277 lines
9.8 KiB
Perl
277 lines
9.8 KiB
Perl
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package Carp;
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=head1 NAME
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carp - warn of errors (from perspective of caller)
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cluck - warn of errors with stack backtrace
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(not exported by default)
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croak - die of errors (from perspective of caller)
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confess - die of errors with stack backtrace
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=head1 SYNOPSIS
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use Carp;
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croak "We're outta here!";
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use Carp qw(cluck);
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cluck "This is how we got here!";
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=head1 DESCRIPTION
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The Carp routines are useful in your own modules because
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they act like die() or warn(), but report where the error
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was in the code they were called from. Thus if you have a
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routine Foo() that has a carp() in it, then the carp()
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will report the error as occurring where Foo() was called,
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not where carp() was called.
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=head2 Forcing a Stack Trace
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As a debugging aid, you can force Carp to treat a croak as a confess
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and a carp as a cluck across I<all> modules. In other words, force a
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detailed stack trace to be given. This can be very helpful when trying
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to understand why, or from where, a warning or error is being generated.
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This feature is enabled by 'importing' the non-existant symbol
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'verbose'. You would typically enable it by saying
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perl -MCarp=verbose script.pl
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or by including the string C<MCarp=verbose> in the L<PERL5OPT>
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environment variable.
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=cut
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# This package is heavily used. Be small. Be fast. Be good.
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# Comments added by Andy Wardley <abw@kfs.org> 09-Apr-98, based on an
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# _almost_ complete understanding of the package. Corrections and
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# comments are welcome.
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# The $CarpLevel variable can be set to "strip off" extra caller levels for
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# those times when Carp calls are buried inside other functions. The
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# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
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# text and function arguments should be formatted when printed.
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$CarpLevel = 0; # How many extra package levels to skip on carp.
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$MaxEvalLen = 0; # How much eval '...text...' to show. 0 = all.
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$MaxArgLen = 64; # How much of each argument to print. 0 = all.
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$MaxArgNums = 8; # How many arguments to print. 0 = all.
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$Verbose = 0; # If true then make shortmess call longmess instead
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require Exporter;
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@ISA = ('Exporter');
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@EXPORT = qw(confess croak carp);
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@EXPORT_OK = qw(cluck verbose);
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@EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
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# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
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# then the following method will be called by the Exporter which knows
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# to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word
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# 'verbose'.
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sub export_fail {
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shift;
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$Verbose = shift if $_[0] eq 'verbose';
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return @_;
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}
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# longmess() crawls all the way up the stack reporting on all the function
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# calls made. The error string, $error, is originally constructed from the
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# arguments passed into longmess() via confess(), cluck() or shortmess().
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# This gets appended with the stack trace messages which are generated for
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# each function call on the stack.
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sub longmess {
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my $error = join '', @_;
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my $mess = "";
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my $i = 1 + $CarpLevel;
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my ($pack,$file,$line,$sub,$hargs,$eval,$require);
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my (@a);
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#
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# crawl up the stack....
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#
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while (do { { package DB; @a = caller($i++) } } ) {
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# get copies of the variables returned from caller()
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($pack,$file,$line,$sub,$hargs,undef,$eval,$require) = @a;
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#
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# if the $error error string is newline terminated then it
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# is copied into $mess. Otherwise, $mess gets set (at the end of
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# the 'else {' section below) to one of two things. The first time
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# through, it is set to the "$error at $file line $line" message.
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# $error is then set to 'called' which triggers subsequent loop
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# iterations to append $sub to $mess before appending the "$error
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# at $file line $line" which now actually reads "called at $file line
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# $line". Thus, the stack trace message is constructed:
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#
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# first time: $mess = $error at $file line $line
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# subsequent times: $mess .= $sub $error at $file line $line
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# ^^^^^^
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# "called"
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if ($error =~ m/\n$/) {
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$mess .= $error;
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} else {
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# Build a string, $sub, which names the sub-routine called.
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# This may also be "require ...", "eval '...' or "eval {...}"
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if (defined $eval) {
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if ($require) {
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$sub = "require $eval";
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} else {
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$eval =~ s/([\\\'])/\\$1/g;
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if ($MaxEvalLen && length($eval) > $MaxEvalLen) {
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substr($eval,$MaxEvalLen) = '...';
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}
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$sub = "eval '$eval'";
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}
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} elsif ($sub eq '(eval)') {
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$sub = 'eval {...}';
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}
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# if there are any arguments in the sub-routine call, format
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# them according to the format variables defined earlier in
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# this file and join them onto the $sub sub-routine string
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if ($hargs) {
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# we may trash some of the args so we take a copy
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@a = @DB::args; # must get local copy of args
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# don't print any more than $MaxArgNums
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if ($MaxArgNums and @a > $MaxArgNums) {
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# cap the length of $#a and set the last element to '...'
