package Carp;
+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
carp - warn of errors (from perspective of caller)
=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 C<carp>
+or C<croak> 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<Carp> works, by
+changing some global variables in the C<Carp> namespace. See the
+section on C<GLOBAL VARIABLES> below.
+
+Here is a more complete description of how c<carp> and c<croak> 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<carp> or C<croak>.)
+
+=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
perl -MCarp=verbose script.pl
-or by including the string C<MCarp=verbose> in the L<PERL5OPT>
+or by including the string C<MCarp=verbose> in the PERL5OPT
environment variable.
-=cut
+Alternately, you can set the global variable C<$Carp::Verbose> to true.
+See the C<GLOBAL VARIABLES> section below.
-# This package is heavily used. Be small. Be fast. Be good.
+=head1 GLOBAL VARIABLES
-# Comments added by Andy Wardley <abw@kfs.org> 09-Apr-98, based on an
-# _almost_ complete understanding of the package. Corrections and
-# comments are welcome.
+=head2 $Carp::MaxEvalLen
-# The $CarpLevel variable can be set to "strip off" extra caller levels for
-# those times when Carp calls are buried inside other functions. The
-# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
-# text and function arguments should be formatted when printed.
+This variable determines how many characters of a string-eval are to
+be shown in the output. Use a value of C<0> to show all text.
-$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::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.
-# 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<64>.
-sub export_fail {
- shift;
- $Verbose = shift if $_[0] eq 'verbose';
- return @_;
-}
+=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.
-# 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 {
- 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-<char>' or '^<char>'
- 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;
-}
+Defaults to C<8>.
+=head2 $Carp::Verbose
-# 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;
- 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(defined @{"${prevpack}::ISA"});
-
- # now we crawl up the calling stack and look at all the packages in
- # there. For each package, we look to see if it has an @ISA and then
- # we see if our caller features in that list. That would imply that
- # our caller is a derived class of that package and its calls can also
- # be ignored
- while (($pack,$file,$line) = caller($i++)) {
- if(defined @{$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(defined @{$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;
-}
+This variable makes C<carp> and C<cluck> generate stack backtraces
+just like C<cluck> and C<confess>. This is how C<use Carp 'verbose'>
+is implemented internally.
+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.
+=head2 %Carp::Internal
-sub croak { die shortmess @_ }
-sub confess { die longmess @_ }
-sub carp { warn shortmess @_ }
-sub cluck { warn longmess @_ }
+This says what packages are internal to Perl. C<Carp> 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<carp> or C<croak>. There errors
+will not be reported on any lines that are calling packages in
+C<%Carp::CarpInternal>.
+
+For example C<Carp> itself is listed in C<%Carp::CarpInternal>.
+Therefore the full stack backtrace from C<confess> will not start
+inside of C<Carp>, and the short message from calling C<croak> is
+not placed on the line where C<croak> was called.
+
+=head2 $Carp::CarpLevel
+
+This variable determines how many additional call frames are to be
+skipped that would not otherwise be when reporting where an error
+occurred on a call to one of C<Carp>'s functions. It is fairly easy
+to count these call frames on calls that generate a full stack
+backtrace. However it is much harder to do this accounting for calls
+that generate a short message. Usually people skip too many call
+frames. If they are lucky they skip enough that C<Carp> goes all of
+the way through the call stack, realizes that something is wrong, and
+then generates a full stack backtrace. If they are unlucky then the
+error is reported from somewhere misleading very high in the call
+stack.
+
+Therefore it is best to avoid C<$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;
https://perl5.git.perl.org / perl5.git / blobdiff