Make Carp.pm even lighter (and Carp::Heavy even heavier)

Also move carp.pm pod to carp.pod

p4raw-id: //depot/perl@24995

6 files changed, 236 insertions, 254 deletions

diff --git a/MANIFEST b/MANIFEST
index 747a1eb363..1ca6bbc7e1 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -1252,6 +1252,7 @@ lib/bytes.t			bytes.pm test
 lib/cacheout.pl			Manages output filehandles when you need too many
 lib/Carp/Heavy.pm		Error message workhorse
 lib/Carp.pm			Error message base class
+lib/Carp.pod			Documentation for Carp
 lib/Carp.t			See if Carp works
 lib/CGI/Apache.pm		Support for Apache's Perl module
 lib/CGI/Carp.pm			Log server errors with helpful context
diff --git a/lib/Carp.pm b/lib/Carp.pm
index d2854c090e..ea7cd05efc 100644
--- a/lib/Carp.pm
+++ b/lib/Carp.pm
@@ -1,196 +1,15 @@
 package Carp;
-
 our $VERSION = '1.04';
+# 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
 
-=head1 NAME
-
-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)
-
-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!";
-
-    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
-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.
-
-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 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.
-
-Alternately, you can set the global variable C<$Carp::Verbose> to true.
-See the C<GLOBAL VARIABLES> section below.
-
-=cut
-
-# This package is heavily used. Be small. Be fast. Be good.
+# $MaxEvalLen, $Verbose
+# are supposed to default to 0, but undef should be close enough
 
-# 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.
-
-# Comments added by Jos I. Boumans <kane@dwim.org> 11-Aug-2004
-# I can not get %CarpInternal or %Internal to work as advertised,
-# therefor leaving it out of the below documentation.
-# $CarpLevel may be decprecated according to the last comment, but
-# after 6 years, it's still around and in heavy use ;)
-
-=pod
-
-=head1 GLOBAL VARIABLES
-
-=head2 $Carp::CarpLevel
-
-This variable determines how many call frames are to be skipped when
-reporting where an error occurred on a call to one of C<Carp>'s
-functions. For example:
-
-    $Carp::CarpLevel = 1;
-    sub bar     { .... or _error('Wrong input') }
-    sub _error  { Carp::carp(@_) }
-
-This would make Carp report the error as coming from C<bar>'s caller,
-rather than from C<_error>'s caller, as it normally would.
-
-Defaults to C<0>.
-
-=head2 $Carp::MaxEvalLen
-
-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.
-
-Defaults to C<0>.
-
-=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.
-
-Defaults to C<64>.
-
-=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.
-
-Defaults to C<8>.
-
-=head2 $Carp::Verbose
-
-This variable makes C<Carp> use the C<longmess> function at all times.
-This effectively means that all calls to C<carp> become C<cluck> and
-all calls to C<croak> become C<confess>.
-
-Note, this is analogous to using C<use Carp 'verbose'>.
-
-Defaults to C<0>.
-
-=cut
-
-# disable these by default, so they can live w/o require Carp
-$CarpInternal{Carp}++;
-$CarpInternal{warnings}++;
-$Internal{Exporter}++;
-$Internal{'Exporter::Heavy'}++;
-$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.
-$MaxEvalLen = 0;    # How much eval '...text...' to show. 0 = all.
+$CarpLevel = 0;
 $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');
@@ -198,75 +17,19 @@ require Exporter;
 @EXPORT_OK = qw(cluck verbose longmess shortmess);
 @EXPORT_FAIL = qw(verbose);	# hook to enable verbose mode
 
-=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
-
 # 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, $error, is originally constructed from the
-# arguments passed into longmess() via confess(), cluck() or shortmess().
-# This gets appended with the stack trace messages which are generated for
-# each function call on the stack.
-
-sub longmess {
-    {
-	local($@, $!);
-	# XXX fix require to not clear $@ or $!?
-	# 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 = $CarpLevel + 1;
-      return longmess_heavy(@_);
-    }
-}
-
-
-# shortmess() is called by carp() and croak() to skip all the way up to
-# the top-level caller's package and report the error from there.  confess()
-# and cluck() generate a full stack trace so they call longmess() to
-# generate that.  In verbose mode shortmess() calls longmess() so
-# you always get a stack trace
-
-sub shortmess {	# Short-circuit &longmess if called via multiple packages
-    {
-	local($@, $!);
-	# XXX fix require to not clear $@ or $!?
-	# 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();
-    local @CARP_NOT = caller();
-    shortmess_heavy(@_);
-}
-
+sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ }
 
