Commit | Line | Data |
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a0d0e21e LW |
1 | =head1 NAME |
2 | ||
3 | perldebug - Perl debugging | |
4 | ||
5 | =head1 DESCRIPTION | |
6 | ||
7 | First of all, have you tried using the B<-w> switch? | |
8 | ||
f6b3c421 MJD |
9 | |
10 | If you're new to the Perl debugger, you may prefer to read | |
11 | L<perldebtut>, which is a tutorial introduction to the debugger . | |
12 | ||
4e1d3b43 | 13 | =head1 The Perl Debugger |
14 | ||
15 | If you invoke Perl with the B<-d> switch, your script runs under the | |
16 | Perl source debugger. This works like an interactive Perl | |
17 | environment, prompting for debugger commands that let you examine | |
68dc0745 | 18 | source code, set breakpoints, get stack backtraces, change the values of |
4e1d3b43 | 19 | variables, etc. This is so convenient that you often fire up |
54310121 | 20 | the debugger all by itself just to test out Perl constructs |
4e1d3b43 | 21 | interactively to see what they do. For example: |
22 | ||
055fd3a9 | 23 | $ perl -d -e 42 |
4e1d3b43 | 24 | |
055fd3a9 | 25 | In Perl, the debugger is not a separate program the way it usually is in the |
4e1d3b43 | 26 | typical compiled environment. Instead, the B<-d> flag tells the compiler |
27 | to insert source information into the parse trees it's about to hand off | |
28 | to the interpreter. That means your code must first compile correctly | |
29 | for the debugger to work on it. Then when the interpreter starts up, it | |
055fd3a9 | 30 | preloads a special Perl library file containing the debugger. |
4e1d3b43 | 31 | |
32 | The program will halt I<right before> the first run-time executable | |
33 | statement (but see below regarding compile-time statements) and ask you | |
34 | to enter a debugger command. Contrary to popular expectations, whenever | |
35 | the debugger halts and shows you a line of code, it always displays the | |
36 | line it's I<about> to execute, rather than the one it has just executed. | |
37 | ||
38 | Any command not recognized by the debugger is directly executed | |
055fd3a9 GS |
39 | (C<eval>'d) as Perl code in the current package. (The debugger |
40 | uses the DB package for keeping its own state information.) | |
4e1d3b43 | 41 | |
ea5ec306 SP |
42 | Note that the said C<eval> is bound by an implicit scope. As a |
43 | result any newly introduced lexical variable or any modified | |
44 | capture buffer content is lost after the eval. The debugger is a | |
45 | nice environment to learn Perl, but if you interactively experiment using | |
46 | material which should be in the same scope, stuff it in one line. | |
47 | ||
055fd3a9 GS |
48 | For any text entered at the debugger prompt, leading and trailing whitespace |
49 | is first stripped before further processing. If a debugger command | |
50 | coincides with some function in your own program, merely precede the | |
51 | function with something that doesn't look like a debugger command, such | |
52 | as a leading C<;> or perhaps a C<+>, or by wrapping it with parentheses | |
53 | or braces. | |
4e1d3b43 | 54 | |
55 | =head2 Debugger Commands | |
56 | ||
57 | The debugger understands the following commands: | |
a0d0e21e LW |
58 | |
59 | =over 12 | |
60 | ||
492652be RF |
61 | =item h |
62 | ||
63 | Prints out a summary help message | |
64 | ||
4e1d3b43 | 65 | =item h [command] |
66 | ||
492652be | 67 | Prints out a help message for the given debugger command. |
4e1d3b43 | 68 | |
492652be | 69 | =item h h |
4e1d3b43 | 70 | |
492652be RF |
71 | The special argument of C<h h> produces the entire help page, which is quite long. |
72 | ||
73 | If the output of the C<h h> command (or any command, for that matter) scrolls | |
055fd3a9 GS |
74 | past your screen, precede the command with a leading pipe symbol so |
75 | that it's run through your pager, as in | |
4e1d3b43 | 76 | |
492652be RF |
77 | DB> |h h |
78 | ||
79 | You may change the pager which is used via C<o pager=...> command. | |
4e1d3b43 | 80 | |
e7ea3e70 | 81 | |
4e1d3b43 | 82 | =item p expr |
83 | ||
36477c24 | 84 | Same as C<print {$DB::OUT} expr> in the current package. In particular, |
c997b287 | 85 | because this is just Perl's own C<print> function, this means that nested |
4e1d3b43 | 86 | data structures and objects are not dumped, unlike with the C<x> command. |
87 | ||
e7ea3e70 IZ |
88 | The C<DB::OUT> filehandle is opened to F</dev/tty>, regardless of |
89 | where STDOUT may be redirected to. | |
90 | ||
3ae893bd | 91 | =item x [maxdepth] expr |
4e1d3b43 | 92 | |
a991b806 JC |
93 | Evaluates its expression in list context and dumps out the result in a |
94 | pretty-printed fashion. Nested data structures are printed out | |
95 | recursively, unlike the real C<print> function in Perl. When dumping | |
96 | hashes, you'll probably prefer 'x \%h' rather than 'x %h'. | |
055fd3a9 | 97 | See L<Dumpvalue> if you'd like to do this yourself. |
4e1d3b43 | 98 | |
055fd3a9 | 99 | The output format is governed by multiple options described under |
13a2d996 | 100 | L<"Configurable Options">. |
36477c24 | 101 | |
3ae893bd MJD |
102 | If the C<maxdepth> is included, it must be a numeral I<N>; the value is |
103 | dumped only I<N> levels deep, as if the C<dumpDepth> option had been | |
5cc082a2 | 104 | temporarily set to I<N>. |
3ae893bd | 105 | |
4e1d3b43 | 106 | =item V [pkg [vars]] |
107 | ||
2e8f3c35 | 108 | Display all (or some) variables in package (defaulting to C<main>) |
055fd3a9 GS |
109 | using a data pretty-printer (hashes show their keys and values so |
110 | you see what's what, control characters are made printable, etc.). | |
111 | Make sure you don't put the type specifier (like C<$>) there, just | |
112 | the symbol names, like this: | |
4e1d3b43 | 113 | |
114 | V DB filename line | |
115 | ||
055fd3a9 | 116 | Use C<~pattern> and C<!pattern> for positive and negative regexes. |
4e1d3b43 | 117 | |
055fd3a9 | 118 | This is similar to calling the C<x> command on each applicable var. |
36477c24 | 119 | |
