
    }
    elsif ($h{class} eq "SVOP" or $h{class} eq "PADOP") {
	unless ($h{name} eq 'aelemfast' and $op->flags & OPf_SPECIAL) {
	    my $idx = ($h{class} eq "SVOP") ? $op->targ : $op->padix;
	    my $preferpv = $h{name} eq "method_named";
	    if ($h{class} eq "PADOP" or !${$op->sv}) {
		my $sv = (($curcv->PADLIST->ARRAY)[1]->ARRAY)[$idx];
		$h{arg} = "[" . concise_sv($sv, \%h, $preferpv) . "]";
		$h{targarglife} = $h{targarg} = "";
	    } else {
		$h{arg} = "(" . concise_sv($op->sv, \%h, $preferpv) . ")";
	    }
	}
    }
    $h{seq} = $h{hyphseq} = seq($op);
    $h{seq} = "" if $h{seq} eq "-";
    if ($] > 5.009) {
	$h{opt} = $op->opt;
	$h{label} = $labels{$$op};
    } else {
	$h{seqnum} = $op->seq;
	$h{label} = $labels{$op->seq};
    }
    $h{next} = $op->next;
    $h{next} = (class($h{next}) eq "NULL") ? "(end)" : seq($h{next});
    $h{nextaddr} = sprintf("%#x", $ {$op->next});
    $h{sibaddr} = sprintf("%#x", $ {$op->sibling});
    $h{firstaddr} = sprintf("%#x", $ {$op->first}) if $op->can("first");
    $h{lastaddr} = sprintf("%#x", $ {$op->last}) if $op->can("last");

    $h{classsym} = $opclass{$h{class}};
    $h{flagval} = $op->flags;
    $h{flags} = op_flags($op->flags);
    $h{privval} = $op->private;
    $h{private} = private_flags($h{name}, $op->private);
    if ($op->can("hints")) {
      $h{hintsval} = $op->hints;
      $h{hints} = hints_flags($h{hintsval});
    } else {
      $h{hintsval} = $h{hints} = '';
    }
    $h{addr} = sprintf("%#x", $$op);
    $h{typenum} = $op->type;
    $h{noise} = $linenoise[$op->type];

    return fmt_line(\%h, $op, $format, $level);
}

sub B::OP::concise {
    my($op, $level) = @_;
    if ($order eq "exec" and $lastnext and $$lastnext != $$op) {
	# insert a 'goto' line
	my $synth = {"seq" => seq($lastnext), "class" => class($lastnext),
		     "addr" => sprintf("%#x", $$lastnext),
		     "goto" => seq($lastnext), # simplify goto '-' removal
	     };
	print $walkHandle fmt_line($synth, $op, $gotofmt, $level+1);
    }
    $lastnext = $op->next;
    print $walkHandle concise_op($op, $level, $format);
}

# B::OP::terse (see Terse.pm) now just calls this
sub b_terse {
    my($op, $level) = @_;

    # This isn't necessarily right, but there's no easy way to get
    # from an OP to the right CV. This is a limitation of the
    # ->terse() interface style, and there isn't much to do about
    # it. In particular, we can die in concise_op if the main pad
    # isn't long enough, or has the wrong kind of entries, compared to
    # the pad a sub was compiled with. The fix for that would be to
    # make a backwards compatible "terse" format that never even
    # looked at the pad, just like the old B::Terse. I don't think
    # that's worth the effort, though.
    $curcv = main_cv unless $curcv;

    if ($order eq "exec" and $lastnext and $$lastnext != $$op) {
	# insert a 'goto'
	my $h = {"seq" => seq($lastnext), "class" => class($lastnext),
		 "addr" => sprintf("%#x", $$lastnext)};
	print # $walkHandle
	    fmt_line($h, $op, $style{"terse"}[1], $level+1);
    }
    $lastnext = $op->next;
    print # $walkHandle 
	concise_op($op, $level, $style{"terse"}[0]);
}

