unofficial mirror of bug-gnu-emacs@gnu.org 
 help / color / mirror / code / Atom feed
blob 8be8307c75fed94d8fe6f46081873d184bf65c86 70142 bytes (raw)
name: doc/lispref/edebug.texi 	 # note: path name is non-authoritative(*)

   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
 
@comment -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1992--1994, 1998--1999, 2001--2020 Free Software
@c Foundation, Inc.
@c See the file elisp.texi for copying conditions.

@c This file can also be used by an independent Edebug User
@c Manual in which case the Edebug node below should be used
@c with the following links to the Bugs section and to the top level:

@c , Bugs and Todo List, Top, Top

@node Edebug
@section Edebug
@cindex Edebug debugging facility

  Edebug is a source-level debugger for Emacs Lisp programs, with which
you can:

@itemize @bullet
@item
Step through evaluation, stopping before and after each expression.

@item
Set conditional or unconditional breakpoints.

@item
Stop when a specified condition is true (the global break event).

@item
Trace slow or fast, stopping briefly at each stop point, or
at each breakpoint.

@item
Display expression results and evaluate expressions as if outside of
Edebug.

@item
Automatically re-evaluate a list of expressions and
display their results each time Edebug updates the display.

@item
Output trace information on function calls and returns.

@item
Stop when an error occurs.

@item
Display a backtrace, omitting Edebug's own frames.

@item
Specify argument evaluation for macros and defining forms.

@item
Obtain rudimentary coverage testing and frequency counts.
@end itemize

The first three sections below should tell you enough about Edebug to
start using it.

@menu
* Using Edebug::                Introduction to use of Edebug.
* Instrumenting::               You must instrument your code
                                  in order to debug it with Edebug.
* Modes: Edebug Execution Modes. Execution modes, stopping more or less often.
* Jumping::                     Commands to jump to a specified place.
* Misc: Edebug Misc.            Miscellaneous commands.
* Breaks::                      Setting breakpoints to make the program stop.
* Trapping Errors::             Trapping errors with Edebug.
* Views: Edebug Views.          Views inside and outside of Edebug.
* Eval: Edebug Eval.            Evaluating expressions within Edebug.
* Eval List::                   Expressions whose values are displayed
                                  each time you enter Edebug.
* Printing in Edebug::          Customization of printing.
* Trace Buffer::                How to produce trace output in a buffer.
* Coverage Testing::            How to test evaluation coverage.
* The Outside Context::         Data that Edebug saves and restores.
* Edebug and Macros::           Specifying how to handle macro calls.
* Options: Edebug Options.      Option variables for customizing Edebug.
@end menu

@node Using Edebug
@subsection Using Edebug

  To debug a Lisp program with Edebug, you must first @dfn{instrument}
the Lisp code that you want to debug.  A simple way to do this is to
first move point into the definition of a function or macro and then do
@kbd{C-u C-M-x} (@code{eval-defun} with a prefix argument).  See
@ref{Instrumenting}, for alternative ways to instrument code.

  Once a function is instrumented, any call to the function activates
Edebug.  Depending on which Edebug execution mode you have selected,
activating Edebug may stop execution and let you step through the
function, or it may update the display and continue execution while
checking for debugging commands.  The default execution mode is step,
which stops execution.  @xref{Edebug Execution Modes}.

  Within Edebug, you normally view an Emacs buffer showing the source of
the Lisp code you are debugging.  This is referred to as the @dfn{source
code buffer}, and it is temporarily read-only.

  An arrow in the left fringe indicates the line where the function is
executing.  Point initially shows where within the line the function is
executing, but this ceases to be true if you move point yourself.

  If you instrument the definition of @code{fac} (shown below) and then
execute @code{(fac 3)}, here is what you would normally see.  Point is
at the open-parenthesis before @code{if}.

@example
(defun fac (n)
=>@point{}(if (< 0 n)
      (* n (fac (1- n)))
    1))
@end example

@cindex stop points
The places within a function where Edebug can stop execution are called
@dfn{stop points}.  These occur both before and after each subexpression
that is a list, and also after each variable reference.
Here we use periods to show the stop points in the function
@code{fac}:

@example
(defun fac (n)
  .(if .(< 0 n.).
      .(* n. .(fac .(1- n.).).).
    1).)
@end example

The special commands of Edebug are available in the source code buffer
in addition to the commands of Emacs Lisp mode.  For example, you can
type the Edebug command @key{SPC} to execute until the next stop point.
If you type @key{SPC} once after entry to @code{fac}, here is the
display you will see:

@example
(defun fac (n)
=>(if @point{}(< 0 n)
      (* n (fac (1- n)))
    1))
@end example

When Edebug stops execution after an expression, it displays the
expression's value in the echo area.

Other frequently used commands are @kbd{b} to set a breakpoint at a stop
point, @kbd{g} to execute until a breakpoint is reached, and @kbd{q} to
exit Edebug and return to the top-level command loop.  Type @kbd{?} to
display a list of all Edebug commands.

@node Instrumenting
@subsection Instrumenting for Edebug
@cindex instrumenting for Edebug

  In order to use Edebug to debug Lisp code, you must first
@dfn{instrument} the code.  Instrumenting code inserts additional code
into it, to invoke Edebug at the proper places.

@kindex C-M-x
@findex eval-defun @r{(Edebug)}
  When you invoke command @kbd{C-M-x} (@code{eval-defun}) with a
prefix argument on a function definition, it instruments the
definition before evaluating it.  (This does not modify the source
code itself.)  If the variable @code{edebug-all-defs} is
non-@code{nil}, that inverts the meaning of the prefix argument: in
this case, @kbd{C-M-x} instruments the definition @emph{unless} it has
a prefix argument.  The default value of @code{edebug-all-defs} is
@code{nil}.  The command @kbd{M-x edebug-all-defs} toggles the value
of the variable @code{edebug-all-defs}.

@findex eval-region @r{(Edebug)}
@findex eval-buffer @r{(Edebug)}
@findex eval-current-buffer @r{(Edebug)}
  If @code{edebug-all-defs} is non-@code{nil}, then the commands
@code{eval-region}, @code{eval-current-buffer}, and @code{eval-buffer}
also instrument any definitions they evaluate.  Similarly,
@code{edebug-all-forms} controls whether @code{eval-region} should
instrument @emph{any} form, even non-defining forms.  This doesn't apply
to loading or evaluations in the minibuffer.  The command @kbd{M-x
edebug-all-forms} toggles this option.

@findex edebug-eval-top-level-form
@findex edebug-defun
  Another command, @kbd{M-x edebug-eval-top-level-form}, is available to
instrument any top-level form regardless of the values of
@code{edebug-all-defs} and @code{edebug-all-forms}.
@code{edebug-defun} is an alias for @code{edebug-eval-top-level-form}.

  While Edebug is active, the command @kbd{I}
(@code{edebug-instrument-callee}) instruments the definition of the
function or macro called by the list form after point, if it is not already
instrumented.  This is possible only if Edebug knows where to find the
source for that function; for this reason, after loading Edebug,
@code{eval-region} records the position of every definition it
evaluates, even if not instrumenting it.  See also the @kbd{i} command
(@pxref{Jumping}), which steps into the call after instrumenting the
function.

  Edebug knows how to instrument all the standard special forms,
@code{interactive} forms with an expression argument, anonymous lambda
expressions, and other defining forms.  However, Edebug cannot determine
on its own what a user-defined macro will do with the arguments of a
macro call, so you must provide that information using Edebug
specifications; for details, @pxref{Edebug and Macros}.

  When Edebug is about to instrument code for the first time in a
session, it runs the hook @code{edebug-setup-hook}, then sets it to
@code{nil}.  You can use this to load Edebug specifications
associated with a package you are using, but only when you use Edebug.

