X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/3132b1504bf3879ca430816411425569340202e8..1edf7ee90536e731f6a7d05142a0786a1862c384:/lib/Carp.pm diff --git a/lib/Carp.pm b/lib/Carp.pm index eaa4d53..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 @@ -40,85 +133,64 @@ This feature is enabled by 'importing' the non-existent symbol 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. -=head1 BUGS +Alternately, you can set the global variable C<$Carp::Verbose> to true. +See the C section below. -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. +=head1 GLOBAL VARIABLES -=cut +=head2 $Carp::CarpLevel -# This package is heavily used. Be small. Be fast. Be good. +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: -# Comments added by Andy Wardley 09-Apr-98, based on an -# _almost_ complete understanding of the package. Corrections and -# comments are welcome. + $Carp::CarpLevel = 1; + sub bar { .... or _error('Wrong input') } + sub _error { Carp::carp(@_) } -# The $CarpLevel variable can be set to "strip off" extra caller levels for -# those times when Carp calls are buried inside other functions. The -# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval -# text and function arguments should be formatted when printed. +This would make Carp report the error as coming from C's caller, +rather than from C<_error>'s caller, as it normally would. -$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. -$MaxArgNums = 8; # How many arguments to print. 0 = all. -$Verbose = 0; # If true then make shortmess call longmess instead +Defaults to C<0>. -require Exporter; -@ISA = ('Exporter'); -@EXPORT = qw(confess croak carp); -@EXPORT_OK = qw(cluck verbose); -@EXPORT_FAIL = qw(verbose); # hook to enable verbose mode +=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. -# 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'. +Defaults to C<0>. -sub export_fail { - shift; - $Verbose = shift if $_[0] eq 'verbose'; - return @_; -} +=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. -# 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. +Defaults to C<64>. -sub longmess { - require Carp::Heavy; - goto &longmess_heavy; -} +=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. -# 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 +Defaults to C<8>. -sub shortmess { # Short-circuit &longmess if called via multiple packages - require Carp::Heavy; - goto &shortmess_heavy; -} +=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. -# 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. +Note, this is analogous to using C. -sub croak { die shortmess @_ } -sub confess { die longmess @_ } -sub carp { warn shortmess @_ } -sub cluck { warn longmess @_ } +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;