Carp was mostly unusable with Safe because it may require

[perl5.git] / lib / Carp.pm

diff --git a/lib/Carp.pm b/lib/Carp.pm
index 1a1b79e..b09efd4 100644 (file)
--- a/lib/Carp.pm
+++ b/lib/Carp.pm
@@ -1,129 +1,206 @@
 package Carp;
 
 package Carp;
 

+our $VERSION = '1.02';
+

 =head1 NAME
 
 =head1 NAME
 

-carp - warn of errors (from perspective of caller)
+carp    - warn 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)
+croak   - die of errors (from perspective of caller)

 
 confess - die of errors with stack backtrace
 
 
 confess - die of errors with stack backtrace
 

+shortmess - return the message that carp and croak produce
+
+longmess - return the message that cluck and confess produce
+

 =head1 SYNOPSIS
 
     use Carp;
     croak "We're outta here!";
 
 =head1 SYNOPSIS
 
     use Carp;
     croak "We're outta here!";
 

+    use Carp qw(cluck);
+    cluck "This is how we got here!";
+
+    print FH Carp::shortmess("This will have caller's details added");
+    print FH Carp::longmess("This will have stack backtrace added");
+

 =head1 DESCRIPTION
 
 The Carp routines are useful in your own modules because
 =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 carp,
+croak or shortmess 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.
+
+Here is a more complete description of how shortmess works.  What
+it does is search the call-stack for a function call stack where
+it hasn't been told that there shouldn't be an error.  If every
+call is marked safe, it then gives up and gives a full stack
+backtrace instead.  In other words it presumes that the first likely
+looking potential suspect is guilty.  Its 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 @CARP_NOT, or
+(if that array is empty) @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 @ISA
+with @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 Carp is safe.  (This rule is what keeps it from
+reporting the error where you call carp/croak/shortmess.)
+
+=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<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-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.
+
+=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.

 
 =cut
 
 
 =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 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
+# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
+# text and function arguments should be formatted when printed.
+
+$CarpInternal{Carp}++;
+$CarpInternal{warnings}++;

 $CarpLevel = 0;                # How many extra package levels to skip on carp.
 $CarpLevel = 0;                # How many extra package levels to skip on carp.

+                        # How many calls to skip on confess.
+                        # Reconciling these notions is hard, use
+                        # %Internal and %CarpInternal instead.

 $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.
 $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;
 
 require Exporter;

-@ISA = Exporter;
+@ISA = ('Exporter');

 @EXPORT = qw(confess croak carp);
 @EXPORT = qw(confess croak carp);

+@EXPORT_OK = qw(cluck verbose longmess shortmess);
+@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 {
 
 sub longmess {

-    my $error = shift;
-    my $mess = "";
-    my $i = 1 + $CarpLevel;
-    my ($pack,$file,$line,$sub,$hargs,$eval,$require);
-    my (@a);
-    while (do { { package DB; @a = caller($i++) } } ) {
-      ($pack,$file,$line,$sub,$hargs,undef,$eval,$require) = @a;
-       if ($error =~ m/\n$/) {
-           $mess .= $error;
-       } else {
-           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)') {
-               $sub = 'eval {...}';
-           }
-           if ($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) . ')';
-           }
-           $mess .= "\t$sub " if $error eq "called";
-           $mess .= "$error at $file line $line\n";
-       }
-       $error = "called";
+    {
+       local $@;
+       # XXX fix require to not clear $@?
+       # don't use require unless we need to (for Safe compartments)
+       require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
+    }
+    # Icky backwards compatibility wrapper. :-(
+    my $call_pack = caller();
+    if ($Internal{$call_pack} or $CarpInternal{$call_pack}) {
+      return longmess_heavy(@_);
+    }
+    else {
+      local $CarpLevel = $CarpLevel + 1;
+      return longmess_heavy(@_);

     }
     }

-    $mess || $error;

 }
 
 }
 

+
+# 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
 sub shortmess {        # Short-circuit &longmess if called via multiple packages

-    my $error = $_[0]; # Instead of "shift"
-    my ($prevpack) = caller(1);
-    my $extra = $CarpLevel;
-    my $i = 2;
-    my ($pack,$file,$line);
-    my %isa = ($prevpack,1);
-
-    @isa{@{"${prevpack}::ISA"}} = ()
-       if(defined @{"${prevpack}::ISA"});
-
-    while (($pack,$file,$line) = caller($i++)) {
-       if(defined @{$pack . "::ISA"}) {
-           my @i = @{$pack . "::ISA"};
-           my %i;
-           @i{@i} = ();
-           @isa{@i,$pack} = ()
-               if(exists $i{$prevpack} || exists $isa{$pack});
-       }
-
-       next
-           if(exists $isa{$pack});
-
-       if ($extra-- > 0) {
-           %isa = ($pack,1);
-           @isa{@{$pack . "::ISA"}} = ()
-               if(defined @{$pack . "::ISA"});
-       }
-       else {
-           return "$error at $file line $line\n";
-       }
-    }
-    continue {
-       $prevpack = $pack;
+    {
+       local $@;
+       # XXX fix require to not clear $@?
+       # don't use require unless we need to (for Safe compartments)
+       require Carp::Heavy unless $INC{"Carp/Heavy.pm"};

     }
     }

-
-    goto &longmess;
+    # Icky backwards compatibility wrapper. :-(
+    my $call_pack = caller();
+    local @CARP_NOT = caller();
+    shortmess_heavy(@_);

 }
 
 }
 

-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;
 
 1;