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sigtrap.pm (handler_traceback): do not clobber $_
[perl5.git] / lib / sigtrap.pm
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1package sigtrap;
2
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3=head1 NAME
4
1ae80e7e 5sigtrap - Perl pragma to enable simple signal handling
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6
7=cut
8
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9use Carp;
10
825b6c4f 11$VERSION = 1.04;
1ae80e7e 12$Verbose ||= 0;
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13
14sub import {
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15 my $pkg = shift;
16 my $handler = \&handler_traceback;
17 my $saw_sig = 0;
18 my $untrapped = 0;
19 local $_;
20
21 Arg_loop:
22 while (@_) {
23 $_ = shift;
24 if (/^[A-Z][A-Z0-9]*$/) {
25 $saw_sig++;
26 unless ($untrapped and $SIG{$_} and $SIG{$_} ne 'DEFAULT') {
27 print "Installing handler $handler for $_\n" if $Verbose;
28 $SIG{$_} = $handler;
29 }
30 }
31 elsif ($_ eq 'normal-signals') {
55497cff 32 unshift @_, grep(exists $SIG{$_}, qw(HUP INT PIPE TERM));
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33 }
34 elsif ($_ eq 'error-signals') {
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35 unshift @_, grep(exists $SIG{$_},
36 qw(ABRT BUS EMT FPE ILL QUIT SEGV SYS TRAP));
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37 }
38 elsif ($_ eq 'old-interface-signals') {
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39 unshift @_,
40 grep(exists $SIG{$_},
41 qw(ABRT BUS EMT FPE ILL PIPE QUIT SEGV SYS TERM TRAP));
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42 }
43 elsif ($_ eq 'stack-trace') {
44 $handler = \&handler_traceback;
45 }
46 elsif ($_ eq 'die') {
47 $handler = \&handler_die;
48 }
49 elsif ($_ eq 'handler') {
50 @_ or croak "No argument specified after 'handler'";
51 $handler = shift;
52 unless (ref $handler or $handler eq 'IGNORE'
53 or $handler eq 'DEFAULT') {
54 require Symbol;
55 $handler = Symbol::qualify($handler, (caller)[0]);
56 }
57 }
58 elsif ($_ eq 'untrapped') {
59 $untrapped = 1;
60 }
61 elsif ($_ eq 'any') {
62 $untrapped = 0;
63 }
64 elsif ($_ =~ /^\d/) {
65 $VERSION >= $_ or croak "sigtrap.pm version $_ required,"
66 . " but this is only version $VERSION";
67 }
68 else {
69 croak "Unrecognized argument $_";
70 }
a0d0e21e 71 }
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72 unless ($saw_sig) {
73 @_ = qw(old-interface-signals);
74 goto Arg_loop;
75 }
76}
77
78sub handler_die {
79 croak "Caught a SIG$_[0]";
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80}
81
1ae80e7e 82sub handler_traceback {
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83 package DB; # To get subroutine args.
84 $SIG{'ABRT'} = DEFAULT;
85 kill 'ABRT', $$ if $panic++;
86 syswrite(STDERR, 'Caught a SIG', 12);
87 syswrite(STDERR, $_[0], length($_[0]));
88 syswrite(STDERR, ' at ', 4);
89 ($pack,$file,$line) = caller;
90 syswrite(STDERR, $file, length($file));
91 syswrite(STDERR, ' line ', 6);
92 syswrite(STDERR, $line, length($line));
93 syswrite(STDERR, "\n", 1);
94
95 # Now go for broke.
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96 for ($i = 1; ($p,$f,$l,$s,$h,$w,$e,$r) = caller($i); $i++) {
97 @a = ();
825b6c4f 98 for (@args) {
d338d6fe 99 s/([\'\\])/\\$1/g;
a0d0e21e 100 s/([^\0]*)/'$1'/
d338d6fe 101 unless /^(?: -?[\d.]+ | \*[\w:]* )$/x;
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102 s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg;
103 s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg;
104 push(@a, $_);
105 }
106 $w = $w ? '@ = ' : '$ = ';
107 $a = $h ? '(' . join(', ', @a) . ')' : '';
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108 $e =~ s/\n\s*\;\s*\Z// if $e;
109 $e =~ s/[\\\']/\\$1/g if $e;
110 if ($r) {
111 $s = "require '$e'";
112 } elsif (defined $r) {
113 $s = "eval '$e'";
114 } elsif ($s eq '(eval)') {
115 $s = "eval {...}";
116 }
117 $f = "file `$f'" unless $f eq '-e';
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118 $mess = "$w$s$a called from $f line $l\n";
119 syswrite(STDERR, $mess, length($mess));
120 }
121 kill 'ABRT', $$;
122}
123
1241;
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125
126__END__
127
128=head1 SYNOPSIS
129
130 use sigtrap;
131 use sigtrap qw(stack-trace old-interface-signals); # equivalent
132 use sigtrap qw(BUS SEGV PIPE ABRT);
133 use sigtrap qw(die INT QUIT);
134 use sigtrap qw(die normal-signals);
135 use sigtrap qw(die untrapped normal-signals);
136 use sigtrap qw(die untrapped normal-signals
137 stack-trace any error-signals);
138 use sigtrap 'handler' => \&my_handler, 'normal-signals';
139 use sigtrap qw(handler my_handler normal-signals
140 stack-trace error-signals);
141
142=head1 DESCRIPTION
143
144The B<sigtrap> pragma is a simple interface to installing signal
145handlers. You can have it install one of two handlers supplied by
146B<sigtrap> itself (one which provides a Perl stack trace and one which
147simply C<die()>s), or alternately you can supply your own handler for it
148to install. It can be told only to install a handler for signals which
149are either untrapped or ignored. It has a couple of lists of signals to
150trap, plus you can supply your own list of signals.