4e1d3b43 | 120 | =item X [vars] |
121 | ||
122 | Same as C<V currentpackage [vars]>. | |
a0d0e21e | 123 | |
a7b657ee PS |
124 | =item y [level [vars]] |
125 | ||
126 | Display all (or some) lexical variables (mnemonic: C<mY> variables) | |
127 | in the current scope or I<level> scopes higher. You can limit the | |
128 | variables that you see with I<vars> which works exactly as it does | |
129 | for the C<V> and C<X> commands. Requires the C<PadWalker> module | |
130 | version 0.08 or higher; will warn if this isn't installed. Output | |
131 | is pretty-printed in the same style as for C<V> and the format is | |
132 | controlled by the same options. | |
133 | ||
a0d0e21e LW |
134 | =item T |
135 | ||
68dc0745 | 136 | Produce a stack backtrace. See below for details on its output. |
a0d0e21e | 137 | |
4e1d3b43 | 138 | =item s [expr] |
a0d0e21e | 139 | |
055fd3a9 | 140 | Single step. Executes until the beginning of another |
4e1d3b43 | 141 | statement, descending into subroutine calls. If an expression is |
142 | supplied that includes function calls, it too will be single-stepped. | |
a0d0e21e | 143 | |
e7ea3e70 | 144 | =item n [expr] |
a0d0e21e | 145 | |
055fd3a9 | 146 | Next. Executes over subroutine calls, until the beginning |
774d564b | 147 | of the next statement. If an expression is supplied that includes |
148 | function calls, those functions will be executed with stops before | |
149 | each statement. | |
a0d0e21e | 150 | |
dce0c882 GS |
151 | =item r |
152 | ||
055fd3a9 GS |
153 | Continue until the return from the current subroutine. |
154 | Dump the return value if the C<PrintRet> option is set (default). | |
dce0c882 | 155 | |
c47ff5f1 | 156 | =item <CR> |
a0d0e21e | 157 | |
4e1d3b43 | 158 | Repeat last C<n> or C<s> command. |
a0d0e21e | 159 | |
36477c24 | 160 | =item c [line|sub] |
a0d0e21e | 161 | |
4e1d3b43 | 162 | Continue, optionally inserting a one-time-only breakpoint |
36477c24 | 163 | at the specified line or subroutine. |
a0d0e21e | 164 | |
4e1d3b43 | 165 | =item l |
a0d0e21e | 166 | |
4e1d3b43 | 167 | List next window of lines. |
a0d0e21e LW |
168 | |
169 | =item l min+incr | |
170 | ||
4e1d3b43 | 171 | List C<incr+1> lines starting at C<min>. |
a0d0e21e LW |
172 | |
173 | =item l min-max | |
174 | ||
c47ff5f1 | 175 | List lines C<min> through C<max>. C<l -> is synonymous to C<->. |
a0d0e21e LW |
176 | |
177 | =item l line | |
178 | ||
4e1d3b43 | 179 | List a single line. |
a0d0e21e | 180 | |
4e1d3b43 | 181 | =item l subname |
a0d0e21e | 182 | |
83ee9e09 | 183 | List first window of lines from subroutine. I<subname> may |
055fd3a9 | 184 | be a variable that contains a code reference. |
a0d0e21e LW |
185 | |
186 | =item - | |
187 | ||
4e1d3b43 | 188 | List previous window of lines. |
a0d0e21e | 189 | |
492652be | 190 | =item v [line] |
a0d0e21e | 191 | |
492652be | 192 | View a few lines of code around the current line. |
a0d0e21e | 193 | |
4e1d3b43 | 194 | =item . |
a0d0e21e | 195 | |
055fd3a9 GS |
196 | Return the internal debugger pointer to the line last |
197 | executed, and print out that line. | |
4e1d3b43 | 198 | |
199 | =item f filename | |
200 | ||
055fd3a9 | 201 | Switch to viewing a different file or C<eval> statement. If I<filename> |
2e8f3c35 | 202 | is not a full pathname found in the values of %INC, it is considered |
055fd3a9 | 203 | a regex. |
a0d0e21e | 204 | |
bee32ff8 GS |
205 | C<eval>ed strings (when accessible) are considered to be filenames: |
206 | C<f (eval 7)> and C<f eval 7\b> access the body of the 7th C<eval>ed string | |
055fd3a9 GS |
207 | (in the order of execution). The bodies of the currently executed C<eval> |
208 | and of C<eval>ed strings that define subroutines are saved and thus | |
209 | accessible. | |
bee32ff8 | 210 | |
a0d0e21e LW |
211 | =item /pattern/ |
212 | ||
055fd3a9 | 213 | Search forwards for pattern (a Perl regex); final / is optional. |
ae55e07e | 214 | The search is case-insensitive by default. |
a0d0e21e LW |
215 | |
216 | =item ?pattern? | |
217 | ||
4e1d3b43 | 218 | Search backwards for pattern; final ? is optional. |
ae55e07e | 219 | The search is case-insensitive by default. |
a0d0e21e | 220 | |
492652be | 221 | =item L [abw] |
a0d0e21e | 222 | |
492652be | 223 | List (default all) actions, breakpoints and watch expressions |
a0d0e21e | 224 | |
055fd3a9 | 225 | =item S [[!]regex] |
a0d0e21e | 226 | |
055fd3a9 | 227 | List subroutine names [not] matching the regex. |
a0d0e21e LW |
228 | |
229 | =item t | |
230 | ||
055fd3a9 | 231 | Toggle trace mode (see also the C<AutoTrace> option). |
4e1d3b43 | 232 | |
233 | =item t expr | |
234 | ||
055fd3a9 GS |
235 | Trace through execution of C<expr>. |
236 | See L<perldebguts/"Frame Listing Output Examples"> for examples. | |
4e1d3b43 | 237 | |
492652be RF |
238 | =item b |
239 | ||
240 | Sets breakpoint on current line | |
241 | ||
4e1d3b43 | 242 | =item b [line] [condition] |
a0d0e21e | 243 | |
492652be | 244 | Set a breakpoint before the given line. If a condition |
055fd3a9 GS |
245 | is specified, it's evaluated each time the statement is reached: a |
246 | breakpoint is taken only if the condition is true. Breakpoints may | |
247 | only be set on lines that begin an executable statement. Conditions | |
c997b287 | 248 | don't use C<if>: |
a0d0e21e LW |
249 | |
250 | b 237 $x > 30 | |
36477c24 | 251 | b 237 ++$count237 < 11 |
a0d0e21e LW |
252 | b 33 /pattern/i |
253 | ||
4e1d3b43 | 254 | =item b subname [condition] |
a0d0e21e | 255 | |
055fd3a9 GS |
256 | Set a breakpoint before the first line of the named subroutine. I<subname> may |
257 | be a variable containing a code reference (in this case I<condition> | |
83ee9e09 | 258 | is not supported). |
a0d0e21e | 259 | |
36477c24 | 260 | =item b postpone subname [condition] |
261 | ||
055fd3a9 | 262 | Set a breakpoint at first line of subroutine after it is compiled. |
36477c24 | 263 | |
264 | =item b load filename | |
265 | ||
055fd3a9 GS |
266 | Set a breakpoint before the first executed line of the I<filename>, |
