/usr/share/perl5/Sub/Uplevel.pm is in libsub-uplevel-perl 0.2200-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 | package Sub::Uplevel;
use 5.006;
use strict;
our $VERSION = '0.22';
$VERSION = eval $VERSION;
# We must override *CORE::GLOBAL::caller if it hasn't already been
# overridden or else Perl won't see our local override later.
if ( not defined *CORE::GLOBAL::caller{CODE} ) {
*CORE::GLOBAL::caller = \&_normal_caller;
}
# modules to force reload if ":aggressive" is specified
my @reload_list = qw/Exporter Exporter::Heavy/;
sub import {
no strict 'refs';
my ($class, @args) = @_;
for my $tag ( @args, 'uplevel' ) {
if ( $tag eq 'uplevel' ) {
my $caller = caller(0);
*{"$caller\::uplevel"} = \&uplevel;
}
elsif( $tag eq ':aggressive' ) {
_force_reload( @reload_list );
}
else {
die qq{"$tag" is not exported by the $class module\n}
}
}
return;
}
sub _force_reload {
no warnings 'redefine';
local $^W = 0;
for my $m ( @_ ) {
$m =~ s{::}{/}g;
$m .= ".pm";
require $m if delete $INC{$m};
}
}
=head1 NAME
Sub::Uplevel - apparently run a function in a higher stack frame
=begin wikidoc
= VERSION
This documentation describes version %%VERSION%%
=end wikidoc
=head1 SYNOPSIS
use Sub::Uplevel;
sub foo {
print join " - ", caller;
}
sub bar {
uplevel 1, \&foo;
}
#line 11
bar(); # main - foo.plx - 11
=head1 DESCRIPTION
Like Tcl's uplevel() function, but not quite so dangerous. The idea
is just to fool caller(). All the really naughty bits of Tcl's
uplevel() are avoided.
B<THIS IS NOT THE SORT OF THING YOU WANT TO DO EVERYDAY>
=over 4
=item B<uplevel>
uplevel $num_frames, \&func, @args;
Makes the given function think it's being executed $num_frames higher
than the current stack level. So when they use caller($frames) it
will actually give caller($frames + $num_frames) for them.
C<uplevel(1, \&some_func, @_)> is effectively C<goto &some_func> but
you don't immediately exit the current subroutine. So while you can't
do this:
sub wrapper {
print "Before\n";
goto &some_func;
print "After\n";
}
you can do this:
sub wrapper {
print "Before\n";
my @out = uplevel 1, &some_func;
print "After\n";
return @out;
}
C<uplevel> will issue a warning if C<$num_frames> is more than the current call
stack depth.
=cut
# @Up_Frames -- uplevel stack
# $Caller_Proxy -- whatever caller() override was in effect before uplevel
our (@Up_Frames, $Caller_Proxy);
sub _apparent_stack_height {
my $height = 1; # start above this function
while ( 1 ) {
last if ! defined scalar $Caller_Proxy->($height);
$height++;
}
return $height - 1; # subtract 1 for this function
}
sub uplevel {
my($num_frames, $func, @args) = @_;
# backwards compatible version of "no warnings 'redefine'"
my $old_W = $^W;
$^W = 0;
# Update the caller proxy if the uplevel override isn't in effect
local $Caller_Proxy = *CORE::GLOBAL::caller{CODE}
if *CORE::GLOBAL::caller{CODE} != \&_uplevel_caller;
local *CORE::GLOBAL::caller = \&_uplevel_caller;
# restore old warnings state
$^W = $old_W;
if ( $num_frames >= _apparent_stack_height() ) {
require Carp;
Carp::carp("uplevel $num_frames is more than the caller stack");
}
local @Up_Frames = ($num_frames, @Up_Frames );
return $func->(@args);
}
sub _normal_caller (;$) { ## no critic Prototypes
my $height = $_[0];
$height++;
if ( CORE::caller() eq 'DB' ) {
# passthrough the @DB::args trick
package DB;
if( wantarray and !@_ ) {
return (CORE::caller($height))[0..2];
}
else {
return CORE::caller($height);
}
}
else {
if( wantarray and !@_ ) {
return (CORE::caller($height))[0..2];
}
else {
return CORE::caller($height);
}
}
}
sub _uplevel_caller (;$) { ## no critic Prototypes
my $height = $_[0] || 0;
# shortcut if no uplevels have been called
# always add +1 to CORE::caller (proxy caller function)
# to skip this function's caller
return $Caller_Proxy->( $height + 1 ) if ! @Up_Frames;
=begin _private
So it has to work like this:
Call stack Actual uplevel 1
CORE::GLOBAL::caller
Carp::short_error_loc 0
Carp::shortmess_heavy 1 0
Carp::croak 2 1
try_croak 3 2
uplevel 4
function_that_called_uplevel 5
caller_we_want_to_see 6 3
its_caller 7 4
So when caller(X) winds up below uplevel(), it only has to use
CORE::caller(X+1) (to skip CORE::GLOBAL::caller). But when caller(X)
winds up no or above uplevel(), it's CORE::caller(X+1+uplevel+1).
