[p5sagit/p5-mst-13.2.git] / lib / CGI / Carp.pm

package CGI::Carp;

=head1 NAME

B<CGI::Carp> - CGI routines for writing to the HTTPD (or other) error log

=head1 SYNOPSIS

    use CGI::Carp;

    croak "We're outta here!";
    confess "It was my fault: $!";
    carp "It was your fault!";   
    warn "I'm confused";
    die  "I'm dying.\n";

    use CGI::Carp qw(cluck);
    cluck "I wouldn't do that if I were you";

    use CGI::Carp qw(fatalsToBrowser);
    die "Fatal error messages are now sent to browser";

=head1 DESCRIPTION

CGI scripts have a nasty habit of leaving warning messages in the error
logs that are neither time stamped nor fully identified.  Tracking down
the script that caused the error is a pain.  This fixes that.  Replace
the usual

    use Carp;

with

    use CGI::Carp

And the standard warn(), die (), croak(), confess() and carp() calls
will automagically be replaced with functions that write out nicely
time-stamped messages to the HTTP server error log.

For example:

   [Fri Nov 17 21:40:43 1995] test.pl: I'm confused at test.pl line 3.
   [Fri Nov 17 21:40:43 1995] test.pl: Got an error message: Permission denied.
   [Fri Nov 17 21:40:43 1995] test.pl: I'm dying.

=head1 REDIRECTING ERROR MESSAGES

By default, error messages are sent to STDERR.  Most HTTPD servers
direct STDERR to the server's error log.  Some applications may wish
to keep private error logs, distinct from the server's error log, or
they may wish to direct error messages to STDOUT so that the browser
will receive them.

The C<carpout()> function is provided for this purpose.  Since
carpout() is not exported by default, you must import it explicitly by
saying

   use CGI::Carp qw(carpout);

The carpout() function requires one argument, which should be a
reference to an open filehandle for writing errors.  It should be
called in a C<BEGIN> block at the top of the CGI application so that
compiler errors will be caught.  Example:

   BEGIN {
     use CGI::Carp qw(carpout);
     open(LOG, ">>/usr/local/cgi-logs/mycgi-log") or
       die("Unable to open mycgi-log: $!\n");
     carpout(LOG);
   }

carpout() does not handle file locking on the log for you at this point.

The real STDERR is not closed -- it is moved to CGI::Carp::SAVEERR.  Some
servers, when dealing with CGI scripts, close their connection to the
browser when the script closes STDOUT and STDERR.  CGI::Carp::SAVEERR is there to
prevent this from happening prematurely.

You can pass filehandles to carpout() in a variety of ways.  The "correct"
way according to Tom Christiansen is to pass a reference to a filehandle 
GLOB:

    carpout(\*LOG);

This looks weird to mere mortals however, so the following syntaxes are
accepted as well:

    carpout(LOG);
    carpout(main::LOG);
    carpout(main'LOG);
    carpout(\LOG);
    carpout(\'main::LOG');

    ... and so on

FileHandle and other objects work as well.

Use of carpout() is not great for performance, so it is recommended
for debugging purposes or for moderate-use applications.  A future
version of this module may delay redirecting STDERR until one of the
CGI::Carp methods is called to prevent the performance hit.

=head1 MAKING PERL ERRORS APPEAR IN THE BROWSER WINDOW

If you want to send fatal (die, confess) errors to the browser, ask to
import the special "fatalsToBrowser" subroutine:

    use CGI::Carp qw(fatalsToBrowser);
    die "Bad error here";

Fatal errors will now be echoed to the browser as well as to the log.  CGI::Carp
arranges to send a minimal HTTP header to the browser so that even errors that
occur in the early compile phase will be seen.
Nonfatal errors will still be directed to the log file only (unless redirected
with carpout).

Note that fatalsToBrowser does B<not> work with mod_perl version 2.0
and higher.

=head2 Changing the default message

By default, the software error message is followed by a note to
contact the Webmaster by e-mail with the time and date of the error.
If this message is not to your liking, you can change it using the
set_message() routine.  This is not imported by default; you should
import it on the use() line:

    use CGI::Carp qw(fatalsToBrowser set_message);
    set_message("It's not a bug, it's a feature!");

You may also pass in a code reference in order to create a custom
error message.  At run time, your code will be called with the text
of the error message that caused the script to die.  Example:

    use CGI::Carp qw(fatalsToBrowser set_message);
    BEGIN {
       sub handle_errors {
          my $msg = shift;
          print "<h1>Oh gosh</h1>";
          print "<p>Got an error: $msg</p>";
      }
      set_message(\&handle_errors);
    }

In order to correctly intercept compile-time errors, you should call
set_message() from within a BEGIN{} block.

=head1 DOING MORE THAN PRINTING A MESSAGE IN THE EVENT OF PERL ERRORS

If fatalsToBrowser in conjunction with set_message does not provide 
you with all of the functionality you need, you can go one step 
further by specifying a function to be executed any time a script
calls "die", has a syntax error, or dies unexpectedly at runtime
with a line like "undef->explode();". 

    use CGI::Carp qw(set_die_handler);
    BEGIN {
       sub handle_errors {
          my $msg = shift;
          print "content-type: text/html\n\n";
          print "<h1>Oh gosh</h1>";
          print "<p>Got an error: $msg</p>";

          #proceed to send an email to a system administrator,
          #write a detailed message to the browser and/or a log,
          #etc....
      }
      set_die_handler(\&handle_errors);
    }

Notice that if you use set_die_handler(), you must handle sending
HTML headers to the browser yourself if you are printing a message.

If you use set_die_handler(), you will most likely interfere with 
the behavior of fatalsToBrowser, so you must use this or that, not 
both. 

