4 perl5db.pl - the perl debugger
8 perl -d your_Perl_script
12 C<perl5db.pl> is the perl debugger. It is loaded automatically by Perl when
13 you invoke a script with C<perl -d>. This documentation tries to outline the
14 structure and services provided by C<perl5db.pl>, and to describe how you
19 The debugger can look pretty forbidding to many Perl programmers. There are
20 a number of reasons for this, many stemming out of the debugger's history.
22 When the debugger was first written, Perl didn't have a lot of its nicer
23 features - no references, no lexical variables, no closures, no object-oriented
24 programming. So a lot of the things one would normally have done using such
25 features was done using global variables, globs and the C<local()> operator
28 Some of these have survived into the current debugger; a few of the more
29 interesting and still-useful idioms are noted in this section, along with notes
30 on the comments themselves.
32 =head2 Why not use more lexicals?
34 Experienced Perl programmers will note that the debugger code tends to use
35 mostly package globals rather than lexically-scoped variables. This is done
36 to allow a significant amount of control of the debugger from outside the
39 Unfortunately, though the variables are accessible, they're not well
40 documented, so it's generally been a decision that hasn't made a lot of
41 difference to most users. Where appropriate, comments have been added to
42 make variables more accessible and usable, with the understanding that these
43 I<are> debugger internals, and are therefore subject to change. Future
44 development should probably attempt to replace the globals with a well-defined
45 API, but for now, the variables are what we've got.
47 =head2 Automated variable stacking via C<local()>
49 As you may recall from reading C<perlfunc>, the C<local()> operator makes a
50 temporary copy of a variable in the current scope. When the scope ends, the
51 old copy is restored. This is often used in the debugger to handle the
52 automatic stacking of variables during recursive calls:
57 # Do some stuff, then ...
61 What happens is that on entry to the subroutine, C<$some_global> is localized,
62 then altered. When the subroutine returns, Perl automatically undoes the
63 localization, restoring the previous value. Voila, automatic stack management.
65 The debugger uses this trick a I<lot>. Of particular note is C<DB::eval>,
66 which lets the debugger get control inside of C<eval>'ed code. The debugger
67 localizes a saved copy of C<$@> inside the subroutine, which allows it to
68 keep C<$@> safe until it C<DB::eval> returns, at which point the previous
69 value of C<$@> is restored. This makes it simple (well, I<simpler>) to keep
70 track of C<$@> inside C<eval>s which C<eval> other C<eval's>.
72 In any case, watch for this pattern. It occurs fairly often.
76 This is used to cleverly reverse the sense of a logical test depending on
77 the value of an auxiliary variable. For instance, the debugger's C<S>
78 (search for subroutines by pattern) allows you to negate the pattern
81 # Find all non-'foo' subs:
84 Boolean algebra states that the truth table for XOR looks like this:
90 (! not present and no match) --> false, don't print
94 (! not present and matches) --> true, print
98 (! present and no match) --> true, print
102 (! present and matches) --> false, don't print
106 As you can see, the first pair applies when C<!> isn't supplied, and
107 the second pair applies when it is. The XOR simply allows us to
108 compact a more complicated if-then-elseif-else into a more elegant
109 (but perhaps overly clever) single test. After all, it needed this
112 =head2 FLAGS, FLAGS, FLAGS
114 There is a certain C programming legacy in the debugger. Some variables,
115 such as C<$single>, C<$trace>, and C<$frame>, have I<magical> values composed
116 of 1, 2, 4, etc. (powers of 2) OR'ed together. This allows several pieces
117 of state to be stored independently in a single scalar.
123 is checking to see if the appropriate bit is on. Since each bit can be
124 "addressed" independently in this way, C<$scalar> is acting sort of like
125 an array of bits. Obviously, since the contents of C<$scalar> are just a
126 bit-pattern, we can save and restore it easily (it will just look like
129 The problem, is of course, that this tends to leave magic numbers scattered
130 all over your program whenever a bit is set, cleared, or checked. So why do
137 First, doing an arithmetical or bitwise operation on a scalar is
138 just about the fastest thing you can do in Perl: C<use constant> actually
139 creates a subroutine call, and array and hash lookups are much slower. Is
140 this over-optimization at the expense of readability? Possibly, but the
141 debugger accesses these variables a I<lot>. Any rewrite of the code will
142 probably have to benchmark alternate implementations and see which is the
143 best balance of readability and speed, and then document how it actually
148 Second, it's very easy to serialize a scalar number. This is done in
149 the restart code; the debugger state variables are saved in C<%ENV> and then
150 restored when the debugger is restarted. Having them be just numbers makes
155 Third, some of these variables are being shared with the Perl core
156 smack in the middle of the interpreter's execution loop. It's much faster for
157 a C program (like the interpreter) to check a bit in a scalar than to access
158 several different variables (or a Perl array).
162 =head2 What are those C<XXX> comments for?
164 Any comment containing C<XXX> means that the comment is either somewhat
165 speculative - it's not exactly clear what a given variable or chunk of
166 code is doing, or that it is incomplete - the basics may be clear, but the
167 subtleties are not completely documented.
169 Send in a patch if you can clear up, fill out, or clarify an C<XXX>.
171 =head1 DATA STRUCTURES MAINTAINED BY CORE
173 There are a number of special data structures provided to the debugger by
174 the Perl interpreter.
176 The array C<@{$main::{'_<'.$filename}}> (aliased locally to C<@dbline>
177 via glob assignment) contains the text from C<$filename>, with each
178 element corresponding to a single line of C<$filename>. Additionally,
179 breakable lines will be dualvars with the numeric component being the
180 memory address of a COP node. Non-breakable lines are dualvar to 0.
182 The hash C<%{'_<'.$filename}> (aliased locally to C<%dbline> via glob
183 assignment) contains breakpoints and actions. The keys are line numbers;
184 you can set individual values, but not the whole hash. The Perl interpreter
185 uses this hash to determine where breakpoints have been set. Any true value is
186 considered to be a breakpoint; C<perl5db.pl> uses C<$break_condition\0$action>.
187 Values are magical in numeric context: 1 if the line is breakable, 0 if not.
189 The scalar C<${"_<$filename"}> simply contains the string C<$filename>.
190 This is also the case for evaluated strings that contain subroutines, or
191 which are currently being executed. The $filename for C<eval>ed strings looks
194 =head1 DEBUGGER STARTUP
196 When C<perl5db.pl> starts, it reads an rcfile (C<perl5db.ini> for
197 non-interactive sessions, C<.perldb> for interactive ones) that can set a number
198 of options. In addition, this file may define a subroutine C<&afterinit>
199 that will be executed (in the debugger's context) after the debugger has
202 Next, it checks the C<PERLDB_OPTS> environment variable and treats its
203 contents as the argument of a C<o> command in the debugger.
205 =head2 STARTUP-ONLY OPTIONS
207 The following options can only be specified at startup.
208 To set them in your rcfile, add a call to
209 C<&parse_options("optionName=new_value")>.
215 the TTY to use for debugging i/o.
219 if set, goes in NonStop mode. On interrupt, if TTY is not set,
220 uses the value of noTTY or F<$HOME/.perldbtty$$> to find TTY using
221 Term::Rendezvous. Current variant is to have the name of TTY in this
226 if false, a dummy ReadLine is used, so you can debug
227 ReadLine applications.
231 if true, no i/o is performed until interrupt.
235 file or pipe to print line number info to. If it is a
236 pipe, a short "emacs like" message is used.
240 host:port to connect to on remote host for remote debugging.
244 file to store session history to. There is no default and so no
245 history file is written unless this variable is explicitly set.
249 number of commands to store to the file specified in C<HistFile>.
256 &parse_options("NonStop=1 LineInfo=db.out");
257 sub afterinit { $trace = 1; }
259 The script will run without human intervention, putting trace
260 information into C<db.out>. (If you interrupt it, you had better
261 reset C<LineInfo> to something I<interactive>!)
263 =head1 INTERNALS DESCRIPTION
265 =head2 DEBUGGER INTERFACE VARIABLES
267 Perl supplies the values for C<%sub>. It effectively inserts
268 a C<&DB::DB();> in front of each place that can have a
269 breakpoint. At each subroutine call, it calls C<&DB::sub> with
270 C<$DB::sub> set to the called subroutine. It also inserts a C<BEGIN
271 {require 'perl5db.pl'}> before the first line.
273 After each C<require>d file is compiled, but before it is executed, a
274 call to C<&DB::postponed($main::{'_<'.$filename})> is done. C<$filename>
275 is the expanded name of the C<require>d file (as found via C<%INC>).
277 =head3 IMPORTANT INTERNAL VARIABLES
281 Used to control when the debugger will attempt to acquire another TTY to be
286 =item * 1 - on C<fork()>
288 =item * 2 - debugger is started inside debugger
290 =item * 4 - on startup
296 The value -2 indicates that no return value should be printed.
297 Any other positive value causes C<DB::sub> to print return values.
301 The item to be eval'ed by C<DB::eval>. Used to prevent messing with the current
302 contents of C<@_> when C<DB::eval> is called.
306 Determines what messages (if any) will get printed when a subroutine (or eval)
307 is entered or exited.
311 =item * 0 - No enter/exit messages
313 =item * 1 - Print I<entering> messages on subroutine entry
315 =item * 2 - Adds exit messages on subroutine exit. If no other flag is on, acts like 1+2.
317 =item * 4 - Extended messages: C<< <in|out> I<context>=I<fully-qualified sub name> from I<file>:I<line> >>. If no other flag is on, acts like 1+4.
319 =item * 8 - Adds parameter information to messages, and overloaded stringify and tied FETCH is enabled on the printed arguments. Ignored if C<4> is not on.
321 =item * 16 - Adds C<I<context> return from I<subname>: I<value>> messages on subroutine/eval exit. Ignored if C<4> is is not on.
325 To get everything, use C<$frame=30> (or C<o f=30> as a debugger command).
326 The debugger internally juggles the value of C<$frame> during execution to
327 protect external modules that the debugger uses from getting traced.
331 Tracks current debugger nesting level. Used to figure out how many
332 C<E<lt>E<gt>> pairs to surround the line number with when the debugger
333 outputs a prompt. Also used to help determine if the program has finished
334 during command parsing.
336 =head4 C<$onetimeDump>
338 Controls what (if anything) C<DB::eval()> will print after evaluating an
343 =item * C<undef> - don't print anything
345 =item * C<dump> - use C<dumpvar.pl> to display the value returned
347 =item * C<methods> - print the methods callable on the first item returned
351 =head4 C<$onetimeDumpDepth>
353 Controls how far down C<dumpvar.pl> will go before printing C<...> while
354 dumping a structure. Numeric. If C<undef>, print all levels.
358 Used to track whether or not an C<INT> signal has been detected. C<DB::DB()>,
359 which is called before every statement, checks this and puts the user into
360 command mode if it finds C<$signal> set to a true value.
364 Controls behavior during single-stepping. Stacked in C<@stack> on entry to
365 each subroutine; popped again at the end of each subroutine.
369 =item * 0 - run continuously.
371 =item * 1 - single-step, go into subs. The C<s> command.
373 =item * 2 - single-step, don't go into subs. The C<n> command.
375 =item * 4 - print current sub depth (turned on to force this when C<too much
382 Controls the output of trace information.
386 =item * 1 - The C<t> command was entered to turn on tracing (every line executed is printed)
388 =item * 2 - watch expressions are active
390 =item * 4 - user defined a C<watchfunction()> in C<afterinit()>
394 =head4 C<$slave_editor>
396 1 if C<LINEINFO> was directed to a pipe; 0 otherwise.
400 Stack of filehandles that C<DB::readline()> will read commands from.
401 Manipulated by the debugger's C<source> command and C<DB::readline()> itself.
405 Local alias to the magical line array, C<@{$main::{'_<'.$filename}}> ,
406 supplied by the Perl interpreter to the debugger. Contains the source.
410 Previous values of watch expressions. First set when the expression is
411 entered; reset whenever the watch expression changes.
415 Saves important globals (C<$@>, C<$!>, C<$^E>, C<$,>, C<$/>, C<$\>, C<$^W>)
416 so that the debugger can substitute safe values while it's running, and
417 restore them when it returns control.
421 Saves the current value of C<$single> on entry to a subroutine.
422 Manipulated by the C<c> command to turn off tracing in all subs above the
427 The 'watch' expressions: to be evaluated before each line is executed.
431 The typeahead buffer, used by C<DB::readline>.
435 Command aliases. Stored as character strings to be substituted for a command
438 =head4 C<%break_on_load>
440 Keys are file names, values are 1 (break when this file is loaded) or undef
441 (don't break when it is loaded).
445 Keys are line numbers, values are C<condition\0action>. If used in numeric
446 context, values are 0 if not breakable, 1 if breakable, no matter what is
447 in the actual hash entry.
449 =head4 C<%had_breakpoints>
451 Keys are file names; values are bitfields:
455 =item * 1 - file has a breakpoint in it.
457 =item * 2 - file has an action in it.
461 A zero or undefined value means this file has neither.
465 Stores the debugger options. These are character string values.
469 Saves breakpoints for code that hasn't been compiled yet.
470 Keys are subroutine names, values are:
474 =item * C<compile> - break when this sub is compiled
476 =item * C<< break +0 if <condition> >> - break (conditionally) at the start of this routine. The condition will be '1' if no condition was specified.
480 =head4 C<%postponed_file>
482 This hash keeps track of breakpoints that need to be set for files that have
483 not yet been compiled. Keys are filenames; values are references to hashes.
484 Each of these hashes is keyed by line number, and its values are breakpoint
485 definitions (C<condition\0action>).
487 =head1 DEBUGGER INITIALIZATION
489 The debugger's initialization actually jumps all over the place inside this
490 package. This is because there are several BEGIN blocks (which of course
491 execute immediately) spread through the code. Why is that?
493 The debugger needs to be able to change some things and set some things up
494 before the debugger code is compiled; most notably, the C<$deep> variable that
495 C<DB::sub> uses to tell when a program has recursed deeply. In addition, the
496 debugger has to turn off warnings while the debugger code is compiled, but then
497 restore them to their original setting before the program being debugged begins
500 The first C<BEGIN> block simply turns off warnings by saving the current
501 setting of C<$^W> and then setting it to zero. The second one initializes
502 the debugger variables that are needed before the debugger begins executing.
503 The third one puts C<$^X> back to its former value.
505 We'll detail the second C<BEGIN> block later; just remember that if you need
506 to initialize something before the debugger starts really executing, that's
515 BEGIN {eval 'use IO::Handle'}; # Needed for flush only? breaks under miniperl
519 $^V =~ /^v(\d+\.\d+)/;
520 feature->import(":$1");
523 # Debugger for Perl 5.00x; perl5db.pl patch level:
524 use vars qw($VERSION $header);
526 $VERSION = '1.39_05';
528 $header = "perl5db.pl version $VERSION";
530 =head1 DEBUGGER ROUTINES
534 This function replaces straight C<eval()> inside the debugger; it simplifies
535 the process of evaluating code in the user's context.
537 The code to be evaluated is passed via the package global variable
538 C<$DB::evalarg>; this is done to avoid fiddling with the contents of C<@_>.
540 Before we do the C<eval()>, we preserve the current settings of C<$trace>,
541 C<$single>, C<$^D> and C<$usercontext>. The latter contains the
542 preserved values of C<$@>, C<$!>, C<$^E>, C<$,>, C<$/>, C<$\>, C<$^W> and the
543 user's current package, grabbed when C<DB::DB> got control. This causes the
544 proper context to be used when the eval is actually done. Afterward, we
545 restore C<$trace>, C<$single>, and C<$^D>.