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$#a = $MaxArgNums;
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$a[$#a] = "...";
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}
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for (@a) {
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# set args to the string "undef" if undefined
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$_ = "undef", next unless defined $_;
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if (ref $_) {
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# dunno what this is for...
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$_ .= '';
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s/'/\\'/g;
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}
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else {
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s/'/\\'/g;
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# terminate the string early with '...' if too long
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substr($_,$MaxArgLen) = '...'
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if $MaxArgLen and $MaxArgLen < length;
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}
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# 'quote' arg unless it looks like a number
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$_ = "'$_'" unless /^-?[\d.]+$/;
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# print high-end chars as 'M-<char>' or '^<char>'
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s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg;
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s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg;
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}
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# append ('all', 'the', 'arguments') to the $sub string
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$sub .= '(' . join(', ', @a) . ')';
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}
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# here's where the error message, $mess, gets constructed
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$mess .= "\t$sub " if $error eq "called";
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$mess .= "$error at $file line $line\n";
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}
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# we don't need to print the actual error message again so we can
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# change this to "called" so that the string "$error at $file line
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# $line" makes sense as "called at $file line $line".
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$error = "called";
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}
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# this kludge circumvents die's incorrect handling of NUL
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my $msg = \($mess || $error);
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$$msg =~ tr/\0//d;
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$$msg;
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}
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# shortmess() is called by carp() and croak() to skip all the way up to
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# the top-level caller's package and report the error from there. confess()
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# and cluck() generate a full stack trace so they call longmess() to
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# generate that. In verbose mode shortmess() calls longmess() so
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# you always get a stack trace
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sub shortmess { # Short-circuit &longmess if called via multiple packages
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goto &longmess if $Verbose;
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my $error = join '', @_;
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my ($prevpack) = caller(1);
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my $extra = $CarpLevel;
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my $i = 2;
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my ($pack,$file,$line);
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# when reporting an error, we want to report it from the context of the
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# calling package. So what is the calling package? Within a module,
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# there may be many calls between methods and perhaps between sub-classes
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# and super-classes, but the user isn't interested in what happens
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# inside the package. We start by building a hash array which keeps
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# track of all the packages to which the calling package belongs. We
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# do this by examining its @ISA variable. Any call from a base class
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# method (one of our caller's @ISA packages) can be ignored
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my %isa = ($prevpack,1);
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# merge all the caller's @ISA packages into %isa.
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@isa{@{"${prevpack}::ISA"}} = ()
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if(defined @{"${prevpack}::ISA"});
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# now we crawl up the calling stack and look at all the packages in
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# there. For each package, we look to see if it has an @ISA and then
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# we see if our caller features in that list. That would imply that
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# our caller is a derived class of that package and its calls can also
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# be ignored
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while (($pack,$file,$line) = caller($i++)) {
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if(defined @{$pack . "::ISA"}) {
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my @i = @{$pack . "::ISA"};
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my %i;
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@i{@i} = ();
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# merge any relevant packages into %isa
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@isa{@i,$pack} = ()
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if(exists $i{$prevpack} || exists $isa{$pack});
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}
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# and here's where we do the ignoring... if the package in
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# question is one of our caller's base or derived packages then
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# we can ignore it (skip it) and go onto the next (but note that
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# the continue { } block below gets called every time)
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next
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if(exists $isa{$pack});
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# Hey! We've found a package that isn't one of our caller's
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# clan....but wait, $extra refers to the number of 'extra' levels
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# we should skip up. If $extra > 0 then this is a false alarm.
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# We must merge the package into the %isa hash (so we can ignore it
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# if it pops up again), decrement $extra, and continue.
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if ($extra-- > 0) {
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%isa = ($pack,1);
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@isa{@{$pack . "::ISA"}} = ()
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if(defined @{$pack . "::ISA"});
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}
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else {
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# OK! We've got a candidate package. Time to construct the
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# relevant error message and return it. die() doesn't like
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# to be given NUL characters (which $msg may contain) so we
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# remove them first.
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(my $msg = "$error at $file line $line\n") =~ tr/\0//d;
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return $msg;
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}
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}
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continue {
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$prevpack = $pack;
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}
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# uh-oh! It looks like we crawled all the way up the stack and
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# never found a candidate package. Oh well, let's call longmess
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# to generate a full stack trace. We use the magical form of 'goto'
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# so that this shortmess() function doesn't appear on the stack
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# to further confuse longmess() about it's calling package.
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goto &longmess;
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}
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# the following four functions call longmess() or shortmess() depending on
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# whether they should generate a full stack trace (confess() and cluck())
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# or simply report the caller's package (croak() and carp()), respectively.
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# confess() and croak() die, carp() and cluck() warn.
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sub croak { die shortmess @_ }
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sub confess { die longmess @_ }
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sub carp { warn shortmess @_ }
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sub cluck { warn longmess @_ }
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1;
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