Using set_die_handler() sets SIG{__DIE__} (as does fatalsToBrowser),
and there is only one SIG{__DIE__}. This means that if you are 
attempting to set SIG{__DIE__} yourself, you may interfere with 
this module's functionality, or this module may interfere with 
your module's functionality.

=head1 MAKING WARNINGS APPEAR AS HTML COMMENTS

It is now also possible to make non-fatal errors appear as HTML
comments embedded in the output of your program.  To enable this
feature, export the new "warningsToBrowser" subroutine.  Since sending
warnings to the browser before the HTTP headers have been sent would
cause an error, any warnings are stored in an internal buffer until
you call the warningsToBrowser() subroutine with a true argument:

    use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
    use CGI qw(:standard);
    print header();
    warningsToBrowser(1);

You may also give a false argument to warningsToBrowser() to prevent
warnings from being sent to the browser while you are printing some
content where HTML comments are not allowed:

    warningsToBrowser(0);    # disable warnings
    print "<script type=\"text/javascript\"><!--\n";
    print_some_javascript_code();
    print "//--></script>\n";
    warningsToBrowser(1);    # re-enable warnings

Note: In this respect warningsToBrowser() differs fundamentally from
fatalsToBrowser(), which you should never call yourself!

=head1 OVERRIDING THE NAME OF THE PROGRAM

CGI::Carp includes the name of the program that generated the error or
warning in the messages written to the log and the browser window.
Sometimes, Perl can get confused about what the actual name of the
executed program was.  In these cases, you can override the program
name that CGI::Carp will use for all messages.

The quick way to do that is to tell CGI::Carp the name of the program
in its use statement.  You can do that by adding
"name=cgi_carp_log_name" to your "use" statement.  For example:

    use CGI::Carp qw(name=cgi_carp_log_name);

.  If you want to change the program name partway through the program,
you can use the C<set_progname()> function instead.  It is not
exported by default, you must import it explicitly by saying

    use CGI::Carp qw(set_progname);

Once you've done that, you can change the logged name of the program
at any time by calling

    set_progname(new_program_name);

You can set the program back to the default by calling

    set_progname(undef);

Note that this override doesn't happen until after the program has
compiled, so any compile-time errors will still show up with the
non-overridden program name
  
=head1 CHANGE LOG

1.29 Patch from Peter Whaite to fix the unfixable problem of CGI::Carp
     not behaving correctly in an eval() context.

1.05 carpout() added and minor corrections by Marc Hedlund
     <hedlund@best.com> on 11/26/95.

1.06 fatalsToBrowser() no longer aborts for fatal errors within
     eval() statements.

1.08 set_message() added and carpout() expanded to allow for FileHandle
     objects.

1.09 set_message() now allows users to pass a code REFERENCE for 
     really custom error messages.  croak and carp are now
     exported by default.  Thanks to Gunther Birznieks for the
     patches.

1.10 Patch from Chris Dean (ctdean@cogit.com) to allow 
     module to run correctly under mod_perl.

1.11 Changed order of &gt; and &lt; escapes.

1.12 Changed die() on line 217 to CORE::die to avoid B<-w> warning.

1.13 Added cluck() to make the module orthogonal with Carp.
     More mod_perl related fixes.

1.20 Patch from Ilmari Karonen (perl@itz.pp.sci.fi):  Added
     warningsToBrowser().  Replaced <CODE> tags with <PRE> in
     fatalsToBrowser() output.

1.23 ineval() now checks both $^S and inspects the message for the "eval" pattern
     (hack alert!) in order to accommodate various combinations of Perl and
     mod_perl.

1.24 Patch from Scott Gifford (sgifford@suspectclass.com): Add support
     for overriding program name.

1.26 Replaced CORE::GLOBAL::die with the evil $SIG{__DIE__} because the
     former isn't working in some people's hands.  There is no such thing
     as reliable exception handling in Perl.

1.27 Replaced tell STDOUT with bytes=tell STDOUT.

=head1 AUTHORS

Copyright 1995-2002, Lincoln D. Stein.  All rights reserved.  

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

Address bug reports and comments to: lstein@cshl.org

=head1 SEE ALSO

Carp, CGI::Base, CGI::BasePlus, CGI::Request, CGI::MiniSvr, CGI::Form,
CGI::Response
    if (defined($CGI::Carp::PROGNAME)) 
    {
      $file = $CGI::Carp::PROGNAME;
    }

=cut

require 5.000;
use Exporter;
#use Carp;
BEGIN { 
  require Carp; 
  *CORE::GLOBAL::die = \&CGI::Carp::die;
}

use File::Spec;

@ISA = qw(Exporter);
@EXPORT = qw(confess croak carp);
@EXPORT_OK = qw(carpout fatalsToBrowser warningsToBrowser wrap set_message set_die_handler set_progname cluck ^name= die);

$main::SIG{__WARN__}=\&CGI::Carp::warn;

$CGI::Carp::VERSION     = '1.30_01';
$CGI::Carp::CUSTOM_MSG  = undef;
$CGI::Carp::DIE_HANDLER = undef;


# fancy import routine detects and handles 'errorWrap' specially.
sub import {
    my $pkg = shift;
    my(%routines);
    my(@name);
    if (@name=grep(/^name=/,@_))
      {
        my($n) = (split(/=/,$name[0]))[1];
        set_progname($n);
        @_=grep(!/^name=/,@_);
      }

    grep($routines{$_}++,@_,@EXPORT);
    $WRAP++ if $routines{'fatalsToBrowser'} || $routines{'wrap'};
    $WARN++ if $routines{'warningsToBrowser'};
    my($oldlevel) = $Exporter::ExportLevel;
    $Exporter::ExportLevel = 1;
    Exporter::import($pkg,keys %routines);
    $Exporter::ExportLevel = $oldlevel;
    $main::SIG{__DIE__} =\&CGI::Carp::die if $routines{'fatalsToBrowser'};
#    $pkg->export('CORE::GLOBAL','die');
}

