=head1 NAME
-carp - warn of errors (from perspective of caller)
+carp - warn of errors (from perspective of caller)
-croak - die of errors (from perspective of caller)
+cluck - warn of errors with stack backtrace
+ (not exported by default)
+
+croak - die of errors (from perspective of caller)
confess - die of errors with stack backtrace
use Carp;
croak "We're outta here!";
+ use Carp qw(cluck);
+ cluck "This is how we got here!";
+
=head1 DESCRIPTION
The Carp routines are useful in your own modules because
will report the error as occurring where Foo() was called,
not where carp() was called.
+=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<all> 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-existant symbol
+'verbose'. You would typically enable it by saying
+
+ perl -MCarp=verbose script.pl
+
+or by including the string C<MCarp=verbose> in the L<PERL5OPT>
+environment variable.
+
=cut
-# This package implements handy routines for modules that wish to throw
-# exceptions outside of the current package.
+# This package is heavily used. Be small. Be fast. Be good.
+
+# 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.
+
+# 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.
$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
require Exporter;
-@ISA = Exporter;
+@ISA = ('Exporter');
@EXPORT = qw(confess croak carp);
+@EXPORT_OK = qw(cluck verbose);
+@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';
+ 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 {
- my $error = shift;
+ 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($i++) } } ) {
- ($pack,$file,$line,$sub,$hargs,undef,$eval,$require) = @a;
+ # 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) {
+ if ($require) {
$sub = "require $eval";
} else {
$eval =~ s/([\\\'])/\\$1/g;
} 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) {
- @a = @DB::args; # must get local copy of args
- if ($MaxArgNums and @a > $MaxArgNums) {
- $#a = $MaxArgNums;
- $a[$#a] = "...";
- }
- for (@a) {
- s/'/\\'/g;
- substr($_,$MaxArgLen) = '...' if $MaxArgLen and $MaxArgLen < length;
- s/([^\0]*)/'$1'/ unless /^-?[\d.]+$/;
- s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg;
- s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg;
- }
- $sub .= '(' . join(', ', @a) . ')';
+ # 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";
}
- $mess || $error;
+ # 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
- my $error = $_[0]; # Instead of "shift"
+ 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 @{$pack . "::ISA"});
}
else {
- return "$error at $file line $line\n";
+ # 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;
}
-sub confess { die longmess @_; }
-sub croak { die shortmess @_; }
-sub carp { warn shortmess @_; }
+
+# 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.
+
+sub croak { die shortmess @_ }
+sub confess { die longmess @_ }
+sub carp { warn shortmess @_ }
+sub cluck { warn longmess @_ }
1;
projects / p5sagit/p5-mst-13.2.git / blobdiff