perl/lib/Carp.pm

package Carp;

our $VERSION = '1.04';

=head1 NAME

carp    - warn of errors (from perspective of caller)

cluck   - warn of errors with stack backtrace
          (not exported by default)

croak   - die of errors (from perspective of caller)

confess - die of errors with stack backtrace

shortmess - return the message that carp and croak produce

longmess - return the message that cluck and confess produce

=head1 SYNOPSIS

    use Carp;
    croak "We're outta here!";

    use Carp qw(cluck);
    cluck "This is how we got here!";

    print FH Carp::shortmess("This will have caller's details added");
    print FH Carp::longmess("This will have stack backtrace added");

=head1 DESCRIPTION

The Carp routines are useful in your own modules because
they act like die() or warn(), but with a message which is more
likely to be useful to a user of your module.  In the case of
cluck, confess, and longmess that context is a summary of every
call in the call-stack.  For a shorter message you can use carp,
croak or shortmess which report the error as being from where
your module was called.  There is no guarantee that that is where
the error was, but it is a good educated guess.

You can also alter the way the output and logic of C<Carp> works, by
changing some global variables in the C<Carp> namespace. See the
section on C<GLOBAL VARIABLES> below.

Here is a more complete description of how shortmess works.  What
it does is search the call-stack for a function call stack where
it hasn't been told that there shouldn't be an error.  If every
call is marked safe, it then gives up and gives a full stack
backtrace instead.  In other words it presumes that the first likely
looking potential suspect is guilty.  Its rules for telling whether
a call shouldn't generate errors work as follows:

=over 4

=item 1.

Any call from a package to itself is safe.

=item 2.

Packages claim that there won't be errors on calls to or from
packages explicitly marked as safe by inclusion in @CARP_NOT, or
(if that array is empty) @ISA.  The ability to override what
@ISA says is new in 5.8.

=item 3.

The trust in item 2 is transitive.  If A trusts B, and B
trusts C, then A trusts C.  So if you do not override @ISA
with @CARP_NOT, then this trust relationship is identical to,
"inherits from".

=item 4.

Any call from an internal Perl module is safe.  (Nothing keeps
user modules from marking themselves as internal to Perl, but
this practice is discouraged.)

=item 5.

Any call to Carp is safe.  (This rule is what keeps it from
reporting the error where you call carp/croak/shortmess.)

=back

=head2 Forcing a Stack Trace

As a debugging aid, you can force Carp to treat a croak as a confess
and a carp as a cluck across I<all> modules. In other words, force a
detailed stack trace to be given.  This can be very helpful when trying
to understand why, or from where, a warning or error is being generated.

This feature is enabled by 'importing' the non-existent symbol
'verbose'. You would typically enable it by saying

    perl -MCarp=verbose script.pl

or by including the string C<MCarp=verbose> in the PERL5OPT
environment variable.

Alternately, you can set the global variable C<$Carp::Verbose> to true.
See the C<GLOBAL VARIABLES> section below.

=cut

# This package is heavily used. Be small. Be fast. Be good.

# Comments added by Andy Wardley <abw@kfs.org> 09-Apr-98, based on an
# _almost_ complete understanding of the package.  Corrections and
# comments are welcome.

# The members of %Internal are packages that are internal to perl.
# Carp will not report errors from within these packages if it
# can.  The members of %CarpInternal are internal to Perl's warning
# system.  Carp will not report errors from within these packages
# either, and will not report calls *to* these packages for carp and
# croak.  They replace $CarpLevel, which is deprecated.    The
# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
# text and function arguments should be formatted when printed.

# Comments added by Jos I. Boumans <kane@dwim.org> 11-Aug-2004
# I can not get %CarpInternal or %Internal to work as advertised,
# therefor leaving it out of the below documentation.
# $CarpLevel may be decprecated according to the last comment, but
# after 6 years, it's still around and in heavy use ;)

=pod

=head1 GLOBAL VARIABLES

=head2 $Carp::CarpLevel

This variable determines how many call frames are to be skipped when
reporting where an error occurred on a call to one of C<Carp>'s
functions. For example:

    $Carp::CarpLevel = 1;
    sub bar     { .... or _error('Wrong input') }
    sub _error  { Carp::carp(@_) }

This would make Carp report the error as coming from C<bar>'s caller,
rather than from C<_error>'s caller, as it normally would.

Defaults to C<0>.