# These are the originals
sub realwarn { CORE::warn(@_); }
sub realdie { CORE::die(@_); }

sub id {
    my $level = shift;
    my($pack,$file,$line,$sub) = caller($level);
    my($dev,$dirs,$id) = File::Spec->splitpath($file);
    return ($file,$line,$id);
}

sub stamp {
    my $time = scalar(localtime);
    my $frame = 0;
    my ($id,$pack,$file,$dev,$dirs);
    if (defined($CGI::Carp::PROGNAME)) {
        $id = $CGI::Carp::PROGNAME;
    } else {
        do {
  	  $id = $file;
	  ($pack,$file) = caller($frame++);
        } until !$file;
    }
    ($dev,$dirs,$id) = File::Spec->splitpath($id);
    return "[$time] $id: ";
}

sub set_progname {
    $CGI::Carp::PROGNAME = shift;
    return $CGI::Carp::PROGNAME;
}


sub warn {
    my $message = shift;
    my($file,$line,$id) = id(1);
    $message .= " at $file line $line.\n" unless $message=~/\n$/;
    _warn($message) if $WARN;
    my $stamp = stamp;
    $message=~s/^/$stamp/gm;
    realwarn $message;
}

sub _warn {
    my $msg = shift;
    if ($EMIT_WARNINGS) {
	# We need to mangle the message a bit to make it a valid HTML
	# comment.  This is done by substituting similar-looking ISO
	# 8859-1 characters for <, > and -.  This is a hack.
	$msg =~ tr/<>-/\253\273\255/;
	chomp $msg;
	print STDOUT "<!-- warning: $msg -->\n";
    } else {
	push @WARNINGS, $msg;
    }
}


# The mod_perl package Apache::Registry loads CGI programs by calling
# eval.  These evals don't count when looking at the stack backtrace.
sub _longmess {
    my $message = Carp::longmess();
    $message =~ s,eval[^\n]+(ModPerl|Apache)/(?:Registry|Dispatch)\w*\.pm.*,,s
        if exists $ENV{MOD_PERL};
    return $message;
}

sub ineval {
  (exists $ENV{MOD_PERL} ? 0 : $^S) || _longmess() =~ /eval [\{\']/m
}

sub die {
  my ($arg,@rest) = @_;

  if ($DIE_HANDLER) {
      &$DIE_HANDLER($arg,@rest);
  }

  if ( ineval() )  {
    if (!ref($arg)) {
      $arg = join("",($arg,@rest)) || "Died";
      my($file,$line,$id) = id(1);
      $arg .= " at $file line $line.\n" unless $arg=~/\n$/;
      realdie($arg);
    }
    else {
      realdie($arg,@rest);
    }
  }

  if (!ref($arg)) {
    $arg = join("", ($arg,@rest));
    my($file,$line,$id) = id(1);
    $arg .= " at $file line $line." unless $arg=~/\n$/;
    &fatalsToBrowser($arg) if $WRAP;
    if (($arg =~ /\n$/) || !exists($ENV{MOD_PERL})) {
      my $stamp = stamp;
      $arg=~s/^/$stamp/gm;
    }
    if ($arg !~ /\n$/) {
      $arg .= "\n";
    }
  }
  realdie $arg;
}

sub set_message {
    $CGI::Carp::CUSTOM_MSG = shift;
    return $CGI::Carp::CUSTOM_MSG;
}

sub set_die_handler {

    my ($handler) = shift;
    
    #setting SIG{__DIE__} here is necessary to catch runtime
    #errors which are not called by literally saying "die",
    #such as the line "undef->explode();". however, doing this
    #will interfere with fatalsToBrowser, which also sets 
    #SIG{__DIE__} in the import() function above (or the 
    #import() function above may interfere with this). for
    #this reason, you should choose to either set the die
    #handler here, or use fatalsToBrowser, not both. 
    $main::SIG{__DIE__} = $handler;
    
    $CGI::Carp::DIE_HANDLER = $handler; 
    
    return $CGI::Carp::DIE_HANDLER;
}

sub confess { CGI::Carp::die Carp::longmess @_; }
sub croak   { CGI::Carp::die Carp::shortmess @_; }
sub carp    { CGI::Carp::warn Carp::shortmess @_; }
sub cluck   { CGI::Carp::warn Carp::longmess @_; }

# We have to be ready to accept a filehandle as a reference
# or a string.
sub carpout {
    my($in) = @_;
    my($no) = fileno(to_filehandle($in));
    realdie("Invalid filehandle $in\n") unless defined $no;
    
    open(SAVEERR, ">&STDERR");
    open(STDERR, ">&$no") or 
	( print SAVEERR "Unable to redirect STDERR: $!\n" and exit(1) );
}

sub warningsToBrowser {
    $EMIT_WARNINGS = @_ ? shift : 1;
    _warn(shift @WARNINGS) while $EMIT_WARNINGS and @WARNINGS;
}

