package Carp; use strict; use warnings; our $VERSION = '1.20'; 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 # 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. our %CarpInternal; our %Internal; # disable these by default, so they can live w/o require Carp $CarpInternal{Carp}++; $CarpInternal{warnings}++; $Internal{Exporter}++; $Internal{'Exporter::Heavy'}++; # 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'; @_ } sub _cgc { no strict 'refs'; return \&{"CORE::GLOBAL::caller"} if defined &{"CORE::GLOBAL::caller"}; return; } sub longmess { # Icky backwards compatibility wrapper. :-( # # The story is that the original implementation hard-coded the # number of call levels to go back, so calls to longmess were off # by one. Other code began calling longmess and expecting this # behaviour, so the replacement has to emulate that behaviour. my $cgc = _cgc(); my $call_pack = $cgc ? $cgc->() : caller(); if ( $Internal{$call_pack} or $CarpInternal{$call_pack} ) { return longmess_heavy(@_); } else { local $CarpLevel = $CarpLevel + 1; return longmess_heavy(@_); } } our @CARP_NOT; sub shortmess { my $cgc = _cgc(); # Icky backwards compatibility wrapper. :-( local @CARP_NOT = $cgc ? $cgc->() : caller(); shortmess_heavy(@_); } sub croak { die shortmess @_ } sub confess { die longmess @_ } sub carp { warn shortmess @_ } sub cluck { warn longmess @_ } sub caller_info { my $i = shift(@_) + 1; my %call_info; my $cgc = _cgc(); { package DB; @DB::args = \$i; # A sentinel, which no-one else has the address of @call_info{ qw(pack file line sub has_args wantarray evaltext is_require) } = $cgc ? $cgc->($i) : caller($i); } unless ( defined $call_info{pack} ) { return (); } my $sub_name = Carp::get_subname( \%call_info ); if ( $call_info{has_args} ) { my @args; if ( @DB::args == 1 && ref $DB::args[0] eq ref \$i && $DB::args[0] == \$i ) { @DB::args = (); # Don't let anyone see the address of $i local $@; my $where = eval { my $func = $cgc or return ''; my $gv = B::svref_2object($func)->GV; my $package = $gv->STASH->NAME; my $subname = $gv->NAME; return unless defined $package && defined $subname; # returning CORE::GLOBAL::caller isn't useful for tracing the cause: return if $package eq 'CORE::GLOBAL' && $subname eq 'caller'; " in &${package}::$subname"; } // ''; @args = "** Incomplete caller override detected$where; \@DB::args were not set **"; } else { @args = map { Carp::format_arg($_) } @DB::args; } if ( $MaxArgNums and @args > $MaxArgNums ) { # More than we want to show? $#args = $MaxArgNums; push @args, '...'; } # Push the args onto the subroutine $sub_name .= '(' . join( ', ', @args ) . ')'; } $call_info{sub_name} = $sub_name; return wantarray() ? %call_info : \%call_info; } # Transform an argument to a function into a string. sub format_arg { my $arg = shift; if ( ref($arg) ) { $arg = defined($overload::VERSION) ? overload::StrVal($arg) : "$arg"; } if ( defined($arg) ) { $arg =~ s/'/\\'/g; $arg = str_len_trim( $arg, $MaxArgLen ); # Quote it? $arg = "'$arg'" unless $arg =~ /^-?[0-9.]+\z/; } # 0-9, not \d, as \d will try to else { # load Unicode tables $arg = 'undef'; } # The following handling of "control chars" is direct from # the original code - it is broken on Unicode though. # Suggestions? utf8::is_utf8($arg) or $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg; return $arg; } # Takes an inheritance cache and a package and returns # an anon hash of known inheritances and anon array of # inheritances which consequences have not been figured # for. sub get_status { my $cache = shift; my $pkg = shift; $cache->{$pkg} ||= [ { $pkg => $pkg }, [ trusts_directly($pkg) ] ]; return @{ $cache->{$pkg} }; } # Takes the info from caller() and figures out the name of # the sub/require/eval sub get_subname { my $info = shift; if ( defined( $info->{evaltext} ) ) { my $eval = $info->{evaltext}; if ( $info->{is_require} ) { return "require $eval"; } else { $eval =~ s/([\\\'])/\\$1/g; return "eval '" . str_len_trim( $eval, $MaxEvalLen ) . "'"; } } return ( $info->{sub} eq '(eval)' ) ? 'eval {...}' : $info->{sub}; } # Figures out what call (from the point of view of the caller) # the long error backtrace should start at. sub long_error_loc { my $i; my $lvl = $CarpLevel; { ++$i; my $cgc = _cgc(); my $pkg = $cgc ? $cgc->($i) : caller($i); unless ( defined($pkg) ) { # This *shouldn't* happen. if (%Internal) { local %Internal; $i = long_error_loc(); last; } else { # OK, now I am irritated. return 2; } } redo if $CarpInternal{$pkg}; redo unless 0 > --$lvl; redo if $Internal{$pkg}; } return $i - 1; } sub longmess_heavy { return @_ if ref( $_[0] ); # don't break references as exceptions my $i = long_error_loc(); return ret_backtrace( $i, @_ ); } # Returns a full stack backtrace starting from where it is # told. sub ret_backtrace { my ( $i, @error ) = @_; my $mess; my $err = join '', @error; $i++; my $tid_msg = ''; if ( defined &threads::tid ) { my $tid = threads->tid; $tid_msg = " thread $tid" if $tid; } my %i = caller_info($i); $mess = "$err at $i{file} line $i{line}$tid_msg\n"; while ( my %i = caller_info( ++$i ) ) { $mess .