X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FCarp.pm;h=c0ffb9c5916b00a4e832f4c4d22011596c4cdb80;hb=7eb7d786de9bebe120f2143ce65237684a3a5d80;hp=5fb88099004c2989d5e1d915d7c2db6830f24429;hpb=697943021785eb8447e25eb51a6f27fd78921863;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Carp.pm b/lib/Carp.pm index 5fb8809..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 @@ -40,245 +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 @_; -} - - -# 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 { - return @_ if ref $_[0]; - my $error = join '', @_; - my $mess = ""; - my $i = 1 + $CarpLevel; - my ($pack,$file,$line,$sub,$hargs,$eval,$require); - my (@a); - # - # crawl up the stack.... - # - while (do { { package DB; @a = caller($i++) } } ) { - # get copies of the variables returned from caller() - ($pack,$file,$line,$sub,$hargs,undef,$eval,$require) = @a; - # - # if the $error error string is newline terminated then it - # is copied into $mess. Otherwise, $mess gets set (at the end of - # the 'else {' section below) to one of two things. The first time - # through, it is set to the "$error at $file line $line" message. - # $error is then set to 'called' which triggers subsequent loop - # iterations to append $sub to $mess before appending the "$error - # at $file line $line" which now actually reads "called at $file line - # $line". Thus, the stack trace message is constructed: - # - # first time: $mess = $error at $file line $line - # subsequent times: $mess .= $sub $error at $file line $line - # ^^^^^^ - # "called" - if ($error =~ m/\n$/) { - $mess .= $error; - } else { - # Build a string, $sub, which names the sub-routine called. - # This may also be "require ...", "eval '...' or "eval {...}" - 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 there are any arguments in the sub-routine call, format - # them according to the format variables defined earlier in - # this file and join them onto the $sub sub-routine string - if ($hargs) { - # we may trash some of the args so we take a copy - @a = @DB::args; # must get local copy of args - # don't print any more than $MaxArgNums - if ($MaxArgNums and @a > $MaxArgNums) { - # cap the length of $#a and set the last element to '...' - $#a = $MaxArgNums; - $a[$#a] = "..."; - } - for (@a) { - # set args to the string "undef" if undefined - $_ = "undef", next unless defined $_; - if (ref $_) { - # dunno what this is for... - $_ .= ''; - s/'/\\'/g; - } - else { - s/'/\\'/g; - # terminate the string early with '...' if too long - substr($_,$MaxArgLen) = '...' - if $MaxArgLen and $MaxArgLen < length; - } - # 'quote' arg unless it looks like a number - $_ = "'$_'" unless /^-?[\d.]+$/; - # print high-end chars as 'M-' or '^' - s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg; - s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg; - } - # append ('all', 'the', 'arguments') to the $sub string - $sub .= '(' . join(', ', @a) . ')'; - } - # here's where the error message, $mess, gets constructed - $mess .= "\t$sub " if $error eq "called"; - $mess .= "$error at $file line $line\n"; - } - # we don't need to print the actual error message again so we can - # change this to "called" so that the string "$error at $file line - # $line" makes sense as "called at $file line $line". - $error = "called"; - } - # this kludge circumvents die's incorrect handling of NUL - my $msg = \($mess || $error); - $$msg =~ tr/\0//d; - $$msg; -} - - -# 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 - goto &longmess if $Verbose; - return @_ if ref $_[0]; - my $error = join '', @_; - my ($prevpack) = caller(1); - my $extra = $CarpLevel; - my $i = 2; - my ($pack,$file,$line); - # when reporting an error, we want to report it from the context of the - # calling package. So what is the calling package? Within a module, - # there may be many calls between methods and perhaps between sub-classes - # and super-classes, but the user isn't interested in what happens - # inside the package. We start by building a hash array which keeps - # track of all the packages to which the calling package belongs. We - # do this by examining its @ISA variable. Any call from a base class - # method (one of our caller's @ISA packages) can be ignored - my %isa = ($prevpack,1); - - # merge all the caller's @ISA packages into %isa. - @isa{@{"${prevpack}::ISA"}} = () - if(@{"${prevpack}::ISA"}); - - # now we crawl up the calling stack and look at all the packages in - # there. For each package, we look to see if it has an @ISA and then - # we see if our caller features in that list. That would imply that - # our caller is a derived class of that package and its calls can also - # be ignored - while (($pack,$file,$line) = caller($i++)) { - if(@{$pack . "::ISA"}) { - my @i = @{$pack . "::ISA"}; - my %i; - @i{@i} = (); - # merge any relevant packages into %isa - @isa{@i,$pack} = () - if(exists $i{$prevpack} || exists $isa{$pack}); - } - - # and here's where we do the ignoring... if the package in - # question is one of our caller's base or derived packages then - # we can ignore it (skip it) and go onto the next (but note that - # the continue { } block below gets called every time) - next - if(exists $isa{$pack}); - - # Hey! We've found a package that isn't one of our caller's - # clan....but wait, $extra refers to the number of 'extra' levels - # we should skip up. If $extra > 0 then this is a false alarm. - # We must merge the package into the %isa hash (so we can ignore it - # if it pops up again), decrement $extra, and continue. - if ($extra-- > 0) { - %isa = ($pack,1); - @isa{@{$pack . "::ISA"}} = () - if(@{$pack . "::ISA"}); - } - else { - # OK! We've got a candidate package. Time to construct the - # relevant error message and return it. die() doesn't like - # to be given NUL characters (which $msg may contain) so we - # remove them first. - (my $msg = "$error at $file line $line\n") =~ tr/\0//d; - return $msg; - } - } - continue { - $prevpack = $pack; - } - - # uh-oh! It looks like we crawled all the way up the stack and - # never found a candidate package. Oh well, let's call longmess - # to generate a full stack trace. We use the magical form of 'goto' - # so that this shortmess() function doesn't appear on the stack - # to further confuse longmess() about it's calling package. - goto &longmess; -} - - -# 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. +=head2 $Carp::MaxArgLen -sub croak { die shortmess @_ } -sub confess { die longmess @_ } -sub carp { warn shortmess @_ } -sub cluck { warn longmess @_ } +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;