@cindex edebug, failure to instrument
  If Edebug detects a syntax error while instrumenting, it leaves point
at the erroneous code and signals an @code{invalid-read-syntax} error.
@c FIXME?  I can't see that it "leaves point at the erroneous code".
Example:

@example
@error{} Invalid read syntax: "Expected lambda expression"
@end example

  One potential reason for such a failure to instrument is that some
macro definitions are not yet known to Emacs.  To work around this,
load the file which defines the function you are about to instrument.

@findex eval-expression @r{(Edebug)}
  To remove instrumentation from a definition, simply re-evaluate its
definition in a way that does not instrument.  There are two ways of
evaluating forms that never instrument them: from a file with
@code{load}, and from the minibuffer with @code{eval-expression}
(@kbd{M-:}).

@findex edebug-remove-instrumentation
  A different way to remove the instrumentation from a definition is
to use the @code{edebug-remove-instrumentation} command.  It also
allows removing the instrumentation from everything that has been
instrumented.

  @xref{Edebug Eval}, for other evaluation functions available
inside of Edebug.

@node Edebug Execution Modes
@subsection Edebug Execution Modes

@cindex Edebug execution modes
Edebug supports several execution modes for running the program you are
debugging.  We call these alternatives @dfn{Edebug execution modes}; do
not confuse them with major or minor modes.  The current Edebug execution mode
determines how far Edebug continues execution before stopping---whether
it stops at each stop point, or continues to the next breakpoint, for
example---and how much Edebug displays the progress of the evaluation
before it stops.

Normally, you specify the Edebug execution mode by typing a command to
continue the program in a certain mode.  Here is a table of these
commands; all except for @kbd{S} resume execution of the program, at
least for a certain distance.

@table @kbd
@item S
Stop: don't execute any more of the program, but wait for more
Edebug commands (@code{edebug-stop}).
@c FIXME Does not work. https://debbugs.gnu.org/9764

@item @key{SPC}
Step: stop at the next stop point encountered (@code{edebug-step-mode}).

@item n
Next: stop at the next stop point encountered after an expression
(@code{edebug-next-mode}).  Also see @code{edebug-forward-sexp} in
@ref{Jumping}.

@item t
Trace: pause (normally one second) at each Edebug stop point
(@code{edebug-trace-mode}).

@item T
Rapid trace: update the display at each stop point, but don't actually
pause (@code{edebug-Trace-fast-mode}).

@item g
Go: run until the next breakpoint (@code{edebug-go-mode}).  @xref{Breakpoints}.

@item c
Continue: pause one second at each breakpoint, and then continue
(@code{edebug-continue-mode}).

@item C
Rapid continue: move point to each breakpoint, but don't pause
(@code{edebug-Continue-fast-mode}).

@item G
Go non-stop: ignore breakpoints (@code{edebug-Go-nonstop-mode}).  You
can still stop the program by typing @kbd{S}, or any editing command.
@end table

In general, the execution modes earlier in the above list run the
program more slowly or stop sooner than the modes later in the list.

When you enter a new Edebug level, Edebug will normally stop at the
first instrumented function it encounters.  If you prefer to stop only
at a break point, or not at all (for example, when gathering coverage
data), change the value of @code{edebug-initial-mode} from its default
@code{step} to @code{go}, or @code{Go-nonstop}, or one of its other
values (@pxref{Edebug Options}).  You can do this readily with
@kbd{C-x C-a C-m} (@code{edebug-set-initial-mode}):

@deffn Command edebug-set-initial-mode
@kindex C-x C-a C-m
This command, bound to @kbd{C-x C-a C-m}, sets
@code{edebug-initial-mode}.  It prompts you for a key to indicate the
mode.  You should enter one of the eight keys listed above, which sets
the corresponding mode.
@end deffn

Note that you may reenter the same Edebug level several times if, for
example, an instrumented function is called several times from one
command.

While executing or tracing, you can interrupt the execution by typing
any Edebug command.  Edebug stops the program at the next stop point and
then executes the command you typed.  For example, typing @kbd{t} during
execution switches to trace mode at the next stop point.  You can use
@kbd{S} to stop execution without doing anything else.

If your function happens to read input, a character you type intending
to interrupt execution may be read by the function instead.  You can
avoid such unintended results by paying attention to when your program
wants input.

@cindex keyboard macros (Edebug)
Keyboard macros containing the commands in this section do not
completely work: exiting from Edebug, to resume the program, loses track
of the keyboard macro.  This is not easy to fix.  Also, defining or
executing a keyboard macro outside of Edebug does not affect commands
inside Edebug.  This is usually an advantage.  See also the
@code{edebug-continue-kbd-macro} option in @ref{Edebug Options}.

@defopt edebug-sit-for-seconds
This option specifies how many seconds to wait between execution steps
in trace mode or continue mode.  The default is 1 second.
@end defopt

@node Jumping
@subsection Jumping

  The commands described in this section execute until they reach a
specified location.  All except @kbd{i} make a temporary breakpoint to
establish the place to stop, then switch to go mode.  Any other
breakpoint reached before the intended stop point will also stop
execution.  @xref{Breakpoints}, for the details on breakpoints.

  These commands may fail to work as expected in case of nonlocal exit,
as that can bypass the temporary breakpoint where you expected the
program to stop.

@table @kbd
@item h
Proceed to the stop point near where point is (@code{edebug-goto-here}).

@item f
Run the program for one expression
(@code{edebug-forward-sexp}).

@item o
Run the program until the end of the containing sexp (@code{edebug-step-out}).

@item i
Step into the function or macro called by the form after point
(@code{edebug-step-in}).
@end table

The @kbd{h} command proceeds to the stop point at or after the current
location of point, using a temporary breakpoint.

The @kbd{f} command runs the program forward over one expression.  More
precisely, it sets a temporary breakpoint at the position that
@code{forward-sexp} would reach, then executes in go mode so that
the program will stop at breakpoints.

With a prefix argument @var{n}, the temporary breakpoint is placed
@var{n} sexps beyond point.  If the containing list ends before @var{n}
more elements, then the place to stop is after the containing
expression.

You must check that the position @code{forward-sexp} finds is a place
that the program will really get to.  In @code{cond}, for example,
this may not be true.

For flexibility, the @kbd{f} command does @code{forward-sexp} starting
at point, rather than at the stop point.  If you want to execute one
expression @emph{from the current stop point}, first type @kbd{w}
(@code{edebug-where}) to move point there, and then type @kbd{f}.

The @kbd{o} command continues out of an expression.  It places a
temporary breakpoint at the end of the sexp containing point.  If the
containing sexp is a function definition itself, @kbd{o} continues until
just before the last sexp in the definition.  If that is where you are
now, it returns from the function and then stops.  In other words, this
command does not exit the currently executing function unless you are
positioned after the last sexp.

Normally, the @kbd{h}, @kbd{f}, and @kbd{o} commands display ``Break''
and pause for @code{edebug-sit-for-seconds} before showing the result
of the form just evaluated.  You can avoid this pause by setting
@code{edebug-sit-on-break} to @code{nil}.  @xref{Edebug Options}.

The @kbd{i} command steps into the function or macro called by the list
form after point, and stops at its first stop point.  Note that the form
need not be the one about to be evaluated.  But if the form is a
function call about to be evaluated, remember to use this command before
any of the arguments are evaluated, since otherwise it will be too late.

The @kbd{i} command instruments the function or macro it's supposed to
step into, if it isn't instrumented already.  This is convenient, but keep
in mind that the function or macro remains instrumented unless you explicitly
arrange to deinstrument it.

@node Edebug Misc
@subsection Miscellaneous Edebug Commands

  Some miscellaneous Edebug commands are described here.

@table @kbd
@item ?
Display the help message for Edebug (@code{edebug-help}).

@item C-]
Abort one level back to the previous command level
(@code{abort-recursive-edit}).

@item q
Return to the top level editor command loop (@code{top-level}).  This
exits all recursive editing levels, including all levels of Edebug
activity.  However, instrumented code protected with
@code{unwind-protect} or @code{condition-case} forms may resume
debugging.