sub tree {
    my $op = shift;
    my $level = shift;
    my $style = $tree_decorations[$tree_style];
    my($space, $single, $kids, $kid, $nokid, $last, $lead, $size) = @$style;
    my $name = concise_op($op, $level, $treefmt);
    if (not $op->flags & OPf_KIDS) {
	return $name . "\n";
    }
    my @lines;
    for (my $kid = $op->first; $$kid; $kid = $kid->sibling) {
	push @lines, tree($kid, $level+1);
    }
    my $i;
    for ($i = $#lines; substr($lines[$i], 0, 1) eq " "; $i--) {
	$lines[$i] = $space . $lines[$i];
    }
    if ($i > 0) {
	$lines[$i] = $last . $lines[$i];
	while ($i-- > 1) {
	    if (substr($lines[$i], 0, 1) eq " ") {
		$lines[$i] = $nokid . $lines[$i];
	    } else {
		$lines[$i] = $kid . $lines[$i];
	    }
	}
	$lines[$i] = $kids . $lines[$i];
    } else {
	$lines[0] = $single . $lines[0];
    }
    return("$name$lead" . shift @lines,
           map(" " x (length($name)+$size) . $_, @lines));
}

# *** Warning: fragile kludge ahead ***
# Because the B::* modules run in the same interpreter as the code
# they're compiling, their presence tends to distort the view we have of
# the code we're looking at. In particular, perl gives sequence numbers
# to COPs. If the program we're looking at were run on its own, this
# would start at 1. Because all of B::Concise and all the modules it
# uses are compiled first, though, by the time we get to the user's
# program the sequence number is already pretty high, which could be
# distracting if you're trying to tell OPs apart. Therefore we'd like to
# subtract an offset from all the sequence numbers we display, to
# restore the simpler view of the world. The trick is to know what that
# offset will be, when we're still compiling B::Concise!  If we
# hardcoded a value, it would have to change every time B::Concise or
# other modules we use do. To help a little, what we do here is compile
# a little code at the end of the module, and compute the base sequence
# number for the user's program as being a small offset later, so all we
# have to worry about are changes in the offset.

# [For 5.8.x and earlier perl is generating sequence numbers for all ops,
#  and using them to reference labels]


# When you say "perl -MO=Concise -e '$a'", the output should look like:

# 4  <@> leave[t1] vKP/REFC ->(end)
# 1     <0> enter ->2
 #^ smallest OP sequence number should be 1
# 2     <;> nextstate(main 1 -e:1) v ->3
 #                         ^ smallest COP sequence number should be 1
# -     <1> ex-rv2sv vK/1 ->4
# 3        <$> gvsv(*a) s ->4

# If the second of the marked numbers there isn't 1, it means you need
# to update the corresponding magic number in the next line.
# Remember, this needs to stay the last things in the module.

# Why is this different for MacOS?  Does it matter?
my $cop_seq_mnum = $^O eq 'MacOS' ? 12 : 11;
$cop_seq_base = svref_2object(eval 'sub{0;}')->START->cop_seq + $cop_seq_mnum;

1;

__END__

=head1 NAME

B::Concise - Walk Perl syntax tree, printing concise info about ops

=head1 SYNOPSIS

    perl -MO=Concise[,OPTIONS] foo.pl

    use B::Concise qw(set_style add_callback);

=head1 DESCRIPTION

This compiler backend prints the internal OPs of a Perl program's syntax
tree in one of several space-efficient text formats suitable for debugging
the inner workings of perl or other compiler backends. It can print OPs in
the order they appear in the OP tree, in the order they will execute, or
in a text approximation to their tree structure, and the format of the
information displayed is customizable. Its function is similar to that of
perl's B<-Dx> debugging flag or the B<B::Terse> module, but it is more
sophisticated and flexible.