Which means I'm probably going to have to do something nasty like walk
up the call stack on each caller() to see if I'm going to wind up
before or after Sub::Uplevel::uplevel().
=end _private
=begin _dagolden
I found the description above a bit confusing. Instead, this is the logic
that I found clearer when CORE::GLOBAL::caller is invoked and we have to
walk up the call stack:
* if searching up to the requested height in the real call stack doesn't find
a call to uplevel, then we can return the result at that height in the
call stack
* if we find a call to uplevel, we need to keep searching upwards beyond the
requested height at least by the amount of upleveling requested for that
call to uplevel (from the Up_Frames stack set during the uplevel call)
* additionally, we need to hide the uplevel subroutine call, too, so we search
upwards one more level for each call to uplevel
* when we've reached the top of the search, we want to return that frame
in the call stack, i.e. the requested height plus any uplevel adjustments
found during the search
=end _dagolden
=cut
my $saw_uplevel = 0;
my $adjust = 0;
# walk up the call stack to fight the right package level to return;
# look one higher than requested for each call to uplevel found
# and adjust by the amount found in the Up_Frames stack for that call.
# We *must* use CORE::caller here since we need the real stack not what
# some other override says the stack looks like, just in case that other
# override breaks things in some horrible way
for ( my $up = 0; $up <= $height + $adjust; $up++ ) {
my @caller = CORE::caller($up + 1);
if( defined $caller[0] && $caller[0] eq __PACKAGE__ ) {
# add one for each uplevel call seen
# and look into the uplevel stack for the offset
$adjust += 1 + $Up_Frames[$saw_uplevel];
$saw_uplevel++;
}
}
# For returning values, we pass through the call to the proxy caller
# function, just at a higher stack level
my @caller;
if ( CORE::caller() eq 'DB' ) {
# passthrough the @DB::args trick
package DB;
@caller = $Sub::Uplevel::Caller_Proxy->($height + $adjust + 1);
}
else {
@caller = $Caller_Proxy->($height + $adjust + 1);
}
if( wantarray ) {
if( !@_ ) {
@caller = @caller[0..2];
}
return @caller;
}
else {
return $caller[0];
}
}
=back
=head1 EXAMPLE
The main reason I wrote this module is so I could write wrappers
around functions and they wouldn't be aware they've been wrapped.
use Sub::Uplevel;
my $original_foo = \&foo;
*foo = sub {
my @output = uplevel 1, $original_foo;
print "foo() returned: @output";
return @output;
};
If this code frightens you B<you should not use this module.>
=head1 BUGS and CAVEATS
Well, the bad news is uplevel() is about 5 times slower than a normal
function call. XS implementation anyone? It also slows down every invocation
of caller(), regardless of whether uplevel() is in effect.
Sub::Uplevel overrides CORE::GLOBAL::caller temporarily for the scope of
each uplevel call. It does its best to work with any previously existing
CORE::GLOBAL::caller (both when Sub::Uplevel is first loaded and within
each uplevel call) such as from Contextual::Return or Hook::LexWrap.
However, if you are routinely using multiple modules that override
CORE::GLOBAL::caller, you are probably asking for trouble.
You B<should> load Sub::Uplevel as early as possible within your program. As
with all CORE::GLOBAL overloading, the overload will not affect modules that
have already been compiled prior to the overload. One module that often is
unavoidably loaded prior to Sub::Uplevel is Exporter. To forceably recompile
Exporter (and Exporter::Heavy) after loading Sub::Uplevel, use it with the
":aggressive" tag:
use Sub::Uplevel qw/:aggressive/;
The private function C<Sub::Uplevel::_force_reload()> may be passed a list of
additional modules to reload if ":aggressive" is not aggressive enough.
Reloading modules may break things, so only use this as a last resort.
As of version 0.20, Sub::Uplevel requires Perl 5.6 or greater.
=head1 HISTORY
Those who do not learn from HISTORY are doomed to repeat it.
The lesson here is simple: Don't sit next to a Tcl programmer at the
dinner table.
=head1 THANKS
Thanks to Brent Welch, Damian Conway and Robin Houston.
=head1 AUTHORS
David A Golden E<lt>dagolden@cpan.orgE<gt> (current maintainer)
Michael G Schwern E<lt>schwern@pobox.comE<gt> (original author)
=head1 LICENSE
Original code Copyright (c) 2001 to 2007 by Michael G Schwern.
Additional code Copyright (c) 2006 to 2008 by David A Golden.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html
=head1 SEE ALSO
PadWalker (for the similar idea with lexicals), Hook::LexWrap,
Tcl's uplevel() at http://www.scriptics.com/man/tcl8.4/TclCmd/uplevel.htm
=cut
1;
|