@item Q
Like @kbd{q}, but don't stop even for protected code
(@code{edebug-top-level-nonstop}).

@item r
Redisplay the most recently known expression result in the echo area
(@code{edebug-previous-result}).

@item d
Display a backtrace, excluding Edebug's own functions for clarity
(@code{edebug-backtrace}).

@xref{Backtraces}, for a description of backtraces
and the commands which work on them.

@findex edebug-backtrace-show-instrumentation
@findex edebug-backtrace-hide-instrumentation
If you would like to see Edebug's functions in the backtrace,
use @kbd{M-x edebug-backtrace-show-instrumentation}.  To hide them
again use @kbd{M-x edebug-backtrace-hide-instrumentation}.

If a backtrace frame starts with @samp{>} that means that Edebug knows
where the source code for the frame is located.  Use @kbd{s} to jump
to the source code for the current frame.

The backtrace buffer is killed automatically when you continue
execution.
@end table

You can invoke commands from Edebug that activate Edebug again
recursively.  Whenever Edebug is active, you can quit to the top level
with @kbd{q} or abort one recursive edit level with @kbd{C-]}.  You can
display a backtrace of all the pending evaluations with @kbd{d}.

@node Breaks
@subsection Breaks

Edebug's step mode stops execution when the next stop point is reached.
There are three other ways to stop Edebug execution once it has started:
breakpoints, the global break condition, and source breakpoints.

@menu
* Breakpoints::                 Breakpoints at stop points.
* Global Break Condition::      Breaking on an event.
* Source Breakpoints::          Embedding breakpoints in source code.
@end menu

@node Breakpoints
@subsubsection Edebug Breakpoints

@cindex breakpoints (Edebug)
While using Edebug, you can specify @dfn{breakpoints} in the program you
are testing: these are places where execution should stop.  You can set a
breakpoint at any stop point, as defined in @ref{Using Edebug}.  For
setting and unsetting breakpoints, the stop point that is affected is
the first one at or after point in the source code buffer.  Here are the
Edebug commands for breakpoints:

@table @kbd
@item b
Set a breakpoint at the stop point at or after point
(@code{edebug-set-breakpoint}).  If you use a prefix argument, the
breakpoint is temporary---it turns off the first time it stops the
program.  An overlay with the @code{edebug-enabled-breakpoint} or
@code{edebug-disabled-breakpoint} faces is put at the breakpoint.

@item u
Unset the breakpoint (if any) at the stop point at or after
point (@code{edebug-unset-breakpoint}).

@item U
Unset any breakpoints in the current form
(@code{edebug-unset-breakpoints}).

@item D
Toggle whether to disable the breakpoint near point
(@code{edebug-toggle-disable-breakpoint}).  This command is mostly
useful if the breakpoint is conditional and it would take some work to
recreate the condition.

@item x @var{condition} @key{RET}
Set a conditional breakpoint which stops the program only if
evaluating @var{condition} produces a non-@code{nil} value
(@code{edebug-set-conditional-breakpoint}).  With a prefix argument,
the breakpoint is temporary.

@item B
Move point to the next breakpoint in the current definition
(@code{edebug-next-breakpoint}).
@end table

While in Edebug, you can set a breakpoint with @kbd{b} and unset one
with @kbd{u}.  First move point to the Edebug stop point of your choice,
then type @kbd{b} or @kbd{u} to set or unset a breakpoint there.
Unsetting a breakpoint where none has been set has no effect.

Re-evaluating or reinstrumenting a definition removes all of its
previous breakpoints.

A @dfn{conditional breakpoint} tests a condition each time the program
gets there.  Any errors that occur as a result of evaluating the
condition are ignored, as if the result were @code{nil}.  To set a
conditional breakpoint, use @kbd{x}, and specify the condition
expression in the minibuffer.  Setting a conditional breakpoint at a
stop point that has a previously established conditional breakpoint puts
the previous condition expression in the minibuffer so you can edit it.

You can make a conditional or unconditional breakpoint
@dfn{temporary} by using a prefix argument with the command to set the
breakpoint.  When a temporary breakpoint stops the program, it is
automatically unset.

Edebug always stops or pauses at a breakpoint, except when the Edebug
mode is Go-nonstop.  In that mode, it ignores breakpoints entirely.

To find out where your breakpoints are, use the @kbd{B} command, which
moves point to the next breakpoint following point, within the same
function, or to the first breakpoint if there are no following
breakpoints.  This command does not continue execution---it just moves
point in the buffer.

@node Global Break Condition
@subsubsection Global Break Condition

@cindex stopping on events
@cindex global break condition
  A @dfn{global break condition} stops execution when a specified
condition is satisfied, no matter where that may occur.  Edebug
evaluates the global break condition at every stop point; if it
evaluates to a non-@code{nil} value, then execution stops or pauses
depending on the execution mode, as if a breakpoint had been hit.  If
evaluating the condition gets an error, execution does not stop.

@findex edebug-set-global-break-condition
  The condition expression is stored in
@code{edebug-global-break-condition}.  You can specify a new expression
using the @kbd{X} command from the source code buffer while Edebug is
active, or using @kbd{C-x X X} from any buffer at any time, as long as
Edebug is loaded (@code{edebug-set-global-break-condition}).

  The global break condition is the simplest way to find where in your
code some event occurs, but it makes code run much more slowly.  So you
should reset the condition to @code{nil} when not using it.

@node Source Breakpoints
@subsubsection Source Breakpoints

@findex edebug
@cindex source breakpoints
  All breakpoints in a definition are forgotten each time you
reinstrument it.  If you wish to make a breakpoint that won't be
forgotten, you can write a @dfn{source breakpoint}, which is simply a
call to the function @code{edebug} in your source code.  You can, of
course, make such a call conditional.  For example, in the @code{fac}
function, you can insert the first line as shown below, to stop when the
argument reaches zero:

@example
(defun fac (n)
  (if (= n 0) (edebug))
  (if (< 0 n)
      (* n (fac (1- n)))
    1))
@end example

  When the @code{fac} definition is instrumented and the function is
called, the call to @code{edebug} acts as a breakpoint.  Depending on
the execution mode, Edebug stops or pauses there.

  If no instrumented code is being executed when @code{edebug} is called,
that function calls @code{debug}.
@c This may not be a good idea anymore.

@node Trapping Errors
@subsection Trapping Errors

  Emacs normally displays an error message when an error is signaled and
not handled with @code{condition-case}.  While Edebug is active and
executing instrumented code, it normally responds to all unhandled
errors.  You can customize this with the options @code{edebug-on-error}
and @code{edebug-on-quit}; see @ref{Edebug Options}.

  When Edebug responds to an error, it shows the last stop point
encountered before the error.  This may be the location of a call to a
function which was not instrumented, and within which the error actually
occurred.  For an unbound variable error, the last known stop point
might be quite distant from the offending variable reference.  In that
case, you might want to display a full backtrace (@pxref{Edebug Misc}).

@c Edebug should be changed for the following: -- dan
  If you change @code{debug-on-error} or @code{debug-on-quit} while
Edebug is active, these changes will be forgotten when Edebug becomes
inactive.  Furthermore, during Edebug's recursive edit, these variables
are bound to the values they had outside of Edebug.

@node Edebug Views
@subsection Edebug Views

  These Edebug commands let you view aspects of the buffer and window
status as they were before entry to Edebug.  The outside window
configuration is the collection of windows and contents that were in
effect outside of Edebug.

@table @kbd
@item v
Switch to viewing the outside window configuration
(@code{edebug-view-outside}).  Type @kbd{C-x X w} to return to Edebug.

@item p
Temporarily display the outside current buffer with point at its
outside position (@code{edebug-bounce-point}), pausing for one second
before returning to Edebug.  With a prefix argument @var{n}, pause for
@var{n} seconds instead.