267 | which should be a full pathname found amongst the %INC values. | |
e7ea3e70 IZ |
268 | |
269 | =item b compile subname | |
270 | ||
055fd3a9 GS |
271 | Sets a breakpoint before the first statement executed after the specified |
272 | subroutine is compiled. | |
36477c24 | 273 | |
492652be | 274 | =item B line |
a0d0e21e | 275 | |
2e8f3c35 | 276 | Delete a breakpoint from the specified I<line>. |
a0d0e21e | 277 | |
492652be | 278 | =item B * |
a0d0e21e | 279 | |
4e1d3b43 | 280 | Delete all installed breakpoints. |
281 | ||
282 | =item a [line] command | |
283 | ||
055fd3a9 GS |
284 | Set an action to be done before the line is executed. If I<line> is |
285 | omitted, set an action on the line about to be executed. | |
4e1d3b43 | 286 | The sequence of steps taken by the debugger is |
287 | ||
8ebc5c01 | 288 | 1. check for a breakpoint at this line |
289 | 2. print the line if necessary (tracing) | |
290 | 3. do any actions associated with that line | |
291 | 4. prompt user if at a breakpoint or in single-step | |
292 | 5. evaluate line | |
a0d0e21e | 293 | |
7b8d334a | 294 | For example, this will print out $foo every time line |
4e1d3b43 | 295 | 53 is passed: |
a0d0e21e | 296 | |
4e1d3b43 | 297 | a 53 print "DB FOUND $foo\n" |
a0d0e21e | 298 | |
492652be | 299 | =item A line |
3fbd6552 | 300 | |
2e8f3c35 | 301 | Delete an action from the specified line. |
3fbd6552 | 302 | |
492652be | 303 | =item A * |
a0d0e21e | 304 | |
4e1d3b43 | 305 | Delete all installed actions. |
306 | ||
492652be | 307 | =item w expr |
6ee623d5 | 308 | |
055fd3a9 | 309 | Add a global watch-expression. We hope you know what one of these |
2e8f3c35 | 310 | is, because they're supposed to be obvious. |
6ee623d5 | 311 | |
492652be RF |
312 | =item W expr |
313 | ||
314 | Delete watch-expression | |
315 | ||
316 | =item W * | |
6ee623d5 GS |
317 | |
318 | Delete all watch-expressions. | |
319 | ||
492652be RF |
320 | =item o |
321 | ||
322 | Display all options | |
323 | ||
324 | =item o booloption ... | |
055fd3a9 GS |
325 | |
326 | Set each listed Boolean option to the value C<1>. | |
327 | ||
492652be | 328 | =item o anyoption? ... |
055fd3a9 GS |
329 | |
330 | Print out the value of one or more options. | |
331 | ||
492652be | 332 | =item o option=value ... |
055fd3a9 GS |
333 | |
334 | Set the value of one or more options. If the value has internal | |
492652be | 335 | whitespace, it should be quoted. For example, you could set C<o |
055fd3a9 GS |
336 | pager="less -MQeicsNfr"> to call B<less> with those specific options. |
337 | You may use either single or double quotes, but if you do, you must | |
338 | escape any embedded instances of same sort of quote you began with, | |
339 | as well as any escaping any escapes that immediately precede that | |
340 | quote but which are not meant to escape the quote itself. In other | |
341 | words, you follow single-quoting rules irrespective of the quote; | |
492652be | 342 | eg: C<o option='this isn\'t bad'> or C<o option="She said, \"Isn't |
055fd3a9 GS |
343 | it?\"">. |
344 | ||
345 | For historical reasons, the C<=value> is optional, but defaults to | |
346 | 1 only where it is safe to do so--that is, mostly for Boolean | |
347 | options. It is always better to assign a specific value using C<=>. | |
348 | The C<option> can be abbreviated, but for clarity probably should | |
2e8f3c35 | 349 | not be. Several options can be set together. See L<"Configurable Options"> |
13a2d996 | 350 | for a list of these. |
055fd3a9 | 351 | |
2e8f3c35 | 352 | =item < ? |
055fd3a9 GS |
353 | |
354 | List out all pre-prompt Perl command actions. | |
355 | ||
356 | =item < [ command ] | |
357 | ||
358 | Set an action (Perl command) to happen before every debugger prompt. | |
2e8f3c35 | 359 | A multi-line command may be entered by backslashing the newlines. |
0d6091f7 | 360 | |
2e8f3c35 | 361 | =item < * |
0d6091f7 RF |
362 | |
363 | Delete all pre-prompt Perl command actions. | |
055fd3a9 GS |
364 | |
365 | =item << command | |
366 | ||
367 | Add an action (Perl command) to happen before every debugger prompt. | |
368 | A multi-line command may be entered by backwhacking the newlines. | |
369 | ||
370 | =item > ? | |
371 | ||
372 | List out post-prompt Perl command actions. | |
373 | ||
374 | =item > command | |
375 | ||
376 | Set an action (Perl command) to happen after the prompt when you've | |
377 | just given a command to return to executing the script. A multi-line | |
378 | command may be entered by backslashing the newlines (we bet you | |
2e8f3c35 | 379 | couldn't've guessed this by now). |
0d6091f7 | 380 | |
2e8f3c35 | 381 | =item > * |
0d6091f7 RF |
382 | |
383 | Delete all post-prompt Perl command actions. | |
055fd3a9 GS |
384 | |
385 | =item >> command | |
386 | ||
387 | Adds an action (Perl command) to happen after the prompt when you've | |
388 | just given a command to return to executing the script. A multi-line | |
b1866b2d | 389 | command may be entered by backslashing the newlines. |
055fd3a9 GS |
390 | |
391 | =item { ? | |
392 | ||
393 | List out pre-prompt debugger commands. | |
394 | ||
395 | =item { [ command ] | |
396 | ||
397 | Set an action (debugger command) to happen before every debugger prompt. | |
2e8f3c35 | 398 | A multi-line command may be entered in the customary fashion. |
055fd3a9 GS |
399 | |
400 | Because this command is in some senses new, a warning is issued if | |
401 | you appear to have accidentally entered a block instead. If that's | |
2e8f3c35 | 402 | what you mean to do, write it as with C<;{ ... }> or even |
055fd3a9 GS |
403 | C<do { ... }>. |
404 | ||
2e8f3c35 | 405 | =item { * |
0d6091f7 RF |
406 | |
407 | Delete all pre-prompt debugger commands. | |
408 | ||
055fd3a9 GS |
409 | =item {{ command |
410 | ||
411 | Add an action (debugger command) to happen before every debugger prompt. | |
412 | A multi-line command may be entered, if you can guess how: see above. | |
413 | ||
414 | =item ! number | |
415 | ||