=head1 EXAMPLE

Here's two outputs (or 'renderings'), using the -exec and -basic
(i.e. default) formatting conventions on the same code snippet.

    % perl -MO=Concise,-exec -e '$a = $b + 42'
    1  <0> enter
    2  <;> nextstate(main 1 -e:1) v
    3  <#> gvsv[*b] s
    4  <$> const[IV 42] s
 *  5  <2> add[t3] sK/2
    6  <#> gvsv[*a] s
    7  <2> sassign vKS/2
    8  <@> leave[1 ref] vKP/REFC

In this -exec rendering, each opcode is executed in the order shown.
The add opcode, marked with '*', is discussed in more detail.

The 1st column is the op's sequence number, starting at 1, and is
displayed in base 36 by default.  Here they're purely linear; the
sequences are very helpful when looking at code with loops and
branches.

The symbol between angle brackets indicates the op's type, for
example; <2> is a BINOP, <@> a LISTOP, and <#> is a PADOP, which is
used in threaded perls. (see L</"OP class abbreviations">).

The opname, as in B<'add[t1]'>, may be followed by op-specific
information in parentheses or brackets (ex B<'[t1]'>).

The op-flags (ex B<'sK/2'>) are described in (L</"OP flags
abbreviations">).

    % perl -MO=Concise -e '$a = $b + 42'
    8  <@> leave[1 ref] vKP/REFC ->(end)
    1     <0> enter ->2
    2     <;> nextstate(main 1 -e:1) v ->3
    7     <2> sassign vKS/2 ->8
 *  5        <2> add[t1] sK/2 ->6
    -           <1> ex-rv2sv sK/1 ->4
    3              <$> gvsv(*b) s ->4
    4           <$> const(IV 42) s ->5
    -        <1> ex-rv2sv sKRM*/1 ->7
    6           <$> gvsv(*a) s ->7

The default rendering is top-down, so they're not in execution order.
This form reflects the way the stack is used to parse and evaluate
expressions; the add operates on the two terms below it in the tree.

Nullops appear as C<ex-opname>, where I<opname> is an op that has been
optimized away by perl.  They're displayed with a sequence-number of
'-', because they are not executed (they don't appear in previous
example), they're printed here because they reflect the parse.

The arrow points to the sequence number of the next op; they're not
displayed in -exec mode, for obvious reasons.

Note that because this rendering was done on a non-threaded perl, the
PADOPs in the previous examples are now SVOPs, and some (but not all)
of the square brackets have been replaced by round ones.  This is a
subtle feature to provide some visual distinction between renderings
on threaded and un-threaded perls.


=head1 OPTIONS

Arguments that don't start with a hyphen are taken to be the names of
subroutines to render; if no such functions are specified, the main
body of the program (outside any subroutines, and not including use'd
or require'd files) is rendered.  Passing C<BEGIN>, C<UNITCHECK>,
C<CHECK>, C<INIT>, or C<END> will cause all of the corresponding
special blocks to be printed.  Arguments must follow options.

Options affect how things are rendered (ie printed).  They're presented
here by their visual effect, 1st being strongest.  They're grouped
according to how they interrelate; within each group the options are
mutually exclusive (unless otherwise stated).

=head2 Options for Opcode Ordering

These options control the 'vertical display' of opcodes.  The display
'order' is also called 'mode' elsewhere in this document.

=over 4

=item B<-basic>

Print OPs in the order they appear in the OP tree (a preorder
traversal, starting at the root). The indentation of each OP shows its
level in the tree, and the '->' at the end of the line indicates the
next opcode in execution order.  This mode is the default, so the flag
is included simply for completeness.

=item B<-exec>

Print OPs in the order they would normally execute (for the majority
of constructs this is a postorder traversal of the tree, ending at the
root). In most cases the OP that usually follows a given OP will
appear directly below it; alternate paths are shown by indentation. In
cases like loops when control jumps out of a linear path, a 'goto'
line is generated.