# headers
sub fatalsToBrowser {
  my($msg) = @_;
  $msg=~s/&/&amp;/g;
  $msg=~s/>/&gt;/g;
  $msg=~s/</&lt;/g;
  $msg=~s/\"/&quot;/g;
  my($wm) = $ENV{SERVER_ADMIN} ? 
    qq[the webmaster (<a href="mailto:$ENV{SERVER_ADMIN}">$ENV{SERVER_ADMIN}</a>)] :
      "this site's webmaster";
  my ($outer_message) = <<END;
For help, please send mail to $wm, giving this error message 
and the time and date of the error.
END
  ;
  my $mod_perl = exists $ENV{MOD_PERL};

  if ($CUSTOM_MSG) {
    if (ref($CUSTOM_MSG) eq 'CODE') {
      print STDOUT "Content-type: text/html\n\n" 
        unless $mod_perl;
      &$CUSTOM_MSG($msg); # nicer to perl 5.003 users
      return;
    } else {
      $outer_message = $CUSTOM_MSG;
    }
  }

  my $mess = <<END;
<h1>Software error:</h1>
<pre>$msg</pre>
<p>
$outer_message
</p>
END
  ;

  if ($mod_perl) {
    my $r;
    if ($ENV{MOD_PERL_API_VERSION} && $ENV{MOD_PERL_API_VERSION} == 2) {
      $mod_perl = 2;
      require Apache2::RequestRec;
      require Apache2::RequestIO;
      require Apache2::RequestUtil;
      require APR::Pool;
      require ModPerl::Util;
      require Apache2::Response;
      $r = Apache2::RequestUtil->request;
    }
    else {
      $r = Apache->request;
    }
    # If bytes have already been sent, then
    # we print the message out directly.
    # Otherwise we make a custom error
    # handler to produce the doc for us.
    if ($r->bytes_sent) {
      $r->print($mess);
      $mod_perl == 2 ? ModPerl::Util::exit(0) : $r->exit;
    } else {
      # MSIE won't display a custom 500 response unless it is >512 bytes!
      if ($ENV{HTTP_USER_AGENT} =~ /MSIE/) {
        $mess = "<!-- " . (' ' x 513) . " -->\n$mess";
      }
      $r->custom_response(500,$mess);
    }
  } else {
    my $bytes_written = eval{tell STDOUT};
    if (defined $bytes_written && $bytes_written > 0) {
        print STDOUT $mess;
    }
    else {
        print STDOUT "Status: 500\n";
        print STDOUT "Content-type: text/html\n\n";
        print STDOUT $mess;
    }
  }

  warningsToBrowser(1);    # emit warnings before dying
}

# Cut and paste from CGI.pm so that we don't have the overhead of
# always loading the entire CGI module.
sub to_filehandle {
    my $thingy = shift;
    return undef unless $thingy;
    return $thingy if UNIVERSAL::isa($thingy,'GLOB');
    return $thingy if UNIVERSAL::isa($thingy,'FileHandle');
    if (!ref($thingy)) {
	my $caller = 1;
	while (my $package = caller($caller++)) {
	    my($tmp) = $thingy=~/[\':]/ ? $thingy : "$package\:\:$thingy"; 
	    return $tmp if defined(fileno($tmp));
	}
    }
    return undef;
}