=head2 $Carp::MaxEvalLen

This variable determines how many characters of a string-eval are to
be shown in the output. Use a value of C<0> to show all text.

Defaults to C<0>.

=head2 $Carp::MaxArgLen

This variable determines how many characters of each argument to a
function to print. Use a value of C<0> to show the full length of the
argument.

Defaults to C<64>.

=head2 $Carp::MaxArgNums

This variable determines how many arguments to each function to show.
Use a value of C<0> to show all arguments to a function call.

Defaults to C<8>.

=head2 $Carp::Verbose

This variable makes C<Carp> use the C<longmess> function at all times.
This effectively means that all calls to C<carp> become C<cluck> and
all calls to C<croak> become C<confess>.

Note, this is analogous to using C<use Carp 'verbose'>.

Defaults to C<0>.

=cut


$CarpInternal{Carp}++;
$CarpInternal{warnings}++;
$CarpLevel = 0;     # How many extra package levels to skip on carp.
                    # How many calls to skip on confess.
                    # Reconciling these notions is hard, use
                    # %Internal and %CarpInternal instead.
$MaxEvalLen = 0;    # How much eval '...text...' to show. 0 = all.
$MaxArgLen = 64;    # How much of each argument to print. 0 = all.
$MaxArgNums = 8;    # How many arguments to print. 0 = all.
$Verbose = 0;       # If true then make shortmess call longmess instead

require Exporter;
@ISA = ('Exporter');
@EXPORT = qw(confess croak carp);
@EXPORT_OK = qw(cluck verbose longmess shortmess);
@EXPORT_FAIL = qw(verbose);     # hook to enable verbose mode

=head1 BUGS

The Carp routines don't handle exception objects currently.
If called with a first argument that is a reference, they simply
call die() or warn(), as appropriate.

=cut

# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
# then the following method will be called by the Exporter which knows
# to do this thanks to @EXPORT_FAIL, above.  $_[1] will contain the word
# 'verbose'.

sub export_fail {
    shift;
    $Verbose = shift if $_[0] eq 'verbose';
    return @_;
}


# longmess() crawls all the way up the stack reporting on all the function
# calls made.  The error string, $error, is originally constructed from the
# arguments passed into longmess() via confess(), cluck() or shortmess().
# This gets appended with the stack trace messages which are generated for
# each function call on the stack.

sub longmess {
    {
        local($@, $!);
        # XXX fix require to not clear $@ or $!?
        # don't use require unless we need to (for Safe compartments)
        require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
    }
    # Icky backwards compatibility wrapper. :-(
    my $call_pack = caller();
    if ($Internal{$call_pack} or $CarpInternal{$call_pack}) {
      return longmess_heavy(@_);
    }
    else {
      local $CarpLevel = $CarpLevel + 1;
      return longmess_heavy(@_);
    }
}


# shortmess() is called by carp() and croak() to skip all the way up to
# the top-level caller's package and report the error from there.  confess()
# and cluck() generate a full stack trace so they call longmess() to
# generate that.  In verbose mode shortmess() calls longmess() so
# you always get a stack trace

sub shortmess { # Short-circuit &longmess if called via multiple packages
    {
        local($@, $!);
        # XXX fix require to not clear $@ or $!?
        # don't use require unless we need to (for Safe compartments)
        require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
    }
    # Icky backwards compatibility wrapper. :-(
    my $call_pack = caller();
    local @CARP_NOT = caller();
    shortmess_heavy(@_);
}


# the following four functions call longmess() or shortmess() depending on
# whether they should generate a full stack trace (confess() and cluck())
# or simply report the caller's package (croak() and carp()), respectively.
# confess() and croak() die, carp() and cluck() warn.

sub croak   { die  shortmess @_ }
sub confess { die  longmess  @_ }
sub carp    { warn shortmess @_ }
sub cluck   { warn longmess  @_ }