416 | Redo a previous command (defaults to the previous command). | |
417 | ||
418 | =item ! -number | |
419 | ||
420 | Redo number'th previous command. | |
421 | ||
422 | =item ! pattern | |
423 | ||
424 | Redo last command that started with pattern. | |
492652be | 425 | See C<o recallCommand>, too. |
055fd3a9 GS |
426 | |
427 | =item !! cmd | |
428 | ||
429 | Run cmd in a subprocess (reads from DB::IN, writes to DB::OUT) See | |
492652be | 430 | C<o shellBang>, also. Note that the user's current shell (well, |
055fd3a9 GS |
431 | their C<$ENV{SHELL}> variable) will be used, which can interfere |
432 | with proper interpretation of exit status or signal and coredump | |
433 | information. | |
434 | ||
947cb114 | 435 | =item source file |
5bad0d9e | 436 | |
947cb114 PS |
437 | Read and execute debugger commands from I<file>. |
438 | I<file> may itself contain C<source> commands. | |
5bad0d9e | 439 | |
055fd3a9 GS |
440 | =item H -number |
441 | ||
442 | Display last n commands. Only commands longer than one character are | |
443 | listed. If I<number> is omitted, list them all. | |
444 | ||
445 | =item q or ^D | |
446 | ||
447 | Quit. ("quit" doesn't work for this, unless you've made an alias) | |
448 | This is the only supported way to exit the debugger, though typing | |
449 | C<exit> twice might work. | |
450 | ||
451 | Set the C<inhibit_exit> option to 0 if you want to be able to step | |
2e8f3c35 | 452 | off the end the script. You may also need to set $finished to 0 |
055fd3a9 GS |
453 | if you want to step through global destruction. |
454 | ||
455 | =item R | |
456 | ||
457 | Restart the debugger by C<exec()>ing a new session. We try to maintain | |
458 | your history across this, but internal settings and command-line options | |
459 | may be lost. | |
460 | ||
461 | The following setting are currently preserved: history, breakpoints, | |
462 | actions, debugger options, and the Perl command-line | |
463 | options B<-w>, B<-I>, and B<-e>. | |
464 | ||
465 | =item |dbcmd | |
466 | ||
467 | Run the debugger command, piping DB::OUT into your current pager. | |
468 | ||
469 | =item ||dbcmd | |
470 | ||
c997b287 | 471 | Same as C<|dbcmd> but DB::OUT is temporarily C<select>ed as well. |
055fd3a9 GS |
472 | |
473 | =item = [alias value] | |
474 | ||
475 | Define a command alias, like | |
476 | ||
477 | = quit q | |
478 | ||
479 | or list current aliases. | |
480 | ||
481 | =item command | |
482 | ||
483 | Execute command as a Perl statement. A trailing semicolon will be | |
484 | supplied. If the Perl statement would otherwise be confused for a | |
485 | Perl debugger, use a leading semicolon, too. | |
486 | ||
487 | =item m expr | |
488 | ||
489 | List which methods may be called on the result of the evaluated | |
2e8f3c35 | 490 | expression. The expression may evaluated to a reference to a |
055fd3a9 GS |
491 | blessed object, or to a package name. |
492 | ||
492652be RF |
493 | =item M |
494 | ||
495 | Displays all loaded modules and their versions | |
496 | ||
497 | ||
055fd3a9 GS |
498 | =item man [manpage] |
499 | ||
500 | Despite its name, this calls your system's default documentation | |
501 | viewer on the given page, or on the viewer itself if I<manpage> is | |
502 | omitted. If that viewer is B<man>, the current C<Config> information | |
503 | is used to invoke B<man> using the proper MANPATH or S<B<-M> | |
504 | I<manpath>> option. Failed lookups of the form C<XXX> that match | |
505 | known manpages of the form I<perlXXX> will be retried. This lets | |
506 | you type C<man debug> or C<man op> from the debugger. | |
507 | ||
508 | On systems traditionally bereft of a usable B<man> command, the | |
509 | debugger invokes B<perldoc>. Occasionally this determination is | |
510 | incorrect due to recalcitrant vendors or rather more felicitously, | |
511 | to enterprising users. If you fall into either category, just | |
512 | manually set the $DB::doccmd variable to whatever viewer to view | |
513 | the Perl documentation on your system. This may be set in an rc | |
514 | file, or through direct assignment. We're still waiting for a | |
515 | working example of something along the lines of: | |
4e1d3b43 | 516 | |
055fd3a9 GS |
517 | $DB::doccmd = 'netscape -remote http://something.here/'; |
518 | ||
519 | =back | |
520 | ||
521 | =head2 Configurable Options | |
522 | ||
492652be | 523 | The debugger has numerous options settable using the C<o> command, |
055fd3a9 | 524 | either interactively or from the environment or an rc file. |
e00d725b MJD |
525 | (./.perldb or ~/.perldb under Unix.) |
526 | ||
4e1d3b43 | 527 | |
528 | =over 12 | |
529 | ||
e7ea3e70 | 530 | =item C<recallCommand>, C<ShellBang> |
4e1d3b43 | 531 | |
532 | The characters used to recall command or spawn shell. By | |
055fd3a9 | 533 | default, both are set to C<!>, which is unfortunate. |
4e1d3b43 | 534 | |
e7ea3e70 | 535 | =item C<pager> |
4e1d3b43 | 536 | |
055fd3a9 GS |
537 | Program to use for output of pager-piped commands (those beginning |
538 | with a C<|> character.) By default, C<$ENV{PAGER}> will be used. | |
539 | Because the debugger uses your current terminal characteristics | |
540 | for bold and underlining, if the chosen pager does not pass escape | |
541 | sequences through unchanged, the output of some debugger commands | |
542 | will not be readable when sent through the pager. | |
4e1d3b43 | 543 | |
e7ea3e70 | 544 | =item C<tkRunning> |
36477c24 | 545 | |
546 | Run Tk while prompting (with ReadLine). | |
547 | ||
e7ea3e70 IZ |
548 | =item C<signalLevel>, C<warnLevel>, C<dieLevel> |
549 | ||
4c82ae22 GS |
550 | Level of verbosity. By default, the debugger leaves your exceptions |
551 | and warnings alone, because altering them can break correctly running | |
552 | programs. It will attempt to print a message when uncaught INT, BUS, or | |
553 | SEGV signals arrive. (But see the mention of signals in L<BUGS> below.) | |
554 | ||
555 | To disable this default safe mode, set these values to something higher | |