1;
Commit	Line	Data
54310121	1	package CGI::Carp;
	2
	3	=head1 NAME
	4
	5	B<CGI::Carp> - CGI routines for writing to the HTTPD (or other) error log
	6
	7	=head1 SYNOPSIS
	8
	9	use CGI::Carp;
	10
	11	croak "We're outta here!";
	12	confess "It was my fault: $!";
	13	carp "It was your fault!";
	14	warn "I'm confused";
	15	die "I'm dying.\n";
	16
71f3e297	17	use CGI::Carp qw(cluck);
	18	cluck "I wouldn't do that if I were you";
	19
	20	use CGI::Carp qw(fatalsToBrowser);
	21	die "Fatal error messages are now sent to browser";
	22
54310121	23	=head1 DESCRIPTION
	24
	25	CGI scripts have a nasty habit of leaving warning messages in the error
	26	logs that are neither time stamped nor fully identified. Tracking down
	27	the script that caused the error is a pain. This fixes that. Replace
	28	the usual
	29
	30	use Carp;
	31
	32	with
	33
	34	use CGI::Carp
	35
	36	And the standard warn(), die (), croak(), confess() and carp() calls
	37	will automagically be replaced with functions that write out nicely
	38	time-stamped messages to the HTTP server error log.
	39
	40	For example:
	41
	42	[Fri Nov 17 21:40:43 1995] test.pl: I'm confused at test.pl line 3.
	43	[Fri Nov 17 21:40:43 1995] test.pl: Got an error message: Permission denied.
	44	[Fri Nov 17 21:40:43 1995] test.pl: I'm dying.
	45
	46	=head1 REDIRECTING ERROR MESSAGES
	47
	48	By default, error messages are sent to STDERR. Most HTTPD servers
	49	direct STDERR to the server's error log. Some applications may wish
	50	to keep private error logs, distinct from the server's error log, or
	51	they may wish to direct error messages to STDOUT so that the browser
	52	will receive them.
	53
	54	The C<carpout()> function is provided for this purpose. Since
	55	carpout() is not exported by default, you must import it explicitly by
	56	saying
	57
	58	use CGI::Carp qw(carpout);
	59
	60	The carpout() function requires one argument, which should be a
	61	reference to an open filehandle for writing errors. It should be
	62	called in a C<BEGIN> block at the top of the CGI application so that
	63	compiler errors will be caught. Example:
	64
	65	BEGIN {
	66	use CGI::Carp qw(carpout);
	67	open(LOG, ">>/usr/local/cgi-logs/mycgi-log") or
	68	die("Unable to open mycgi-log: $!\n");
	69	carpout(LOG);
	70	}
	71
	72	carpout() does not handle file locking on the log for you at this point.
	73
ba056755	74	The real STDERR is not closed -- it is moved to CGI::Carp::SAVEERR. Some
54310121	75	servers, when dealing with CGI scripts, close their connection to the
ba056755	76	browser when the script closes STDOUT and STDERR. CGI::Carp::SAVEERR is there to
54310121	77	prevent this from happening prematurely.
	78
	79	You can pass filehandles to carpout() in a variety of ways. The "correct"
	80	way according to Tom Christiansen is to pass a reference to a filehandle
	81	GLOB:
	82
	83	carpout(\*LOG);
	84
	85	This looks weird to mere mortals however, so the following syntaxes are
	86	accepted as well:
	87
	88	carpout(LOG);
	89	carpout(main::LOG);
	90	carpout(main'LOG);
	91	carpout(\LOG);
	92	carpout(\'main::LOG');
	93
	94	... and so on
	95
424ec8fa	96	FileHandle and other objects work as well.
424ec8fa	97
54310121	98	Use of carpout() is not great for performance, so it is recommended
	99	for debugging purposes or for moderate-use applications. A future
	100	version of this module may delay redirecting STDERR until one of the
	101	CGI::Carp methods is called to prevent the performance hit.
	102
	103	=head1 MAKING PERL ERRORS APPEAR IN THE BROWSER WINDOW
	104
55b5d700	105	If you want to send fatal (die, confess) errors to the browser, ask to
54310121	106	import the special "fatalsToBrowser" subroutine:
	107
	108	use CGI::Carp qw(fatalsToBrowser);
	109	die "Bad error here";
	110
	111	Fatal errors will now be echoed to the browser as well as to the log. CGI::Carp
	112	arranges to send a minimal HTTP header to the browser so that even errors that
	113	occur in the early compile phase will be seen.
	114	Nonfatal errors will still be directed to the log file only (unless redirected
	115	with carpout).
	116
55b5d700	117	Note that fatalsToBrowser does B<not> work with mod_perl version 2.0
	118	and higher.
	119
424ec8fa	120	=head2 Changing the default message
	121
	122	By default, the software error message is followed by a note to
	123	contact the Webmaster by e-mail with the time and date of the error.
	124	If this message is not to your liking, you can change it using the
	125	set_message() routine. This is not imported by default; you should
	126	import it on the use() line:
	127
	128	use CGI::Carp qw(fatalsToBrowser set_message);
	129	set_message("It's not a bug, it's a feature!");
	130
	131	You may also pass in a code reference in order to create a custom
	132	error message. At run time, your code will be called with the text
	133	of the error message that caused the script to die. Example:
	134
	135	use CGI::Carp qw(fatalsToBrowser set_message);
	136	BEGIN {
	137	sub handle_errors {
	138	my $msg = shift;
	139	print "<h1>Oh gosh</h1>";
b2d0d414	140	print "<p>Got an error: $msg</p>";
424ec8fa	141	}
	142	set_message(\&handle_errors);
	143	}
	144
	145	In order to correctly intercept compile-time errors, you should call