=item B<-tree>

Print OPs in a text approximation of a tree, with the root of the tree
at the left and 'left-to-right' order of children transformed into
'top-to-bottom'. Because this mode grows both to the right and down,
it isn't suitable for large programs (unless you have a very wide
terminal).

=back

=head2 Options for Line-Style

These options select the line-style (or just style) used to render
each opcode, and dictates what info is actually printed into each line.

=over 4

=item B<-concise>

Use the author's favorite set of formatting conventions. This is the
default, of course.

=item B<-terse>

Use formatting conventions that emulate the output of B<B::Terse>. The
basic mode is almost indistinguishable from the real B<B::Terse>, and the
exec mode looks very similar, but is in a more logical order and lacks
curly brackets. B<B::Terse> doesn't have a tree mode, so the tree mode
is only vaguely reminiscent of B<B::Terse>.

=item B<-linenoise>

Use formatting conventions in which the name of each OP, rather than being
written out in full, is represented by a one- or two-character abbreviation.
This is mainly a joke.

=item B<-debug>

Use formatting conventions reminiscent of B<B::Debug>; these aren't
very concise at all.

=item B<-env>

Use formatting conventions read from the environment variables
C<B_CONCISE_FORMAT>, C<B_CONCISE_GOTO_FORMAT>, and C<B_CONCISE_TREE_FORMAT>.

=back

=head2 Options for tree-specific formatting

=over 4

=item B<-compact>

Use a tree format in which the minimum amount of space is used for the
lines connecting nodes (one character in most cases). This squeezes out
a few precious columns of screen real estate.

=item B<-loose>

Use a tree format that uses longer edges to separate OP nodes. This format
tends to look better than the compact one, especially in ASCII, and is
the default.

=item B<-vt>

Use tree connecting characters drawn from the VT100 line-drawing set.
This looks better if your terminal supports it.

=item B<-ascii>

Draw the tree with standard ASCII characters like C<+> and C<|>. These don't
look as clean as the VT100 characters, but they'll work with almost any
terminal (or the horizontal scrolling mode of less(1)) and are suitable
for text documentation or email. This is the default.

=back

These are pairwise exclusive, i.e. compact or loose, vt or ascii.

=head2 Options controlling sequence numbering

=over 4

=item B<-base>I<n>

Print OP sequence numbers in base I<n>. If I<n> is greater than 10, the
digit for 11 will be 'a', and so on. If I<n> is greater than 36, the digit
for 37 will be 'A', and so on until 62. Values greater than 62 are not
currently supported. The default is 36.

=item B<-bigendian>

Print sequence numbers with the most significant digit first. This is the
usual convention for Arabic numerals, and the default.

=item B<-littleendian>

Print seqence numbers with the least significant digit first.  This is
obviously mutually exclusive with bigendian.

=back

=head2 Other options

=over 4

=item B<-src>

With this option, the rendering of each statement (starting with the
nextstate OP) will be preceded by the 1st line of source code that
generates it.  For example:

    1  <0> enter
    # 1: my $i;
    2  <;> nextstate(main 1 junk.pl:1) v:{
    3  <0> padsv[$i:1,10] vM/LVINTRO
    # 3: for $i (0..9) {
    4  <;> nextstate(main 3 junk.pl:3) v:{
    5  <0> pushmark s
    6  <$> const[IV 0] s
    7  <$> const[IV 9] s
    8  <{> enteriter(next->j last->m redo->9)[$i:1,10] lKS
    k  <0> iter s
    l  <|> and(other->9) vK/1
    # 4:     print "line ";
    9      <;> nextstate(main 2 junk.pl:4) v
    a      <0> pushmark s
    b      <$> const[PV "line "] s
    c      <@> print vK
    # 5:     print "$i\n";
    ...

=item B<-stash="somepackage">

With this, "somepackage" will be required, then the stash is
inspected, and each function is rendered.