556 | than 0. At a level of 1, you get backtraces upon receiving any kind | |
557 | of warning (this is often annoying) or exception (this is | |
558 | often valuable). Unfortunately, the debugger cannot discern fatal | |
559 | exceptions from non-fatal ones. If C<dieLevel> is even 1, then your | |
560 | non-fatal exceptions are also traced and unceremoniously altered if they | |
561 | came from C<eval'd> strings or from any kind of C<eval> within modules | |
562 | you're attempting to load. If C<dieLevel> is 2, the debugger doesn't | |
563 | care where they came from: It usurps your exception handler and prints | |
564 | out a trace, then modifies all exceptions with its own embellishments. | |
565 | This may perhaps be useful for some tracing purposes, but tends to hopelessly | |
566 | destroy any program that takes its exception handling seriously. | |
36477c24 | 567 | |
e7ea3e70 | 568 | =item C<AutoTrace> |
36477c24 | 569 | |
e7ea3e70 IZ |
570 | Trace mode (similar to C<t> command, but can be put into |
571 | C<PERLDB_OPTS>). | |
36477c24 | 572 | |
e7ea3e70 | 573 | =item C<LineInfo> |
36477c24 | 574 | |
e7ea3e70 | 575 | File or pipe to print line number info to. If it is a pipe (say, |
055fd3a9 GS |
576 | C<|visual_perl_db>), then a short message is used. This is the |
577 | mechanism used to interact with a slave editor or visual debugger, | |
578 | such as the special C<vi> or C<emacs> hooks, or the C<ddd> graphical | |
579 | debugger. | |
36477c24 | 580 | |
581 | =item C<inhibit_exit> | |
582 | ||
583 | If 0, allows I<stepping off> the end of the script. | |
584 | ||
54310121 | 585 | =item C<PrintRet> |
36477c24 | 586 | |
04cf9722 | 587 | Print return value after C<r> command if set (default). |
36477c24 | 588 | |
28d1fb14 IZ |
589 | =item C<ornaments> |
590 | ||
055fd3a9 GS |
591 | Affects screen appearance of the command line (see L<Term::ReadLine>). |
592 | There is currently no way to disable these, which can render | |
593 | some output illegible on some displays, or with some pagers. | |
594 | This is considered a bug. | |
28d1fb14 | 595 | |
54310121 | 596 | =item C<frame> |
36477c24 | 597 | |
055fd3a9 | 598 | Affects the printing of messages upon entry and exit from subroutines. If |
36477c24 | 599 | C<frame & 2> is false, messages are printed on entry only. (Printing |
055fd3a9 | 600 | on exit might be useful if interspersed with other messages.) |
36477c24 | 601 | |
055fd3a9 GS |
602 | If C<frame & 4>, arguments to functions are printed, plus context |
603 | and caller info. If C<frame & 8>, overloaded C<stringify> and | |
604 | C<tie>d C<FETCH> is enabled on the printed arguments. If C<frame | |
605 | & 16>, the return value from the subroutine is printed. | |
28d1fb14 IZ |
606 | |
607 | The length at which the argument list is truncated is governed by the | |
608 | next option: | |
e7ea3e70 IZ |
609 | |
610 | =item C<maxTraceLen> | |
611 | ||
055fd3a9 | 612 | Length to truncate the argument list when the C<frame> option's |
e7ea3e70 | 613 | bit 4 is set. |
36477c24 | 614 | |
6f891d7d SM |
615 | =item C<windowSize> |
616 | ||
617 | Change the size of code list window (default is 10 lines). | |
618 | ||
4e1d3b43 | 619 | =back |
620 | ||
621 | The following options affect what happens with C<V>, C<X>, and C<x> | |
622 | commands: | |
623 | ||
624 | =over 12 | |
625 | ||
e7ea3e70 | 626 | =item C<arrayDepth>, C<hashDepth> |
4e1d3b43 | 627 | |
628 | Print only first N elements ('' for all). | |
629 | ||
d03c2a1b MJD |
630 | =item C<dumpDepth> |
631 | ||
632 | Limit recursion depth to N levels when dumping structures. | |
633 | Negative values are interpreted as infinity. Default: infinity. | |
634 | ||
e7ea3e70 | 635 | =item C<compactDump>, C<veryCompact> |
4e1d3b43 | 636 | |
055fd3a9 | 637 | Change the style of array and hash output. If C<compactDump>, short array |
e7ea3e70 | 638 | may be printed on one line. |
4e1d3b43 | 639 | |
e7ea3e70 | 640 | =item C<globPrint> |
4e1d3b43 | 641 | |
642 | Whether to print contents of globs. | |
643 | ||
e7ea3e70 | 644 | =item C<DumpDBFiles> |
4e1d3b43 | 645 | |
646 | Dump arrays holding debugged files. | |
647 | ||
e7ea3e70 | 648 | =item C<DumpPackages> |
4e1d3b43 | 649 | |
650 | Dump symbol tables of packages. | |
651 | ||
6ee623d5 GS |
652 | =item C<DumpReused> |
653 | ||
654 | Dump contents of "reused" addresses. | |
655 | ||
e7ea3e70 IZ |
656 | =item C<quote>, C<HighBit>, C<undefPrint> |
657 | ||
055fd3a9 GS |
658 | Change the style of string dump. The default value for C<quote> |
659 | is C<auto>; one can enable double-quotish or single-quotish format | |
660 | by setting it to C<"> or C<'>, respectively. By default, characters | |
661 | with their high bit set are printed verbatim. | |
e7ea3e70 | 662 | |
54310121 | 663 | =item C<UsageOnly> |
4e1d3b43 | 664 | |
055fd3a9 GS |
665 | Rudimentary per-package memory usage dump. Calculates total |
666 | size of strings found in variables in the package. This does not | |
667 | include lexicals in a module's file scope, or lost in closures. | |
4e1d3b43 | 668 | |
36477c24 | 669 | =back |
4e1d3b43 | 670 | |
e00d725b | 671 | After the rc file is read, the debugger reads the C<$ENV{PERLDB_OPTS}> |
66a1b24b | 672 | environment variable and parses this as the remainder of a "O ..." |
e00d725b MJD |
673 | line as one might enter at the debugger prompt. You may place the |
674 | initialization options C<TTY>, C<noTTY>, C<ReadLine>, and C<NonStop> | |
675 | there. | |
36477c24 | 676 | |
055fd3a9 | 677 | If your rc file contains: |
4e1d3b43 | 678 | |
055fd3a9 | 679 | parse_options("NonStop=1 LineInfo=db.out AutoTrace"); |
4e1d3b43 | 680 | |
055fd3a9 GS |
681 | then your script will run without human intervention, putting trace |
682 | information into the file I<db.out>. (If you interrupt it, you'd | |
683 | better reset C<LineInfo> to F</dev/tty> if you expect to see anything.) | |
4e1d3b43 | 684 | |
36477c24 | 685 | =over 12 |
4e1d3b43 | 686 | |
36477c24 | 687 | =item C<TTY> |
4e1d3b43 | 688 | |
36477c24 | 689 | The TTY to use for debugging I/O. |