	146	set_message() from within a BEGIN{} block.
	147
8869a4b7	148	=head1 DOING MORE THAN PRINTING A MESSAGE IN THE EVENT OF PERL ERRORS
	149
	150	If fatalsToBrowser in conjunction with set_message does not provide
	151	you with all of the functionality you need, you can go one step
	152	further by specifying a function to be executed any time a script
	153	calls "die", has a syntax error, or dies unexpectedly at runtime
	154	with a line like "undef->explode();".
	155
	156	use CGI::Carp qw(set_die_handler);
	157	BEGIN {
	158	sub handle_errors {
	159	my $msg = shift;
	160	print "content-type: text/html\n\n";
	161	print "<h1>Oh gosh</h1>";
	162	print "<p>Got an error: $msg</p>";
	163
	164	#proceed to send an email to a system administrator,
	165	#write a detailed message to the browser and/or a log,
	166	#etc....
	167	}
	168	set_die_handler(\&handle_errors);
	169	}
	170
	171	Notice that if you use set_die_handler(), you must handle sending
	172	HTML headers to the browser yourself if you are printing a message.
	173
	174	If you use set_die_handler(), you will most likely interfere with
	175	the behavior of fatalsToBrowser, so you must use this or that, not
	176	both.
	177
	178	Using set_die_handler() sets SIG{__DIE__} (as does fatalsToBrowser),
	179	and there is only one SIG{__DIE__}. This means that if you are
	180	attempting to set SIG{__DIE__} yourself, you may interfere with
	181	this module's functionality, or this module may interfere with
	182	your module's functionality.
	183
6b4ac661	184	=head1 MAKING WARNINGS APPEAR AS HTML COMMENTS
	185
	186	It is now also possible to make non-fatal errors appear as HTML
	187	comments embedded in the output of your program. To enable this
	188	feature, export the new "warningsToBrowser" subroutine. Since sending
	189	warnings to the browser before the HTTP headers have been sent would
	190	cause an error, any warnings are stored in an internal buffer until
	191	you call the warningsToBrowser() subroutine with a true argument:
	192
	193	use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
	194	use CGI qw(:standard);
	195	print header();
	196	warningsToBrowser(1);
	197
	198	You may also give a false argument to warningsToBrowser() to prevent
	199	warnings from being sent to the browser while you are printing some
	200	content where HTML comments are not allowed:
	201
	202	warningsToBrowser(0); # disable warnings
b2d0d414	203	print "<script type=\"text/javascript\"><!--\n";
6b4ac661	204	print_some_javascript_code();
b2d0d414	205	print "//--></script>\n";
6b4ac661	206	warningsToBrowser(1); # re-enable warnings
	207
	208	Note: In this respect warningsToBrowser() differs fundamentally from
	209	fatalsToBrowser(), which you should never call yourself!
	210
188ba755	211	=head1 OVERRIDING THE NAME OF THE PROGRAM
	212
	213	CGI::Carp includes the name of the program that generated the error or
	214	warning in the messages written to the log and the browser window.
	215	Sometimes, Perl can get confused about what the actual name of the
	216	executed program was. In these cases, you can override the program
	217	name that CGI::Carp will use for all messages.
	218
	219	The quick way to do that is to tell CGI::Carp the name of the program
	220	in its use statement. You can do that by adding
	221	"name=cgi_carp_log_name" to your "use" statement. For example:
	222
	223	use CGI::Carp qw(name=cgi_carp_log_name);
	224
	225	. If you want to change the program name partway through the program,
	226	you can use the C<set_progname()> function instead. It is not
	227	exported by default, you must import it explicitly by saying
	228
	229	use CGI::Carp qw(set_progname);
	230
	231	Once you've done that, you can change the logged name of the program
	232	at any time by calling
	233
	234	set_progname(new_program_name);
	235
	236	You can set the program back to the default by calling
	237
	238	set_progname(undef);
	239
	240	Note that this override doesn't happen until after the program has
	241	compiled, so any compile-time errors will still show up with the
	242	non-overridden program name
	243
54310121	244	=head1 CHANGE LOG
54310121	245
c29edf6c	246	1.29 Patch from Peter Whaite to fix the unfixable problem of CGI::Carp
	247	not behaving correctly in an eval() context.
	248
54310121	249	1.05 carpout() added and minor corrections by Marc Hedlund
	250	<hedlund@best.com> on 11/26/95.
	251
	252	1.06 fatalsToBrowser() no longer aborts for fatal errors within
	253	eval() statements.
	254
424ec8fa	255	1.08 set_message() added and carpout() expanded to allow for FileHandle
	256	objects.
	257
	258	1.09 set_message() now allows users to pass a code REFERENCE for
	259	really custom error messages. croak and carp are now
	260	exported by default. Thanks to Gunther Birznieks for the
	261	patches.
	262
	263	1.10 Patch from Chris Dean (ctdean@cogit.com) to allow
	264	module to run correctly under mod_perl.
	265
71f3e297	266	1.11 Changed order of > and < escapes.
	267
	268	1.12 Changed die() on line 217 to CORE::die to avoid B<-w> warning.
	269
	270	1.13 Added cluck() to make the module orthogonal with Carp.
6b4ac661	271	More mod_perl related fixes.
	272
	273	1.20 Patch from Ilmari Karonen (perl@itz.pp.sci.fi): Added