1;
Revision:	1.1
Committed:	Thu Jun 30 14:27:08 2005 UTC (21 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	package Carp;
2
3			our $VERSION = '1.04';
4
5			=head1 NAME
6
7			carp - warn of errors (from perspective of caller)
8
9			cluck - warn of errors with stack backtrace
10			(not exported by default)
11
12			croak - die of errors (from perspective of caller)
13
14			confess - die of errors with stack backtrace
15
16			shortmess - return the message that carp and croak produce
17
18			longmess - return the message that cluck and confess produce
19
20			=head1 SYNOPSIS
21
22			use Carp;
23			croak "We're outta here!";
24
25			use Carp qw(cluck);
26			cluck "This is how we got here!";
27
28			print FH Carp::shortmess("This will have caller's details added");
29			print FH Carp::longmess("This will have stack backtrace added");
30
31			=head1 DESCRIPTION
32
33			The Carp routines are useful in your own modules because
34			they act like die() or warn(), but with a message which is more
35			likely to be useful to a user of your module. In the case of
36			cluck, confess, and longmess that context is a summary of every
37			call in the call-stack. For a shorter message you can use carp,
38			croak or shortmess which report the error as being from where
39			your module was called. There is no guarantee that that is where
40			the error was, but it is a good educated guess.
41
42			You can also alter the way the output and logic of C<Carp> works, by
43			changing some global variables in the C<Carp> namespace. See the
44			section on C<GLOBAL VARIABLES> below.
45
46			Here is a more complete description of how shortmess works. What
47			it does is search the call-stack for a function call stack where
48			it hasn't been told that there shouldn't be an error. If every
49			call is marked safe, it then gives up and gives a full stack
50			backtrace instead. In other words it presumes that the first likely
51			looking potential suspect is guilty. Its rules for telling whether
52			a call shouldn't generate errors work as follows:
53
54			=over 4
55
56			=item 1.
57
58			Any call from a package to itself is safe.
59
60			=item 2.
61
62			Packages claim that there won't be errors on calls to or from
63			packages explicitly marked as safe by inclusion in @CARP_NOT, or
64			(if that array is empty) @ISA. The ability to override what
65			@ISA says is new in 5.8.
66
67			=item 3.
68
69			The trust in item 2 is transitive. If A trusts B, and B
70			trusts C, then A trusts C. So if you do not override @ISA
71			with @CARP_NOT, then this trust relationship is identical to,
72			"inherits from".
73
74			=item 4.
75
76			Any call from an internal Perl module is safe. (Nothing keeps
77			user modules from marking themselves as internal to Perl, but
78			this practice is discouraged.)
79
80			=item 5.
81
82			Any call to Carp is safe. (This rule is what keeps it from
83			reporting the error where you call carp/croak/shortmess.)
84
85			=back
86
87			=head2 Forcing a Stack Trace
88
89			As a debugging aid, you can force Carp to treat a croak as a confess
90			and a carp as a cluck across I<all> modules. In other words, force a
91			detailed stack trace to be given. This can be very helpful when trying
92			to understand why, or from where, a warning or error is being generated.
93
94			This feature is enabled by 'importing' the non-existent symbol
95			'verbose'. You would typically enable it by saying
96
97			perl -MCarp=verbose script.pl
98
99			or by including the string C<MCarp=verbose> in the PERL5OPT
100			environment variable.
101
102			Alternately, you can set the global variable C<$Carp::Verbose> to true.
103			See the C<GLOBAL VARIABLES> section below.
104
105			=cut
106
107			# This package is heavily used. Be small. Be fast. Be good.
108
109			# Comments added by Andy Wardley <abw@kfs.org> 09-Apr-98, based on an
110			# _almost_ complete understanding of the package. Corrections and
111			# comments are welcome.
112
113			# The members of %Internal are packages that are internal to perl.
114			# Carp will not report errors from within these packages if it
115			# can. The members of %CarpInternal are internal to Perl's warning
116			# system. Carp will not report errors from within these packages
117			# either, and will not report calls to these packages for carp and
118			# croak. They replace $CarpLevel, which is deprecated. The
119			# $Max(EvalLen\|(Arg(Len\|Nums)) variables are used to specify how the eval
120			# text and function arguments should be formatted when printed.
121
122			# Comments added by Jos I. Boumans <kane@dwim.org> 11-Aug-2004
123			# I can not get %CarpInternal or %Internal to work as advertised,
124			# therefor leaving it out of the below documentation.
125			# $CarpLevel may be decprecated according to the last comment, but
126			# after 6 years, it's still around and in heavy use ;)
127
128			=pod
129
130			=head1 GLOBAL VARIABLES
131
132			=head2 $Carp::CarpLevel
