X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FCarp.pm;h=393b126d4a22f08ea3fb2a5d31a5489f4f1f31e6;hb=8d5f6fc7a37e9f9386ec9c97cc0b1609d9c13e71;hp=4ceecda23a453326bb498d2c88917f2d226f2605;hpb=1129fd022cb7a362c2ea03105d1a4b2127589595;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Carp.pm b/lib/Carp.pm index 4ceecda..393b126 100644 --- a/lib/Carp.pm +++ b/lib/Carp.pm @@ -1,6 +1,53 @@ package Carp; -our $VERSION = '1.01'; +our $VERSION = '1.08'; +# 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 @@ -26,38 +73,42 @@ confess - die of errors with stack backtrace 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 and confess that context is a summary of every -call in the call-stack. For a shorter message you can use carp -or croak which try to 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. - -Here is a more complete description of how the shorter message 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 +cluck, confess, and longmess that context is a summary of every +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 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 =item 1. -Any call from a package to itself is safe. +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. @@ -68,8 +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 or croak.) +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 @@ -88,101 +146,92 @@ This feature is enabled by 'importing' the non-existent symbol 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 - -# 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 -# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval -# text and function arguments should be formatted when printed. - -$CarpInternal{Carp}++; -$CarpLevel = 0; # How many extra package levels to skip on carp. - # How many calls to skip on confess. - # Reconciling these notions is hard, use - # %Internal and %CarpInternal instead. -$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::MaxEvalLen -require Exporter; -@ISA = ('Exporter'); -@EXPORT = qw(confess croak carp); -@EXPORT_OK = qw(cluck); - -# we handle verbose usage ("perl -MCarp=verbose script.pl") ourselves -# and then erase all traces of this call so that Exporter doesn't -# know that we have been here. BTW subclasses shouldn't try to -# do anything useful with 'verbose', including have that be their -# name... -sub import { - if (grep 'verbose' eq $_, @_) { - @_ = grep 'verbose' ne $_, @_; - $Verbose = "verbose"; - } - goto &Exporter::import; -} +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>. -# 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 $@; require Carp::Heavy; } # XXX fix require to not clear $@? - # 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(@_); - } -} +=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. -# 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<64>. -sub shortmess { # Short-circuit &longmess if called via multiple packages - { local $@; require Carp::Heavy; } # XXX fix require to not clear $@? - # Icky backwards compatibility wrapper. :-( - my $call_pack = caller(); - local @CARP_NOT = caller(); - shortmess_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. -# 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. +Defaults to C<8>. -sub croak { die shortmess @_ } -sub confess { die longmess @_ } -sub carp { warn shortmess @_ } -sub cluck { warn longmess @_ } +=head2 $Carp::Verbose + +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>. + +=head2 %Carp::Internal + +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: + + $Carp::Internal{ __PACKAGE__ }++; + # time passes... + sub foo { ... or confess("whatever") }; + +would give a full stack backtrace starting from the first caller +outside of __PACKAGE__. (Unless that package was also internal to +Perl.) + +=head2 %Carp::CarpInternal + +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>. + +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 $Carp::CarpLevel + +This variable determines how many additional call frames are to be +skipped that would not otherwise be when reporting where an error +occurred on a call to one of C's functions. It is fairly easy +to count these call frames on calls that generate a full stack +backtrace. However it is much harder to do this accounting for calls +that generate a short message. Usually people skip too many call +frames. If they are lucky they skip enough that C goes all of +the way through the call stack, realizes that something is wrong, and +then generates a full stack backtrace. If they are unlucky then the +error is reported from somewhere misleading very high in the call +stack. + +Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use +C<@CARP_NOT>, C<%Carp::Internal> and %Carp::CarpInternal>. + +Defaults to C<0>. + +=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;