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1package DynaLoader;
2
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3# And Gandalf said: 'Many folk like to know beforehand what is to
4# be set on the table; but those who have laboured to prepare the
5# feast like to keep their secret; for wonder makes the words of
6# praise louder.'
7
8# (Quote from Tolkien sugested by Anno Siegel.)
9#
10# See pod text at end of file for documentation.
11# See also ext/DynaLoader/README in source tree for other information.
12#
13# Tim.Bunce@ig.co.uk, August 1994
14
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15use vars qw($VERSION @ISA) ;
16
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17require Carp;
18require Config;
19require AutoLoader;
20
21@ISA=qw(AutoLoader);
22
73c78b0a 23$VERSION = "1.00" ;
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24
25sub import { } # override import inherited from AutoLoader
26
27# enable debug/trace messages from DynaLoader perl code
28$dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
29
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30($dl_dlext, $dlsrc)
31 = @Config::Config{'dlext', 'dlsrc'};
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32
33# Some systems need special handling to expand file specifications
34# (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
35# See dl_expandspec() for more details. Should be harmless but
36# inefficient to define on systems that don't need it.
d404d5bf 37$do_expand = $Is_VMS = $^O eq 'VMS';
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38
39@dl_require_symbols = (); # names of symbols we need
40@dl_resolve_using = (); # names of files to link with
41@dl_library_path = (); # path to look for files
42
43# This is a fix to support DLD's unfortunate desire to relink -lc
44@dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
45
46# Initialise @dl_library_path with the 'standard' library path
47# for this platform as determined by Configure
48push(@dl_library_path, split(' ',$Config::Config{'libpth'}));
49
50# Add to @dl_library_path any extra directories we can gather from
51# environment variables. So far LD_LIBRARY_PATH is the only known
52# variable used for this purpose. Others may be added later.
53push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
54 if $ENV{LD_LIBRARY_PATH};
55
56
57# No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
54d6a3b3 58boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader);
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59
60
61if ($dl_debug) {
62 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
63 print STDERR "DynaLoader not linked into this perl\n"
64 unless defined(&boot_DynaLoader);
65}
66
671; # End of main code
68
69
70# The bootstrap function cannot be autoloaded (without complications)
71# so we define it here:
72
73sub bootstrap {
74 # use local vars to enable $module.bs script to edit values
75 local(@args) = @_;
76 local($module) = $args[0];
77 local(@dirs, $file);
78
4633a7c4 79 Carp::confess("Usage: DynaLoader::bootstrap(module)") unless $module;
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80
81 # A common error on platforms which don't support dynamic loading.
82 # Since it's fatal and potentially confusing we give a detailed message.
83 Carp::croak("Can't load module $module, dynamic loading not available in this perl.\n".
84 " (You may need to build a new perl executable which either supports\n".
85 " dynamic loading or has the $module module statically linked into it.)\n")
86 unless defined(&dl_load_file);
87
88 my @modparts = split(/::/,$module);
89 my $modfname = $modparts[-1];
90
91 # Some systems have restrictions on files names for DLL's etc.
92 # mod2fname returns appropriate file base name (typically truncated)
93 # It may also edit @modparts if required.
94 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
95
96 my $modpname = join('/',@modparts);
97
98 print STDERR "DynaLoader::bootstrap for $module ",
99 "(auto/$modpname/$modfname.$dl_dlext)\n" if $dl_debug;
100
101 foreach (@INC) {
54d6a3b3 102 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
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103 my $dir = "$_/auto/$modpname";
104 next unless -d $dir; # skip over uninteresting directories
105
106 # check for common cases to avoid autoload of dl_findfile
107 last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
108
109 # no luck here, save dir for possible later dl_findfile search
110 push(@dirs, "-L$dir");
111 }
112 # last resort, let dl_findfile have a go in all known locations
113 $file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
114
4633a7c4 115 Carp::croak("Can't find loadable object for module $module in \@INC (@INC)")
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116 unless $file;
117
118 my $bootname = "boot_$module";
119 $bootname =~ s/\W/_/g;
120 @dl_require_symbols = ($bootname);
121
122 # Execute optional '.bootstrap' perl script for this module.
123 # The .bs file can be used to configure @dl_resolve_using etc to
124 # match the needs of the individual module on this architecture.
125 my $bs = $file;
126 $bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
127 if (-s $bs) { # only read file if it's not empty
d404d5bf 128 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
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129 eval { do $bs; };
130 warn "$bs: $@\n" if $@;
131 }
132
133 # Many dynamic extension loading problems will appear to come from
134 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
135 # Often these errors are actually occurring in the initialisation
136 # C code of the extension XS file. Perl reports the error as being
137 # in this perl code simply because this was the last perl code
138 # it executed.