133
134			This variable determines how many call frames are to be skipped when
135			reporting where an error occurred on a call to one of C<Carp>'s
136			functions. For example:
137
138			$Carp::CarpLevel = 1;
139			sub bar { .... or _error('Wrong input') }
140			sub _error { Carp::carp(@_) }
141
142			This would make Carp report the error as coming from C<bar>'s caller,
143			rather than from C<_error>'s caller, as it normally would.
144
145			Defaults to C<0>.
146
147			=head2 $Carp::MaxEvalLen
148
149			This variable determines how many characters of a string-eval are to
150			be shown in the output. Use a value of C<0> to show all text.
151
152			Defaults to C<0>.
153
154			=head2 $Carp::MaxArgLen
155
156			This variable determines how many characters of each argument to a
157			function to print. Use a value of C<0> to show the full length of the
158			argument.
159
160			Defaults to C<64>.
161
162			=head2 $Carp::MaxArgNums
163
164			This variable determines how many arguments to each function to show.
165			Use a value of C<0> to show all arguments to a function call.
166
167			Defaults to C<8>.
168
169			=head2 $Carp::Verbose
170
171			This variable makes C<Carp> use the C<longmess> function at all times.
172			This effectively means that all calls to C<carp> become C<cluck> and
173			all calls to C<croak> become C<confess>.
174
175			Note, this is analogous to using C<use Carp 'verbose'>.
176
177			Defaults to C<0>.
178
179			=cut
180
181
182			$CarpInternal{Carp}++;
183			$CarpInternal{warnings}++;
184			$CarpLevel = 0; # How many extra package levels to skip on carp.
185			# How many calls to skip on confess.
186			# Reconciling these notions is hard, use
187			# %Internal and %CarpInternal instead.
188			$MaxEvalLen = 0; # How much eval '...text...' to show. 0 = all.
189			$MaxArgLen = 64; # How much of each argument to print. 0 = all.
190			$MaxArgNums = 8; # How many arguments to print. 0 = all.
191			$Verbose = 0; # If true then make shortmess call longmess instead
192
193			require Exporter;
194			@ISA = ('Exporter');
195			@EXPORT = qw(confess croak carp);
196			@EXPORT_OK = qw(cluck verbose longmess shortmess);
197			@EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
198
199			=head1 BUGS
200
201			The Carp routines don't handle exception objects currently.
202			If called with a first argument that is a reference, they simply
203			call die() or warn(), as appropriate.
204
205			=cut
206
207			# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
208			# then the following method will be called by the Exporter which knows
209			# to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word
210			# 'verbose'.
211
212			sub export_fail {
213			shift;
214			$Verbose = shift if $_[0] eq 'verbose';
215			return @_;
216			}
217
218
219			# longmess() crawls all the way up the stack reporting on all the function
220			# calls made. The error string, $error, is originally constructed from the
221			# arguments passed into longmess() via confess(), cluck() or shortmess().
222			# This gets appended with the stack trace messages which are generated for
223			# each function call on the stack.
224
225			sub longmess {
226			{
227			local($@, $!);
228			# XXX fix require to not clear $@ or $!?
229			# don't use require unless we need to (for Safe compartments)
230			require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
231			}
232			# Icky backwards compatibility wrapper. :-(
233			my $call_pack = caller();
234			if ($Internal{$call_pack} or $CarpInternal{$call_pack}) {
235			return longmess_heavy(@_);
236			}
237			else {
238			local $CarpLevel = $CarpLevel + 1;
239			return longmess_heavy(@_);
240			}
241			}
242
243
244			# shortmess() is called by carp() and croak() to skip all the way up to
245			# the top-level caller's package and report the error from there. confess()
246			# and cluck() generate a full stack trace so they call longmess() to
247			# generate that. In verbose mode shortmess() calls longmess() so
248			# you always get a stack trace
249
250			sub shortmess { # Short-circuit &longmess if called via multiple packages
251			{
252			local($@, $!);
253			# XXX fix require to not clear $@ or $!?
254			# don't use require unless we need to (for Safe compartments)
255			require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
256			}
257			# Icky backwards compatibility wrapper. :-(
258			my $call_pack = caller();
259			local @CARP_NOT = caller();
260			shortmess_heavy(@_);
261			}
262
263
264			# the following four functions call longmess() or shortmess() depending on
265			# whether they should generate a full stack trace (confess() and cluck())
266			# or simply report the caller's package (croak() and carp()), respectively.
267			# confess() and croak() die, carp() and cluck() warn.
268
269			sub croak { die shortmess @_ }
270			sub confess { die longmess @_ }
271			sub carp { warn shortmess @_ }
272			sub cluck { warn longmess @_ }
273
274			1;