=back

The following options are pairwise exclusive.

=over 4

=item B<-main>

Include the main program in the output, even if subroutines were also
specified.  This rendering is normally suppressed when a subroutine
name or reference is given.

=item B<-nomain>

This restores the default behavior after you've changed it with '-main'
(it's not normally needed).  If no subroutine name/ref is given, main is
rendered, regardless of this flag.

=item B<-nobanner>

Renderings usually include a banner line identifying the function name
or stringified subref.  This suppresses the printing of the banner.

TBC: Remove the stringified coderef; while it provides a 'cookie' for
each function rendered, the cookies used should be 1,2,3.. not a
random hex-address.  It also complicates string comparison of two
different trees.

=item B<-banner>

restores default banner behavior.

=item B<-banneris> => subref

TBC: a hookpoint (and an option to set it) for a user-supplied
function to produce a banner appropriate for users needs.  It's not
ideal, because the rendering-state variables, which are a natural
candidate for use in concise.t, are unavailable to the user.

=back

=head2 Option Stickiness

If you invoke Concise more than once in a program, you should know that
the options are 'sticky'.  This means that the options you provide in
the first call will be remembered for the 2nd call, unless you
re-specify or change them.

=head1 ABBREVIATIONS

The concise style uses symbols to convey maximum info with minimal
clutter (like hex addresses).  With just a little practice, you can
start to see the flowers, not just the branches, in the trees.

=head2 OP class abbreviations

These symbols appear before the op-name, and indicate the
B:: namespace that represents the ops in your Perl code.

    0      OP (aka BASEOP)  An OP with no children
    1      UNOP             An OP with one child
    2      BINOP            An OP with two children
    |      LOGOP            A control branch OP
    @      LISTOP           An OP that could have lots of children
    /      PMOP             An OP with a regular expression
    $      SVOP             An OP with an SV
    "      PVOP             An OP with a string
    {      LOOP             An OP that holds pointers for a loop
    ;      COP              An OP that marks the start of a statement
    #      PADOP            An OP with a GV on the pad

=head2 OP flags abbreviations

OP flags are either public or private.  The public flags alter the
behavior of each opcode in consistent ways, and are represented by 0
or more single characters.

    v      OPf_WANT_VOID    Want nothing (void context)
    s      OPf_WANT_SCALAR  Want single value (scalar context)
    l      OPf_WANT_LIST    Want list of any length (list context)
                            Want is unknown
    K      OPf_KIDS         There is a firstborn child.
    P      OPf_PARENS       This operator was parenthesized.
                             (Or block needs explicit scope entry.)
    R      OPf_REF          Certified reference.
                             (Return container, not containee).
    M      OPf_MOD          Will modify (lvalue).
    S      OPf_STACKED      Some arg is arriving on the stack.
    *      OPf_SPECIAL      Do something weird for this op (see op.h)

Private flags, if any are set for an opcode, are displayed after a '/'

    8  <@> leave[1 ref] vKP/REFC ->(end)
    7     <2> sassign vKS/2 ->8

They're opcode specific, and occur less often than the public ones, so
they're represented by short mnemonics instead of single-chars; see
F<op.h> for gory details, or try this quick 2-liner:

  $> perl -MB::Concise -de 1
  DB<1> |x \%B::Concise::priv

=head1 FORMATTING SPECIFICATIONS

For each line-style ('concise', 'terse', 'linenoise', etc.) there are
3 format-specs which control how OPs are rendered.

The first is the 'default' format, which is used in both basic and exec
modes to print all opcodes.  The 2nd, goto-format, is used in exec
mode when branches are encountered.  They're not real opcodes, and are
inserted to look like a closing curly brace.  The tree-format is tree
specific.

When a line is rendered, the correct format-spec is copied and scanned
for the following items; data is substituted in, and other
manipulations like basic indenting are done, for each opcode rendered.