547 Next we need to handle C<$@> without getting confused. We save C<$@> in a
548 local lexical, localize C<$saved[0]> (which is where C<save()> will put
549 C<$@>), and then call C<save()> to capture C<$@>, C<$!>, C<$^E>, C<$,>,
550 C<$/>, C<$\>, and C<$^W>) and set C<$,>, C<$/>, C<$\>, and C<$^W> to values
551 considered sane by the debugger. If there was an C<eval()> error, we print
552 it on the debugger's output. If C<$onetimedump> is defined, we call
553 C<dumpit> if it's set to 'dump', or C<methods> if it's set to
554 'methods'. Setting it to something else causes the debugger to do the eval
555 but not print the result - handy if you want to do something else with it
556 (the "watch expressions" code does this to get the value of the watch
557 expression but not show it unless it matters).
559 In any case, we then return the list of output from C<eval> to the caller,
560 and unwinding restores the former version of C<$@> in C<@saved> as well
561 (the localization of C<$saved[0]> goes away at the end of this scope).
563 =head3 Parameters and variables influencing execution of DB::eval()
565 C<DB::eval> isn't parameterized in the standard way; this is to keep the
566 debugger's calls to C<DB::eval()> from mucking with C<@_>, among other things.
567 The variables listed below influence C<DB::eval()>'s execution directly.
571 =item C<$evalarg> - the thing to actually be eval'ed
573 =item C<$trace> - Current state of execution tracing
575 =item C<$single> - Current state of single-stepping
577 =item C<$onetimeDump> - what is to be displayed after the evaluation
579 =item C<$onetimeDumpDepth> - how deep C<dumpit()> should go when dumping results
583 The following variables are altered by C<DB::eval()> during its execution. They
584 are "stacked" via C<local()>, enabling recursive calls to C<DB::eval()>.
588 =item C<@res> - used to capture output from actual C<eval>.
590 =item C<$otrace> - saved value of C<$trace>.
592 =item C<$osingle> - saved value of C<$single>.
594 =item C<$od> - saved value of C<$^D>.
596 =item C<$saved[0]> - saved value of C<$@>.
598 =item $\ - for output of C<$@> if there is an evaluation error.
602 =head3 The problem of lexicals
604 The context of C<DB::eval()> presents us with some problems. Obviously,
605 we want to be 'sandboxed' away from the debugger's internals when we do
606 the eval, but we need some way to control how punctuation variables and
607 debugger globals are used.
609 We can't use local, because the code inside C<DB::eval> can see localized
610 variables; and we can't use C<my> either for the same reason. The code
611 in this routine compromises and uses C<my>.
613 After this routine is over, we don't have user code executing in the debugger's
614 context, so we can use C<my> freely.
618 ############################################## Begin lexical danger zone
620 # 'my' variables used here could leak into (that is, be visible in)
621 # the context that the code being evaluated is executing in. This means that
622 # the code could modify the debugger's variables.
624 # Fiddling with the debugger's context could be Bad. We insulate things as
689 # Used to save @ARGV and extract any debugger-related flags.
692 # Used to prevent multiple entries to diesignal()
693 # (if for instance diesignal() itself dies)
696 # Used to prevent the debugger from running nonstop
700 sub _calc_usercontext {
703 # Cancel strict completely for the evaluated code, so the code
704 # the user evaluates won't be affected by it. (Shlomi Fish)
705 return 'no strict; ($@, $!, $^E, $,, $/, $\, $^W) = @DB::saved;'
706 . "package $package;"; # this won't let them modify, alas
711 # 'my' would make it visible from user code
712 # but so does local! --tchrist
713 # Remember: this localizes @DB::res, not @main::res.
717 # Try to keep the user code from messing with us. Save these so that
718 # even if the eval'ed code changes them, we can put them back again.
719 # Needed because the user could refer directly to the debugger's
720 # package globals (and any 'my' variables in this containing scope)
721 # inside the eval(), and we want to try to stay safe.
722 local $otrace = $trace;
723 local $osingle = $single;
726 # Untaint the incoming eval() argument.
727 { ($evalarg) = $evalarg =~ /(.*)/s; }
729 # $usercontext built in DB::DB near the comment
730 # "set up the context for DB::eval ..."
731 # Evaluate and save any results.
732 @res = eval "$usercontext $evalarg;\n"; # '\n' for nice recursive debug
734 # Restore those old values.
740 # Save the current value of $@, and preserve it in the debugger's copy
741 # of the saved precious globals.
744 # Since we're only saving $@, we only have to localize the array element
745 # that it will be stored in.
746 local $saved[0]; # Preserve the old value of $@
749 # Now see whether we need to report an error back to the user.
755 # Display as required by the caller. $onetimeDump and $onetimedumpDepth
756 # are package globals.
757 elsif ($onetimeDump) {
758 if ( $onetimeDump eq 'dump' ) {
759 local $option{dumpDepth} = $onetimedumpDepth
760 if defined $onetimedumpDepth;
761 dumpit( $OUT, \@res );
763 elsif ( $onetimeDump eq 'methods' ) {
766 } ## end elsif ($onetimeDump)
770 ############################################## End lexical danger zone
772 # After this point it is safe to introduce lexicals.
773 # The code being debugged will be executing in its own context, and
774 # can't see the inside of the debugger.
776 # However, one should not overdo it: leave as much control from outside as
777 # possible. If you make something a lexical, it's not going to be addressable
778 # from outside the debugger even if you know its name.
780 # This file is automatically included if you do perl -d.
781 # It's probably not useful to include this yourself.
783 # Before venturing further into these twisty passages, it is
784 # wise to read the perldebguts man page or risk the ire of dragons.
786 # (It should be noted that perldebguts will tell you a lot about
787 # the underlying mechanics of how the debugger interfaces into the
788 # Perl interpreter, but not a lot about the debugger itself. The new
789 # comments in this code try to address this problem.)
791 # Note that no subroutine call is possible until &DB::sub is defined
792 # (for subroutines defined outside of the package DB). In fact the same is
793 # true if $deep is not defined.
795 # Enhanced by ilya@math.ohio-state.edu (Ilya Zakharevich)
797 # modified Perl debugger, to be run from Emacs in perldb-mode
798 # Ray Lischner (uunet!mntgfx!lisch) as of 5 Nov 1990
799 # Johan Vromans -- upgrade to 4.0 pl 10
800 # Ilya Zakharevich -- patches after 5.001 (and some before ;-)
801 ########################################################################
803 =head1 DEBUGGER INITIALIZATION
805 The debugger starts up in phases.
809 First, it initializes the environment it wants to run in: turning off
810 warnings during its own compilation, defining variables which it will need
811 to avoid warnings later, setting itself up to not exit when the program
812 terminates, and defaulting to printing return values for the C<r> command.
816 # Needed for the statement after exec():
818 # This BEGIN block is simply used to switch off warnings during debugger
819 # compilation. Probably it would be better practice to fix the warnings,
820 # but this is how it's done at the moment.
825 } # Switch compilation warnings off until another BEGIN.
827 local ($^W) = 0; # Switch run-time warnings off during init.
829 =head2 THREADS SUPPORT
831 If we are running under a threaded Perl, we require threads and threads::shared
832 if the environment variable C<PERL5DB_THREADED> is set, to enable proper
833 threaded debugger control. C<-dt> can also be used to set this.
835 Each new thread will be announced and the debugger prompt will always inform
836 you of each new thread created. It will also indicate the thread id in which
837 we are currently running within the prompt like this:
841 Where C<[tid]> is an integer thread id and C<$i> is the familiar debugger
842 command prompt. The prompt will show: C<[0]> when running under threads, but
843 not actually in a thread. C<[tid]> is consistent with C<gdb> usage.
845 While running under threads, when you set or delete a breakpoint (etc.), this
846 will apply to all threads, not just the currently running one. When you are
847 in a currently executing thread, you will stay there until it completes. With
848 the current implementation it is not currently possible to hop from one thread
851 The C<e> and C<E> commands are currently fairly minimal - see C<h e> and C<h E>.
853 Note that threading support was built into the debugger as of Perl version
854 C<5.8.6> and debugger version C<1.2.8>.
859 # ensure we can share our non-threaded variables or no-op
860 if ($ENV{PERL5DB_THREADED}) {
862 require threads::shared;
863 import threads::shared qw(share);
867 print "Threads support enabled\n";
869 *share = sub(\[$@%]) {};
873 # These variables control the execution of 'dumpvar.pl'.
888 # used to control die() reporting in diesignal()
891 use vars qw($CarpLevel);
894 # without threads, $filename is not defined until DB::DB is called
895 share($main::{'_<'.$filename}) if defined $filename;
897 # Command-line + PERLLIB:
898 # Save the contents of @INC before they are modified elsewhere.
901 # This was an attempt to clear out the previous values of various
902 # trapped errors. Apparently it didn't help. XXX More info needed!
903 # $prevwarn = $prevdie = $prevbus = $prevsegv = ''; # Does not help?!
905 # We set these variables to safe values. We don't want to blindly turn
906 # off warnings, because other packages may still want them.
907 $trace = $signal = $single = 0; # Uninitialized warning suppression
908 # (local $^W cannot help - other packages!).
910 # Default to not exiting when program finishes; print the return
911 # value when the 'r' command is used to return from a subroutine.
912 $inhibit_exit = $option{PrintRet} = 1;
914 use vars qw($trace_to_depth);
916 # Default to 1E9 so it won't be limited to a certain recursion depth.
917 $trace_to_depth = 1E9;
919 =head1 OPTION PROCESSING
921 The debugger's options are actually spread out over the debugger itself and
922 C<dumpvar.pl>; some of these are variables to be set, while others are
923 subs to be called with a value. To try to make this a little easier to
924 manage, the debugger uses a few data structures to define what options
925 are legal and how they are to be processed.
927 First, the C<@options> array defines the I<names> of all the options that
933 CommandSet HistFile HistSize
934 hashDepth arrayDepth dumpDepth
935 DumpDBFiles DumpPackages DumpReused
936 compactDump veryCompact quote
937 HighBit undefPrint globPrint
938 PrintRet UsageOnly frame
940 ReadLine NonStop LineInfo
941 maxTraceLen recallCommand ShellBang
942 pager tkRunning ornaments
943 signalLevel warnLevel dieLevel
944 inhibit_exit ImmediateStop bareStringify
945 CreateTTY RemotePort windowSize
949 @RememberOnROptions = qw(DollarCaretP);
953 Second, C<optionVars> lists the variables that each option uses to save its
958 use vars qw(%optionVars);
961 hashDepth => \$dumpvar::hashDepth,
962 arrayDepth => \$dumpvar::arrayDepth,
963 CommandSet => \$CommandSet,
964 DumpDBFiles => \$dumpvar::dumpDBFiles,
965 DumpPackages => \$dumpvar::dumpPackages,
966 DumpReused => \$dumpvar::dumpReused,
967 HighBit => \$dumpvar::quoteHighBit,
968 undefPrint => \$dumpvar::printUndef,
969 globPrint => \$dumpvar::globPrint,
970 UsageOnly => \$dumpvar::usageOnly,
971 CreateTTY => \$CreateTTY,
972 bareStringify => \$dumpvar::bareStringify,
974 AutoTrace => \$trace,
975 inhibit_exit => \$inhibit_exit,
976 maxTraceLen => \$maxtrace,
977 ImmediateStop => \$ImmediateStop,
978 RemotePort => \$remoteport,
979 windowSize => \$window,
980 HistFile => \$histfile,
981 HistSize => \$histsize,
986 Third, C<%optionAction> defines the subroutine to be called to process each
991 use vars qw(%optionAction);
994 compactDump => \&dumpvar::compactDump,
995 veryCompact => \&dumpvar::veryCompact,
996 quote => \&dumpvar::quote,
999 ReadLine => \&ReadLine,
1000 NonStop => \&NonStop,
1001 LineInfo => \&LineInfo,
1002 recallCommand => \&recallCommand,
1003 ShellBang => \&shellBang,
1005 signalLevel => \&signalLevel,
1006 warnLevel => \&warnLevel,
1007 dieLevel => \&dieLevel,
1008 tkRunning => \&tkRunning,
1009 ornaments => \&ornaments,
1010 RemotePort => \&RemotePort,
1011 DollarCaretP => \&DollarCaretP,
1016 Last, the C<%optionRequire> notes modules that must be C<require>d if an
1021 # Note that this list is not complete: several options not listed here
1022 # actually require that dumpvar.pl be loaded for them to work, but are
1023 # not in the table. A subsequent patch will correct this problem; for
1024 # the moment, we're just recommenting, and we are NOT going to change
1026 use vars qw(%optionRequire);
1029 compactDump => 'dumpvar.pl',
1030 veryCompact => 'dumpvar.pl',
1031 quote => 'dumpvar.pl',
1036 There are a number of initialization-related variables which can be set
1037 by putting code to set them in a BEGIN block in the C<PERL5DB> environment
1038 variable. These are:
1042 =item C<$rl> - readline control XXX needs more explanation
1044 =item C<$warnLevel> - whether or not debugger takes over warning handling
1046 =item C<$dieLevel> - whether or not debugger takes over die handling
1048 =item C<$signalLevel> - whether or not debugger takes over signal handling
1050 =item C<$pre> - preprompt actions (array reference)
1052 =item C<$post> - postprompt actions (array reference)
1056 =item C<$CreateTTY> - whether or not to create a new TTY for this debugger
1058 =item C<$CommandSet> - which command set to use (defaults to new, documented set)
1064 # These guys may be defined in $ENV{PERL5DB} :
1065 $rl = 1 unless defined $rl;
1066 $warnLevel = 1 unless defined $warnLevel;
1067 $dieLevel = 1 unless defined $dieLevel;
1068 $signalLevel = 1 unless defined $signalLevel;
1069 $pre = [] unless defined $pre;
1070 $post = [] unless defined $post;
1071 $pretype = [] unless defined $pretype;
1072 $CreateTTY = 3 unless defined $CreateTTY;
1073 $CommandSet = '580' unless defined $CommandSet;
1078 share($signalLevel);
1088 The default C<die>, C<warn>, and C<signal> handlers are set up.
1092 warnLevel($warnLevel);
1093 dieLevel($dieLevel);
1094 signalLevel($signalLevel);
1098 The pager to be used is needed next. We try to get it from the
1099 environment first. If it's not defined there, we try to find it in
1100 the Perl C<Config.pm>. If it's not there, we default to C<more>. We
1101 then call the C<pager()> function to save the pager name.
1105 # This routine makes sure $pager is set up so that '|' can use it.
1108 # If PAGER is defined in the environment, use it.
1112 # If not, see if Config.pm defines it.
1113 : eval { require Config }
1114 && defined $Config::Config{pager}
1115 ? $Config::Config{pager}
1117 # If not, fall back to 'more'.
1120 unless defined $pager;
1124 We set up the command to be used to access the man pages, the command
1125 recall character (C<!> unless otherwise defined) and the shell escape
1126 character (C<!> unless otherwise defined). Yes, these do conflict, and
1127 neither works in the debugger at the moment.
1133 # Set up defaults for command recall and shell escape (note:
1134 # these currently don't work in linemode debugging).
1135 recallCommand("!") unless defined $prc;
1136 shellBang("!") unless defined $psh;
1140 We then set up the gigantic string containing the debugger help.
1141 We also set the limit on the number of arguments we'll display during a
1148 # If we didn't get a default for the length of eval/stack trace args,
1150 $maxtrace = 400 unless defined $maxtrace;
1152 =head2 SETTING UP THE DEBUGGER GREETING
1154 The debugger I<greeting> helps to inform the user how many debuggers are
1155 running, and whether the current debugger is the primary or a child.
1157 If we are the primary, we just hang onto our pid so we'll have it when
1158 or if we start a child debugger. If we are a child, we'll set things up
1159 so we'll have a unique greeting and so the parent will give us our own
1162 We save the current contents of the C<PERLDB_PIDS> environment variable
1163 because we mess around with it. We'll also need to hang onto it because
1164 we'll need it if we restart.
1166 Child debuggers make a label out of the current PID structure recorded in
1167 PERLDB_PIDS plus the new PID. They also mark themselves as not having a TTY
1168 yet so the parent will give them one later via C<resetterm()>.
1172 # Save the current contents of the environment; we're about to
1173 # much with it. We'll need this if we have to restart.