690 | ||
36477c24 | 691 | =item C<noTTY> |
692 | ||
055fd3a9 GS |
693 | If set, the debugger goes into C<NonStop> mode and will not connect to a TTY. If |
694 | interrupted (or if control goes to the debugger via explicit setting of | |
695 | $DB::signal or $DB::single from the Perl script), it connects to a TTY | |
696 | specified in the C<TTY> option at startup, or to a tty found at | |
697 | runtime using the C<Term::Rendezvous> module of your choice. | |
36477c24 | 698 | |
055fd3a9 | 699 | This module should implement a method named C<new> that returns an object |
200f06d0 | 700 | with two methods: C<IN> and C<OUT>. These should return filehandles to use |
055fd3a9 GS |
701 | for debugging input and output correspondingly. The C<new> method should |
702 | inspect an argument containing the value of C<$ENV{PERLDB_NOTTY}> at | |
2e8f3c35 | 703 | startup, or C<"$ENV{HOME}/.perldbtty$$"> otherwise. This file is not |
055fd3a9 GS |
704 | inspected for proper ownership, so security hazards are theoretically |
705 | possible. | |
36477c24 | 706 | |
707 | =item C<ReadLine> | |
708 | ||
055fd3a9 GS |
709 | If false, readline support in the debugger is disabled in order |
710 | to debug applications that themselves use ReadLine. | |
36477c24 | 711 | |
712 | =item C<NonStop> | |
713 | ||
055fd3a9 | 714 | If set, the debugger goes into non-interactive mode until interrupted, or |
36477c24 | 715 | programmatically by setting $DB::signal or $DB::single. |
716 | ||
717 | =back | |
718 | ||
719 | Here's an example of using the C<$ENV{PERLDB_OPTS}> variable: | |
4e1d3b43 | 720 | |
055fd3a9 | 721 | $ PERLDB_OPTS="NonStop frame=2" perl -d myprogram |
4e1d3b43 | 722 | |
055fd3a9 GS |
723 | That will run the script B<myprogram> without human intervention, |
724 | printing out the call tree with entry and exit points. Note that | |
725 | C<NonStop=1 frame=2> is equivalent to C<N f=2>, and that originally, | |
726 | options could be uniquely abbreviated by the first letter (modulo | |
727 | the C<Dump*> options). It is nevertheless recommended that you | |
728 | always spell them out in full for legibility and future compatibility. | |
4e1d3b43 | 729 | |
055fd3a9 | 730 | Other examples include |
a0d0e21e | 731 | |
1472e7de | 732 | $ PERLDB_OPTS="NonStop LineInfo=listing frame=2" perl -d myprogram |
a0d0e21e | 733 | |
055fd3a9 GS |
734 | which runs script non-interactively, printing info on each entry |
735 | into a subroutine and each executed line into the file named F<listing>. | |
736 | (If you interrupt it, you would better reset C<LineInfo> to something | |
36477c24 | 737 | "interactive"!) |
738 | ||
055fd3a9 GS |
739 | Other examples include (using standard shell syntax to show environment |
740 | variable settings): | |
36477c24 | 741 | |
055fd3a9 GS |
742 | $ ( PERLDB_OPTS="NonStop frame=1 AutoTrace LineInfo=tperl.out" |
743 | perl -d myprogram ) | |
36477c24 | 744 | |
055fd3a9 GS |
745 | which may be useful for debugging a program that uses C<Term::ReadLine> |
746 | itself. Do not forget to detach your shell from the TTY in the window that | |
747 | corresponds to F</dev/ttyXX>, say, by issuing a command like | |
36477c24 | 748 | |
e7ea3e70 | 749 | $ sleep 1000000 |
36477c24 | 750 | |
055fd3a9 | 751 | See L<perldebguts/"Debugger Internals"> for details. |
a0d0e21e | 752 | |
e7ea3e70 IZ |
753 | =head2 Debugger input/output |
754 | ||
755 | =over 8 | |
756 | ||
757 | =item Prompt | |
758 | ||
4e1d3b43 | 759 | The debugger prompt is something like |
760 | ||
761 | DB<8> | |
762 | ||
763 | or even | |
764 | ||
765 | DB<<17>> | |
766 | ||
055fd3a9 GS |
767 | where that number is the command number, and which you'd use to |
768 | access with the built-in B<csh>-like history mechanism. For example, | |
769 | C<!17> would repeat command number 17. The depth of the angle | |
770 | brackets indicates the nesting depth of the debugger. You could | |
771 | get more than one set of brackets, for example, if you'd already | |
772 | at a breakpoint and then printed the result of a function call that | |
773 | itself has a breakpoint, or you step into an expression via C<s/n/t | |
774 | expression> command. | |
4e1d3b43 | 775 | |
54310121 | 776 | =item Multiline commands |
e7ea3e70 | 777 | |
4a6725af | 778 | If you want to enter a multi-line command, such as a subroutine |
055fd3a9 GS |
779 | definition with several statements or a format, escape the newline |
780 | that would normally end the debugger command with a backslash. | |
e7ea3e70 | 781 | Here's an example: |
a0d0e21e | 782 | |
4e1d3b43 | 783 | DB<1> for (1..4) { \ |
784 | cont: print "ok\n"; \ | |
785 | cont: } | |
786 | ok | |
787 | ok | |
788 | ok | |
789 | ok | |
790 | ||
791 | Note that this business of escaping a newline is specific to interactive | |
792 | commands typed into the debugger. | |
793 | ||
e7ea3e70 IZ |
794 | =item Stack backtrace |
795 | ||
68dc0745 | 796 | Here's an example of what a stack backtrace via C<T> command might |
e7ea3e70 | 797 | look like: |
4e1d3b43 | 798 | |
799 | $ = main::infested called from file `Ambulation.pm' line 10 | |
800 | @ = Ambulation::legs(1, 2, 3, 4) called from file `camel_flea' line 7 | |
801 | $ = main::pests('bactrian', 4) called from file `camel_flea' line 4 | |
802 | ||
055fd3a9 GS |
803 | The left-hand character up there indicates the context in which the |
804 | function was called, with C<$> and C<@> meaning scalar or list | |
805 | contexts respectively, and C<.> meaning void context (which is | |
806 | actually a sort of scalar context). The display above says | |
807 | that you were in the function C<main::infested> when you ran the | |
808 | stack dump, and that it was called in scalar context from line | |
809 | 10 of the file I<Ambulation.pm>, but without any arguments at all, | |
810 | meaning it was called as C<&infested>. The next stack frame shows | |
811 | that the function C<Ambulation::legs> was called in list context | |
812 | from the I<camel_flea> file with four arguments. The last stack | |