151
152The arguments passed to the C<use> statement which invokes B<sigtrap>
153are processed in order. When a signal name or the name of one of
154B<sigtrap>'s signal lists is encountered a handler is immediately
155installed, when an option is encountered it affects subsequently
156installed handlers.
157
158=head1 OPTIONS
159
160=head2 SIGNAL HANDLERS
161
162These options affect which handler will be used for subsequently
163installed signals.
164
84dc3c4d 165=over 4
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166
167=item B<stack-trace>
168
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169The handler used for subsequently installed signals outputs a Perl stack
170trace to STDERR and then tries to dump core. This is the default signal
171handler.
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172
173=item B<die>
174
175The handler used for subsequently installed signals calls C<die>
176(actually C<croak>) with a message indicating which signal was caught.
177
178=item B<handler> I<your-handler>
179
180I<your-handler> will be used as the handler for subsequently installed
181signals. I<your-handler> can be any value which is valid as an
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182assignment to an element of C<%SIG>. See L<perlvar> for examples of
183handler functions.
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184
185=back
186
187=head2 SIGNAL LISTS
188
36477c24 189B<sigtrap> has a few built-in lists of signals to trap. They are:
1ae80e7e 190
84dc3c4d 191=over 4
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192
193=item B<normal-signals>
194
195These are the signals which a program might normally expect to encounter
196and which by default cause it to terminate. They are HUP, INT, PIPE and
197TERM.
198
199=item B<error-signals>
200
201These signals usually indicate a serious problem with the Perl
202interpreter or with your script. They are ABRT, BUS, EMT, FPE, ILL,
203QUIT, SEGV, SYS and TRAP.
204
205=item B<old-interface-signals>
206
207These are the signals which were trapped by default by the old
208B<sigtrap> interface, they are ABRT, BUS, EMT, FPE, ILL, PIPE, QUIT,
209SEGV, SYS, TERM, and TRAP. If no signals or signals lists are passed to
55497cff 210B<sigtrap>, this list is used.
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211
212=back
213
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214For each of these three lists, the collection of signals set to be
215trapped is checked before trapping; if your architecture does not
216implement a particular signal, it will not be trapped but rather
217silently ignored.
218
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219=head2 OTHER
220
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221=over 4
222
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223=item B<untrapped>
224
36477c24 225This token tells B<sigtrap> to install handlers only for subsequently
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226listed signals which aren't already trapped or ignored.
227
228=item B<any>
229
230This token tells B<sigtrap> to install handlers for all subsequently
231listed signals. This is the default behavior.
232
233=item I<signal>
234
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235Any argument which looks like a signal name (that is,
236C</^[A-Z][A-Z0-9]*$/>) indicates that B<sigtrap> should install a
237handler for that name.
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238
239=item I<number>
240
241Require that at least version I<number> of B<sigtrap> is being used.
242
243=back
244
245=head1 EXAMPLES
246
247Provide a stack trace for the old-interface-signals:
248
249 use sigtrap;
250
251Ditto:
252
253 use sigtrap qw(stack-trace old-interface-signals);
254
255Provide a stack trace on the 4 listed signals only:
256
257 use sigtrap qw(BUS SEGV PIPE ABRT);
258
259Die on INT or QUIT:
260
261 use sigtrap qw(die INT QUIT);
262
263Die on HUP, INT, PIPE or TERM:
264
265 use sigtrap qw(die normal-signals);
266
267Die on HUP, INT, PIPE or TERM, except don't change the behavior for
268signals which are already trapped or ignored:
269
270 use sigtrap qw(die untrapped normal-signals);
271
272Die on receipt one of an of the B<normal-signals> which is currently
273B<untrapped>, provide a stack trace on receipt of B<any> of the
274B<error-signals>:
275
276 use sigtrap qw(die untrapped normal-signals
277 stack-trace any error-signals);
278
279Install my_handler() as the handler for the B<normal-signals>:
280
281 use sigtrap 'handler', \&my_handler, 'normal-signals';
282
283Install my_handler() as the handler for the normal-signals, provide a
284Perl stack trace on receipt of one of the error-signals:
285
286 use sigtrap qw(handler my_handler normal-signals
287 stack-trace error-signals);
288
289=cut