@item w
Move point back to the current stop point in the source code buffer
(@code{edebug-where}).

If you use this command in a different window displaying the same
buffer, that window will be used instead to display the current
definition in the future.

@item W
@c Its function is not simply to forget the saved configuration -- dan
Toggle whether Edebug saves and restores the outside window
configuration (@code{edebug-toggle-save-windows}).

With a prefix argument, @code{W} only toggles saving and restoring of
the selected window.  To specify a window that is not displaying the
source code buffer, you must use @kbd{C-x X W} from the global keymap.
@end table

  You can view the outside window configuration with @kbd{v} or just
bounce to the point in the current buffer with @kbd{p}, even if
it is not normally displayed.

  After moving point, you may wish to jump back to the stop point.
You can do that with @kbd{w} from a source code buffer.  You can jump
back to the stop point in the source code buffer from any buffer using
@kbd{C-x X w}.

  Each time you use @kbd{W} to turn saving @emph{off}, Edebug forgets the
saved outside window configuration---so that even if you turn saving
back @emph{on}, the current window configuration remains unchanged when
you next exit Edebug (by continuing the program).  However, the
automatic redisplay of @file{*edebug*} and @file{*edebug-trace*} may
conflict with the buffers you wish to see unless you have enough windows
open.

@node Edebug Eval
@subsection Evaluation

  While within Edebug, you can evaluate expressions as if Edebug
were not running.  Edebug tries to be invisible to the expression's
evaluation and printing.  Evaluation of expressions that cause side
effects will work as expected, except for changes to data that Edebug
explicitly saves and restores.  @xref{The Outside Context}, for details
on this process.

@table @kbd
@item e @var{exp} @key{RET}
Evaluate expression @var{exp} in the context outside of Edebug
(@code{edebug-eval-expression}).  That is, Edebug tries to minimize its
interference with the evaluation.

@item M-: @var{exp} @key{RET}
Evaluate expression @var{exp} in the context of Edebug itself
(@code{eval-expression}).

@item C-x C-e
Evaluate the expression before point, in the context outside of Edebug
(@code{edebug-eval-last-sexp}).  With the prefix argument of zero
(@kbd{C-u 0 C-x C-e}), don't shorten long items (like strings and
lists).
@end table

@cindex lexical binding (Edebug)
  Edebug supports evaluation of expressions containing references to
lexically bound symbols created by the following constructs in
@file{cl.el}: @code{lexical-let}, @code{macrolet}, and
@code{symbol-macrolet}.
@c FIXME?  What about lexical-binding = t?

@node Eval List
@subsection Evaluation List Buffer

  You can use the @dfn{evaluation list buffer}, called @file{*edebug*}, to
evaluate expressions interactively.  You can also set up the
@dfn{evaluation list} of expressions to be evaluated automatically each
time Edebug updates the display.

@table @kbd
@item E
Switch to the evaluation list buffer @file{*edebug*}
(@code{edebug-visit-eval-list}).
@end table

  In the @file{*edebug*} buffer you can use the commands of Lisp
Interaction mode (@pxref{Lisp Interaction,,, emacs, The GNU Emacs
Manual}) as well as these special commands:

@table @kbd
@item C-j
Evaluate the expression before point, in the outside context, and
insert the value in the buffer (@code{edebug-eval-print-last-sexp}).
With prefix argument of zero (@kbd{C-u 0 C-j}), don't shorten long
items (like strings and lists).

@item C-x C-e
Evaluate the expression before point, in the context outside of Edebug
(@code{edebug-eval-last-sexp}).

@item C-c C-u
Build a new evaluation list from the contents of the buffer
(@code{edebug-update-eval-list}).

@item C-c C-d
Delete the evaluation list group that point is in
(@code{edebug-delete-eval-item}).

@item C-c C-w
Switch back to the source code buffer at the current stop point
(@code{edebug-where}).
@end table

  You can evaluate expressions in the evaluation list window with
@kbd{C-j} or @kbd{C-x C-e}, just as you would in @file{*scratch*};
but they are evaluated in the context outside of Edebug.

  The expressions you enter interactively (and their results) are lost
when you continue execution; but you can set up an @dfn{evaluation list}
consisting of expressions to be evaluated each time execution stops.

@cindex evaluation list group
  To do this, write one or more @dfn{evaluation list groups} in the
evaluation list buffer.  An evaluation list group consists of one or
more Lisp expressions.  Groups are separated by comment lines.

  The command @kbd{C-c C-u} (@code{edebug-update-eval-list}) rebuilds the
evaluation list, scanning the buffer and using the first expression of
each group.  (The idea is that the second expression of the group is the
value previously computed and displayed.)

  Each entry to Edebug redisplays the evaluation list by inserting each
expression in the buffer, followed by its current value.  It also
inserts comment lines so that each expression becomes its own group.
Thus, if you type @kbd{C-c C-u} again without changing the buffer text,
the evaluation list is effectively unchanged.

  If an error occurs during an evaluation from the evaluation list,
the error message is displayed in a string as if it were the result.
Therefore, expressions using variables that are not currently valid do
not interrupt your debugging.

  Here is an example of what the evaluation list window looks like after
several expressions have been added to it:

@smallexample
(current-buffer)
#<buffer *scratch*>
;---------------------------------------------------------------
(selected-window)
#<window 16 on *scratch*>
;---------------------------------------------------------------
(point)
196
;---------------------------------------------------------------
bad-var
"Symbol's value as variable is void: bad-var"
;---------------------------------------------------------------
(recursion-depth)
0
;---------------------------------------------------------------
this-command
eval-last-sexp
;---------------------------------------------------------------
@end smallexample

To delete a group, move point into it and type @kbd{C-c C-d}, or simply
delete the text for the group and update the evaluation list with
@kbd{C-c C-u}.  To add a new expression to the evaluation list, insert
the expression at a suitable place, insert a new comment line, then type
@kbd{C-c C-u}.  You need not insert dashes in the comment line---its
contents don't matter.

After selecting @file{*edebug*}, you can return to the source code
buffer with @kbd{C-c C-w}.  The @file{*edebug*} buffer is killed when
you continue execution, and recreated next time it is needed.

@node Printing in Edebug
@subsection Printing in Edebug

@cindex printing (Edebug)
@cindex printing circular structures
@pindex cust-print
  If an expression in your program produces a value containing circular
list structure, you may get an error when Edebug attempts to print it.

  One way to cope with circular structure is to set @code{print-length}
or @code{print-level} to truncate the printing.  Edebug does this for
you; it binds @code{print-length} and @code{print-level} to the values
of the variables @code{edebug-print-length} and
@code{edebug-print-level} (so long as they have non-@code{nil}
values).  @xref{Output Variables}.

@defopt edebug-print-length
If non-@code{nil}, Edebug binds @code{print-length} to this value while
printing results.  The default value is @code{50}.
@end defopt

@defopt edebug-print-level
If non-@code{nil}, Edebug binds @code{print-level} to this value while
printing results.  The default value is @code{50}.
@end defopt

  You can also print circular structures and structures that share
elements more informatively by binding @code{print-circle}
to a non-@code{nil} value.

  Here is an example of code that creates a circular structure:

@example
(setq a '(x y))
(setcar a a)
@end example

@noindent
Custom printing prints this as @samp{Result: #1=(#1# y)}.  The
@samp{#1=} notation labels the structure that follows it with the label
@samp{1}, and the @samp{#1#} notation references the previously labeled
structure.  This notation is used for any shared elements of lists or
vectors.

@defopt edebug-print-circle
If non-@code{nil}, Edebug binds @code{print-circle} to this value while
printing results.  The default value is @code{t}.
@end defopt

  Other programs can also use custom printing; see @file{cust-print.el}
for details.

