X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FCarp.pm;h=52ccd76092dc25eb72a2a68d8c014e8e5c45fdab;hb=810a0276062cd558105294bfe7bf18a98deb624a;hp=b2e634ca5fec09db280139ebc746976806ea9a38;hpb=09e96b99c215ed417c37d0d188dd576c5464c72a;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Carp.pm b/lib/Carp.pm index b2e634c..52ccd76 100644 --- a/lib/Carp.pm +++ b/lib/Carp.pm @@ -1,6 +1,53 @@ package Carp; -our $VERSION = '1.04'; +our $VERSION = '1.07'; +# 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 $_[0] eq 'verbose'; @_ } + +# fixed hooks for stashes to point to +sub longmess { goto &longmess_jmp } +sub shortmess { goto &shortmess_jmp } +# these two are replaced when Carp::Heavy is loaded +sub longmess_jmp { + local($@, $!); + eval { require Carp::Heavy }; + return $@ if $@; + goto &longmess_real; +} +sub shortmess_jmp { + local($@, $!); + eval { require Carp::Heavy }; + return $@ if $@; + goto &shortmess_real; +} + +sub croak { die shortmess @_ } +sub confess { die longmess @_ } +sub carp { warn shortmess @_ } +sub cluck { warn longmess @_ } + +1; +__END__ =head1 NAME @@ -13,10 +60,6 @@ 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; @@ -25,30 +68,27 @@ longmess - return the message that cluck and confess produce 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. +call in the call-stack. For a shorter message you can use C +or C 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 +Here is a more complete description of how c and c work. +What they do is search the call-stack for a function call stack where +they have not been told that there shouldn't be an error. If every +call is marked safe, they give up and give a full stack backtrace +instead. In other words they presume that the first likely looking +potential suspect is guilty. Their rules for telling whether a call shouldn't generate errors work as follows: =over 4 @@ -60,15 +100,15 @@ 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 +packages explicitly marked as safe by inclusion in C<@CARP_NOT>, or +(if that array is empty) C<@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, +trusts C, then A trusts C. So if you do not override C<@ISA> +with C<@CARP_NOT>, then this trust relationship is identical to, "inherits from". =item 4. @@ -79,8 +119,15 @@ 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.) +Any call to Perl's warning system (eg Carp itself) is safe. +(This rule is what keeps it from reporting the error at the +point where you call C or C.) + +=item 6. + +C<$Carp::CarpLevel> can be set to skip a fixed number of additional +call levels. Using this is not recommended because it is very +difficult to get it to behave correctly. =back @@ -102,48 +149,8 @@ environment variable. Alternately, you can set the global variable C<$Carp::Verbose> to true. See the C section below. -=cut - -# This package is heavily used. Be small. Be fast. Be good. - -# Comments added by Andy Wardley 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 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'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 @@ -168,109 +175,63 @@ Defaults to C<8>. =head2 $Carp::Verbose -This variable makes C use the C function at all times. -This effectively means that all calls to C become C and -all calls to C become C. - -Note, this is analogous to using C. +This variable makes C and C generate stack backtraces +just like C and C. This is how C +is implemented internally. Defaults to C<0>. -=cut - -# disable these by default, so they can live w/o require Carp -$CarpInternal{Carp}++; -$CarpInternal{warnings}++; -$Internal{Exporter}++; -$Internal{'Exporter::Heavy'}++; -$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 +=head2 %Carp::Internal -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 +This says what packages are internal to Perl. C will never +report an error as being from a line in a package that is internal to +Perl. For example: -=head1 BUGS + $Carp::Internal{ __PACKAGE__ }++; + # time passes... + sub foo { ... or confess("whatever") }; -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. +would give a full stack backtrace starting from the first caller +outside of __PACKAGE__. (Unless that package was also internal to +Perl.) -=cut +=head2 %Carp::CarpInternal -# 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'. +This says which packages are internal to Perl's warning system. For +generating a full stack backtrace this is the same as being internal +to Perl, the stack backtrace will not start inside packages that are +listed in C<%Carp::CarpInternal>. But it is slightly different for +the summary message generated by C or C. There errors +will not be reported on any lines that are calling packages in +C<%Carp::CarpInternal>. -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 $@? - # 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(@_); - } -} +For example C itself is listed in C<%Carp::CarpInternal>. +Therefore the full stack backtrace from C will not start +inside of C, and the short message from calling C is +not placed on the line where C was called. +=head2 $Carp::CarpLevel -# 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 $@? - # don't use require unless we need to (for Safe compartments) - require Carp::Heavy unless $INC{"Carp/Heavy.pm"}; - } - # Icky backwards compatibility wrapper. :-( - my $call_pack = caller(); - local @CARP_NOT = caller(); - shortmess_heavy(@_); -} +This variable determines how many additional call frames are to be +skipped that would not otherwise be when reporting where an error +occurred on a call to one of C's functions. It is fairly easy +to count these call frames on calls that generate a full stack +backtrace. However it is much harder to do this accounting for calls +that generate a short message. Usually people skip too many call +frames. If they are lucky they skip enough that C goes all of +the way through the call stack, realizes that something is wrong, and +then generates a full stack backtrace. If they are unlucky then the +error is reported from somewhere misleading very high in the call +stack. + +Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use +C<@CARP_NOT>, C<%Carp::Internal> and %Carp::CarpInternal>. +Defaults to C<0>. -# 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. +=head1 BUGS -sub croak { die shortmess @_ } -sub confess { die longmess @_ } -sub carp { warn shortmess @_ } -sub cluck { warn longmess @_ } +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;