813 | frame shows that C<main::pests> was called in scalar context, | |
814 | also from I<camel_flea>, but from line 4. | |
4e1d3b43 | 815 | |
055fd3a9 GS |
816 | If you execute the C<T> command from inside an active C<use> |
817 | statement, the backtrace will contain both a C<require> frame and | |
818 | an C<eval>) frame. | |
e7ea3e70 | 819 | |
055fd3a9 | 820 | =item Line Listing Format |
e7ea3e70 | 821 | |
055fd3a9 | 822 | This shows the sorts of output the C<l> command can produce: |
e7ea3e70 IZ |
823 | |
824 | DB<<13>> l | |
825 | 101: @i{@i} = (); | |
826 | 102:b @isa{@i,$pack} = () | |
827 | 103 if(exists $i{$prevpack} || exists $isa{$pack}); | |
828 | 104 } | |
829 | 105 | |
830 | 106 next | |
831 | 107==> if(exists $isa{$pack}); | |
832 | 108 | |
833 | 109:a if ($extra-- > 0) { | |
834 | 110: %isa = ($pack,1); | |
835 | ||
055fd3a9 GS |
836 | Breakable lines are marked with C<:>. Lines with breakpoints are |
837 | marked by C<b> and those with actions by C<a>. The line that's | |
838 | about to be executed is marked by C<< ==> >>. | |
e7ea3e70 | 839 | |
003183f2 GS |
840 | Please be aware that code in debugger listings may not look the same |
841 | as your original source code. Line directives and external source | |
842 | filters can alter the code before Perl sees it, causing code to move | |
843 | from its original positions or take on entirely different forms. | |
844 | ||
e7ea3e70 IZ |
845 | =item Frame listing |
846 | ||
055fd3a9 GS |
847 | When the C<frame> option is set, the debugger would print entered (and |
848 | optionally exited) subroutines in different styles. See L<perldebguts> | |
849 | for incredibly long examples of these. | |
e7ea3e70 IZ |
850 | |
851 | =back | |
852 | ||
853 | =head2 Debugging compile-time statements | |
854 | ||
055fd3a9 GS |
855 | If you have compile-time executable statements (such as code within |
856 | BEGIN and CHECK blocks or C<use> statements), these will I<not> be | |
857 | stopped by debugger, although C<require>s and INIT blocks will, and | |
858 | compile-time statements can be traced with C<AutoTrace> option set | |
859 | in C<PERLDB_OPTS>). From your own Perl code, however, you can | |
4e1d3b43 | 860 | transfer control back to the debugger using the following statement, |
861 | which is harmless if the debugger is not running: | |
a0d0e21e LW |
862 | |
863 | $DB::single = 1; | |
864 | ||
055fd3a9 | 865 | If you set C<$DB::single> to 2, it's equivalent to having |
4e1d3b43 | 866 | just typed the C<n> command, whereas a value of 1 means the C<s> |
867 | command. The C<$DB::trace> variable should be set to 1 to simulate | |
868 | having typed the C<t> command. | |
869 | ||
055fd3a9 GS |
870 | Another way to debug compile-time code is to start the debugger, set a |
871 | breakpoint on the I<load> of some module: | |
e7ea3e70 IZ |
872 | |
873 | DB<7> b load f:/perllib/lib/Carp.pm | |
874 | Will stop on load of `f:/perllib/lib/Carp.pm'. | |
875 | ||
055fd3a9 | 876 | and then restart the debugger using the C<R> command (if possible). One can use C<b |
e7ea3e70 IZ |
877 | compile subname> for the same purpose. |
878 | ||
4e1d3b43 | 879 | =head2 Debugger Customization |
a0d0e21e | 880 | |
055fd3a9 GS |
881 | The debugger probably contains enough configuration hooks that you |
882 | won't ever have to modify it yourself. You may change the behaviour | |
492652be | 883 | of debugger from within the debugger using its C<o> command, from |
055fd3a9 GS |
884 | the command line via the C<PERLDB_OPTS> environment variable, and |
885 | from customization files. | |
a0d0e21e | 886 | |
055fd3a9 | 887 | You can do some customization by setting up a F<.perldb> file, which |
a0d0e21e | 888 | contains initialization code. For instance, you could make aliases |
4e1d3b43 | 889 | like these (the last one is one people expect to be there): |
a0d0e21e | 890 | |
4e1d3b43 | 891 | $DB::alias{'len'} = 's/^len(.*)/p length($1)/'; |
a0d0e21e | 892 | $DB::alias{'stop'} = 's/^stop (at|in)/b/'; |
4e1d3b43 | 893 | $DB::alias{'ps'} = 's/^ps\b/p scalar /'; |
055fd3a9 | 894 | $DB::alias{'quit'} = 's/^quit(\s*)/exit/'; |
4e1d3b43 | 895 | |
055fd3a9 | 896 | You can change options from F<.perldb> by using calls like this one; |
36477c24 | 897 | |
898 | parse_options("NonStop=1 LineInfo=db.out AutoTrace=1 frame=2"); | |
899 | ||
055fd3a9 | 900 | The code is executed in the package C<DB>. Note that F<.perldb> is |
774d564b | 901 | processed before processing C<PERLDB_OPTS>. If F<.perldb> defines the |
055fd3a9 | 902 | subroutine C<afterinit>, that function is called after debugger |
774d564b | 903 | initialization ends. F<.perldb> may be contained in the current |
055fd3a9 GS |
904 | directory, or in the home directory. Because this file is sourced |
905 | in by Perl and may contain arbitrary commands, for security reasons, | |
906 | it must be owned by the superuser or the current user, and writable | |
907 | by no one but its owner. | |
36477c24 | 908 | |
bea98532 JH |
909 | You can mock TTY input to debugger by adding arbitrary commands to |
910 | @DB::typeahead. For example, your F<.perldb> file might contain: | |
911 | ||
912 | sub afterinit { push @DB::typeahead, "b 4", "b 6"; } | |
913 | ||
914 | Which would attempt to set breakpoints on lines 4 and 6 immediately | |
915 | after debugger initilization. Note that @DB::typeahead is not a supported | |
916 | interface and is subject to change in future releases. | |
917 | ||
055fd3a9 GS |
918 | If you want to modify the debugger, copy F<perl5db.pl> from the |
919 | Perl library to another name and hack it to your heart's content. | |
920 | You'll then want to set your C<PERL5DB> environment variable to say | |
921 | something like this: | |
36477c24 | 922 | |
923 | BEGIN { require "myperl5db.pl" } | |
924 | ||
055fd3a9 GS |
925 | As a last resort, you could also use C<PERL5DB> to customize the debugger |
926 | by directly setting internal variables or calling debugger functions. | |
927 | ||