There are 3 kinds of items that may be populated; special patterns,
#vars, and literal text, which is copied verbatim.  (Yes, it's a set
of s///g steps.)

=head2 Special Patterns

These items are the primitives used to perform indenting, and to
select text from amongst alternatives.

=over 4

=item B<(x(>I<exec_text>B<;>I<basic_text>B<)x)>

Generates I<exec_text> in exec mode, or I<basic_text> in basic mode.

=item B<(*(>I<text>B<)*)>

Generates one copy of I<text> for each indentation level.

=item B<(*(>I<text1>B<;>I<text2>B<)*)>

Generates one fewer copies of I<text1> than the indentation level, followed
by one copy of I<text2> if the indentation level is more than 0.

=item B<(?(>I<text1>B<#>I<var>I<Text2>B<)?)>

If the value of I<var> is true (not empty or zero), generates the
value of I<var> surrounded by I<text1> and I<Text2>, otherwise
nothing.

=item B<~>

Any number of tildes and surrounding whitespace will be collapsed to
a single space.

=back

=head2 # Variables

These #vars represent opcode properties that you may want as part of
your rendering.  The '#' is intended as a private sigil; a #var's
value is interpolated into the style-line, much like "read $this".

These vars take 3 forms:

=over 4

=item B<#>I<var>

A property named 'var' is assumed to exist for the opcodes, and is
interpolated into the rendering.

=item B<#>I<var>I<N>

Generates the value of I<var>, left justified to fill I<N> spaces.
Note that this means while you can have properties 'foo' and 'foo2',
you cannot render 'foo2', but you could with 'foo2a'.  You would be
wise not to rely on this behavior going forward ;-)

=item B<#>I<Var>

This ucfirst form of #var generates a tag-value form of itself for
display; it converts '#Var' into a 'Var => #var' style, which is then
handled as described above.  (Imp-note: #Vars cannot be used for
conditional-fills, because the => #var transform is done after the check
for #Var's value).

=back

The following variables are 'defined' by B::Concise; when they are
used in a style, their respective values are plugged into the
rendering of each opcode.

Only some of these are used by the standard styles, the others are
provided for you to delve into optree mechanics, should you wish to
add a new style (see L</add_style> below) that uses them.  You can
also add new ones using L</add_callback>.

=over 4

=item B<#addr>

The address of the OP, in hexadecimal.

=item B<#arg>

The OP-specific information of the OP (such as the SV for an SVOP, the
non-local exit pointers for a LOOP, etc.) enclosed in parentheses.

=item B<#class>

The B-determined class of the OP, in all caps.

=item B<#classsym>

A single symbol abbreviating the class of the OP.

=item B<#coplabel>

The label of the statement or block the OP is the start of, if any.

=item B<#exname>

The name of the OP, or 'ex-foo' if the OP is a null that used to be a foo.

=item B<#extarg>

The target of the OP, or nothing for a nulled OP.

=item B<#firstaddr>

The address of the OP's first child, in hexadecimal.

=item B<#flags>

The OP's flags, abbreviated as a series of symbols.

=item B<#flagval>

The numeric value of the OP's flags.

=item B<#hints>

The COP's hint flags, rendered with abbreviated names if possible. An empty
string if this is not a COP. Here are the symbols used:

    $ strict refs
    & strict subs
    * strict vars
    i integers
    l locale
    b bytes
    [ arybase
    { block scope
    % localise %^H
    < open in
    > open out
    I overload int
    F overload float
    B overload binary
    S overload string
    R overload re
    T taint
    E eval
    X filetest access
    U utf-8

=item B<#hintsval>

The numeric value of the COP's hint flags, or an empty string if this is not
a COP.

=item B<#hyphseq>

The sequence number of the OP, or a hyphen if it doesn't have one.

=item B<#label>

'NEXT', 'LAST', or 'REDO' if the OP is a target of one of those in exec
mode, or empty otherwise.