1174 use vars qw($ini_pids);
1175 $ini_pids = $ENV{PERLDB_PIDS};
1177 use vars qw ($pids $term_pid);
1179 if ( defined $ENV{PERLDB_PIDS} ) {
1181 # We're a child. Make us a label out of the current PID structure
1182 # recorded in PERLDB_PIDS plus our (new) PID. Mark us as not having
1183 # a term yet so the parent will give us one later via resetterm().
1185 my $env_pids = $ENV{PERLDB_PIDS};
1186 $pids = "[$env_pids]";
1188 # Unless we are on OpenVMS, all programs under the DCL shell run under
1191 if (($^O eq 'VMS') && ($env_pids =~ /\b$$\b/)) {
1195 $ENV{PERLDB_PIDS} .= "->$$";
1199 } ## end if (defined $ENV{PERLDB_PIDS...
1202 # We're the parent PID. Initialize PERLDB_PID in case we end up with a
1203 # child debugger, and mark us as the parent, so we'll know to set up
1204 # more TTY's is we have to.
1205 $ENV{PERLDB_PIDS} = "$$";
1210 use vars qw($pidprompt);
1213 # Sets up $emacs as a synonym for $slave_editor.
1214 our ($slave_editor);
1215 *emacs = $slave_editor if $slave_editor; # May be used in afterinit()...
1217 =head2 READING THE RC FILE
1219 The debugger will read a file of initialization options if supplied. If
1220 running interactively, this is C<.perldb>; if not, it's C<perldb.ini>.
1224 # As noted, this test really doesn't check accurately that the debugger
1225 # is running at a terminal or not.
1227 use vars qw($rcfile);
1229 my $dev_tty = (($^O eq 'VMS') ? 'TT:' : '/dev/tty');
1230 # this is the wrong metric!
1231 $rcfile = ((-e $dev_tty) ? ".perldb" : "perldb.ini");
1236 The debugger does a safety test of the file to be read. It must be owned
1237 either by the current user or root, and must only be writable by the owner.
1241 # This wraps a safety test around "do" to read and evaluate the init file.
1243 # This isn't really safe, because there's a race
1244 # between checking and opening. The solution is to
1245 # open and fstat the handle, but then you have to read and
1246 # eval the contents. But then the silly thing gets
1247 # your lexical scope, which is unfortunate at best.
1251 # Just exactly what part of the word "CORE::" don't you understand?
1252 local $SIG{__WARN__};
1253 local $SIG{__DIE__};
1255 unless ( is_safe_file($file) ) {
1256 CORE::warn <<EO_GRIPE;
1257 perldb: Must not source insecure rcfile $file.
1258 You or the superuser must be the owner, and it must not
1259 be writable by anyone but its owner.
1262 } ## end unless (is_safe_file($file...
1265 CORE::warn("perldb: couldn't parse $file: $@") if $@;
1266 } ## end sub safe_do
1268 # This is the safety test itself.
1270 # Verifies that owner is either real user or superuser and that no
1271 # one but owner may write to it. This function is of limited use
1272 # when called on a path instead of upon a handle, because there are
1273 # no guarantees that filename (by dirent) whose file (by ino) is
1274 # eventually accessed is the same as the one tested.
1275 # Assumes that the file's existence is not in doubt.
1278 stat($path) || return; # mysteriously vaporized
1279 my ( $dev, $ino, $mode, $nlink, $uid, $gid ) = stat(_);
1281 return 0 if $uid != 0 && $uid != $<;
1282 return 0 if $mode & 022;
1284 } ## end sub is_safe_file
1286 # If the rcfile (whichever one we decided was the right one to read)
1287 # exists, we safely do it.
1289 safe_do("./$rcfile");
1292 # If there isn't one here, try the user's home directory.
1293 elsif ( defined $ENV{HOME} && -f "$ENV{HOME}/$rcfile" ) {
1294 safe_do("$ENV{HOME}/$rcfile");
1297 # Else try the login directory.
1298 elsif ( defined $ENV{LOGDIR} && -f "$ENV{LOGDIR}/$rcfile" ) {
1299 safe_do("$ENV{LOGDIR}/$rcfile");
1302 # If the PERLDB_OPTS variable has options in it, parse those out next.
1303 if ( defined $ENV{PERLDB_OPTS} ) {
1304 parse_options( $ENV{PERLDB_OPTS} );
1309 The last thing we do during initialization is determine which subroutine is
1310 to be used to obtain a new terminal when a new debugger is started. Right now,
1311 the debugger only handles TCP sockets, X11, OS/2, amd Mac OS X
1316 # Set up the get_fork_TTY subroutine to be aliased to the proper routine.
1317 # Works if you're running an xterm or xterm-like window, or you're on
1318 # OS/2, or on Mac OS X. This may need some expansion.
1320 if (not defined &get_fork_TTY) # only if no routine exists
1322 if ( defined $remoteport ) {
1323 # Expect an inetd-like server
1324 *get_fork_TTY = \&socket_get_fork_TTY; # to listen to us
1326 elsif (defined $ENV{TERM} # If we know what kind
1327 # of terminal this is,
1328 and $ENV{TERM} eq 'xterm' # and it's an xterm,
1329 and defined $ENV{DISPLAY} # and what display it's on,
1332 *get_fork_TTY = \&xterm_get_fork_TTY; # use the xterm version
1334 elsif ( $^O eq 'os2' ) { # If this is OS/2,
1335 *get_fork_TTY = \&os2_get_fork_TTY; # use the OS/2 version
1337 elsif ( $^O eq 'darwin' # If this is Mac OS X
1338 and defined $ENV{TERM_PROGRAM} # and we're running inside
1339 and $ENV{TERM_PROGRAM}
1340 eq 'Apple_Terminal' # Terminal.app
1343 *get_fork_TTY = \&macosx_get_fork_TTY; # use the Mac OS X version
1345 } ## end if (not defined &get_fork_TTY...
1347 # untaint $^O, which may have been tainted by the last statement.
1348 # see bug [perl #24674]
1352 # Here begin the unreadable code. It needs fixing.
1354 =head2 RESTART PROCESSING
1356 This section handles the restart command. When the C<R> command is invoked, it
1357 tries to capture all of the state it can into environment variables, and
1358 then sets C<PERLDB_RESTART>. When we start executing again, we check to see
1359 if C<PERLDB_RESTART> is there; if so, we reload all the information that
1360 the R command stuffed into the environment variables.
1362 PERLDB_RESTART - flag only, contains no restart data itself.
1363 PERLDB_HIST - command history, if it's available
1364 PERLDB_ON_LOAD - breakpoints set by the rc file
1365 PERLDB_POSTPONE - subs that have been loaded/not executed, and have actions
1366 PERLDB_VISITED - files that had breakpoints
1367 PERLDB_FILE_... - breakpoints for a file
1368 PERLDB_OPT - active options
1369 PERLDB_INC - the original @INC
1370 PERLDB_PRETYPE - preprompt debugger actions
1371 PERLDB_PRE - preprompt Perl code
1372 PERLDB_POST - post-prompt Perl code
1373 PERLDB_TYPEAHEAD - typeahead captured by readline()
1375 We chug through all these variables and plug the values saved in them
1376 back into the appropriate spots in the debugger.
1380 use vars qw(%postponed_file @typeahead);
1382 our (@hist, @truehist);
1384 sub _restore_shared_globals_after_restart
1386 @hist = get_list('PERLDB_HIST');
1387 %break_on_load = get_list("PERLDB_ON_LOAD");
1388 %postponed = get_list("PERLDB_POSTPONE");
1392 share(%break_on_load);
1396 sub _restore_breakpoints_and_actions {
1398 my @had_breakpoints = get_list("PERLDB_VISITED");
1400 for my $file_idx ( 0 .. $#had_breakpoints ) {
1401 my $filename = $had_breakpoints[$file_idx];
1402 my %pf = get_list("PERLDB_FILE_$file_idx");
1403 $postponed_file{ $filename } = \%pf if %pf;
1404 my @lines = sort {$a <=> $b} keys(%pf);
1405 my @enabled_statuses = get_list("PERLDB_FILE_ENABLED_$file_idx");
1406 for my $line_idx (0 .. $#lines) {
1407 _set_breakpoint_enabled_status(
1410 ($enabled_statuses[$line_idx] ? 1 : ''),
1418 sub _restore_options_after_restart
1420 my %options_map = get_list("PERLDB_OPT");
1422 while ( my ( $opt, $val ) = each %options_map ) {
1423 $val =~ s/[\\\']/\\$1/g;
1424 parse_options("$opt'$val'");
1430 sub _restore_globals_after_restart
1432 # restore original @INC
1433 @INC = get_list("PERLDB_INC");
1436 # return pre/postprompt actions and typeahead buffer
1437 $pretype = [ get_list("PERLDB_PRETYPE") ];
1438 $pre = [ get_list("PERLDB_PRE") ];
1439 $post = [ get_list("PERLDB_POST") ];
1440 @typeahead = get_list( "PERLDB_TYPEAHEAD", @typeahead );
1446 if ( exists $ENV{PERLDB_RESTART} ) {
1448 # We're restarting, so we don't need the flag that says to restart anymore.
1449 delete $ENV{PERLDB_RESTART};
1452 _restore_shared_globals_after_restart();
1454 _restore_breakpoints_and_actions();
1457 _restore_options_after_restart();
1459 _restore_globals_after_restart();
1460 } ## end if (exists $ENV{PERLDB_RESTART...
1462 =head2 SETTING UP THE TERMINAL
1464 Now, we'll decide how the debugger is going to interact with the user.
1465 If there's no TTY, we set the debugger to run non-stop; there's not going
1466 to be anyone there to enter commands.
1470 use vars qw($notty $console $tty $LINEINFO);
1471 use vars qw($lineinfo $doccmd);
1482 If there is a TTY, we have to determine who it belongs to before we can
1483 proceed. If this is a slave editor or graphical debugger (denoted by
1484 the first command-line switch being '-emacs'), we shift this off and
1485 set C<$rl> to 0 (XXX ostensibly to do straight reads).
1491 # Is Perl being run from a slave editor or graphical debugger?
1492 # If so, don't use readline, and set $slave_editor = 1.
1493 if ($slave_editor = ( @main::ARGV && ( $main::ARGV[0] eq '-emacs' ) )) {
1498 #require Term::ReadLine;
1502 We then determine what the console should be on various systems:
1506 =item * Cygwin - We use C<stdin> instead of a separate device.
1510 if ( $^O eq 'cygwin' ) {
1512 # /dev/tty is binary. use stdin for textmode
1516 =item * Unix - use C</dev/tty>.
1520 elsif ( -e "/dev/tty" ) {
1521 $console = "/dev/tty";
1524 =item * Windows or MSDOS - use C<con>.
1528 elsif ( $^O eq 'dos' or -e "con" or $^O eq 'MSWin32' ) {
1532 =item * VMS - use C<sys$command>.
1538 # everything else is ...
1539 $console = "sys\$command";
1546 Several other systems don't use a specific console. We C<undef $console>
1547 for those (Windows using a slave editor/graphical debugger, NetWare, OS/2
1548 with a slave editor, Epoc).
1552 if ( ( $^O eq 'MSWin32' ) and ( $slave_editor or defined $ENV{EMACS} ) ) {
1554 # /dev/tty is binary. use stdin for textmode
1558 if ( $^O eq 'NetWare' ) {
1560 # /dev/tty is binary. use stdin for textmode
1564 # In OS/2, we need to use STDIN to get textmode too, even though
1565 # it pretty much looks like Unix otherwise.
1566 if ( defined $ENV{OS2_SHELL} and ( $slave_editor or $ENV{WINDOWID} ) )
1571 # EPOC also falls into the 'got to use STDIN' camp.
1572 if ( $^O eq 'epoc' ) {
1578 If there is a TTY hanging around from a parent, we use that as the console.
1582 $console = $tty if defined $tty;
1584 =head2 SOCKET HANDLING
1586 The debugger is capable of opening a socket and carrying out a debugging
1587 session over the socket.
1589 If C<RemotePort> was defined in the options, the debugger assumes that it
1590 should try to start a debugging session on that port. It builds the socket
1591 and then tries to connect the input and output filehandles to it.
1595 # Handle socket stuff.
1597 if ( defined $remoteport ) {
1599 # If RemotePort was defined in the options, connect input and output
1601 $IN = $OUT = connect_remoteport();
1602 } ## end if (defined $remoteport)
1606 If no C<RemotePort> was defined, and we want to create a TTY on startup,
1607 this is probably a situation where multiple debuggers are running (for example,
1608 a backticked command that starts up another debugger). We create a new IN and
1609 OUT filehandle, and do the necessary mojo to create a new TTY if we know how
1617 # Two debuggers running (probably a system or a backtick that invokes
1618 # the debugger itself under the running one). create a new IN and OUT
1619 # filehandle, and do the necessary mojo to create a new tty if we
1620 # know how, and we can.
1621 create_IN_OUT(4) if $CreateTTY & 4;
1624 # If we have a console, check to see if there are separate ins and
1625 # outs to open. (They are assumed identical if not.)
1627 my ( $i, $o ) = split /,/, $console;
1628 $o = $i unless defined $o;
1630 # read/write on in, or just read, or read on STDIN.
1632 || open( IN, "<$i" )
1633 || open( IN, "<&STDIN" );
1635 # read/write/create/clobber out, or write/create/clobber out,
1636 # or merge with STDERR, or merge with STDOUT.
1638 || open( OUT, ">$o" )
1639 || open( OUT, ">&STDERR" )
1640 || open( OUT, ">&STDOUT" ); # so we don't dongle stdout
1642 } ## end if ($console)
1643 elsif ( not defined $console ) {
1645 # No console. Open STDIN.
1646 open( IN, "<&STDIN" );
1648 # merge with STDERR, or with STDOUT.
1649 open( OUT, ">&STDERR" )
1650 || open( OUT, ">&STDOUT" ); # so we don't dongle stdout
1651 $console = 'STDIN/OUT';
1652 } ## end elsif (not defined $console)
1654 # Keep copies of the filehandles so that when the pager runs, it
1655 # can close standard input without clobbering ours.
1656 if ($console or (not defined($console))) {
1660 } ## end elsif (from if(defined $remoteport))
1662 # Unbuffer DB::OUT. We need to see responses right away.
1665 # Line info goes to debugger output unless pointed elsewhere.
1666 # Pointing elsewhere makes it possible for slave editors to
1667 # keep track of file and position. We have both a filehandle
1668 # and a I/O description to keep track of.
1669 $LINEINFO = $OUT unless defined $LINEINFO;
1670 $lineinfo = $console unless defined $lineinfo;
1671 # share($LINEINFO); # <- unable to share globs
1676 To finish initialization, we show the debugger greeting,
1677 and then call the C<afterinit()> subroutine if there is one.
1681 # Show the debugger greeting.
1682 $header =~ s/.Header: ([^,]+),v(\s+\S+\s+\S+).*$/$1$2/;
1683 unless ($runnonstop) {
1686 if ( $term_pid eq '-1' ) {
1687 print $OUT "\nDaughter DB session started...\n";
1690 print $OUT "\nLoading DB routines from $header\n";
1693 $slave_editor ? "enabled" : "available", ".\n"
1696 "\nEnter h or 'h h' for help, or '$doccmd perldebug' for more help.\n\n";
1697 } ## end else [ if ($term_pid eq '-1')
1698 } ## end unless ($runnonstop)
1699 } ## end else [ if ($notty)
1701 # XXX This looks like a bug to me.
1702 # Why copy to @ARGS and then futz with @args?
1705 # Make sure backslashes before single quotes are stripped out, and
1706 # keep args unless they are numeric (XXX why?)
1707 # s/\'/\\\'/g; # removed while not justified understandably
1708 # s/(.*)/'$1'/ unless /^-?[\d.]+$/; # ditto
1711 # If there was an afterinit() sub defined, call it. It will get
1712 # executed in our scope, so it can fiddle with debugger globals.
1713 if ( defined &afterinit ) { # May be defined in $rcfile
1717 # Inform us about "Stack dump during die enabled ..." in dieLevel().