928 | Note that any variables and functions that are not documented in | |
929 | this document (or in L<perldebguts>) are considered for internal | |
930 | use only, and as such are subject to change without notice. | |
36477c24 | 931 | |
4e1d3b43 | 932 | =head2 Readline Support |
933 | ||
055fd3a9 | 934 | As shipped, the only command-line history supplied is a simplistic one |
4e1d3b43 | 935 | that checks for leading exclamation points. However, if you install |
936 | the Term::ReadKey and Term::ReadLine modules from CPAN, you will | |
937 | have full editing capabilities much like GNU I<readline>(3) provides. | |
938 | Look for these in the F<modules/by-module/Term> directory on CPAN. | |
055fd3a9 | 939 | These do not support normal B<vi> command-line editing, however. |
4e1d3b43 | 940 | |
055fd3a9 | 941 | A rudimentary command-line completion is also available. |
e7ea3e70 IZ |
942 | Unfortunately, the names of lexical variables are not available for |
943 | completion. | |
944 | ||
4e1d3b43 | 945 | =head2 Editor Support for Debugging |
946 | ||
055fd3a9 GS |
947 | If you have the FSF's version of B<emacs> installed on your system, |
948 | it can interact with the Perl debugger to provide an integrated | |
949 | software development environment reminiscent of its interactions | |
950 | with C debuggers. | |
4e1d3b43 | 951 | |
055fd3a9 GS |
952 | Perl comes with a start file for making B<emacs> act like a |
953 | syntax-directed editor that understands (some of) Perl's syntax. | |
954 | Look in the I<emacs> directory of the Perl source distribution. | |
4e1d3b43 | 955 | |
055fd3a9 GS |
956 | A similar setup by Tom Christiansen for interacting with any |
957 | vendor-shipped B<vi> and the X11 window system is also available. | |
958 | This works similarly to the integrated multiwindow support that | |
959 | B<emacs> provides, where the debugger drives the editor. At the | |
960 | time of this writing, however, that tool's eventual location in the | |
961 | Perl distribution was uncertain. | |
4e1d3b43 | 962 | |
055fd3a9 | 963 | Users of B<vi> should also look into B<vim> and B<gvim>, the mousey |
2e8f3c35 | 964 | and windy version, for coloring of Perl keywords. |
a0d0e21e | 965 | |
055fd3a9 GS |
966 | Note that only perl can truly parse Perl, so all such CASE tools |
967 | fall somewhat short of the mark, especially if you don't program | |
968 | your Perl as a C programmer might. | |
e7ea3e70 | 969 | |
055fd3a9 | 970 | =head2 The Perl Profiler |
e7ea3e70 | 971 | |
055fd3a9 GS |
972 | If you wish to supply an alternative debugger for Perl to run, just |
973 | invoke your script with a colon and a package argument given to the | |
974 | B<-d> flag. The most popular alternative debuggers for Perl is the | |
975 | Perl profiler. Devel::DProf is now included with the standard Perl | |
976 | distribution. To profile your Perl program in the file F<mycode.pl>, | |
977 | just type: | |
36477c24 | 978 | |
055fd3a9 | 979 | $ perl -d:DProf mycode.pl |
36477c24 | 980 | |
055fd3a9 GS |
981 | When the script terminates the profiler will dump the profile |
982 | information to a file called F<tmon.out>. A tool like B<dprofpp>, | |
983 | also supplied with the standard Perl distribution, can be used to | |
984 | interpret the information in that profile. | |
36477c24 | 985 | |
055fd3a9 | 986 | =head1 Debugging regular expressions |
36477c24 | 987 | |
3d555cb8 WL |
988 | C<use re 'debug'> enables you to see the gory details of how the Perl |
989 | regular expression engine works. In order to understand this typically | |
990 | voluminous output, one must not only have some idea about how regular | |
991 | expression matching works in general, but also know how Perl's regular | |
992 | expressions are internally compiled into an automaton. These matters | |
993 | are explored in some detail in | |
055fd3a9 | 994 | L<perldebguts/"Debugging regular expressions">. |
36477c24 | 995 | |
055fd3a9 | 996 | =head1 Debugging memory usage |
36477c24 | 997 | |
055fd3a9 GS |
998 | Perl contains internal support for reporting its own memory usage, |
999 | but this is a fairly advanced concept that requires some understanding | |
1000 | of how memory allocation works. | |
1001 | See L<perldebguts/"Debugging Perl memory usage"> for the details. | |
36477c24 | 1002 | |
055fd3a9 | 1003 | =head1 SEE ALSO |
a0d0e21e LW |
1004 | |
1005 | You did try the B<-w> switch, didn't you? | |
1006 | ||
f6b3c421 | 1007 | L<perldebtut>, |
055fd3a9 GS |
1008 | L<perldebguts>, |
1009 | L<re>, | |
1010 | L<DB>, | |
fe854a6f | 1011 | L<Devel::DProf>, |
055fd3a9 GS |
1012 | L<dprofpp>, |
1013 | L<Dumpvalue>, | |
1014 | and | |
1015 | L<perlrun>. | |
a0d0e21e | 1016 | |
fa3aa65a JC |
1017 | When debugging a script that uses #! and is thus normally found in |
1018 | $PATH, the -S option causes perl to search $PATH for it, so you don't | |
66a1b24b | 1019 | have to type the path or C<which $scriptname>. |
fa3aa65a JC |
1020 | |
1021 | $ perl -Sd foo.pl | |
1022 | ||
055fd3a9 GS |
1023 | =head1 BUGS |
1024 | ||
1025 | You cannot get stack frame information or in any fashion debug functions | |
1026 | that were not compiled by Perl, such as those from C or C++ extensions. | |
a0d0e21e | 1027 | |
c997b287 | 1028 | If you alter your @_ arguments in a subroutine (such as with C<shift> |
6edf2346 | 1029 | or C<pop>), the stack backtrace will not show the original values. |
c997b287 GS |
1030 | |
1031 | The debugger does not currently work in conjunction with the B<-W> | |
1032 | command-line switch, because it itself is not free of warnings. | |
4c82ae22 GS |
1033 | |
1034 | If you're in a slow syscall (like C<wait>ing, C<accept>ing, or C<read>ing | |
1035 | from your keyboard or a socket) and haven't set up your own C<$SIG{INT}> | |
1036 | handler, then you won't be able to CTRL-C your way back to the debugger, | |
1037 | because the debugger's own C<$SIG{INT}> handler doesn't understand that | |
1038 | it needs to raise an exception to longjmp(3) out of slow syscalls. |