=item B<#lastaddr>

The address of the OP's last child, in hexadecimal.

=item B<#name>

The OP's name.

=item B<#NAME>

The OP's name, in all caps.

=item B<#next>

The sequence number of the OP's next OP.

=item B<#nextaddr>

The address of the OP's next OP, in hexadecimal.

=item B<#noise>

A one- or two-character abbreviation for the OP's name.

=item B<#private>

The OP's private flags, rendered with abbreviated names if possible.

=item B<#privval>

The numeric value of the OP's private flags.

=item B<#seq>

The sequence number of the OP. Note that this is a sequence number
generated by B::Concise.

=item B<#seqnum>

5.8.x and earlier only. 5.9 and later do not provide this.

The real sequence number of the OP, as a regular number and not adjusted
to be relative to the start of the real program. (This will generally be
a fairly large number because all of B<B::Concise> is compiled before
your program is).

=item B<#opt>

Whether or not the op has been optimised by the peephole optimiser.

Only available in 5.9 and later.

=item B<#sibaddr>

The address of the OP's next youngest sibling, in hexadecimal.

=item B<#svaddr>

The address of the OP's SV, if it has an SV, in hexadecimal.

=item B<#svclass>

The class of the OP's SV, if it has one, in all caps (e.g., 'IV').

=item B<#svval>

The value of the OP's SV, if it has one, in a short human-readable format.

=item B<#targ>

The numeric value of the OP's targ.

=item B<#targarg>

The name of the variable the OP's targ refers to, if any, otherwise the
letter t followed by the OP's targ in decimal.

=item B<#targarglife>

Same as B<#targarg>, but followed by the COP sequence numbers that delimit
the variable's lifetime (or 'end' for a variable in an open scope) for a
variable.

=item B<#typenum>

The numeric value of the OP's type, in decimal.

=back

=head1 One-Liner Command tips

=over 4

=item perl -MO=Concise,bar foo.pl

Renders only bar() from foo.pl.  To see main, drop the ',bar'.  To see
both, add ',-main'

=item perl -MDigest::MD5=md5 -MO=Concise,md5 -e1

Identifies md5 as an XS function.  The export is needed so that BC can
find it in main.

=item perl -MPOSIX -MO=Concise,_POSIX_ARG_MAX -e1

Identifies _POSIX_ARG_MAX as a constant sub, optimized to an IV.
Although POSIX isn't entirely consistent across platforms, this is
likely to be present in virtually all of them.

=item perl -MPOSIX -MO=Concise,a -e 'print _POSIX_SAVED_IDS'

This renders a print statement, which includes a call to the function.
It's identical to rendering a file with a use call and that single
statement, except for the filename which appears in the nextstate ops.

=item perl -MPOSIX -MO=Concise,a -e 'sub a{_POSIX_SAVED_IDS}'

This is B<very> similar to previous, only the first two ops differ.  This
subroutine rendering is more representative, insofar as a single main
program will have many subs.

=item perl -MB::Concise -e 'B::Concise::compile("-exec","-src", \%B::Concise::)->()'

This renders all functions in the B::Concise package with the source
lines.  It eschews the O framework so that the stashref can be passed
directly to B::Concise::compile().  See -stash option for a more
convenient way to render a package.

=back

=head1 Using B::Concise outside of the O framework

The common (and original) usage of B::Concise was for command-line
renderings of simple code, as given in EXAMPLE.  But you can also use
B<B::Concise> from your code, and call compile() directly, and
repeatedly.  By doing so, you can avoid the compile-time only
operation of O.pm, and even use the debugger to step through
B::Concise::compile() itself.

Once you're doing this, you may alter Concise output by adding new
rendering styles, and by optionally adding callback routines which
populate new variables, if such were referenced from those (just
added) styles.  