1718 use vars qw($I_m_init);
1722 ############################################################ Subroutines
1728 This gigantic subroutine is the heart of the debugger. Called before every
1729 statement, its job is to determine if a breakpoint has been reached, and
1730 stop if so; read commands from the user, parse them, and execute
1731 them, and then send execution off to the next statement.
1733 Note that the order in which the commands are processed is very important;
1734 some commands earlier in the loop will actually alter the C<$cmd> variable
1735 to create other commands to be executed later. This is all highly I<optimized>
1736 but can be confusing. Check the comments for each C<$cmd ... && do {}> to
1737 see what's happening in any given command.
1741 # $cmd cannot be an our() variable unfortunately (possible perl bug?).
1771 sub _DB__determine_if_we_should_break
1773 # if we have something here, see if we should break.
1774 # $stop is lexical and local to this block - $action on the other hand
1779 && _is_breakpoint_enabled($filename, $line)
1780 && (( $stop, $action ) = split( /\0/, $dbline{$line} ) ) )
1783 # Stop if the stop criterion says to just stop.
1784 if ( $stop eq '1' ) {
1788 # It's a conditional stop; eval it in the user's context and
1789 # see if we should stop. If so, remove the one-time sigil.
1791 $evalarg = "\$DB::signal |= 1 if do {$stop}";
1793 # If the breakpoint is temporary, then delete its enabled status.
1794 if ($dbline{$line} =~ s/;9($|\0)/$1/) {
1795 _cancel_breakpoint_temp_enabled_status($filename, $line);
1798 } ## end if ($dbline{$line} && ...
1801 sub _DB__is_finished {
1802 if ($finished and $level <= 1) {
1811 sub _DB__read_next_cmd
1815 # We have a terminal, or can get one ...
1820 # ... and it belogs to this PID or we get one for this PID ...
1821 if ($term_pid != $$) {
1825 # ... and we got a line of command input ...
1826 $cmd = DB::readline(
1827 "$pidprompt $tid DB"
1830 . ( '>' x $level ) . " "
1833 return defined($cmd);
1836 sub _DB__trim_command_and_return_first_component {
1837 $cmd =~ s/\A\s+//s; # trim annoying leading whitespace
1838 $cmd =~ s/\s+\z//s; # trim annoying trailing whitespace
1844 sub _DB__handle_f_command {
1845 if (($file) = $cmd =~ /\Af\b\s*(.*)/) {
1848 # help for no arguments (old-style was return from sub).
1851 "The old f command is now the r command.\n"; # hint
1852 print $OUT "The new f command switches filenames.\n";
1854 } ## end if (!$file)
1856 # if not in magic file list, try a close match.
1857 if ( !defined $main::{ '_<' . $file } ) {
1858 if ( ($try) = grep( m#^_<.*$file#, keys %main:: ) ) {
1860 $try = substr( $try, 2 );
1861 print $OUT "Choosing $try matching '$file':\n";
1864 } ## end if (($try) = grep(m#^_<.*$file#...
1865 } ## end if (!defined $main::{ ...
1867 # If not successfully switched now, we failed.
1868 if ( !defined $main::{ '_<' . $file } ) {
1869 print $OUT "No file matching '$file' is loaded.\n";
1873 # We switched, so switch the debugger internals around.
1874 elsif ( $file ne $filename ) {
1875 *dbline = $main::{ '_<' . $file };
1880 } ## end elsif ($file ne $filename)
1882 # We didn't switch; say we didn't.
1884 print $OUT "Already in $file.\n";
1892 sub _DB__handle_dot_command {
1897 $incr = -1; # stay at current line
1899 # Reset everything to the old location.
1901 $filename = $filename_ini;
1902 *dbline = $main::{ '_<' . $filename };
1906 print_lineinfo($obj->position());
1913 sub _DB__handle_y_command {
1916 if (my ($match_level, $match_vars)
1917 = $cmd =~ /^y(?:\s+(\d*)\s*(.*))?$/) {
1919 # See if we've got the necessary support.
1920 if (!eval { require PadWalker; PadWalker->VERSION(0.08) }) {
1924 ? "PadWalker module not found - please install\n"
1930 # Load up dumpvar if we don't have it. If we can, that is.
1931 do 'dumpvar.pl' || die $@ unless defined &main::dumpvar;
1932 defined &main::dumpvar
1933 or print $OUT "dumpvar.pl not available.\n"
1936 # Got all the modules we need. Find them and print them.
1937 my @vars = split( ' ', $match_vars || '' );
1940 my $h = eval { PadWalker::peek_my( ( $match_level || 0 ) + 1 ) };
1942 # Oops. Can't find it.
1949 # Show the desired vars with dumplex().
1950 my $savout = select($OUT);
1952 # Have dumplex dump the lexicals.
1953 foreach my $key (sort keys %$h) {
1954 dumpvar::dumplex( $key, $h->{$key},
1955 defined $option{dumpDepth} ? $option{dumpDepth} : -1,
1963 sub _DB__handle_c_command {
1966 if (my ($new_i) = $cmd =~ m#\Ac\b\s*([\w:]*)\s*\z#) {
1968 $obj->i_cmd($new_i);
1970 # Hey, show's over. The debugged program finished
1971 # executing already.
1972 next CMD if _DB__is_finished();
1974 # Capture the place to put a one-time break.
1975 $subname = $obj->i_cmd;
1977 # Probably not needed, since we finish an interactive
1978 # sub-session anyway...
1979 # local $filename = $filename;
1980 # local *dbline = *dbline; # XXX Would this work?!
1982 # The above question wonders if localizing the alias
1983 # to the magic array works or not. Since it's commented
1984 # out, we'll just leave that to speculation for now.
1986 # If the "subname" isn't all digits, we'll assume it
1987 # is a subroutine name, and try to find it.
1988 if ( $subname =~ /\D/ ) { # subroutine name
1989 # Qualify it to the current package unless it's
1990 # already qualified.
1991 $subname = $package . "::" . $subname
1992 unless $subname =~ /::/;
1994 # find_sub will return "file:line_number" corresponding
1995 # to where the subroutine is defined; we call find_sub,
1996 # break up the return value, and assign it in one
1998 ( $file, $new_i ) = ( find_sub($subname) =~ /^(.*):(.*)$/ );
2000 # Force the line number to be numeric.
2001 $obj->i_cmd($new_i + 0);
2003 # If we got a line number, we found the sub.
2006 # Switch all the debugger's internals around so
2007 # we're actually working with that file.
2009 *dbline = $main::{ '_<' . $filename };
2011 # Mark that there's a breakpoint in this file.
2012 $had_breakpoints{$filename} |= 1;
2014 # Scan forward to the first executable line
2015 # after the 'sub whatever' line.
2017 my $ii = $obj->i_cmd;
2018 ++$ii while $dbline[$ii] == 0 && $ii < $max;
2022 # We didn't find a sub by that name.
2024 print $OUT "Subroutine $subname not found.\n";
2027 } ## end if ($subname =~ /\D/)
2029 # At this point, either the subname was all digits (an
2030 # absolute line-break request) or we've scanned through
2031 # the code following the definition of the sub, looking
2032 # for an executable, which we may or may not have found.
2034 # If $i (which we set $subname from) is non-zero, we
2035 # got a request to break at some line somewhere. On
2036 # one hand, if there wasn't any real subroutine name
2037 # involved, this will be a request to break in the current
2038 # file at the specified line, so we have to check to make
2039 # sure that the line specified really is breakable.
2041 # On the other hand, if there was a subname supplied, the
2042 # preceding block has moved us to the proper file and
2043 # location within that file, and then scanned forward
2044 # looking for the next executable line. We have to make
2045 # sure that one was found.
2047 # On the gripping hand, we can't do anything unless the
2048 # current value of $i points to a valid breakable line.
2053 if ( $dbline[$obj->i_cmd] == 0 ) {
2054 print $OUT "Line " . $obj->i_cmd . " not breakable.\n";
2058 # Yes. Set up the one-time-break sigil.
2059 $dbline{$obj->i_cmd} =~ s/($|\0)/;9$1/; # add one-time-only b.p.
2060 _enable_breakpoint_temp_enabled_status($filename, $obj->i_cmd);
2063 # Turn off stack tracing from here up.
2064 for my $i (0 .. $stack_depth) {
2073 sub _DB__handle_forward_slash_command {
2076 # The pattern as a string.
2077 use vars qw($inpat);
2079 if (($inpat) = $cmd =~ m#\A/(.*)\z#) {
2081 # Remove the final slash.
2082 $inpat =~ s:([^\\])/$:$1:;
2084 # If the pattern isn't null ...
2085 if ( $inpat ne "" ) {
2087 # Turn of warn and die procesing for a bit.
2088 local $SIG{__DIE__};
2089 local $SIG{__WARN__};
2091 # Create the pattern.
2092 eval 'no strict q/vars/; $inpat =~ m' . "\a$inpat\a";
2095 # Oops. Bad pattern. No biscuit.
2096 # Print the eval error and go back for more
2102 } ## end if ($inpat ne "")
2104 # Set up to stop on wrap-around.
2107 # Don't move off the current line.
2110 my $pat = $obj->pat;
2112 # Done in eval so nothing breaks if the pattern
2113 # does something weird.
2118 # Move ahead one line.
2121 # Wrap if we pass the last line.
2122 $start = 1 if ($start > $max);
2124 # Stop if we have gotten back to this line again,
2125 last if ($start == $end);
2127 # A hit! (Note, though, that we are doing
2128 # case-insensitive matching. Maybe a qr//
2129 # expression would be better, so the user could
2130 # do case-sensitive matching if desired.
2131 if ($dbline[$start] =~ m/$pat/i) {
2132 if ($slave_editor) {
2133 # Handle proper escaping in the slave.
2134 print $OUT "\032\032$filename:$start:0\n";
2137 # Just print the line normally.
2138 print $OUT "$start:\t",$dbline[$start],"\n";
2140 # And quit since we found something.
2150 # If we wrapped, there never was a match.
2151 if ( $start == $end ) {
2152 print {$OUT} "/$pat/: not found\n";
2160 sub _DB__handle_question_mark_command {
2163 # ? - backward pattern search.
2164 if (my ($inpat) = $cmd =~ m#\A\?(.*)\z#) {
2166 # Get the pattern, remove trailing question mark.
2167 $inpat =~ s:([^\\])\?$:$1:;
2169 # If we've got one ...
2170 if ( $inpat ne "" ) {
2172 # Turn off die & warn handlers.
2173 local $SIG{__DIE__};
2174 local $SIG{__WARN__};
2175 eval '$inpat =~ m' . "\a$inpat\a";
2179 # Ouch. Not good. Print the error.
2184 } ## end if ($inpat ne "")
2186 # Where we are now is where to stop after wraparound.
2189 # Don't move away from this line.
2192 my $pat = $obj->pat;
2193 # Search inside the eval to prevent pattern badness
2201 # Wrap if we pass the first line.
2203 $start = $max if ($start <= 0);
2205 # Quit if we get back where we started,
2206 last if ($start == $end);
2209 if ($dbline[$start] =~ m/$pat/i) {
2210 if ($slave_editor) {
2211 # Yep, follow slave editor requirements.
2212 print $OUT "\032\032$filename:$start:0\n";
2215 # Yep, just print normally.
2216 print $OUT "$start:\t",$dbline[$start],"\n";
2225 # Say we failed if the loop never found anything,
2226 if ( $start == $end ) {
2227 print {$OUT} "?$pat?: not found\n";
2235 sub _DB__handle_restart_and_rerun_commands {
2238 # R - restart execution.
2239 # rerun - controlled restart execution.
2240 if (my ($cmd_cmd, $cmd_params) =
2241 $cmd =~ /\A((?:R)|(?:rerun\s*(.*)))\z/) {
2242 my @args = ($cmd_cmd eq 'R' ? restart() : rerun($cmd_params));
2244 # Close all non-system fds for a clean restart. A more
2245 # correct method would be to close all fds that were not
2246 # open when the process started, but this seems to be
2247 # hard. See "debugger 'R'estart and open database
2248 # connections" on p5p.
2250 my $max_fd = 1024; # default if POSIX can't be loaded
2251 if (eval { require POSIX }) {
2252 eval { $max_fd = POSIX::sysconf(POSIX::_SC_OPEN_MAX()) };
2255 if (defined $max_fd) {
2256 foreach ($^F+1 .. $max_fd-1) {
2257 next unless open FD_TO_CLOSE, "<&=$_";
2262 # And run Perl again. We use exec() to keep the
2263 # PID stable (and that way $ini_pids is still valid).
2264 exec(@args) or print {$OUT} "exec failed: $!\n";
2272 sub _DB__handle_run_command_in_pager_command {
2275 if ($cmd =~ m#\A\|\|?\s*[^|]#) {
2276 if ( $pager =~ /^\|/ ) {
2278 # Default pager is into a pipe. Redirect I/O.
2279 open( SAVEOUT, ">&STDOUT" )
2280 || DB::warn("Can't save STDOUT");
2281 open( STDOUT, ">&OUT" )
2282 || DB::warn("Can't redirect STDOUT");
2283 } ## end if ($pager =~ /^\|/)
2286 # Not into a pipe. STDOUT is safe.
2287 open( SAVEOUT, ">&OUT" ) || &warn("Can't save DB::OUT");
2290 # Fix up environment to record we have less if so.
2293 unless ( $obj->piped(scalar ( open( OUT, $pager ) ) ) ) {
2295 # Couldn't open pipe to pager.
2296 DB::warn("Can't pipe output to '$pager'");
2297 if ( $pager =~ /^\|/ ) {
2299 # Redirect I/O back again.
2300 open( OUT, ">&STDOUT" ) # XXX: lost message
2301 || DB::warn("Can't restore DB::OUT");
2302 open( STDOUT, ">&SAVEOUT" )
2303 || DB::warn("Can't restore STDOUT");
2305 } ## end if ($pager =~ /^\|/)
2308 # Redirect I/O. STDOUT already safe.
2309 open( OUT, ">&STDOUT" ) # XXX: lost message
2310 || DB::warn("Can't restore DB::OUT");
2313 } ## end unless ($piped = open(OUT,...
2315 # Set up broken-pipe handler if necessary.
2316 $SIG{PIPE} = \&DB::catch
2318 && ( "" eq $SIG{PIPE} || "DEFAULT" eq $SIG{PIPE} );
2321 # Save current filehandle, and put it back.
2322 $obj->selected(scalar( select(OUT) ));
2323 # Don't put it back if pager was a pipe.
2324 if ($cmd !~ /\A\|\|/)
2326 select($obj->selected());
2330 # Trim off the pipe symbols and run the command now.
2331 $cmd =~ s#\A\|+\s*##;
2341 # lock the debugger and get the thread id for the prompt
2345 my ($prefix, $after, $infix);
2351 if ($ENV{PERL5DB_THREADED}) {
2352 $tid = eval { "[".threads->tid."]" };
2357 my $obj = DB::Obj->new(
2359 position => \$position,
2362 explicit_stop => \$explicit_stop,
2367 selected => \$selected,
2371 $obj->_DB_on_init__initialize_globals(@_);
2373 # Preserve current values of $@, $!, $^E, $,, $/, $\, $^W.
2374 # The code being debugged may have altered them.
2377 # Since DB::DB gets called after every line, we can use caller() to
2378 # figure out where we last were executing. Sneaky, eh? This works because
2379 # caller is returning all the extra information when called from the
2381 local ( $package, $filename, $line ) = caller;
2382 $filename_ini = $filename;
2384 # set up the context for DB::eval, so it can properly execute
2385 # code on behalf of the user. We add the package in so that the
2386 # code is eval'ed in the proper package (not in the debugger!).
2387 local $usercontext = _calc_usercontext($package);
2389 # Create an alias to the active file magical array to simplify
2391 local (*dbline) = $main::{ '_<' . $filename };
2393 # Last line in the program.
2396 _DB__determine_if_we_should_break(@_);
2398 # Preserve the current stop-or-not, and see if any of the W
2399 # (watch expressions) has changed.
