X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/4d935a29ed6e2adbac68dfedbe6b3bc917152461..1edf7ee90536e731f6a7d05142a0786a1862c384:/lib/Carp.pm diff --git a/lib/Carp.pm b/lib/Carp.pm index 351f83b..c0ffb9c 100644 --- a/lib/Carp.pm +++ b/lib/Carp.pm @@ -1,5 +1,44 @@ package Carp; +our $VERSION = '1.05'; +# this file is an utra-lightweight stub. The first time a function is +# called, Carp::Heavy is loaded, and the real short/longmessmess_jmp +# subs are installed + +our $MaxEvalLen = 0; +our $Verbose = 0; +our $CarpLevel = 0; +our $MaxArgLen = 64; # How much of each argument to print. 0 = all. +our $MaxArgNums = 8; # How many arguments to print. 0 = all. + +require Exporter; +our @ISA = ('Exporter'); +our @EXPORT = qw(confess croak carp); +our @EXPORT_OK = qw(cluck verbose longmess shortmess); +our @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode + +# 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 $_[0] eq 'verbose'; @_ } + +# fixed hooks for stashes to point to +sub longmess { goto &longmess_jmp } +sub shortmess { goto &shortmess_jmp } +# these two are replaced when Carp::Heavy is loaded +sub longmess_jmp {{ local($@, $!); require Carp::Heavy} goto &longmess_jmp} +sub shortmess_jmp {{ local($@, $!); require Carp::Heavy} goto &shortmess_jmp} + +sub croak { die shortmess @_ } +sub confess { die longmess @_ } +sub carp { warn shortmess @_ } +sub cluck { warn longmess @_ } + +1; +__END__ + =head1 NAME carp - warn of errors (from perspective of caller) @@ -11,6 +50,10 @@ 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; @@ -19,14 +62,64 @@ confess - die of errors with stack backtrace 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 report where the error -was in the code they were called from. Thus if you have a -routine Foo() that has a carp() in it, then the carp() -will report the error as occurring where Foo() was called, -not where carp() was called. +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 works, by +changing some global variables in the C namespace. See the +section on C 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 @@ -35,142 +128,69 @@ and a carp as a cluck across I 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-existant symbol +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 in the L +or by including the string C in the PERL5OPT environment variable. -=cut +Alternately, you can set the global variable C<$Carp::Verbose> to true. +See the C section below. -# This package is heavily used. Be small. Be fast. Be good. +=head1 GLOBAL VARIABLES -$CarpLevel = 0; # How many extra package levels to skip on carp. -$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. +=head2 $Carp::CarpLevel -require Exporter; -@ISA = Exporter; -@EXPORT = qw(confess croak carp); -@EXPORT_OK = qw(cluck verbose); -@EXPORT_FAIL = qw(verbose); # hook to enable verbose mode - -sub export_fail { - shift; - if ($_[0] eq 'verbose') { - local $^W = 0; - *shortmess = \&longmess; - shift; - } - return @_; -} - - -sub longmess { - my $error = join '', @_; - my $mess = ""; - my $i = 1 + $CarpLevel; - my ($pack,$file,$line,$sub,$hargs,$eval,$require); - my (@a); - while (do { { package DB; @a = caller($i++) } } ) { - ($pack,$file,$line,$sub,$hargs,undef,$eval,$require) = @a; - if ($error =~ m/\n$/) { - $mess .= $error; - } else { - if (defined $eval) { - if ($require) { - $sub = "require $eval"; - } else { - $eval =~ s/([\\\'])/\\$1/g; - if ($MaxEvalLen && length($eval) > $MaxEvalLen) { - substr($eval,$MaxEvalLen) = '...'; - } - $sub = "eval '$eval'"; - } - } elsif ($sub eq '(eval)') { - $sub = 'eval {...}'; - } - if ($hargs) { - @a = @DB::args; # must get local copy of args - if ($MaxArgNums and @a > $MaxArgNums) { - $#a = $MaxArgNums; - $a[$#a] = "..."; - } - for (@a) { - $_ = "undef", next unless defined $_; - if (ref $_) { - $_ .= ''; - s/'/\\'/g; - } - else { - s/'/\\'/g; - substr($_,$MaxArgLen) = '...' - if $MaxArgLen and $MaxArgLen < length; - } - $_ = "'$_'" unless /^-?[\d.]+$/; - s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg; - s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg; - } - $sub .= '(' . join(', ', @a) . ')'; - } - $mess .= "\t$sub " if $error eq "called"; - $mess .= "$error at $file line $line\n"; - } - $error = "called"; - } - # this kludge circumvents die's incorrect handling of NUL - my $msg = \($mess || $error); - $$msg =~ tr/\0//d; - $$msg; -} - -sub shortmess { # Short-circuit &longmess if called via multiple packages - my $error = join '', @_; - my ($prevpack) = caller(1); - my $extra = $CarpLevel; - my $i = 2; - my ($pack,$file,$line); - my %isa = ($prevpack,1); - - @isa{@{"${prevpack}::ISA"}} = () - if(defined @{"${prevpack}::ISA"}); - - while (($pack,$file,$line) = caller($i++)) { - if(defined @{$pack . "::ISA"}) { - my @i = @{$pack . "::ISA"}; - my %i; - @i{@i} = (); - @isa{@i,$pack} = () - if(exists $i{$prevpack} || exists $isa{$pack}); - } - - next - if(exists $isa{$pack}); - - if ($extra-- > 0) { - %isa = ($pack,1); - @isa{@{$pack . "::ISA"}} = () - if(defined @{$pack . "::ISA"}); - } - else { - # this kludge circumvents die's incorrect handling of NUL - (my $msg = "$error at $file line $line\n") =~ tr/\0//d; - return $msg; - } - } - continue { - $prevpack = $pack; - } - - goto &longmess; -} - -sub confess { die longmess @_; } -sub croak { die shortmess @_; } -sub carp { warn shortmess @_; } -sub cluck { warn longmess @_; } +This variable determines how many call frames are to be skipped when +reporting where an error occurred on a call to one of C'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'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 use the C function at all times. +This effectively means that all calls to C become C and +all calls to C become C. + +Note, this is analogous to using C. + +Defaults to C<0>. + +=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. -1;