	274	warningsToBrowser(). Replaced <CODE> tags with <PRE> in
	275	fatalsToBrowser() output.
71f3e297	276
b2d0d414	277	1.23 ineval() now checks both $^S and inspects the message for the "eval" pattern
3c4b39be	278	(hack alert!) in order to accommodate various combinations of Perl and
b2d0d414	279	mod_perl.
b2d0d414	280
188ba755	281	1.24 Patch from Scott Gifford (sgifford@suspectclass.com): Add support
	282	for overriding program name.
	283
1c87da1d	284	1.26 Replaced CORE::GLOBAL::die with the evil $SIG{__DIE__} because the
	285	former isn't working in some people's hands. There is no such thing
	286	as reliable exception handling in Perl.
	287
2ed511ec	288	1.27 Replaced tell STDOUT with bytes=tell STDOUT.
2ed511ec	289
54310121	290	=head1 AUTHORS
54310121	291
b2d0d414	292	Copyright 1995-2002, Lincoln D. Stein. All rights reserved.
71f3e297	293
	294	This library is free software; you can redistribute it and/or modify
	295	it under the same terms as Perl itself.
54310121	296
71f3e297	297	Address bug reports and comments to: lstein@cshl.org
54310121	298
	299	=head1 SEE ALSO
	300
	301	Carp, CGI::Base, CGI::BasePlus, CGI::Request, CGI::MiniSvr, CGI::Form,
	302	CGI::Response
188ba755	303	if (defined($CGI::Carp::PROGNAME))
	304	{
	305	$file = $CGI::Carp::PROGNAME;
	306	}
54310121	307
	308	=cut
	309
	310	require 5.000;
	311	use Exporter;
3acbd4f5	312	#use Carp;
1c87da1d	313	BEGIN {
	314	require Carp;
	315	*CORE::GLOBAL::die = \&CGI::Carp::die;
	316	}
	317
7f16a916	318	use File::Spec;
54310121	319
	320	@ISA = qw(Exporter);
	321	@EXPORT = qw(confess croak carp);
8869a4b7	322	@EXPORT_OK = qw(carpout fatalsToBrowser warningsToBrowser wrap set_message set_die_handler set_progname cluck ^name= die);
3538e1d5	323
54310121	324	$main::SIG{__WARN__}=\&CGI::Carp::warn;
1c87da1d	325
bb8b3399	326	$CGI::Carp::VERSION = '1.30_01';
8869a4b7	327	$CGI::Carp::CUSTOM_MSG = undef;
8869a4b7	328	$CGI::Carp::DIE_HANDLER = undef;
54310121	329
1c87da1d	330
54310121	331	# fancy import routine detects and handles 'errorWrap' specially.
	332	sub import {
	333	my $pkg = shift;
	334	my(%routines);
188ba755	335	my(@name);
188ba755	336	if (@name=grep(/^name=/,@_))
	337	{
	338	my($n) = (split(/=/,$name[0]))[1];
	339	set_progname($n);
	340	@_=grep(!/^name=/,@_);
	341	}
	342
424ec8fa	343	grep($routines{$_}++,@_,@EXPORT);
424ec8fa	344	$WRAP++ if $routines{'fatalsToBrowser'} \|\| $routines{'wrap'};
6b4ac661	345	$WARN++ if $routines{'warningsToBrowser'};
54310121	346	my($oldlevel) = $Exporter::ExportLevel;
	347	$Exporter::ExportLevel = 1;
	348	Exporter::import($pkg,keys %routines);
	349	$Exporter::ExportLevel = $oldlevel;
1c87da1d	350	$main::SIG{__DIE__} =\&CGI::Carp::die if $routines{'fatalsToBrowser'};
1c87da1d	351	# $pkg->export('CORE::GLOBAL','die');
54310121	352	}
	353
	354	# These are the originals
9014bb8e	355	sub realwarn { CORE::warn(@_); }
9014bb8e	356	sub realdie { CORE::die(@_); }
54310121	357
	358	sub id {
	359	my $level = shift;
	360	my($pack,$file,$line,$sub) = caller($level);
7f16a916	361	my($dev,$dirs,$id) = File::Spec->splitpath($file);
54310121	362	return ($file,$line,$id);
	363	}
	364
	365	sub stamp {
	366	my $time = scalar(localtime);
	367	my $frame = 0;
ac734d8b	368	my ($id,$pack,$file,$dev,$dirs);
188ba755	369	if (defined($CGI::Carp::PROGNAME)) {
	370	$id = $CGI::Carp::PROGNAME;
	371	} else {
	372	do {
	373	$id = $file;
	374	($pack,$file) = caller($frame++);
	375	} until !$file;
	376	}
7f16a916	377	($dev,$dirs,$id) = File::Spec->splitpath($id);
54310121	378	return "[$time] $id: ";
	379	}
	380
188ba755	381	sub set_progname {
	382	$CGI::Carp::PROGNAME = shift;
	383	return $CGI::Carp::PROGNAME;
	384	}
	385
	386
54310121	387	sub warn {
	388	my $message = shift;
	389	my($file,$line,$id) = id(1);
	390	$message .= " at $file line $line.\n" unless $message=~/\n$/;
6b4ac661	391	_warn($message) if $WARN;
54310121	392	my $stamp = stamp;
	393	$message=~s/^/$stamp/gm;
	394	realwarn $message;
	395	}
	396
6b4ac661	397	sub _warn {
	398	my $msg = shift;
	399	if ($EMIT_WARNINGS) {
	400	# We need to mangle the message a bit to make it a valid HTML
	401	# comment. This is done by substituting similar-looking ISO
	402	# 8859-1 characters for <, > and -. This is a hack.
	403	$msg =~ tr/<>-/\253\273\255/;
	404	chomp $msg;
	405	print STDOUT "<!-- warning: $msg -->\n";
	406	} else {
	407	push @WARNINGS, $msg;
	408	}
	409	}
	410
6b4ac661	411
424ec8fa	412	# The mod_perl package Apache::Registry loads CGI programs by calling
	413	# eval. These evals don't count when looking at the stack backtrace.
	414	sub _longmess {
	415	my $message = Carp::longmess();
29ddc2a4	416	$message =~ s,eval[^\n]+(ModPerl\|Apache)/(?:Registry\|Dispatch)\w\.pm.,,s
8f3ccfa2	417	if exists $ENV{MOD_PERL};
	418	return $message;
	419	}
	420
	421	sub ineval {
	422	(exists $ENV{MOD_PERL} ? 0 : $^S) \|\| _longmess() =~ /eval [\{\']/m
424ec8fa	423	}
424ec8fa	424
54310121	425	sub die {
13548fdf	426	my ($arg,@rest) = @_;
c29edf6c	427
8869a4b7	428	if ($DIE_HANDLER) {
	429	&$DIE_HANDLER($arg,@rest);
	430	}
	431
c29edf6c	432	if ( ineval() ) {
	433	if (!ref($arg)) {
	434	$arg = join("",($arg,@rest)) \|\| "Died";
	435	my($file,$line,$id) = id(1);
	436	$arg .= " at $file line $line.\n" unless $arg=~/\n$/;
	437	realdie($arg);
	438	}
	439	else {