2400 my $was_signal = $signal;
2402 # If we have any watch expressions ...
2403 $obj->_DB__handle_watch_expressions(@_);
2405 =head2 C<watchfunction()>
2407 C<watchfunction()> is a function that can be defined by the user; it is a
2408 function which will be run on each entry to C<DB::DB>; it gets the
2409 current package, filename, and line as its parameters.
2411 The watchfunction can do anything it likes; it is executing in the
2412 debugger's context, so it has access to all of the debugger's internal
2413 data structures and functions.
2415 C<watchfunction()> can control the debugger's actions. Any of the following
2416 will cause the debugger to return control to the user's program after
2417 C<watchfunction()> executes:
2423 Returning a false value from the C<watchfunction()> itself.
2427 Altering C<$single> to a false value.
2431 Altering C<$signal> to a false value.
2435 Turning off the C<4> bit in C<$trace> (this also disables the
2436 check for C<watchfunction()>. This can be done with
2444 # If there's a user-defined DB::watchfunction, call it with the
2445 # current package, filename, and line. The function executes in
2447 if ( $trace & 4 ) { # User-installed watch
2449 if watchfunction( $package, $filename, $line )
2452 and not( $trace & ~4 );
2453 } ## end if ($trace & 4)
2455 # Pick up any alteration to $signal in the watchfunction, and
2456 # turn off the signal now.
2457 $was_signal = $signal;
2460 =head2 GETTING READY TO EXECUTE COMMANDS
2462 The debugger decides to take control if single-step mode is on, the
2463 C<t> command was entered, or the user generated a signal. If the program
2464 has fallen off the end, we set things up so that entering further commands
2465 won't cause trouble, and we say that the program is over.
2469 # Make sure that we always print if asked for explicitly regardless
2470 # of $trace_to_depth .
2471 $explicit_stop = ($single || $was_signal);
2473 # Check to see if we should grab control ($single true,
2474 # trace set appropriately, or we got a signal).
2475 if ( $explicit_stop || ( $trace & 1 ) ) {
2476 $obj->_DB__grab_control(@_);
2477 } ## end if ($single || ($trace...
2481 If there's an action to be executed for the line we stopped at, execute it.
2482 If there are any preprompt actions, execute those as well.
2486 # If there's an action, do it now.
2492 # Are we nested another level (e.g., did we evaluate a function
2493 # that had a breakpoint in it at the debugger prompt)?
2494 if ( $single || $was_signal ) {
2496 # Yes, go down a level.
2497 local $level = $level + 1;
2499 # Do any pre-prompt actions.
2500 foreach $evalarg (@$pre) {
2504 # Complain about too much recursion if we passed the limit.
2506 print $OUT $stack_depth . " levels deep in subroutine calls!\n";
2509 # The line we're currently on. Set $incr to -1 to stay here
2510 # until we get a command that tells us to advance.
2512 $incr = -1; # for backward motion.
2514 # Tack preprompt debugger actions ahead of any actual input.
2515 @typeahead = ( @$pretype, @typeahead );
2517 =head2 WHERE ARE WE?
2519 XXX Relocate this section?
2521 The debugger normally shows the line corresponding to the current line of
2522 execution. Sometimes, though, we want to see the next line, or to move elsewhere
2523 in the file. This is done via the C<$incr>, C<$start>, and C<$max> variables.
2525 C<$incr> controls by how many lines the I<current> line should move forward
2526 after a command is executed. If set to -1, this indicates that the I<current>
2527 line shouldn't change.
2529 C<$start> is the I<current> line. It is used for things like knowing where to
2530 move forwards or backwards from when doing an C<L> or C<-> command.
2532 C<$max> tells the debugger where the last line of the current file is. It's
2533 used to terminate loops most often.
2535 =head2 THE COMMAND LOOP
2537 Most of C<DB::DB> is actually a command parsing and dispatch loop. It comes
2544 The outer part of the loop, starting at the C<CMD> label. This loop
2545 reads a command and then executes it.
2549 The inner part of the loop, starting at the C<PIPE> label. This part
2550 is wholly contained inside the C<CMD> block and only executes a command.
2551 Used to handle commands running inside a pager.
2555 So why have two labels to restart the loop? Because sometimes, it's easier to
2556 have a command I<generate> another command and then re-execute the loop to do
2557 the new command. This is faster, but perhaps a bit more convoluted.
2561 # The big command dispatch loop. It keeps running until the
2562 # user yields up control again.
2564 # If we have a terminal for input, and we get something back
2565 # from readline(), keep on processing.
2568 while (_DB__read_next_cmd($tid))
2572 # ... try to execute the input as debugger commands.
2574 # Don't stop running.
2577 # No signal is active.
2580 # Handle continued commands (ending with \):
2581 if ($cmd =~ s/\\\z/\n/) {
2582 $cmd .= DB::readline(" cont: ");
2586 =head4 The null command
2588 A newline entered by itself means I<re-execute the last command>. We grab the
2589 command out of C<$laststep> (where it was recorded previously), and copy it
2590 back into C<$cmd> to be executed below. If there wasn't any previous command,
2591 we'll do nothing below (no command will match). If there was, we also save it
2592 in the command history and fall through to allow the command parsing to pick
2597 # Empty input means repeat the last command.
2601 chomp($cmd); # get rid of the annoying extra newline
2602 if (length($cmd) >= 2) {
2603 push( @hist, $cmd );
2605 push( @truehist, $cmd );
2609 # This is a restart point for commands that didn't arrive
2610 # via direct user input. It allows us to 'redo PIPE' to
2611 # re-execute command processing without reading a new command.
2613 $i = _DB__trim_command_and_return_first_component();
2615 =head3 COMMAND ALIASES
2617 The debugger can create aliases for commands (these are stored in the
2618 C<%alias> hash). Before a command is executed, the command loop looks it up
2619 in the alias hash and substitutes the contents of the alias for the command,
2620 completely replacing it.
2624 # See if there's an alias for the command, and set it up if so.
2627 # Squelch signal handling; we want to keep control here
2628 # if something goes loco during the alias eval.
2629 local $SIG{__DIE__};
2630 local $SIG{__WARN__};
2632 # This is a command, so we eval it in the DEBUGGER's
2633 # scope! Otherwise, we can't see the special debugger
2634 # variables, or get to the debugger's subs. (Well, we
2635 # _could_, but why make it even more complicated?)
2636 eval "\$cmd =~ $alias{$i}";
2639 print $OUT "Couldn't evaluate '$i' alias: $@";
2642 } ## end if ($alias{$i})
2644 =head3 MAIN-LINE COMMANDS
2646 All of these commands work up to and after the program being debugged has
2651 Quit the debugger. This entails setting the C<$fall_off_end> flag, so we don't
2652 try to execute further, cleaning any restart-related stuff out of the
2653 environment, and executing with the last value of C<$?>.
2663 =head4 C<t> - trace [n]
2665 Turn tracing on or off. Inverts the appropriate bit in C<$trace> (q.v.).
2666 If level is specified, set C<$trace_to_depth>.
2670 $obj->_handle_t_command;
2672 =head4 C<S> - list subroutines matching/not matching a pattern
2674 Walks through C<%sub>, checking to see whether or not to print the name.
2678 $obj->_handle_S_command;
2680 =head4 C<X> - list variables in current package
2682 Since the C<V> command actually processes this, just change this to the
2683 appropriate C<V> command and fall through.
2685 =head4 C<V> - list variables
2687 Uses C<dumpvar.pl> to dump out the current values for selected variables.
2691 $obj->_handle_V_command_and_X_command;
2693 =head4 C<x> - evaluate and print an expression
2695 Hands the expression off to C<DB::eval>, setting it up to print the value
2696 via C<dumpvar.pl> instead of just printing it directly.
2700 if ($cmd =~ s#\Ax\b# #) { # Remainder gets done by DB::eval()
2701 $onetimeDump = 'dump'; # main::dumpvar shows the output
2703 # handle special "x 3 blah" syntax XXX propagate
2704 # doc back to special variables.
2705 if ( $cmd =~ s#\A\s*(\d+)(?=\s)# #) {
2706 $onetimedumpDepth = $1;
2710 =head4 C<m> - print methods
2712 Just uses C<DB::methods> to determine what methods are available.
2716 if ($cmd =~ s#\Am\s+([\w:]+)\s*\z# #) {
2721 # m expr - set up DB::eval to do the work
2722 if ($cmd =~ s#\Am\b# #) { # Rest gets done by DB::eval()
2723 $onetimeDump = 'methods'; # method output gets used there
2726 =head4 C<f> - switch files
2730 _DB__handle_f_command();
2732 =head4 C<.> - return to last-executed line.
2734 We set C<$incr> to -1 to indicate that the debugger shouldn't move ahead,
2735 and then we look up the line in the magical C<%dbline> hash.
2739 _DB__handle_dot_command($obj);
2741 =head4 C<-> - back one window
2743 We change C<$start> to be one window back; if we go back past the first line,
2744 we set it to be the first line. We ser C<$incr> to put us back at the
2745 currently-executing line, and then put a C<l $start +> (list one window from
2746 C<$start>) in C<$cmd> to be executed later.
2750 # - - back a window.
2751 $obj->_handle_dash_command;
2753 =head3 PRE-580 COMMANDS VS. NEW COMMANDS: C<a, A, b, B, h, l, L, M, o, O, P, v, w, W, E<lt>, E<lt>E<lt>, E<0x7B>, E<0x7B>E<0x7B>>
2755 In Perl 5.8.0, a realignment of the commands was done to fix up a number of
2756 problems, most notably that the default case of several commands destroying
2757 the user's work in setting watchpoints, actions, etc. We wanted, however, to
2758 retain the old commands for those who were used to using them or who preferred
2759 them. At this point, we check for the new commands and call C<cmd_wrapper> to
2760 deal with them instead of processing them in-line.
2764 # All of these commands were remapped in perl 5.8.0;
2765 # we send them off to the secondary dispatcher (see below).
2766 if (my ($cmd_letter, $my_arg) = $cmd =~ /\A([aAbBeEhilLMoOPvwW]\b|[<>\{]{1,2})\s*(.*)/so) {
2767 &cmd_wrapper( $cmd_letter, $my_arg, $line );
2771 =head4 C<y> - List lexicals in higher scope
2773 Uses C<PadWalker> to find the lexicals supplied as arguments in a scope
2774 above the current one and then displays then using C<dumpvar.pl>.
2778 _DB__handle_y_command($obj);
2780 =head3 COMMANDS NOT WORKING AFTER PROGRAM ENDS
2782 All of the commands below this point don't work after the program being
2783 debugged has ended. All of them check to see if the program has ended; this
2784 allows the commands to be relocated without worrying about a 'line of
2785 demarcation' above which commands can be entered anytime, and below which
2788 =head4 C<n> - single step, but don't trace down into subs
2790 Done by setting C<$single> to 2, which forces subs to execute straight through
2791 when entered (see C<DB::sub>). We also save the C<n> command in C<$laststep>,
2792 so a null command knows what to re-execute.
2797 $obj->_handle_n_command;
2799 =head4 C<s> - single-step, entering subs
2801 Sets C<$single> to 1, which causes C<DB::sub> to continue tracing inside
2802 subs. Also saves C<s> as C<$lastcmd>.
2806 $obj->_handle_s_command;
2808 =head4 C<c> - run continuously, setting an optional breakpoint
2810 Most of the code for this command is taken up with locating the optional
2811 breakpoint, which is either a subroutine name or a line number. We set
2812 the appropriate one-time-break in C<@dbline> and then turn off single-stepping
2813 in this and all call levels above this one.
2817 # c - start continuous execution.
2818 _DB__handle_c_command($obj);
2820 =head4 C<r> - return from a subroutine
2822 For C<r> to work properly, the debugger has to stop execution again
2823 immediately after the return is executed. This is done by forcing
2824 single-stepping to be on in the call level above the current one. If
2825 we are printing return values when a C<r> is executed, set C<$doret>
2826 appropriately, and force us out of the command loop.
2830 # r - return from the current subroutine.
2831 $obj->_handle_r_command;
2833 =head4 C<T> - stack trace
2835 Just calls C<DB::print_trace>.
2839 $obj->_handle_T_command;
2841 =head4 C<w> - List window around current line.
2843 Just calls C<DB::cmd_w>.
2847 $obj->_handle_w_command;
2849 =head4 C<W> - watch-expression processing.
2851 Just calls C<DB::cmd_W>.
2855 $obj->_handle_W_command;
2857 =head4 C</> - search forward for a string in the source
2859 We take the argument and treat it as a pattern. If it turns out to be a
2860 bad one, we return the error we got from trying to C<eval> it and exit.
2861 If not, we create some code to do the search and C<eval> it so it can't
2866 _DB__handle_forward_slash_command($obj);
2868 =head4 C<?> - search backward for a string in the source
2870 Same as for C</>, except the loop runs backwards.
2874 _DB__handle_question_mark_command($obj);
2876 =head4 C<$rc> - Recall command
2878 Manages the commands in C<@hist> (which is created if C<Term::ReadLine> reports
2879 that the terminal supports history). It find the the command required, puts it
2880 into C<$cmd>, and redoes the loop to execute it.
2884 # $rc - recall command.
2885 $obj->_handle_rc_recall_command;
2887 =head4 C<$sh$sh> - C<system()> command
2889 Calls the C<DB::system()> to handle the command. This keeps the C<STDIN> and
2890 C<STDOUT> from getting messed up.
2894 $obj->_handle_sh_sh_command;
2896 =head4 C<$rc I<pattern> $rc> - Search command history
2898 Another command to manipulate C<@hist>: this one searches it with a pattern.
2899 If a command is found, it is placed in C<$cmd> and executed via C<redo>.
2903 $obj->_handle_rc_search_history_command;
2905 =head4 C<$sh> - Invoke a shell
2907 Uses C<DB::system> to invoke a shell.
2911 # $sh - start a shell.
2912 if ($cmd =~ /\A$sh\z/) {
2914 # Run the user's shell. If none defined, run Bourne.
2915 # We resume execution when the shell terminates.
2916 DB::system( $ENV{SHELL} || "/bin/sh" );
2920 =head4 C<$sh I<command>> - Force execution of a command in a shell
2922 Like the above, but the command is passed to the shell. Again, we use
2923 C<DB::system> to avoid problems with C<STDIN> and C<STDOUT>.
2927 # $sh command - start a shell and run a command in it.
2928 if (my ($arg) = $cmd =~ m#\A$sh\s*(.*)#ms) {
2930 # XXX: using csh or tcsh destroys sigint retvals!
2931 #&system($1); # use this instead
2933 # use the user's shell, or Bourne if none defined.
2934 &system( $ENV{SHELL} || "/bin/sh", "-c", $arg );
2938 =head4 C<H> - display commands in history
2940 Prints the contents of C<@hist> (if any).
2944 $obj->_handle_H_command;
2946 =head4 C<man, doc, perldoc> - look up documentation
2948 Just calls C<runman()> to print the appropriate document.
2952 $obj->_handle_doc_command;
2956 Builds a C<print EXPR> expression in the C<$cmd>; this will get executed at
2957 the bottom of the loop.
2961 $obj->_handle_p_command;
2963 =head4 C<=> - define command alias
2965 Manipulates C<%alias> to add or list command aliases.
2969 # = - set up a command alias.
2970 $obj->_handle_equal_sign_command;
2972 =head4 C<source> - read commands from a file.
2974 Opens a lexical filehandle and stacks it on C<@cmdfhs>; C<DB::readline> will
2979 $obj->_handle_source_command;
2981 =head4 C<enable> C<disable> - enable or disable breakpoints
2983 This enables or disables breakpoints.
2987 $obj->_handle_enable_disable_commands;
2989 =head4 C<save> - send current history to a file
2991 Takes the complete history, (not the shrunken version you see with C<H>),
2992 and saves it to the given filename, so it can be replayed using C<source>.