@node Trace Buffer
@subsection Trace Buffer
@cindex trace buffer

  Edebug can record an execution trace, storing it in a buffer named
@file{*edebug-trace*}.  This is a log of function calls and returns,
showing the function names and their arguments and values.  To enable
trace recording, set @code{edebug-trace} to a non-@code{nil} value.

  Making a trace buffer is not the same thing as using trace execution
mode (@pxref{Edebug Execution Modes}).

  When trace recording is enabled, each function entry and exit adds
lines to the trace buffer.  A function entry record consists of
@samp{::::@{}, followed by the function name and argument values.  A
function exit record consists of @samp{::::@}}, followed by the function
name and result of the function.

  The number of @samp{:}s in an entry shows its recursion depth.  You
can use the braces in the trace buffer to find the matching beginning or
end of function calls.

@findex edebug-print-trace-before
@findex edebug-print-trace-after
  You can customize trace recording for function entry and exit by
redefining the functions @code{edebug-print-trace-before} and
@code{edebug-print-trace-after}.

@defmac edebug-tracing string body@dots{}
This macro requests additional trace information around the execution
of the @var{body} forms.  The argument @var{string} specifies text
to put in the trace buffer, after the @samp{@{} or @samp{@}}.  All
the arguments are evaluated, and @code{edebug-tracing} returns the
value of the last form in @var{body}.
@end defmac

@defun edebug-trace format-string &rest format-args
This function inserts text in the trace buffer.  It computes the text
with @code{(apply 'format @var{format-string} @var{format-args})}.
It also appends a newline to separate entries.
@end defun

  @code{edebug-tracing} and @code{edebug-trace} insert lines in the
trace buffer whenever they are called, even if Edebug is not active.
Adding text to the trace buffer also scrolls its window to show the last
lines inserted.

@node Coverage Testing
@subsection Coverage Testing

@cindex coverage testing (Edebug)
@cindex frequency counts
@cindex performance analysis (Edebug)
  Edebug provides rudimentary coverage testing and display of execution
frequency.

  Coverage testing works by comparing the result of each expression with
the previous result; each form in the program is considered covered
if it has returned two different values since you began testing coverage
in the current Emacs session.  Thus, to do coverage testing on your
program, execute it under various conditions and note whether it behaves
correctly; Edebug will tell you when you have tried enough different
conditions that each form has returned two different values.

  Coverage testing makes execution slower, so it is only done if
@code{edebug-test-coverage} is non-@code{nil}.  Frequency counting is
performed for all executions of an instrumented function, even if the
execution mode is Go-nonstop, and regardless of whether coverage testing
is enabled.

@kindex C-x X =
@findex edebug-temp-display-freq-count
  Use @kbd{C-x X =} (@code{edebug-display-freq-count}) to display both
the coverage information and the frequency counts for a definition.
Just @kbd{=} (@code{edebug-temp-display-freq-count}) displays the same
information temporarily, only until you type another key.

@deffn Command edebug-display-freq-count
This command displays the frequency count data for each line of the
current definition.

It inserts frequency counts as comment lines after each line of code.
You can undo all insertions with one @code{undo} command.  The counts
appear under the @samp{(} before an expression or the @samp{)} after
an expression, or on the last character of a variable.  To simplify
the display, a count is not shown if it is equal to the count of an
earlier expression on the same line.

The character @samp{=} following the count for an expression says that
the expression has returned the same value each time it was evaluated.
In other words, it is not yet covered for coverage testing purposes.

To clear the frequency count and coverage data for a definition,
simply reinstrument it with @code{eval-defun}.
@end deffn

For example, after evaluating @code{(fac 5)} with a source
breakpoint, and setting @code{edebug-test-coverage} to @code{t}, when
the breakpoint is reached, the frequency data looks like this:

@example
(defun fac (n)
  (if (= n 0) (edebug))
;#6           1      = =5
  (if (< 0 n)
;#5         =
      (* n (fac (1- n)))
;#    5               0
    1))
;#   0
@end example

The comment lines show that @code{fac} was called 6 times.  The
first @code{if} statement returned 5 times with the same result each
time; the same is true of the condition on the second @code{if}.
The recursive call of @code{fac} did not return at all.


@node The Outside Context
@subsection The Outside Context

Edebug tries to be transparent to the program you are debugging, but it
does not succeed completely.  Edebug also tries to be transparent when
you evaluate expressions with @kbd{e} or with the evaluation list
buffer, by temporarily restoring the outside context.  This section
explains precisely what context Edebug restores, and how Edebug fails to
be completely transparent.

@menu
* Checking Whether to Stop::    When Edebug decides what to do.
* Edebug Display Update::       When Edebug updates the display.
* Edebug Recursive Edit::       When Edebug stops execution.
@end menu

@node Checking Whether to Stop
@subsubsection Checking Whether to Stop

Whenever Edebug is entered, it needs to save and restore certain data
before even deciding whether to make trace information or stop the
program.

@itemize @bullet
@item
@vindex edebug-max-depth
@code{max-lisp-eval-depth} (@pxref{Eval}) and @code{max-specpdl-size}
(@pxref{Local Variables}) are both increased to reduce Edebug's impact
on the stack.  You could, however, still run out of stack space when
using Edebug.  You can also enlarge the value of
@code{edebug-max-depth} if Edebug reaches the limit of recursion depth
instrumenting code that contains very large quoted lists.

@item
The state of keyboard macro execution is saved and restored.  While
Edebug is active, @code{executing-kbd-macro} is bound to @code{nil}
unless @code{edebug-continue-kbd-macro} is non-@code{nil}.
@end itemize


@node Edebug Display Update
@subsubsection Edebug Display Update

@c This paragraph is not filled, because LaLiberte's conversion script
@c needs an xref to be on just one line.
When Edebug needs to display something (e.g., in trace mode), it saves
the current window configuration from outside Edebug
(@pxref{Window Configurations}).  When you exit Edebug, it restores
the previous window configuration.

Emacs redisplays only when it pauses.  Usually, when you continue
execution, the program re-enters Edebug at a breakpoint or after
stepping, without pausing or reading input in between.  In such cases,
Emacs never gets a chance to redisplay the outside configuration.
Consequently, what you see is the same window configuration as the last
time Edebug was active, with no interruption.

Entry to Edebug for displaying something also saves and restores the
following data (though some of them are deliberately not restored if an
error or quit signal occurs).

@itemize @bullet
@item
@cindex current buffer point and mark (Edebug)
Which buffer is current, and the positions of point and the mark in the
current buffer, are saved and restored.

@item
@cindex window configuration (Edebug)
The outside window configuration is saved and restored if
@code{edebug-save-windows} is non-@code{nil} (@pxref{Edebug Options}).

The window configuration is not restored on error or quit, but the
outside selected window @emph{is} reselected even on error or quit in
case a @code{save-excursion} is active.  If the value of
@code{edebug-save-windows} is a list, only the listed windows are saved
and restored.

The window start and horizontal scrolling of the source code buffer are
not restored, however, so that the display remains coherent within Edebug.

@item
The value of point in each displayed buffer is saved and restored if
@code{edebug-save-displayed-buffer-points} is non-@code{nil}.

@item
The variables @code{overlay-arrow-position} and
@code{overlay-arrow-string} are saved and restored, so you can safely
invoke Edebug from the recursive edit elsewhere in the same buffer.

@item
@code{cursor-in-echo-area} is locally bound to @code{nil} so that
the cursor shows up in the window.
@end itemize

@node Edebug Recursive Edit
@subsubsection Edebug Recursive Edit

When Edebug is entered and actually reads commands from the user, it
saves (and later restores) these additional data:

@itemize @bullet
@item
The current match data.  @xref{Match Data}.

@item
The variables @code{last-command}, @code{this-command},
@code{last-command-event}, @code{last-input-event},
@code{last-event-frame}, @code{last-nonmenu-event}, and
@code{track-mouse}.  Commands in Edebug do not affect these variables
outside of Edebug.