=head2 Example: Altering Concise Renderings

    use B::Concise qw(set_style add_callback);
    add_style($yourStyleName => $defaultfmt, $gotofmt, $treefmt);
    add_callback
      ( sub {
            my ($h, $op, $format, $level, $stylename) = @_;
            $h->{variable} = some_func($op);
        });
    $walker = B::Concise::compile(@options,@subnames,@subrefs);
    $walker->();

=head2 set_style()

B<set_style> accepts 3 arguments, and updates the three format-specs
comprising a line-style (basic-exec, goto, tree).  It has one minor
drawback though; it doesn't register the style under a new name.  This
can become an issue if you render more than once and switch styles.
Thus you may prefer to use add_style() and/or set_style_standard()
instead.

=head2 set_style_standard($name)

This restores one of the standard line-styles: C<terse>, C<concise>,
C<linenoise>, C<debug>, C<env>, into effect.  It also accepts style
names previously defined with add_style().

=head2 add_style()

This subroutine accepts a new style name and three style arguments as
above, and creates, registers, and selects the newly named style.  It is
an error to re-add a style; call set_style_standard() to switch between
several styles.

=head2 add_callback()

If your newly minted styles refer to any new #variables, you'll need
to define a callback subroutine that will populate (or modify) those
variables.  They are then available for use in the style you've
chosen.

The callbacks are called for each opcode visited by Concise, in the
same order as they are added.  Each subroutine is passed five
parameters.

  1. A hashref, containing the variable names and values which are
     populated into the report-line for the op
  2. the op, as a B<B::OP> object
  3. a reference to the format string
  4. the formatting (indent) level
  5. the selected stylename

To define your own variables, simply add them to the hash, or change
existing values if you need to.  The level and format are passed in as
references to scalars, but it is unlikely that they will need to be
changed or even used.

=head2 Running B::Concise::compile()

B<compile> accepts options as described above in L</OPTIONS>, and
arguments, which are either coderefs, or subroutine names.

It constructs and returns a $treewalker coderef, which when invoked,
traverses, or walks, and renders the optrees of the given arguments to
STDOUT.  You can reuse this, and can change the rendering style used
each time; thereafter the coderef renders in the new style.

B<walk_output> lets you change the print destination from STDOUT to
another open filehandle, or into a string passed as a ref (unless
you've built perl with -Uuseperlio).

    my $walker = B::Concise::compile('-terse','aFuncName', \&aSubRef);  # 1
    walk_output(\my $buf);
    $walker->();			# 1 renders -terse
    set_style_standard('concise');	# 2
    $walker->();			# 2 renders -concise
    $walker->(@new);			# 3 renders whatever
    print "3 different renderings: terse, concise, and @new: $buf\n";

When $walker is called, it traverses the subroutines supplied when it
was created, and renders them using the current style.  You can change
the style afterwards in several different ways:

  1. call C<compile>, altering style or mode/order
  2. call C<set_style_standard>
  3. call $walker, passing @new options

Passing new options to the $walker is the easiest way to change
amongst any pre-defined styles (the ones you add are automatically
recognized as options), and is the only way to alter rendering order
without calling compile again.  Note however that rendering state is
still shared amongst multiple $walker objects, so they must still be
used in a coordinated manner.

=head2 B::Concise::reset_sequence()

This function (not exported) lets you reset the sequence numbers (note
that they're numbered arbitrarily, their goal being to be human
readable).  Its purpose is mostly to support testing, i.e. to compare
the concise output from two identical anonymous subroutines (but
different instances).  Without the reset, B::Concise, seeing that
they're separate optrees, generates different sequence numbers in
the output.

=head2 Errors

Errors in rendering (non-existent function-name, non-existent coderef)
are written to the STDOUT, or wherever you've set it via
walk_output().

Errors using the various *style* calls, and bad args to walk_output(),
result in die().  Use an eval if you wish to catch these errors and
continue processing.

=head1 AUTHOR

Stephen McCamant, E<lt>smcc@CSUA.Berkeley.EDUE<gt>.

=cut