2994 Note that all C<^(save|source)>'s are commented out with a view to minimise recursion.
2998 # save source - write commands to a file for later use
2999 $obj->_handle_save_command;
3001 =head4 C<R> - restart
3003 Restart the debugger session.
3005 =head4 C<rerun> - rerun the current session
3007 Return to any given position in the B<true>-history list
3011 # R - restart execution.
3012 # rerun - controlled restart execution.
3013 _DB__handle_restart_and_rerun_commands($obj);
3015 =head4 C<|, ||> - pipe output through the pager.
3017 For C<|>, we save C<OUT> (the debugger's output filehandle) and C<STDOUT>
3018 (the program's standard output). For C<||>, we only save C<OUT>. We open a
3019 pipe to the pager (restoring the output filehandles if this fails). If this
3020 is the C<|> command, we also set up a C<SIGPIPE> handler which will simply
3021 set C<$signal>, sending us back into the debugger.
3023 We then trim off the pipe symbols and C<redo> the command loop at the
3024 C<PIPE> label, causing us to evaluate the command in C<$cmd> without
3029 # || - run command in the pager, with output to DB::OUT.
3030 _DB__handle_run_command_in_pager_command($obj);
3032 =head3 END OF COMMAND PARSING
3034 Anything left in C<$cmd> at this point is a Perl expression that we want to
3035 evaluate. We'll always evaluate in the user's context, and fully qualify
3036 any variables we might want to address in the C<DB> package.
3042 # Make sure the flag that says "the debugger's running" is
3043 # still on, to make sure we get control again.
3044 $evalarg = "\$^D = \$^D | \$DB::db_stop;\n$cmd";
3046 # Run *our* eval that executes in the caller's context.
3049 # Turn off the one-time-dump stuff now.
3051 $onetimeDump = undef;
3052 $onetimedumpDepth = undef;
3054 elsif ( $term_pid == $$ ) {
3055 eval { # May run under miniperl, when not available...
3060 # XXX If this is the master pid, print a newline.
3063 } ## end while (($term || &setterm...
3065 =head3 POST-COMMAND PROCESSING
3067 After each command, we check to see if the command output was piped anywhere.
3068 If so, we go through the necessary code to unhook the pipe and go back to
3069 our standard filehandles for input and output.
3075 # At the end of every command:
3078 # Unhook the pipe mechanism now.
3079 if ( $pager =~ /^\|/ ) {
3081 # No error from the child.
3084 # we cannot warn here: the handle is missing --tchrist
3085 close(OUT) || print SAVEOUT "\nCan't close DB::OUT\n";
3087 # most of the $? crud was coping with broken cshisms
3088 # $? is explicitly set to 0, so this never runs.
3090 print SAVEOUT "Pager '$pager' failed: ";
3092 print SAVEOUT "shell returned -1\n";
3095 print SAVEOUT ( $? & 127 )
3096 ? " (SIG#" . ( $? & 127 ) . ")"
3097 : "", ( $? & 128 ) ? " -- core dumped" : "", "\n";
3100 print SAVEOUT "status ", ( $? >> 8 ), "\n";
3104 # Reopen filehandle for our output (if we can) and
3105 # restore STDOUT (if we can).
3106 open( OUT, ">&STDOUT" ) || &warn("Can't restore DB::OUT");
3107 open( STDOUT, ">&SAVEOUT" )
3108 || &warn("Can't restore STDOUT");
3110 # Turn off pipe exception handler if necessary.
3111 $SIG{PIPE} = "DEFAULT" if $SIG{PIPE} eq \&DB::catch;
3113 # Will stop ignoring SIGPIPE if done like nohup(1)
3114 # does SIGINT but Perl doesn't give us a choice.
3115 } ## end if ($pager =~ /^\|/)
3118 # Non-piped "pager". Just restore STDOUT.
3119 open( OUT, ">&SAVEOUT" ) || &warn("Can't restore DB::OUT");
3122 # Close filehandle pager was using, restore the normal one
3125 select($selected), $selected = "" unless $selected eq "";
3129 } ## end if ($piped)
3132 =head3 COMMAND LOOP TERMINATION
3134 When commands have finished executing, we come here. If the user closed the
3135 input filehandle, we turn on C<$fall_off_end> to emulate a C<q> command. We
3136 evaluate any post-prompt items. We restore C<$@>, C<$!>, C<$^E>, C<$,>, C<$/>,
3137 C<$\>, and C<$^W>, and return a null list as expected by the Perl interpreter.
3138 The interpreter will then execute the next line and then return control to us
3143 # No more commands? Quit.
3144 $fall_off_end = 1 unless defined $cmd; # Emulate 'q' on EOF
3146 # Evaluate post-prompt commands.
3147 foreach $evalarg (@$post) {
3150 } # if ($single || $signal)
3152 # Put the user's globals back where you found them.
3153 ( $@, $!, $^E, $,, $/, $\, $^W ) = @saved;
3162 my $self = bless {}, $class;
3170 my ($self, $args) = @_;
3172 %{$self} = (%$self, %$args);
3179 foreach my $slot_name (qw(
3180 after explicit_stop infix pat piped position prefix selected i_cmd
3182 my $slot = $slot_name;
3187 ${ $self->{$slot} } = shift;
3190 return ${ $self->{$slot} };
3193 *{"append_to_$slot"} = sub {
3197 return $self->$slot($self->$slot . $s);
3202 sub _DB_on_init__initialize_globals
3206 # Check for whether we should be running continuously or not.
3207 # _After_ the perl program is compiled, $single is set to 1:
3208 if ( $single and not $second_time++ ) {
3210 # Options say run non-stop. Run until we get an interrupt.
3211 if ($runnonstop) { # Disable until signal
3212 # If there's any call stack in place, turn off single
3213 # stepping into subs throughout the stack.
3214 for my $i (0 .. $stack_depth) {
3218 # And we are now no longer in single-step mode.
3221 # If we simply returned at this point, we wouldn't get
3222 # the trace info. Fall on through.
3224 } ## end if ($runnonstop)
3226 elsif ($ImmediateStop) {
3228 # We are supposed to stop here; XXX probably a break.
3229 $ImmediateStop = 0; # We've processed it; turn it off
3230 $signal = 1; # Simulate an interrupt to force
3231 # us into the command loop
3233 } ## end if ($single and not $second_time...
3235 # If we're in single-step mode, or an interrupt (real or fake)
3236 # has occurred, turn off non-stop mode.
3237 $runnonstop = 0 if $single or $signal;
3242 sub _DB__handle_watch_expressions
3247 for my $n (0 .. $#to_watch) {
3248 $evalarg = $to_watch[$n];
3249 local $onetimeDump; # Tell DB::eval() to not output results
3251 # Fix context DB::eval() wants to return an array, but
3252 # we need a scalar here.
3253 my ($val) = join( "', '", DB::eval() );
3254 $val = ( ( defined $val ) ? "'$val'" : 'undef' );
3257 if ( $val ne $old_watch[$n] ) {
3259 # Yep! Show the difference, and fake an interrupt.
3262 Watchpoint $n:\t$to_watch[$n] changed:
3263 old value:\t$old_watch[$n]
3266 $old_watch[$n] = $val;
3267 } ## end if ($val ne $old_watch...
3268 } ## end for my $n (0 ..
3269 } ## end if ($trace & 2)
3274 sub _my_print_lineinfo
3276 my ($self, $i, $incr_pos) = @_;
3279 # Print it indented if tracing is on.
3280 DB::print_lineinfo( ' ' x $stack_depth,
3281 "$i:\t$DB::dbline[$i]" . $self->after );
3284 DB::depth_print_lineinfo($self->explicit_stop, $incr_pos);
3289 return $DB::dbline[$line];
3292 sub _DB__grab_control
3296 # Yes, grab control.
3297 if ($slave_editor) {
3299 # Tell the editor to update its position.
3300 $self->position("\032\032${DB::filename}:$line:0\n");
3301 DB::print_lineinfo($self->position());
3306 Special check: if we're in package C<DB::fake>, we've gone through the
3307 C<END> block at least once. We set up everything so that we can continue
3308 to enter commands and have a valid context to be in.
3312 elsif ( $DB::package eq 'DB::fake' ) {
3314 # Fallen off the end already.
3319 DB::print_help(<<EOP);
3320 Debugged program terminated. Use B<q> to quit or B<R> to restart,
3321 use B<o> I<inhibit_exit> to avoid stopping after program termination,
3322 B<h q>, B<h R> or B<h o> to get additional info.
3325 # Set the DB::eval context appropriately.
3326 $DB::package = 'main';
3327 $DB::usercontext = DB::_calc_usercontext($DB::package);
3328 } ## end elsif ($package eq 'DB::fake')
3332 If the program hasn't finished executing, we scan forward to the
3333 next executable line, print that out, build the prompt from the file and line
3334 number information, and print that.
3341 # Still somewhere in the midst of execution. Set up the
3343 $DB::sub =~ s/\'/::/; # Swap Perl 4 package separators (') to
3344 # Perl 5 ones (sorry, we don't print Klingon
3347 $self->prefix($DB::sub =~ /::/ ? "" : ($DB::package . '::'));
3348 $self->append_to_prefix( "$DB::sub(${DB::filename}:" );
3349 $self->after( $self->_curr_line =~ /\n$/ ? '' : "\n" );
3351 # Break up the prompt if it's really long.
3352 if ( length($self->prefix()) > 30 ) {
3353 $self->position($self->prefix . "$line):\n$line:\t" . $self->_curr_line . $self->after);
3355 $self->infix(":\t");
3358 $self->infix("):\t");
3360 $self->prefix . $line. $self->infix
3361 . $self->_curr_line . $self->after
3365 # Print current line info, indenting if necessary.
3366 $self->_my_print_lineinfo($line, $self->position);
3369 my $line_i = sub { return $DB::dbline[$i]; };
3371 # Scan forward, stopping at either the end or the next
3373 for ( $i = $line + 1 ; $i <= $DB::max && $line_i->() == 0 ; ++$i )
3376 # Drop out on null statements, block closers, and comments.
3377 last if $line_i->() =~ /^\s*[\;\}\#\n]/;
3379 # Drop out if the user interrupted us.
3382 # Append a newline if the line doesn't have one. Can happen
3383 # in eval'ed text, for instance.
3384 $self->after( $line_i->() =~ /\n$/ ? '' : "\n" );
3386 # Next executable line.
3387 my $incr_pos = $self->prefix . $i . $self->infix . $line_i->()
3389 $self->append_to_position($incr_pos);
3390 $self->_my_print_lineinfo($i, $incr_pos);
3391 } ## end for ($i = $line + 1 ; $i...
3392 } ## end else [ if ($slave_editor)
3397 sub _handle_t_command {
3398 if (my ($levels) = $DB::cmd =~ /\At(?:\s+(\d+))?\z/) {
3401 $DB::trace_to_depth = $levels ? $stack_depth + $levels : 1E9;
3402 print {$OUT} "Trace = "
3404 ? ( $levels ? "on (to level $DB::trace_to_depth)" : "on" )
3413 sub _handle_S_command {
3414 if (my ($print_all_subs, $should_reverse, $Spatt)
3415 = $DB::cmd =~ /\AS(\s+(!)?(.+))?\z/) {
3416 # $Spatt is the pattern (if any) to use.
3418 my $Srev = defined $should_reverse;
3419 # No args - print all subs.
3420 my $Snocheck = !defined $print_all_subs;
3422 # Need to make these sane here.
3426 # Search through the debugger's magical hash of subs.
3427 # If $nocheck is true, just print the sub name.
3428 # Otherwise, check it against the pattern. We then use
3429 # the XOR trick to reverse the condition as required.
3430 foreach $subname ( sort( keys %sub ) ) {
3431 if ( $Snocheck or $Srev ^ ( $subname =~ /$Spatt/ ) ) {
3432 print $OUT $subname, "\n";
3441 sub _handle_V_command_and_X_command {
3443 $DB::cmd =~ s/^X\b/V $DB::package/;
3445 # Bare V commands get the currently-being-debugged package
3447 if ($DB::cmd eq "V") {
3448 $DB::cmd = "V $DB::package";
3451 # V - show variables in package.
3452 if (my ($new_packname, $new_vars_str) =
3453 $DB::cmd =~ /\AV\b\s*(\S+)\s*(.*)/) {
3455 # Save the currently selected filehandle and
3456 # force output to debugger's filehandle (dumpvar
3457 # just does "print" for output).
3458 my $savout = select($OUT);
3460 # Grab package name and variables to dump.
3461 $packname = $new_packname;
3462 my @vars = split( ' ', $new_vars_str );
3464 # If main::dumpvar isn't here, get it.
3465 do 'dumpvar.pl' || die $@ unless defined &main::dumpvar;
3466 if ( defined &main::dumpvar ) {
3468 # We got it. Turn off subroutine entry/exit messages
3469 # for the moment, along with return values.
3473 # must detect sigpipe failures - not catching
3474 # then will cause the debugger to die.
3478 defined $option{dumpDepth}
3479 ? $option{dumpDepth}
3480 : -1, # assume -1 unless specified
3485 # The die doesn't need to include the $@, because
3486 # it will automatically get propagated for us.
3488 die unless $@ =~ /dumpvar print failed/;
3490 } ## end if (defined &main::dumpvar)
3493 # Couldn't load dumpvar.
3494 print $OUT "dumpvar.pl not available.\n";
3497 # Restore the output filehandle, and go round again.
3505 sub _handle_dash_command {
3507 if ($DB::cmd eq '-') {
3509 # back up by a window; go to 1 if back too far.
3510 $start -= $incr + $window + 1;
3511 $start = 1 if $start <= 0;
3512 $incr = $window - 1;
3514 # Generate and execute a "l +" command (handled below).
3515 $DB::cmd = 'l ' . ($start) . '+';
3520 sub _n_or_s_commands_generic {
3521 my ($self, $new_val) = @_;
3523 next CMD if DB::_DB__is_finished();
3525 # Single step, but don't enter subs.
3528 # Save for empty command (repeat last).
3529 $laststep = $DB::cmd;
3534 my ($self, $letter, $new_val) = @_;
3536 if ($DB::cmd eq $letter) {
3537 $self->_n_or_s_commands_generic($new_val);
3539 elsif ($DB::cmd =~ m#\A\Q$letter\E\b#) {
3540 $self->_n_or_s_and_arg_commands_generic($letter, $new_val);
3546 sub _handle_n_command {
3549 return $self->_n_or_s('n', 2);
3552 sub _handle_s_command {
3555 return $self->_n_or_s('s', 1);
3558 sub _handle_r_command {
3560 # r - return from the current subroutine.
3561 if ($DB::cmd eq 'r') {
3563 # Can't do anything if the program's over.
3564 next CMD if DB::_DB__is_finished();
3566 # Turn on stack trace.
3567 $stack[$stack_depth] |= 1;
3569 # Print return value unless the stack is empty.
3570 $doret = $option{PrintRet} ? $stack_depth - 1 : -2;
3577 sub _handle_T_command {
3578 if ($DB::cmd eq 'T') {
3579 DB::print_trace( $OUT, 1 ); # skip DB
3586 sub _handle_w_command {
3587 if (my ($arg) = $DB::cmd =~ /\Aw\b\s*(.*)/s) {
3588 DB::cmd_w( 'w', $arg );
3595 sub _handle_W_command {
3596 if (my ($arg) = $DB::cmd =~ /\AW\b\s*(.*)/s) {
3597 DB::cmd_W( 'W', $arg );
3604 sub _handle_rc_recall_command {
3607 # $rc - recall command.
3608 if (my ($minus, $arg) = $DB::cmd =~ m#\A$rc+\s*(-)?(\d+)?\z#) {
3610 # No arguments, take one thing off history.
3611 pop(@hist) if length($DB::cmd) > 1;
3613 # Relative (- found)?
3614 # Y - index back from most recent (by 1 if bare minus)
3615 # N - go to that particular command slot or the last
3616 # thing if nothing following.
3617 my $new_i = $minus ? ( $#hist - ( $arg || 1 ) ) : ( $arg || $#hist );
3619 $self->i_cmd($new_i);
3621 # Pick out the command desired.