	440	realdie($arg,@rest);
	441	}
	442	}
13548fdf	443
8f3ccfa2	444	if (!ref($arg)) {
13548fdf	445	$arg = join("", ($arg,@rest));
8f3ccfa2	446	my($file,$line,$id) = id(1);
	447	$arg .= " at $file line $line." unless $arg=~/\n$/;
	448	&fatalsToBrowser($arg) if $WRAP;
	449	if (($arg =~ /\n$/) \|\| !exists($ENV{MOD_PERL})) {
	450	my $stamp = stamp;
	451	$arg=~s/^/$stamp/gm;
	452	}
	453	if ($arg !~ /\n$/) {
	454	$arg .= "\n";
	455	}
	456	}
	457	realdie $arg;
54310121	458	}
54310121	459
424ec8fa	460	sub set_message {
	461	$CGI::Carp::CUSTOM_MSG = shift;
	462	return $CGI::Carp::CUSTOM_MSG;
	463	}
	464
8869a4b7	465	sub set_die_handler {
	466
	467	my ($handler) = shift;
	468
	469	#setting SIG{__DIE__} here is necessary to catch runtime
	470	#errors which are not called by literally saying "die",
	471	#such as the line "undef->explode();". however, doing this
	472	#will interfere with fatalsToBrowser, which also sets
	473	#SIG{__DIE__} in the import() function above (or the
	474	#import() function above may interfere with this). for
	475	#this reason, you should choose to either set the die
	476	#handler here, or use fatalsToBrowser, not both.
	477	$main::SIG{__DIE__} = $handler;
	478
	479	$CGI::Carp::DIE_HANDLER = $handler;
	480
	481	return $CGI::Carp::DIE_HANDLER;
	482	}
	483
2371fea9	484	sub confess { CGI::Carp::die Carp::longmess @_; }
	485	sub croak { CGI::Carp::die Carp::shortmess @_; }
	486	sub carp { CGI::Carp::warn Carp::shortmess @_; }
	487	sub cluck { CGI::Carp::warn Carp::longmess @_; }
54310121	488
	489	# We have to be ready to accept a filehandle as a reference
	490	# or a string.
	491	sub carpout {
	492	my($in) = @_;
424ec8fa	493	my($no) = fileno(to_filehandle($in));
71f3e297	494	realdie("Invalid filehandle $in\n") unless defined $no;
54310121	495
	496	open(SAVEERR, ">&STDERR");
	497	open(STDERR, ">&$no") or
	498	( print SAVEERR "Unable to redirect STDERR: $!\n" and exit(1) );
	499	}
	500
6b4ac661	501	sub warningsToBrowser {
	502	$EMIT_WARNINGS = @_ ? shift : 1;
	503	_warn(shift @WARNINGS) while $EMIT_WARNINGS and @WARNINGS;
	504	}
	505
54310121	506	# headers
54310121	507	sub fatalsToBrowser {
8f3ccfa2	508	my($msg) = @_;
	509	$msg=~s/&/&/g;
	510	$msg=~s/>/>/g;
	511	$msg=~s/</</g;
	512	$msg=~s/\"/"/g;
	513	my($wm) = $ENV{SERVER_ADMIN} ?
	514	qq[the webmaster (<a href="mailto:$ENV{SERVER_ADMIN}">$ENV{SERVER_ADMIN}</a>)] :
	515	"this site's webmaster";
	516	my ($outer_message) = <<END;
424ec8fa	517	For help, please send mail to $wm, giving this error message
	518	and the time and date of the error.
	519	END
8f3ccfa2	520	;
8f3ccfa2	521	my $mod_perl = exists $ENV{MOD_PERL};
8f3ccfa2	522
8f3ccfa2	523	if ($CUSTOM_MSG) {
8f3ccfa2	524	if (ref($CUSTOM_MSG) eq 'CODE') {
0c45d622	525	print STDOUT "Content-type: text/html\n\n"
0c45d622	526	unless $mod_perl;
8f3ccfa2	527	&$CUSTOM_MSG($msg); # nicer to perl 5.003 users
	528	return;
	529	} else {
	530	$outer_message = $CUSTOM_MSG;
424ec8fa	531	}
8f3ccfa2	532	}
1c87da1d	533
8f3ccfa2	534	my $mess = <<END;
b2d0d414	535	<h1>Software error:</h1>
	536	<pre>$msg</pre>
	537	<p>
71f3e297	538	$outer_message
b2d0d414	539	</p>
54310121	540	END
8f3ccfa2	541	;
1c87da1d	542
8f3ccfa2	543	if ($mod_perl) {
741ff09d	544	my $r;
0a9bdad4	545	if ($ENV{MOD_PERL_API_VERSION} && $ENV{MOD_PERL_API_VERSION} == 2) {
8f3ccfa2	546	$mod_perl = 2;
741ff09d	547	require Apache2::RequestRec;
	548	require Apache2::RequestIO;
	549	require Apache2::RequestUtil;
8f3ccfa2	550	require APR::Pool;
8f3ccfa2	551	require ModPerl::Util;
741ff09d	552	require Apache2::Response;
	553	$r = Apache2::RequestUtil->request;
	554	}
	555	else {
	556	$r = Apache->request;
8f3ccfa2	557	}
8f3ccfa2	558	# If bytes have already been sent, then
	559	# we print the message out directly.
	560	# Otherwise we make a custom error
	561	# handler to produce the doc for us.
	562	if ($r->bytes_sent) {
	563	$r->print($mess);
	564	$mod_perl == 2 ? ModPerl::Util::exit(0) : $r->exit;
71f3e297	565	} else {
1c87da1d	566	# MSIE won't display a custom 500 response unless it is >512 bytes!
8f3ccfa2	567	if ($ENV{HTTP_USER_AGENT} =~ /MSIE/) {
1c87da1d	568	$mess = "<!-- " . (' ' x 513) . " -->\n$mess";
8f3ccfa2	569	}
1c87da1d	570	$r->custom_response(500,$mess);
71f3e297	571	}
8f3ccfa2	572	} else {
2ed511ec	573	my $bytes_written = eval{tell STDOUT};
2ed511ec	574	if (defined $bytes_written && $bytes_written > 0) {
0c45d622	575	print STDOUT $mess;
	576	}
	577	else {
bb8b3399	578	print STDOUT "Status: 500\n";
0c45d622	579	print STDOUT "Content-type: text/html\n\n";
	580	print STDOUT $mess;
	581	}
8f3ccfa2	582	}
13548fdf	583
13548fdf	584	warningsToBrowser(1); # emit warnings before dying
424ec8fa	585	}
	586
	587	# Cut and paste from CGI.pm so that we don't have the overhead of
	588	# always loading the entire CGI module.
	589	sub to_filehandle {
	590	my $thingy = shift;
	591	return undef unless $thingy;
	592	return $thingy if UNIVERSAL::isa($thingy,'GLOB');
	593	return $thingy if UNIVERSAL::isa($thingy,'FileHandle');
	594	if (!ref($thingy)) {
	595	my $caller = 1;
	596	while (my $package = caller($caller++)) {
	597	my($tmp) = $thingy=~/[\':]/ ? $thingy : "$package\:\:$thingy";
	598	return $tmp if defined(fileno($tmp));
	599	}
	600	}
	601	return undef;
54310121	602	}
	603
	604	1;