= "\t$i{sub_name} called at $i{file} line $i{line}$tid_msg\n"; } return $mess; } sub ret_summary { my ( $i, @error ) = @_; my $err = join '', @error; $i++; my $tid_msg = ''; if ( defined &threads::tid ) { my $tid = threads->tid; $tid_msg = " thread $tid" if $tid; } my %i = caller_info($i); return "$err at $i{file} line $i{line}$tid_msg\n"; } sub short_error_loc { # You have to create your (hash)ref out here, rather than defaulting it # inside trusts *on a lexical*, as you want it to persist across calls. # (You can default it on $_[2], but that gets messy) my $cache = {}; my $i = 1; my $lvl = $CarpLevel; { my $cgc = _cgc(); my $called = $cgc ? $cgc->($i) : caller($i); $i++; my $caller = $cgc ? $cgc->($i) : caller($i); return 0 unless defined($caller); # What happened? redo if $Internal{$caller}; redo if $CarpInternal{$caller}; redo if $CarpInternal{$called}; redo if trusts( $called, $caller, $cache ); redo if trusts( $caller, $called, $cache ); redo unless 0 > --$lvl; } return $i - 1; } sub shortmess_heavy { return longmess_heavy(@_) if $Verbose; return @_ if ref( $_[0] ); # don't break references as exceptions my $i = short_error_loc(); if ($i) { ret_summary( $i, @_ ); } else { longmess_heavy(@_); } } # If a string is too long, trims it with ... sub str_len_trim { my $str = shift; my $max = shift || 0; if ( 2 < $max and $max < length($str) ) { substr( $str, $max - 3 ) = '...'; } return $str; } # Takes two packages and an optional cache. Says whether the # first inherits from the second. # # Recursive versions of this have to work to avoid certain # possible endless loops, and when following long chains of # inheritance are less efficient. sub trusts { my $child = shift; my $parent = shift; my $cache = shift; my ( $known, $partial ) = get_status( $cache, $child ); # Figure out consequences until we have an answer while ( @$partial and not exists $known->{$parent} ) { my $anc = shift @$partial; next if exists $known->{$anc}; $known->{$anc}++; my ( $anc_knows, $anc_partial ) = get_status( $cache, $anc ); my @found = keys %$anc_knows; @$known{@found} = (); push @$partial, @$anc_partial; } return exists $known->{$parent}; } # Takes a package and gives a list of those trusted directly sub trusts_directly { my $class = shift; no strict 'refs'; no warnings 'once'; return @{"$class\::CARP_NOT"} ? @{"$class\::CARP_NOT"} : @{"$class\::ISA"}; } 1; __END__ =head1 NAME Carp - alternative warn and die for modules =head1 SYNOPSIS use Carp; # warn user (from perspective of caller) carp "string trimmed to 80 chars"; # die of errors (from perspective of caller) croak "We're outta here!"; # die of errors with stack backtrace confess "not implemented"; # cluck not exported by default use Carp qw(cluck); cluck "This is how we got here!"; =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 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. =item 2. Packages claim that there won't be errors on calls to or from 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 C<@ISA> with C<@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 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<$Carp::CarpLevel> can be set to skip a fixed number of additional call levels. Using this is not recommended because it is very difficult to get it to behave correctly. =back =head2 Forcing a Stack Trace As a debugging aid, you can force Carp to treat a croak as a confess and a carp as a cluck across I modules. In other words, force a detailed stack trace to be given. This can be very helpful when trying to understand why, or from where, a warning or error is being generated. This feature is enabled by 'importing' the non-existent symbol 'verbose'. You would typically enable it by saying perl -MCarp=verbose script.pl or by including the string C<-MCarp=verbose> in the PERL5OPT environment variable. Alternately, you can set the global variable C<$Carp::Verbose> to true. See the C section below. =head1 GLOBAL VARIABLES =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 $Carp::Verbose This variable makes C and C generate stack backtraces just like C and C. This is how C is implemented internally. Defaults to C<0>. =head2 @CARP_NOT This variable, I, says which packages are I to be considered as the location of an error. The C and C functions will skip over callers when reporting where an error occurred. NB: This variable must be in the package's symbol table, thus: # These work our @CARP_NOT; # file scope use vars qw(@CARP_NOT); # package scope @My::Package::CARP_NOT = ... ; # explicit package variable # These don't work sub xyz { ... @CARP_NOT = ... } # w/o declarations above my @CARP_NOT; # even at top-level Example of use: package My::Carping::Package; use Carp; our @CARP_NOT; sub bar { .... or _error('Wrong input') } sub _error { # temporary control of where'ness, __PACKAGE__ is implicit local @CARP_NOT = qw(My::Friendly::Caller); carp(@_) } This would make C report the error as coming from a caller not in C, nor from C. Also read the L section above, about how C decides where the error is reported from. Use C<@CARP_NOT>, instead of C<$Carp::CarpLevel>. Overrides C's use of C<@ISA>. =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 C<%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.