3622 $DB::cmd = $hist[$self->i_cmd];
3624 # Print the command to be executed and restart the loop
3625 # with that command in the buffer.
3626 print {$OUT} $DB::cmd, "\n";
3633 sub _handle_rc_search_history_command {
3636 # $rc pattern $rc - find a command in the history.
3637 if (my ($arg) = $DB::cmd =~ /\A$rc([^$rc].*)\z/) {
3639 # Create the pattern to use.
3643 # Toss off last entry if length is >1 (and it always is).
3644 pop(@hist) if length($DB::cmd) > 1;
3646 my $i = $self->i_cmd;
3648 # Look backward through the history.
3650 for ( $i = $#hist ; $i ; --$i ) {
3651 # Stop if we find it.
3652 last SEARCH_HIST if $hist[$i] =~ /$pat/;
3657 if ( !$self->i_cmd ) {
3660 print $OUT "No such command!\n\n";
3664 # Found it. Put it in the buffer, print it, and process it.
3665 $DB::cmd = $hist[$self->i_cmd];
3666 print $OUT $DB::cmd, "\n";
3673 sub _handle_H_command {
3676 if ($DB::cmd =~ /\AH\b\s*\*/) {
3677 @hist = @truehist = ();
3678 print $OUT "History cleansed\n";
3683 = $DB::cmd =~ /\AH\b\s*(?:-(\d+))?/) {
3685 # Anything other than negative numbers is ignored by
3686 # the (incorrect) pattern, so this test does nothing.
3687 $end = $num ? ( $#hist - $num ) : 0;
3689 # Set to the minimum if less than zero.
3690 $hist = 0 if $hist < 0;
3692 # Start at the end of the array.
3693 # Stay in while we're still above the ending value.
3694 # Tick back by one each time around the loop.
3697 for ( $i = $#hist ; $i > $end ; $i-- ) {
3699 # Print the command unless it has no arguments.
3700 print $OUT "$i: ", $hist[$i], "\n"
3701 unless $hist[$i] =~ /^.?$/;
3712 sub _handle_doc_command {
3715 # man, perldoc, doc - show manual pages.
3717 = $DB::cmd =~ /\A(?:man|(?:perl)?doc)\b(?:\s+([^(]*))?\z/) {
3725 sub _handle_p_command {
3728 my $print_cmd = 'print {$DB::OUT} ';
3729 # p - print (no args): print $_.
3730 if ($DB::cmd eq 'p') {
3731 $DB::cmd = $print_cmd . '$_';
3734 # p - print the given expression.
3735 $DB::cmd =~ s/\Ap\b/$print_cmd /;
3740 sub _handle_equal_sign_command {
3743 if ($DB::cmd =~ s/\A=\s*//) {
3745 if ( length $DB::cmd == 0 ) {
3747 # No args, get current aliases.
3748 @keys = sort keys %alias;
3750 elsif ( my ( $k, $v ) = ( $DB::cmd =~ /^(\S+)\s+(\S.*)/ ) ) {
3752 # Creating a new alias. $k is alias name, $v is
3755 # can't use $_ or kill //g state
3756 for my $x ( $k, $v ) {
3758 # Escape "alarm" characters.
3762 # Substitute key for value, using alarm chars
3763 # as separators (which is why we escaped them in
3765 $alias{$k} = "s\a$k\a$v\a";
3767 # Turn off standard warn and die behavior.
3768 local $SIG{__DIE__};
3769 local $SIG{__WARN__};
3772 unless ( eval "sub { s\a$k\a$v\a }; 1" ) {
3774 # Nope. Bad alias. Say so and get out.
3775 print $OUT "Can't alias $k to $v: $@\n";
3780 # We'll only list the new one.
3782 } ## end elsif (my ($k, $v) = ($DB::cmd...
3784 # The argument is the alias to list.
3792 # Messy metaquoting: Trim the substitution code off.
3793 # We use control-G as the delimiter because it's not
3794 # likely to appear in the alias.
3795 if ( ( my $v = $alias{$k} ) =~ s
\as\a$k\a(.*)\a$
\a1
\a ) {
3798 print $OUT "$k\t= $1\n";
3800 elsif ( defined $alias{$k} ) {
3802 # Couldn't trim it off; just print the alias code.
3803 print $OUT "$k\t$alias{$k}\n";
3808 print "No alias for $k\n";
3810 } ## end for my $k (@keys)
3817 sub _handle_source_command {
3820 # source - read commands from a file (or pipe!) and execute.
3821 if (my ($sourced_fn) = $DB::cmd =~ /\Asource\s+(.*\S)/) {
3822 if ( open my $fh, $sourced_fn ) {
3824 # Opened OK; stick it in the list of file handles.
3830 DB::warn("Can't execute '$sourced_fn': $!\n");
3838 sub _handle_enable_disable_commands {
3841 if (my ($which_cmd, $position)
3842 = $DB::cmd =~ /\A(enable|disable)\s+(\S+)\s*\z/) {
3844 my ($fn, $line_num);
3845 if ($position =~ m{\A\d+\z})
3847 $fn = $DB::filename;
3848 $line_num = $position;
3850 elsif (my ($new_fn, $new_line_num)
3851 = $position =~ m{\A(.*):(\d+)\z}) {
3852 ($fn, $line_num) = ($new_fn, $new_line_num);
3856 DB::warn("Wrong spec for enable/disable argument.\n");
3860 if (DB::_has_breakpoint_data_ref($fn, $line_num)) {
3861 DB::_set_breakpoint_enabled_status($fn, $line_num,
3862 ($which_cmd eq 'enable' ? 1 : '')
3866 DB::warn("No breakpoint set at ${fn}:${line_num}\n");
3876 sub _handle_save_command {
3879 if (my ($new_fn) = $DB::cmd =~ /\Asave\s*(.*)\z/) {
3880 my $filename = $new_fn || '.perl5dbrc'; # default?
3881 if ( open my $fh, '>', $filename ) {
3883 # chomp to remove extraneous newlines from source'd files
3884 chomp( my @truelist =
3885 map { m/\A\s*(save|source)/ ? "#$_" : $_ }
3887 print {$fh} join( "\n", @truelist );
3888 print "commands saved in $filename\n";
3891 DB::warn("Can't save debugger commands in '$new_fn': $!\n");
3899 sub _n_or_s_and_arg_commands_generic {
3900 my ($self, $letter, $new_val) = @_;
3902 # s - single-step. Remember the last command was 's'.
3903 if ($DB::cmd =~ s#\A\Q$letter\E\s#\$DB::single = $new_val;\n#) {
3904 $laststep = $letter;
3910 sub _handle_sh_sh_command {
3913 # $sh$sh - run a shell command (if it's all ASCII).
3914 # Can't run shell commands with Unicode in the debugger, hmm.
3915 if (my ($arg) = $DB::cmd =~ m#\A$sh$sh\s*(.*)#ms) {
3925 # The following code may be executed now:
3930 C<sub> is called whenever a subroutine call happens in the program being
3931 debugged. The variable C<$DB::sub> contains the name of the subroutine
3934 The core function of this subroutine is to actually call the sub in the proper
3935 context, capturing its output. This of course causes C<DB::DB> to get called
3936 again, repeating until the subroutine ends and returns control to C<DB::sub>
3937 again. Once control returns, C<DB::sub> figures out whether or not to dump the
3938 return value, and returns its captured copy of the return value as its own
3939 return value. The value then feeds back into the program being debugged as if
3940 C<DB::sub> hadn't been there at all.
3942 C<sub> does all the work of printing the subroutine entry and exit messages
3943 enabled by setting C<$frame>. It notes what sub the autoloader got called for,
3944 and also prints the return value if needed (for the C<r> command and if
3945 the 16 bit is set in C<$frame>).
3947 It also tracks the subroutine call depth by saving the current setting of
3948 C<$single> in the C<@stack> package global; if this exceeds the value in
3949 C<$deep>, C<sub> automatically turns on printing of the current depth by
3950 setting the C<4> bit in C<$single>. In any case, it keeps the current setting
3951 of stop/don't stop on entry to subs set as it currently is set.
3953 =head3 C<caller()> support
3955 If C<caller()> is called from the package C<DB>, it provides some
3956 additional data, in the following order:
3962 The package name the sub was in
3964 =item * C<$filename>
3966 The filename it was defined in
3970 The line number it was defined on
3972 =item * C<$subroutine>
3974 The subroutine name; C<(eval)> if an C<eval>().
3978 1 if it has arguments, 0 if not
3980 =item * C<$wantarray>
3982 1 if array context, 0 if scalar context
3984 =item * C<$evaltext>
3986 The C<eval>() text, if any (undefined for C<eval BLOCK>)
3988 =item * C<$is_require>
3990 frame was created by a C<use> or C<require> statement
3994 pragma information; subject to change between versions
3998 pragma information; subject to change between versions
4000 =item * C<@DB::args>
4002 arguments with which the subroutine was invoked
4010 # We need to fully qualify the name ("DB::sub") to make "use strict;"
4011 # happy. -- Shlomi Fish
4013 # Do not use a regex in this subroutine -> results in corrupted memory
4014 # See: [perl #66110]
4016 # lock ourselves under threads
4019 # Whether or not the autoloader was running, a scalar to put the
4020 # sub's return value in (if needed), and an array to put the sub's
4021 # return value in (if needed).
4022 my ( $al, $ret, @ret ) = "";
4023 if ($sub eq 'threads::new' && $ENV{PERL5DB_THREADED}) {
4024 print "creating new thread\n";
4027 # If the last ten characters are '::AUTOLOAD', note we've traced
4028 # into AUTOLOAD for $sub.
4029 if ( length($sub) > 10 && substr( $sub, -10, 10 ) eq '::AUTOLOAD' ) {
4031 $al = " for $$sub" if defined $$sub;
4034 # We stack the stack pointer and then increment it to protect us
4035 # from a situation that might unwind a whole bunch of call frames
4036 # at once. Localizing the stack pointer means that it will automatically
4037 # unwind the same amount when multiple stack frames are unwound.
4038 local $stack_depth = $stack_depth + 1; # Protect from non-local exits
4041 $#stack = $stack_depth;
4043 # Save current single-step setting.
4044 $stack[-1] = $single;
4046 # Turn off all flags except single-stepping.
4049 # If we've gotten really deeply recursed, turn on the flag that will
4050 # make us stop with the 'deep recursion' message.
4051 $single |= 4 if $stack_depth == $deep;
4053 # If frame messages are on ...
4055 $frame & 4 # Extended frame entry message
4057 print_lineinfo( ' ' x ( $stack_depth - 1 ), "in " ),
4059 # Why -1? But it works! :-(
4060 # Because print_trace will call add 1 to it and then call
4061 # dump_trace; this results in our skipping -1+1 = 0 stack frames
4063 print_trace( $LINEINFO, -1, 1, 1, "$sub$al" )
4065 : print_lineinfo( ' ' x ( $stack_depth - 1 ), "entering $sub$al\n" )
4067 # standard frame entry message
4071 # Determine the sub's return type, and capture appropriately.
4074 # Called in array context. call sub and capture output.
4075 # DB::DB will recursively get control again if appropriate; we'll come
4076 # back here when the sub is finished.
4082 # Pop the single-step value back off the stack.
4083 $single |= $stack[ $stack_depth-- ];
4085 # Check for exit trace messages...
4087 $frame & 4 # Extended exit message
4089 print_lineinfo( ' ' x $stack_depth, "out " ),
4090 print_trace( $LINEINFO, -1, 1, 1, "$sub$al" )
4092 : print_lineinfo( ' ' x $stack_depth, "exited $sub$al\n" )
4094 # Standard exit message
4098 # Print the return info if we need to.
4099 if ( $doret eq $stack_depth or $frame & 16 ) {
4101 # Turn off output record separator.
4103 my $fh = ( $doret eq $stack_depth ? $OUT : $LINEINFO );
4105 # Indent if we're printing because of $frame tracing.
4106 print $fh ' ' x $stack_depth if $frame & 16;
4108 # Print the return value.
4109 print $fh "list context return from $sub:\n";
4110 dumpit( $fh, \@ret );
4112 # And don't print it again.
4114 } ## end if ($doret eq $stack_depth...
4115 # And we have to return the return value now.
4117 } ## end if (wantarray)
4121 if ( defined wantarray ) {
4123 # Save the value if it's wanted at all.
4128 # Void return, explicitly.
4133 # Pop the single-step value off the stack.
4134 $single |= $stack[ $stack_depth-- ];
4136 # If we're doing exit messages...
4138 $frame & 4 # Extended messages
4140 print_lineinfo( ' ' x $stack_depth, "out " ),
4141 print_trace( $LINEINFO, -1, 1, 1, "$sub$al" )
4143 : print_lineinfo( ' ' x $stack_depth, "exited $sub$al\n" )
4149 # If we are supposed to show the return value... same as before.
4150 if ( $doret eq $stack_depth or $frame & 16 and defined wantarray ) {
4152 my $fh = ( $doret eq $stack_depth ? $OUT : $LINEINFO );
4153 print $fh ( ' ' x $stack_depth ) if $frame & 16;
4156 ? "scalar context return from $sub: "
4157 : "void context return from $sub\n"
4159 dumpit( $fh, $ret ) if defined wantarray;
4161 } ## end if ($doret eq $stack_depth...
4163 # Return the appropriate scalar value.
4165 } ## end else [ if (wantarray)
4172 # lock ourselves under threads
4175 # Whether or not the autoloader was running, a scalar to put the
4176 # sub's return value in (if needed), and an array to put the sub's
4177 # return value in (if needed).
4178 my ( $al, $ret, @ret ) = "";
4179 if ($sub =~ /^threads::new$/ && $ENV{PERL5DB_THREADED}) {
4180 print "creating new thread\n";
4183 # If the last ten characters are C'::AUTOLOAD', note we've traced
4184 # into AUTOLOAD for $sub.
4185 if ( length($sub) > 10 && substr( $sub, -10, 10 ) eq '::AUTOLOAD' ) {
4189 # We stack the stack pointer and then increment it to protect us
4190 # from a situation that might unwind a whole bunch of call frames
4191 # at once. Localizing the stack pointer means that it will automatically
4192 # unwind the same amount when multiple stack frames are unwound.
4193 local $stack_depth = $stack_depth + 1; # Protect from non-local exits
4196 $#stack = $stack_depth;
4198 # Save current single-step setting.
4199 $stack[-1] = $single;
4201 # Turn off all flags except single-stepping.
4204 # If we've gotten really deeply recursed, turn on the flag that will
4205 # make us stop with the 'deep recursion' message.
4206 $single |= 4 if $stack_depth == $deep;
4208 # If frame messages are on ...
4210 $frame & 4 # Extended frame entry message
4212 print_lineinfo( ' ' x ( $stack_depth - 1 ), "in " ),
4214 # Why -1? But it works! :-(
4215 # Because print_trace will call add 1 to it and then call
4216 # dump_trace; this results in our skipping -1+1 = 0 stack frames
4218 print_trace( $LINEINFO, -1, 1, 1, "$sub$al" )
4220 : print_lineinfo( ' ' x ( $stack_depth - 1 ), "entering $sub$al\n" )
4222 # standard frame entry message
4226 # Pop the single-step value back off the stack.
4227 $single |= $stack[ $stack_depth-- ];
4229 # call the original lvalue sub.
4233 # Abstracting common code from multiple places elsewhere:
4234 sub depth_print_lineinfo {
4235 my $always_print = shift;
4237 print_lineinfo( @_ ) if ($always_print or $stack_depth < $trace_to_depth);
4240 =head1 EXTENDED COMMAND HANDLING AND THE COMMAND API
4242 In Perl 5.8.0, there was a major realignment of the commands and what they did,
4243 Most of the changes were to systematize the command structure and to eliminate
4244 commands that threw away user input without checking.
4246 The following sections describe the code added to make it easy to support
4247 multiple command sets with conflicting command names. This section is a start
4248 at unifying all command processing to make it simpler to develop commands.