Executing commands within Edebug can change the key sequence that
would be returned by @code{this-command-keys}, and there is no way to
reset the key sequence from Lisp.

Edebug cannot save and restore the value of
@code{unread-command-events}.  Entering Edebug while this variable has a
nontrivial value can interfere with execution of the program you are
debugging.

@item
Complex commands executed while in Edebug are added to the variable
@code{command-history}.  In rare cases this can alter execution.

@item
Within Edebug, the recursion depth appears one deeper than the recursion
depth outside Edebug.  This is not true of the automatically updated
evaluation list window.

@item
@code{standard-output} and @code{standard-input} are bound to @code{nil}
by the @code{recursive-edit}, but Edebug temporarily restores them during
evaluations.

@item
The state of keyboard macro definition is saved and restored.  While
Edebug is active, @code{defining-kbd-macro} is bound to
@code{edebug-continue-kbd-macro}.
@end itemize

@node Edebug and Macros
@subsection Edebug and Macros

To make Edebug properly instrument expressions that call macros, some
extra care is needed.  This subsection explains the details.

@menu
* Instrumenting Macro Calls::   The basic problem.
* Specification List::          How to specify complex patterns of evaluation.
* Backtracking::                What Edebug does when matching fails.
* Specification Examples::      To help understand specifications.
@end menu

@node Instrumenting Macro Calls
@subsubsection Instrumenting Macro Calls

  When Edebug instruments an expression that calls a Lisp macro, it needs
additional information about the macro to do the job properly.  This is
because there is no a-priori way to tell which subexpressions of the
macro call are forms to be evaluated.  (Evaluation may occur explicitly
in the macro body, or when the resulting expansion is evaluated, or any
time later.)

  Therefore, you must define an Edebug specification for each macro
that Edebug will encounter, to explain the format of calls to that
macro.  To do this, add a @code{debug} declaration to the macro
definition.  Here is a simple example that shows the specification for
the @code{for} example macro (@pxref{Argument Evaluation}).

@smallexample
(defmacro for (var from init to final do &rest body)
  "Execute a simple \"for\" loop.
For example, (for i from 1 to 10 do (print i))."
  (declare (debug (symbolp "from" form "to" form "do" &rest form)))
  ...)
@end smallexample

  The Edebug specification says which parts of a call to the macro are
forms to be evaluated.  For simple macros, the specification
often looks very similar to the formal argument list of the macro
definition, but specifications are much more general than macro
arguments.  @xref{Defining Macros}, for more explanation of
the @code{declare} form.

@c See, e.g., https://debbugs.gnu.org/10577
@c FIXME  Maybe there should be an Edebug option to get it to
@c automatically load the entire source file containing the function
@c being instrumented.  That would avoid this.
  Take care to ensure that the specifications are known to Edebug when
you instrument code.  If you are instrumenting a function which uses a
macro defined in another file, you may first need to either evaluate
the @code{require} forms in the file containing your function, or
explicitly load the file containing the macro.  If the definition of a
macro is wrapped by @code{eval-when-compile}, you may need to evaluate
it.

  You can also define an edebug specification for a macro separately
from the macro definition with @code{def-edebug-spec}.  Adding
@code{debug} declarations is preferred, and more convenient, for macro
definitions in Lisp, but @code{def-edebug-spec} makes it possible to
define Edebug specifications for special forms implemented in C.

@defmac def-edebug-spec macro specification
Specify which expressions of a call to macro @var{macro} are forms to be
evaluated.  @var{specification} should be the edebug specification.
Neither argument is evaluated.

The @var{macro} argument can actually be any symbol, not just a macro
name.
@end defmac

Here is a table of the possibilities for @var{specification} and how each
directs processing of arguments.

@table @asis
@item @code{t}
All arguments are instrumented for evaluation.

@item @code{0}
None of the arguments is instrumented.

@item a symbol
The symbol must have an Edebug specification, which is used instead.
This indirection is repeated until another kind of specification is
found.  This allows you to inherit the specification from another macro.

@item a list
The elements of the list describe the types of the arguments of a
calling form.  The possible elements of a specification list are
described in the following sections.
@end table

If a macro has no Edebug specification, neither through a @code{debug}
declaration nor through a @code{def-edebug-spec} call, the variable
@code{edebug-eval-macro-args} comes into play.

@defopt edebug-eval-macro-args
This controls the way Edebug treats macro arguments with no explicit
Edebug specification.  If it is @code{nil} (the default), none of the
arguments is instrumented for evaluation.  Otherwise, all arguments
are instrumented.
@end defopt

@node Specification List
@subsubsection Specification List

@cindex Edebug specification list
A @dfn{specification list} is required for an Edebug specification if
some arguments of a macro call are evaluated while others are not.  Some
elements in a specification list match one or more arguments, but others
modify the processing of all following elements.  The latter, called
@dfn{specification keywords}, are symbols beginning with @samp{&} (such
as @code{&optional}).

A specification list may contain sublists, which match arguments that are
themselves lists, or it may contain vectors used for grouping.  Sublists
and groups thus subdivide the specification list into a hierarchy of
levels.  Specification keywords apply only to the remainder of the
sublist or group they are contained in.

When a specification list involves alternatives or repetition, matching
it against an actual macro call may require backtracking.  For more
details, @pxref{Backtracking}.

Edebug specifications provide the power of regular expression matching,
plus some context-free grammar constructs: the matching of sublists with
balanced parentheses, recursive processing of forms, and recursion via
indirect specifications.

Here's a table of the possible elements of a specification list, with
their meanings (see @ref{Specification Examples}, for the referenced
examples):

@table @code
@item sexp
A single unevaluated Lisp object, which is not instrumented.
@c an "expression" is not necessarily intended for evaluation.

@item form
A single evaluated expression, which is instrumented.  If your macro
wraps the expression with @code{lambda} before it is evaluated, use
@code{def-form} instead.  See @code{def-form} below.

@item place
A generalized variable.  @xref{Generalized Variables}.

@item body
Short for @code{&rest form}.  See @code{&rest} below.  If your macro
wraps its body of code with @code{lambda} before it is evaluated, use
@code{def-body} instead.  See @code{def-body} below.

@item function-form
A function form: either a quoted function symbol, a quoted lambda
expression, or a form (that should evaluate to a function symbol or
lambda expression).  This is useful when an argument that's a lambda
expression might be quoted with @code{quote} rather than
@code{function}, since it instruments the body of the lambda expression
either way.

@item lambda-expr
A lambda expression with no quoting.

@item &optional
@c @kindex &optional @r{(Edebug)}
All following elements in the specification list are optional; as soon
as one does not match, Edebug stops matching at this level.

To make just a few elements optional, followed by non-optional elements,
use @code{[&optional @var{specs}@dots{}]}.  To specify that several
elements must all match or none, use @code{&optional
[@var{specs}@dots{}]}.  See the @code{defun} example.

@item &rest
@c @kindex &rest @r{(Edebug)}
All following elements in the specification list are repeated zero or
more times.  In the last repetition, however, it is not a problem if the
expression runs out before matching all of the elements of the
specification list.

To repeat only a few elements, use @code{[&rest @var{specs}@dots{}]}.
To specify several elements that must all match on every repetition, use
@code{&rest [@var{specs}@dots{}]}.

@item &or
@c @kindex &or @r{(Edebug)}
Each of the following elements in the specification list is an
alternative.  One of the alternatives must match, or the @code{&or}
specification fails.

Each list element following @code{&or} is a single alternative.  To
group two or more list elements as a single alternative, enclose them in
@code{[@dots{}]}.

@item &not
@c @kindex &not @r{(Edebug)}
Each of the following elements is matched as alternatives as if by using
@code{&or}, but if any of them match, the specification fails.  If none
of them match, nothing is matched, but the @code{&not} specification
succeeds.

@c FIXME &key?