-# 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.
+# 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($@, $!); require Carp::Heavy} goto &longmess_jmp}
+sub shortmess_jmp {{ local($@, $!); require Carp::Heavy} goto &shortmess_jmp}
 
 sub croak   { die  shortmess @_ }
 sub confess { die  longmess  @_ }
diff --git a/lib/Carp.pod b/lib/Carp.pod
new file mode 100644
index 0000000000..f77420de77
--- /dev/null
+++ b/lib/Carp.pod
@@ -0,0 +1,156 @@
+=head1 NAME
+
+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)
+
+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!";
+
+    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
+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.
+
+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 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.
+
+Alternately, you can set the global variable C<$Carp::Verbose> to true.
+See the C<GLOBAL VARIABLES> section below.
+
+=head1 GLOBAL VARIABLES
+
+=head2 $Carp::CarpLevel
+
+This variable determines how many call frames are to be skipped when
+reporting where an error occurred on a call to one of C<Carp>'s
+functions. For example:
+
+    $Carp::CarpLevel = 1;
+    sub bar     { .... or _error('Wrong input') }
+    sub _error  { Carp::carp(@_) }
+
+This would make Carp report the error as coming from C<bar>'s caller,
+rather than from C<_error>'s caller, as it normally would.
+
+Defaults to C<0>.
+
+=head2 $Carp::MaxEvalLen
+
+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.
+
+Defaults to C<0>.
+
+=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.
+
+Defaults to C<64>.
+
+=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.
+
+Defaults to C<8>.
+
+=head2 $Carp::Verbose
+
+This variable makes C<Carp> use the C<longmess> function at all times.
+This effectively means that all calls to C<carp> become C<cluck> and
+all calls to C<croak> become C<confess>.
+
+Note, this is analogous to using C<use Carp 'verbose'>.
+
+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.
+
diff --git a/lib/Carp/Heavy.pm b/lib/Carp/Heavy.pm
index fe7fec4585..0180dcfda4 100644
--- a/lib/Carp/Heavy.pm
+++ b/lib/Carp/Heavy.pm
@@ -7,13 +7,73 @@ Carp::Heavy - heavy machinery, no user serviceable parts inside
 
 =cut
 
-# use strict; # not yet
-
 # On one line so MakeMaker will see it.
 use Carp;  our $VERSION = $Carp::VERSION;
+# use strict; # not yet
+
+# 'use Carp' just installs some very lightweight stubs; the first time
+# these are called, they require Carp::Heavy which installs the real
+# routines.
+
+# 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.
+
+# Comments added by Jos I. Boumans <kane@dwim.org> 11-Aug-2004
+# I can not get %CarpInternal or %Internal to work as advertised,
+# therefore leaving it out of the below documentation.
+# $CarpLevel may be decprecated according to the last comment, but
+# after 6 years, it's still around and in heavy use ;)
+
+# disable these by default, so they can live w/o require Carp
+$CarpInternal{Carp}++;
+$CarpInternal{warnings}++;
+$Internal{Exporter}++;
+$Internal{'Exporter::Heavy'}++;
+
 
 our ($CarpLevel, $MaxArgNums, $MaxEvalLen, $MaxArgLen, $Verbose);
 
+# XXX longmess_real and shortmess_real should really be merged into
+# XXX {long|sort}mess_heavy at some point
+
+sub  longmess_real {
+    # 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(@_);
+    }
+};
+
+sub shortmess_real {
+    # Icky backwards compatibility wrapper. :-(
+    my $call_pack = caller();
+    local @CARP_NOT = caller();
+    shortmess_heavy(@_);
+};
+
+# replace the two hooks added by Carp
+
+# aliasing the whole glob rather than just the CV slot avoids 'redefined'
+# warnings, even in the presence of perl -W (as used by lib/warnings.t !)
+
+*longmess_jmp  = *longmess_real;
+*shortmess_jmp = *shortmess_real;
+
+
 sub caller_info {
   my $i = shift(@_) + 1;
   package DB;
@@ -171,6 +231,7 @@ sub short_error_loc {
   {
     my $called = caller($i++);
     my $caller = caller($i);
+
     return 0 unless defined($caller); # What happened?
     redo if $Internal{$caller};
     redo if $CarpInternal{$called};
@@ -181,6 +242,7 @@ sub short_error_loc {
   return $i - 1;
 }
 
+
 sub shortmess_heavy {
   return longmess_heavy(@_) if $Verbose;
   return @_ if ref($_[0]); # don't break references as exceptions
diff --git a/lib/warnings.pm b/lib/warnings.pm
index 5fe108d83e..85ce3de747 100644
--- a/lib/warnings.pm
+++ b/lib/warnings.pm
@@ -295,7 +295,7 @@ $All = "" ; vec($All, $Offsets{'all'}, 2) = 3 ;
 
 sub Croaker
 {
-    require Carp;
+    require Carp::Heavy; # this initializes %CarpInternal
     delete $Carp::CarpInternal{'warnings'};
     Carp::croak(@_);
 }
diff --git a/warnings.pl b/warnings.pl
index 94b983904d..1f14fde86c 100644
--- a/warnings.pl
+++ b/warnings.pl
@@ -609,7 +609,7 @@ $All = "" ; vec($All, $Offsets{'all'}, 2) = 3 ;
 
 sub Croaker
 {
-    require Carp;
+    require Carp::Heavy; # this initializes %CarpInternal
     delete $Carp::CarpInternal{'warnings'};
     Carp::croak(@_);
 }