4250 Note that all the cmd_[a-zA-Z] subroutines require the command name, a line
4251 number, and C<$dbline> (the current line) as arguments.
4253 Support functions in this section which have multiple modes of failure C<die>
4254 on error; the rest simply return a false value.
4256 The user-interface functions (all of the C<cmd_*> functions) just output
4261 The C<%set> hash defines the mapping from command letter to subroutine
4264 C<%set> is a two-level hash, indexed by set name and then by command name.
4265 Note that trying to set the CommandSet to C<foobar> simply results in the
4266 5.8.0 command set being used, since there's no top-level entry for C<foobar>.
4275 'A' => 'pre580_null',
4277 'B' => 'pre580_null',
4278 'd' => 'pre580_null',
4281 'M' => 'pre580_null',
4283 'o' => 'pre580_null',
4289 '<' => 'pre590_prepost',
4290 '<<' => 'pre590_prepost',
4291 '>' => 'pre590_prepost',
4292 '>>' => 'pre590_prepost',
4293 '{' => 'pre590_prepost',
4294 '{{' => 'pre590_prepost',
4298 my %breakpoints_data;
4300 sub _has_breakpoint_data_ref {
4301 my ($filename, $line) = @_;
4304 exists( $breakpoints_data{$filename} )
4306 exists( $breakpoints_data{$filename}{$line} )
4310 sub _get_breakpoint_data_ref {
4311 my ($filename, $line) = @_;
4313 return ($breakpoints_data{$filename}{$line} ||= +{});
4316 sub _delete_breakpoint_data_ref {
4317 my ($filename, $line) = @_;
4319 delete($breakpoints_data{$filename}{$line});
4320 if (! scalar(keys( %{$breakpoints_data{$filename}} )) ) {
4321 delete($breakpoints_data{$filename});
4327 sub _set_breakpoint_enabled_status {
4328 my ($filename, $line, $status) = @_;
4330 _get_breakpoint_data_ref($filename, $line)->{'enabled'} =
4337 sub _enable_breakpoint_temp_enabled_status {
4338 my ($filename, $line) = @_;
4340 _get_breakpoint_data_ref($filename, $line)->{'temp_enabled'} = 1;
4345 sub _cancel_breakpoint_temp_enabled_status {
4346 my ($filename, $line) = @_;
4348 my $ref = _get_breakpoint_data_ref($filename, $line);
4350 delete ($ref->{'temp_enabled'});
4353 _delete_breakpoint_data_ref($filename, $line);
4359 sub _is_breakpoint_enabled {
4360 my ($filename, $line) = @_;
4362 my $data_ref = _get_breakpoint_data_ref($filename, $line);
4363 return ($data_ref->{'enabled'} || $data_ref->{'temp_enabled'});
4366 =head2 C<cmd_wrapper()> (API)
4368 C<cmd_wrapper()> allows the debugger to switch command sets
4369 depending on the value of the C<CommandSet> option.
4371 It tries to look up the command in the C<%set> package-level I<lexical>
4372 (which means external entities can't fiddle with it) and create the name of
4373 the sub to call based on the value found in the hash (if it's there). I<All>
4374 of the commands to be handled in a set have to be added to C<%set>; if they
4375 aren't found, the 5.8.0 equivalent is called (if there is one).
4377 This code uses symbolic references.
4384 my $dblineno = shift;
4386 # Assemble the command subroutine's name by looking up the
4387 # command set and command name in %set. If we can't find it,
4388 # default to the older version of the command.
4390 . ( $set{$CommandSet}{$cmd}
4391 || ( $cmd =~ /^[<>{]+/o ? 'prepost' : $cmd ) );
4393 # Call the command subroutine, call it by name.
4394 return __PACKAGE__->can($call)->( $cmd, $line, $dblineno );
4395 } ## end sub cmd_wrapper
4397 =head3 C<cmd_a> (command)
4399 The C<a> command handles pre-execution actions. These are associated with a
4400 particular line, so they're stored in C<%dbline>. We default to the current
4401 line if none is specified.
4407 my $line = shift || ''; # [.|line] expr
4410 # If it's dot (here), or not all digits, use the current line.
4411 $line =~ s/\A\./$dbline/;
4413 # Should be a line number followed by an expression.
4414 if ( my ($lineno, $expr) = $line =~ /^\s*(\d*)\s*(\S.+)/ ) {
4416 if (! length($lineno)) {
4420 # If we have an expression ...
4421 if ( length $expr ) {
4423 # ... but the line isn't breakable, complain.
4424 if ( $dbline[$lineno] == 0 ) {
4426 "Line $lineno($dbline[$lineno]) does not have an action?\n";
4430 # It's executable. Record that the line has an action.
4431 $had_breakpoints{$filename} |= 2;
4433 # Remove any action, temp breakpoint, etc.
4434 $dbline{$lineno} =~ s/\0[^\0]*//;
4436 # Add the action to the line.
4437 $dbline{$lineno} .= "\0" . action($expr);
4439 _set_breakpoint_enabled_status($filename, $lineno, 1);
4441 } ## end if (length $expr)
4442 } ## end if ($line =~ /^\s*(\d*)\s*(\S.+)/)
4447 "Adding an action requires an optional lineno and an expression\n"
4452 =head3 C<cmd_A> (command)
4454 Delete actions. Similar to above, except the delete code is in a separate
4455 subroutine, C<delete_action>.
4461 my $line = shift || '';
4465 $line =~ s/^\./$dbline/;
4467 # Call delete_action with a null param to delete them all.
4468 # The '1' forces the eval to be true. It'll be false only
4469 # if delete_action blows up for some reason, in which case
4470 # we print $@ and get out.
4471 if ( $line eq '*' ) {
4472 if (! eval { _delete_all_actions(); 1 }) {
4478 # There's a real line number. Pass it to delete_action.
4479 # Error trapping is as above.
4480 elsif ( $line =~ /^(\S.*)/ ) {
4481 if (! eval { delete_action($1); 1 }) {
4487 # Swing and a miss. Bad syntax.
4490 "Deleting an action requires a line number, or '*' for all\n" ; # hint
4494 =head3 C<delete_action> (API)
4496 C<delete_action> accepts either a line number or C<undef>. If a line number
4497 is specified, we check for the line being executable (if it's not, it
4498 couldn't have had an action). If it is, we just take the action off (this
4499 will get any kind of an action, including breakpoints).
4503 sub _remove_action_from_dbline {
4506 $dbline{$i} =~ s/\0[^\0]*//; # \^a
4507 delete $dbline{$i} if $dbline{$i} eq '';
4512 sub _delete_all_actions {
4513 print {$OUT} "Deleting all actions...\n";
4515 for my $file ( keys %had_breakpoints ) {
4516 local *dbline = $main::{ '_<' . $file };
4519 for my $i (1 .. $max) {
4520 if ( defined $dbline{$i} ) {
4521 _remove_action_from_dbline($i);
4525 unless ( $had_breakpoints{$file} &= ~2 ) {
4526 delete $had_breakpoints{$file};
4536 if ( defined($i) ) {
4538 die "Line $i has no action .\n" if $dbline[$i] == 0;
4540 # Nuke whatever's there.
4541 _remove_action_from_dbline($i);
4544 _delete_all_actions();
4548 =head3 C<cmd_b> (command)
4550 Set breakpoints. Since breakpoints can be set in so many places, in so many
4551 ways, conditionally or not, the breakpoint code is kind of complex. Mostly,
4552 we try to parse the command type, and then shuttle it off to an appropriate
4553 subroutine to actually do the work of setting the breakpoint in the right
4560 my $line = shift; # [.|line] [cond]
4563 my $default_cond = sub {
4565 return length($cond) ? $cond : '1';
4568 # Make . the current line number if it's there..
4569 $line =~ s/^\.(\s|\z)/$dbline$1/;
4571 # No line number, no condition. Simple break on current line.
4572 if ( $line =~ /^\s*$/ ) {
4573 cmd_b_line( $dbline, 1 );
4576 # Break on load for a file.
4577 elsif ( my ($file) = $line =~ /^load\b\s*(.*)/ ) {
4582 # b compile|postpone <some sub> [<condition>]
4583 # The interpreter actually traps this one for us; we just put the
4584 # necessary condition in the %postponed hash.
4585 elsif ( my ($action, $subname, $cond)
4586 = $line =~ /^(postpone|compile)\b\s*([':A-Za-z_][':\w]*)\s*(.*)/ ) {
4588 # De-Perl4-ify the name - ' separators to ::.
4589 $subname =~ s/'/::/g;
4591 # Qualify it into the current package unless it's already qualified.
4592 $subname = "${package}::" . $subname unless $subname =~ /::/;
4594 # Add main if it starts with ::.
4595 $subname = "main" . $subname if substr( $subname, 0, 2 ) eq "::";
4597 # Save the break type for this sub.
4598 $postponed{$subname} = (($action eq 'postpone')
4599 ? ( "break +0 if " . $default_cond->($cond) )
4601 } ## end elsif ($line =~ ...
4602 # b <filename>:<line> [<condition>]
4603 elsif (my ($filename, $line_num, $cond)
4604 = $line =~ /\A(\S+[^:]):(\d+)\s*(.*)/ms) {
4605 cmd_b_filename_line(
4608 (length($cond) ? $cond : '1'),
4611 # b <sub name> [<condition>]
4612 elsif ( my ($new_subname, $new_cond) =
4613 $line =~ /^([':A-Za-z_][':\w]*(?:\[.*\])?)\s*(.*)/ ) {
4616 $subname = $new_subname;
4617 cmd_b_sub( $subname, $default_cond->($new_cond) );
4620 # b <line> [<condition>].
4621 elsif ( my ($line_n, $cond) = $line =~ /^(\d*)\s*(.*)/ ) {
4623 # Capture the line. If none, it's the current line.
4624 $line = $line_n || $dbline;
4627 cmd_b_line( $line, $default_cond->($cond) );
4630 # Line didn't make sense.
4632 print "confused by line($line)?\n";
4638 =head3 C<break_on_load> (API)
4640 We want to break when this file is loaded. Mark this file in the
4641 C<%break_on_load> hash, and note that it has a breakpoint in
4642 C<%had_breakpoints>.
4648 $break_on_load{$file} = 1;
4649 $had_breakpoints{$file} |= 1;
4652 =head3 C<report_break_on_load> (API)
4654 Gives us an array of filenames that are set to break on load. Note that
4655 only files with break-on-load are in here, so simply showing the keys
4660 sub report_break_on_load {
4661 sort keys %break_on_load;
4664 =head3 C<cmd_b_load> (command)
4666 We take the file passed in and try to find it in C<%INC> (which maps modules
4667 to files they came from). We mark those files for break-on-load via
4668 C<break_on_load> and then report that it was done.
4676 # This is a block because that way we can use a redo inside it
4677 # even without there being any looping structure at all outside it.
4680 # Save short name and full path if found.
4682 push @files, $::INC{$file} if $::INC{$file};
4684 # Tack on .pm and do it again unless there was a '.' in the name
4686 $file .= '.pm', redo unless $file =~ /\./;
4689 # Do the real work here.
4690 break_on_load($_) for @files;
4692 # All the files that have break-on-load breakpoints.
4693 @files = report_break_on_load;
4695 # Normalize for the purposes of our printing this.
4698 print $OUT "Will stop on load of '@files'.\n";
4699 } ## end sub cmd_b_load
4701 =head3 C<$filename_error> (API package global)
4703 Several of the functions we need to implement in the API need to work both
4704 on the current file and on other files. We don't want to duplicate code, so
4705 C<$filename_error> is used to contain the name of the file that's being
4706 worked on (if it's not the current one).
4708 We can now build functions in pairs: the basic function works on the current
4709 file, and uses C<$filename_error> as part of its error message. Since this is
4710 initialized to C<"">, no filename will appear when we are working on the
4713 The second function is a wrapper which does the following:
4719 Localizes C<$filename_error> and sets it to the name of the file to be processed.
4723 Localizes the C<*dbline> glob and reassigns it to point to the file we want to process.
4727 Calls the first function.
4729 The first function works on the I<current> file (i.e., the one we changed to),
4730 and prints C<$filename_error> in the error message (the name of the other file)
4731 if it needs to. When the functions return, C<*dbline> is restored to point
4732 to the actual current file (the one we're executing in) and
4733 C<$filename_error> is restored to C<"">. This restores everything to
4734 the way it was before the second function was called at all.
4736 See the comments in C<breakable_line> and C<breakable_line_in_file> for more
4743 use vars qw($filename_error);
4744 $filename_error = '';
4746 =head3 breakable_line(from, to) (API)
4748 The subroutine decides whether or not a line in the current file is breakable.
4749 It walks through C<@dbline> within the range of lines specified, looking for
4750 the first line that is breakable.
4752 If C<$to> is greater than C<$from>, the search moves forwards, finding the
4753 first line I<after> C<$to> that's breakable, if there is one.
4755 If C<$from> is greater than C<$to>, the search goes I<backwards>, finding the
4756 first line I<before> C<$to> that's breakable, if there is one.
4760 sub breakable_line {
4762 my ( $from, $to ) = @_;
4764 # $i is the start point. (Where are the FORTRAN programs of yesteryear?)
4767 # If there are at least 2 arguments, we're trying to search a range.
4770 # $delta is positive for a forward search, negative for a backward one.
4771 my $delta = $from < $to ? +1 : -1;
4773 # Keep us from running off the ends of the file.
4774 my $limit = $delta > 0 ? $#dbline : 1;
4776 # Clever test. If you're a mathematician, it's obvious why this
4777 # test works. If not:
4778 # If $delta is positive (going forward), $limit will be $#dbline.
4779 # If $to is less than $limit, ($limit - $to) will be positive, times
4780 # $delta of 1 (positive), so the result is > 0 and we should use $to
4781 # as the stopping point.
4783 # If $to is greater than $limit, ($limit - $to) is negative,
4784 # times $delta of 1 (positive), so the result is < 0 and we should
4785 # use $limit ($#dbline) as the stopping point.
4787 # If $delta is negative (going backward), $limit will be 1.
4788 # If $to is zero, ($limit - $to) will be 1, times $delta of -1
4789 # (negative) so the result is > 0, and we use $to as the stopping
4792 # If $to is less than zero, ($limit - $to) will be positive,
4793 # times $delta of -1 (negative), so the result is not > 0, and
4794 # we use $limit (1) as the stopping point.
4796 # If $to is 1, ($limit - $to) will zero, times $delta of -1
4797 # (negative), still giving zero; the result is not > 0, and
4798 # we use $limit (1) as the stopping point.
4800 # if $to is >1, ($limit - $to) will be negative, times $delta of -1
4801 # (negative), giving a positive (>0) value, so we'll set $limit to
4804 $limit = $to if ( $limit - $to ) * $delta > 0;
4806 # The real search loop.
4807 # $i starts at $from (the point we want to start searching from).
4808 # We move through @dbline in the appropriate direction (determined
4809 # by $delta: either -1 (back) or +1 (ahead).
4810 # We stay in as long as we haven't hit an executable line
4811 # ($dbline[$i] == 0 means not executable) and we haven't reached
4812 # the limit yet (test similar to the above).
4813 $i += $delta while $dbline[$i] == 0 and ( $limit - $i ) * $delta > 0;
4815 } ## end if (@_ >= 2)
4817 # If $i points to a line that is executable, return that.
4818 return $i unless $dbline[$i] == 0;
4820 # Format the message and print it: no breakable lines in range.
4821 my ( $pl, $upto ) = ( '', '' );
4822 ( $pl, $upto ) = ( 's', "..$to" ) if @_ >= 2 and $from != $to;
4824 # If there's a filename in filename_error, we'll see it.
4826 die "Line$pl $from$upto$filename_error not breakable\n";
4827 } ## end sub breakable_line
4829 =head3 breakable_line_in_filename(file, from, to) (API)
4831 Like C<breakable_line>, but look in another file.
4835 sub breakable_line_in_filename {
4837 # Capture the file name.
4840 # Swap the magic line array over there temporarily.