@item &define
@c @kindex &define @r{(Edebug)}
Indicates that the specification is for a defining form.  Edebug's
definition of a defining form is a form containing one or more code
forms which are saved and executed later, after the execution of the
defining form.

The defining form itself is not instrumented (that is, Edebug does not
stop before and after the defining form), but forms inside it
typically will be instrumented.  The @code{&define} keyword should be
the first element in a list specification.

@item nil
This is successful when there are no more arguments to match at the
current argument list level; otherwise it fails.  See sublist
specifications and the backquote example.

@item gate
@cindex preventing backtracking
No argument is matched but backtracking through the gate is disabled
while matching the remainder of the specifications at this level.  This
is primarily used to generate more specific syntax error messages.  See
@ref{Backtracking}, for more details.  Also see the @code{let} example.

@item @var{other-symbol}
@cindex indirect specifications
Any other symbol in a specification list may be a predicate or an
indirect specification.

If the symbol has an Edebug specification, this @dfn{indirect
specification} should be either a list specification that is used in
place of the symbol, or a function that is called to process the
arguments.  The specification may be defined with @code{def-edebug-spec}
just as for macros.  See the @code{defun} example.

Otherwise, the symbol should be a predicate.  The predicate is called
with the argument, and if the predicate returns @code{nil}, the
specification fails and the argument is not instrumented.

Some suitable predicates include @code{symbolp}, @code{integerp},
@code{stringp}, @code{vectorp}, and @code{atom}.

@item [@var{elements}@dots{}]
@cindex [@dots{}] (Edebug)
A vector of elements groups the elements into a single @dfn{group
specification}.  Its meaning has nothing to do with vectors.

@item "@var{string}"
The argument should be a symbol named @var{string}.  This specification
is equivalent to the quoted symbol, @code{'@var{symbol}}, where the name
of @var{symbol} is the @var{string}, but the string form is preferred.

@item (vector @var{elements}@dots{})
The argument should be a vector whose elements must match the
@var{elements} in the specification.  See the backquote example.

@item (@var{elements}@dots{})
Any other list is a @dfn{sublist specification} and the argument must be
a list whose elements match the specification @var{elements}.

@cindex dotted lists (Edebug)
A sublist specification may be a dotted list and the corresponding list
argument may then be a dotted list.  Alternatively, the last @sc{cdr} of a
dotted list specification may be another sublist specification (via a
grouping or an indirect specification, e.g., @code{(spec .  [(more
specs@dots{})])}) whose elements match the non-dotted list arguments.
This is useful in recursive specifications such as in the backquote
example.  Also see the description of a @code{nil} specification
above for terminating such recursion.

Note that a sublist specification written as @code{(specs .  nil)}
is equivalent to @code{(specs)}, and @code{(specs .
(sublist-elements@dots{}))} is equivalent to @code{(specs
sublist-elements@dots{})}.
@end table

@c Need to document extensions with &symbol and :symbol

Here is a list of additional specifications that may appear only after
@code{&define}.  See the @code{defun} example.

@table @code
@item name
The argument, a symbol, is the name of the defining form.

A defining form is not required to have a name field; and it may have
multiple name fields.

@item :name
This construct does not actually match an argument.  The element
following @code{:name} should be a symbol; it is used as an additional
name component for the definition.  You can use this to add a unique,
static component to the name of the definition.  It may be used more
than once.

@item arg
The argument, a symbol, is the name of an argument of the defining form.
However, lambda-list keywords (symbols starting with @samp{&})
are not allowed.

@item lambda-list
@cindex lambda-list (Edebug)
This matches a lambda list---the argument list of a lambda expression.

@item def-body
The argument is the body of code in a definition.  This is like
@code{body}, described above, but a definition body must be instrumented
with a different Edebug call that looks up information associated with
the definition.  Use @code{def-body} for the highest level list of forms
within the definition.

@item def-form
The argument is a single, highest-level form in a definition.  This is
like @code{def-body}, except it is used to match a single form rather than
a list of forms.  As a special case, @code{def-form} also means that
tracing information is not output when the form is executed.  See the
@code{interactive} example.
@end table

@node Backtracking
@subsubsection Backtracking in Specifications

@cindex backtracking
@cindex syntax error (Edebug)
If a specification fails to match at some point, this does not
necessarily mean a syntax error will be signaled; instead,
@dfn{backtracking} will take place until all alternatives have been
exhausted.  Eventually every element of the argument list must be
matched by some element in the specification, and every required element
in the specification must match some argument.

When a syntax error is detected, it might not be reported until much
later, after higher-level alternatives have been exhausted, and with the
point positioned further from the real error.  But if backtracking is
disabled when an error occurs, it can be reported immediately.  Note
that backtracking is also reenabled automatically in several situations;
when a new alternative is established by @code{&optional},
@code{&rest}, or @code{&or}, or at the start of processing a sublist,
group, or indirect specification.  The effect of enabling or disabling
backtracking is limited to the remainder of the level currently being
processed and lower levels.

Backtracking is disabled while matching any of the
form specifications (that is, @code{form}, @code{body}, @code{def-form}, and
@code{def-body}).  These specifications will match any form so any error
must be in the form itself rather than at a higher level.

Backtracking is also disabled after successfully matching a quoted
symbol or string specification, since this usually indicates a
recognized construct.  But if you have a set of alternative constructs that
all begin with the same symbol, you can usually work around this
constraint by factoring the symbol out of the alternatives, e.g.,
@code{["foo" &or [first case] [second case] ...]}.

Most needs are satisfied by these two ways that backtracking is
automatically disabled, but occasionally it is useful to explicitly
disable backtracking by using the @code{gate} specification.  This is
useful when you know that no higher alternatives could apply.  See the
example of the @code{let} specification.

@node Specification Examples
@subsubsection Specification Examples

It may be easier to understand Edebug specifications by studying
the examples provided here.

A @code{let} special form has a sequence of bindings and a body.  Each
of the bindings is either a symbol or a sublist with a symbol and
optional expression.  In the specification below, notice the @code{gate}
inside of the sublist to prevent backtracking once a sublist is found.

@ignore
@c FIXME?  The actual definition in edebug.el looks like this (and always
@c has AFAICS).  In fact, nothing in edebug.el uses gate.  So maybe
@c this is just an example for illustration?
(def-edebug-spec let
  ((&rest
    &or (symbolp &optional form) symbolp)
   body))
@end ignore
@example
(def-edebug-spec let
  ((&rest
    &or symbolp (gate symbolp &optional form))
   body))
@end example

Edebug uses the following specifications for @code{defun} and the
associated argument list and @code{interactive} specifications.  It is
necessary to handle interactive forms specially since an expression
argument is actually evaluated outside of the function body.  (The
specification for @code{defmacro} is very similar to that for
@code{defun}, but allows for the @code{declare} statement.)

@smallexample
(def-edebug-spec defun
  (&define name lambda-list
           [&optional stringp]   ; @r{Match the doc string, if present.}
           [&optional ("interactive" interactive)]
           def-body))

(def-edebug-spec lambda-list
  (([&rest arg]
    [&optional ["&optional" arg &rest arg]]
    &optional ["&rest" arg]
    )))

(def-edebug-spec interactive
  (&optional &or stringp def-form))    ; @r{Notice: @code{def-form}}
@end smallexample

The specification for backquote below illustrates how to match
dotted lists and use @code{nil} to terminate recursion.  It also
illustrates how components of a vector may be matched.  (The actual
specification defined by Edebug is a little different, and does not
support dotted lists because doing so causes very deep recursion that
could fail.)

@smallexample
(def-edebug-spec \` (backquote-form))   ; @r{Alias just for clarity.}

(def-edebug-spec backquote-form
  (&or ([&or "," ",@@"] &or ("quote" backquote-form) form)
       (backquote-form . [&or nil backquote-form])
       (vector &rest backquote-form)
       sexp))
@end smallexample


@node Edebug Options
@subsection Edebug Options

  These options affect the behavior of Edebug:
@c Previously defopt'd:
@c edebug-sit-for-seconds, edebug-print-length, edebug-print-level
@c edebug-print-circle, edebug-eval-macro-args

@defopt edebug-setup-hook
Functions to call before Edebug is used.  Each time it is set to a new
value, Edebug will call those functions once and then
reset @code{edebug-setup-hook} to @code{nil}.  You could use this to
load up Edebug specifications associated with a package you are using,
but only when you also use Edebug.
@xref{Instrumenting}.
@end defopt

@defopt edebug-all-defs
If this is non-@code{nil}, normal evaluation of defining forms such as
@code{defun} and @code{defmacro} instruments them for Edebug.  This
applies to @code{eval-defun}, @code{eval-region}, @code{eval-buffer},
and @code{eval-current-buffer}.

Use the command @kbd{M-x edebug-all-defs} to toggle the value of this
option.  @xref{Instrumenting}.
@end defopt

@defopt edebug-all-forms
If this is non-@code{nil}, the commands @code{eval-defun},
@code{eval-region}, @code{eval-buffer}, and @code{eval-current-buffer}
instrument all forms, even those that don't define anything.
This doesn't apply to loading or evaluations in the minibuffer.

Use the command @kbd{M-x edebug-all-forms} to toggle the value of this
option.  @xref{Instrumenting}.
@end defopt

@defopt edebug-eval-macro-args
When this is non-@code{nil}, all macro arguments will be instrumented
in the generated code.  For any macro, an @code{edebug-form-spec}
overrides this option.  So to specify exceptions for macros that have
some arguments evaluated and some not, use @code{def-edebug-spec} to
specify an @code{edebug-form-spec}.
@end defopt

@defopt edebug-save-windows
If this is non-@code{nil}, Edebug saves and restores the window
configuration.  That takes some time, so if your program does not care
what happens to the window configurations, it is better to set this
variable to @code{nil}.

If the value is a list, only the listed windows are saved and
restored.

You can use the @kbd{W} command in Edebug to change this variable
interactively.  @xref{Edebug Display Update}.
@end defopt

@defopt edebug-save-displayed-buffer-points
If this is non-@code{nil}, Edebug saves and restores point in all
displayed buffers.

Saving and restoring point in other buffers is necessary if you are
debugging code that changes the point of a buffer that is displayed in
a non-selected window.  If Edebug or the user then selects the window,
point in that buffer will move to the window's value of point.

Saving and restoring point in all buffers is expensive, since it
requires selecting each window twice, so enable this only if you need
it.  @xref{Edebug Display Update}.
@end defopt

@defopt edebug-initial-mode
If this variable is non-@code{nil}, it specifies the initial execution
mode for Edebug when it is first activated.  Possible values are
@code{step}, @code{next}, @code{go}, @code{Go-nonstop}, @code{trace},
@code{Trace-fast}, @code{continue}, and @code{Continue-fast}.

The default value is @code{step}.  This variable can be set
interactively with @kbd{C-x C-a C-m} (@code{edebug-set-initial-mode}).
@xref{Edebug Execution Modes}.
@end defopt

@defopt edebug-trace
If this is non-@code{nil}, trace each function entry and exit.
Tracing output is displayed in a buffer named @file{*edebug-trace*}, one
function entry or exit per line, indented by the recursion level.

Also see @code{edebug-tracing}, in @ref{Trace Buffer}.
@end defopt

@defopt edebug-test-coverage
If non-@code{nil}, Edebug tests coverage of all expressions debugged.
@xref{Coverage Testing}.
@end defopt

@defopt edebug-continue-kbd-macro
If non-@code{nil}, continue defining or executing any keyboard macro
that is executing outside of Edebug.   Use this with caution since it is not
debugged.
@xref{Edebug Execution Modes}.
@end defopt

@defopt edebug-print-length
If non-@code{nil}, the default value of @code{print-length} for
printing results in Edebug.  @xref{Output Variables}.
@end defopt

@defopt edebug-print-level
If non-@code{nil}, the default value of @code{print-level} for
printing results in Edebug.  @xref{Output Variables}.
@end defopt

@defopt edebug-print-circle
If non-@code{nil}, the default value of @code{print-circle} for
printing results in Edebug.  @xref{Output Variables}.
@end defopt

@defopt edebug-unwrap-results
If non-@code{nil}, Edebug tries to remove any of its own
instrumentation when showing the results of expressions.  This is
relevant when debugging macros where the results of expressions are
themselves instrumented expressions.  As a very artificial example,
suppose that the example function @code{fac} has been instrumented,
and consider a macro of the form:

@c FIXME find a less silly example.
@smallexample
(defmacro test () "Edebug example."
  (if (symbol-function 'fac)
      @dots{}))
@end smallexample

If you instrument the @code{test} macro and step through it, then by
default the result of the @code{symbol-function} call has numerous
@code{edebug-after} and @code{edebug-before} forms, which can make it
difficult to see the actual result.  If
@code{edebug-unwrap-results} is non-@code{nil}, Edebug tries to remove
these forms from the result.
@end defopt

@defopt edebug-on-error
Edebug binds @code{debug-on-error} to this value, if
@code{debug-on-error} was previously @code{nil}.  @xref{Trapping
Errors}.
@end defopt

@defopt edebug-on-quit
Edebug binds @code{debug-on-quit} to this value, if
@code{debug-on-quit} was previously @code{nil}.  @xref{Trapping
Errors}.
@end defopt

  If you change the values of @code{edebug-on-error} or
@code{edebug-on-quit} while Edebug is active, their values won't be used
until the @emph{next} time Edebug is invoked via a new command.
@c Not necessarily a deeper command level.
@c A new command is not precisely true, but that is close enough -- dan

@defopt edebug-global-break-condition
If non-@code{nil}, an expression to test for at every stop point.  If
the result is non-@code{nil}, then break.  Errors are ignored.
@xref{Global Break Condition}.
@end defopt

@defopt edebug-sit-for-seconds
Number of seconds to pause when a breakpoint is reached and the execution
mode is trace or continue.  @xref{Edebug Execution Modes}.
@end defopt

@defopt edebug-sit-on-break
Whether or not to pause for @code{edebug-sit-for-seconds} on reaching
a breakpoint.  Set to @code{nil} to prevent the pause, non-@code{nil}
to allow it.
@end defopt

@defopt edebug-behavior-alist
By default, this alist contains one entry with the key @code{edebug}
and a list of three functions, which are the default implementations
of the functions inserted in instrumented code: @code{edebug-enter},
@code{edebug-before} and @code{edebug-after}.  To change Edebug's
behavior globally, modify the default entry.

Edebug's behavior may also be changed on a per-definition basis by
adding an entry to this alist, with a key of your choice and three
functions.  Then set the @code{edebug-behavior} symbol property of an
instrumented definition to the key of the new entry, and Edebug will
call the new functions in place of its own for that definition.
@end defopt

@defopt edebug-new-definition-function
A function run by Edebug after it wraps the body of a definition
or closure.  After Edebug has initialized its own data, this function
is called with one argument, the symbol associated with the
definition, which may be the actual symbol defined or one generated by
Edebug.  This function may be used to set the @code{edebug-behavior}
symbol property of each definition instrumented by Edebug.
@end defopt

@defopt edebug-after-instrumentation-function
To inspect or modify Edebug's instrumentation before it is used, set
this variable to a function which takes one argument, an instrumented
top-level form, and returns either the same or a replacement form,
which Edebug will then use as the final result of instrumentation.
@end defopt

debug log:

solving 8be8307c75 ...
found 8be8307c75 in https://git.savannah.gnu.org/cgit/emacs.git

(*) Git path names are given by the tree(s) the blob belongs to.
    Blobs themselves have no identifier aside from the hash of its contents.^

Code repositories for project(s) associated with this public inbox

	https://git.savannah.gnu.org/cgit/emacs.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).