139
140 my $libref = dl_load_file($file) or
4633a7c4 141 Carp::croak("Can't load '$file' for module $module: ".dl_error()."\n");
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142
143 my @unresolved = dl_undef_symbols();
4633a7c4 144 Carp::carp("Undefined symbols present after loading $file: @unresolved\n")
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145 if @unresolved;
146
147 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
4633a7c4 148 Carp::croak("Can't find '$bootname' symbol in $file\n");
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149
150 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
151
152 # See comment block above
153 &$xs(@args);
154}
155
156
157sub _check_file { # private utility to handle dl_expandspec vs -f tests
158 my($file) = @_;
159 return $file if (!$do_expand && -f $file); # the common case
160 return $file if ( $do_expand && ($file=dl_expandspec($file)));
161 return undef;
162}
163
164
165# Let autosplit and the autoloader deal with these functions:
166__END__
167
168
169sub dl_findfile {
170 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
171 # This function does not automatically consider the architecture
172 # or the perl library auto directories.
173 my (@args) = @_;
174 my (@dirs, $dir); # which directories to search
175 my (@found); # full paths to real files we have found
d404d5bf 176 my $dl_ext= $Config::Config{'dlext'}; # suffix for perl extensions
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177 my $dl_so = $Config::Config{'so'}; # suffix for shared libraries
178
179 print STDERR "dl_findfile(@args)\n" if $dl_debug;
180
181 # accumulate directories but process files as they appear
182 arg: foreach(@args) {
183 # Special fast case: full filepath requires no search
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184 if ($Is_VMS && m%[:>/\]]% && -f $_) {
185 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
186 last arg unless wantarray;
187 next;
188 }
189 elsif (m:/: && -f $_ && !$do_expand) {
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190 push(@found,$_);
191 last arg unless wantarray;
192 next;
193 }
194
195 # Deal with directories first:
196 # Using a -L prefix is the preferred option (faster and more robust)
197 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
198
199 # Otherwise we try to try to spot directories by a heuristic
200 # (this is a more complicated issue than it first appears)
201 if (m:/: && -d $_) { push(@dirs, $_); next; }
202
203 # VMS: we may be using native VMS directry syntax instead of
204 # Unix emulation, so check this as well
54d6a3b3 205 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
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206
207 # Only files should get this far...
208 my(@names, $name); # what filenames to look for
209 if (m:-l: ) { # convert -lname to appropriate library name
210 s/-l//;
211 push(@names,"lib$_.$dl_so");
212 push(@names,"lib$_.a");
213 } else { # Umm, a bare name. Try various alternatives:
214 # these should be ordered with the most likely first
d404d5bf 215 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
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216 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
217 push(@names,"lib$_.$dl_so") unless m:/:;
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218 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
219 push(@names, $_);
220 }
221 foreach $dir (@dirs, @dl_library_path) {
222 next unless -d $dir;
54d6a3b3 223 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
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224 foreach $name (@names) {
225 my($file) = "$dir/$name";
226 print STDERR " checking in $dir for $name\n" if $dl_debug;
227 $file = _check_file($file);
228 if ($file) {
229 push(@found, $file);
230 next arg; # no need to look any further
231 }
232 }
233 }
234 }
235 if ($dl_debug) {
236 foreach(@dirs) {
237 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
238 }
239 print STDERR "dl_findfile found: @found\n";
240 }
241 return $found[0] unless wantarray;
242 @found;
243}
244
245
246sub dl_expandspec {
247 my($spec) = @_;
248 # Optional function invoked if DynaLoader.pm sets $do_expand.
249 # Most systems do not require or use this function.
250 # Some systems may implement it in the dl_*.xs file in which case
251 # this autoload version will not be called but is harmless.
252
253 # This function is designed to deal with systems which treat some
254 # 'filenames' in a special way. For example VMS 'Logical Names'
255 # (something like unix environment variables - but different).
256 # This function should recognise such names and expand them into
257 # full file paths.
258 # Must return undef if $spec is invalid or file does not exist.
259
260 my $file = $spec; # default output to input
261
d404d5bf 262 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
4633a7c4 263 Carp::croak("dl_expandspec: should be defined in XS file!\n");
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264 } else {
265 return undef unless -f $file;
266 }
267 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
268 $file;
269}
270
271
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272=head1 NAME
273
274DynaLoader - Dynamically load C libraries into Perl code
275
1fef88e7 276dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_undef_symbols(), dl_install_xsub(), bootstrap() - routines used by DynaLoader modules
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277
278=head1 SYNOPSIS
279
8e07c86e 280 package YourPackage;
3b35bae3 281 require DynaLoader;
c2960299 282 @ISA = qw(... DynaLoader ...);
8e07c86e 283 bootstrap YourPackage;
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284
285
286=head1 DESCRIPTION
287
c2960299 288This document defines a standard generic interface to the dynamic
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289linking mechanisms available on many platforms. Its primary purpose is
290to implement automatic dynamic loading of Perl modules.
291
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292This document serves as both a specification for anyone wishing to
293implement the DynaLoader for a new platform and as a guide for
294anyone wishing to use the DynaLoader directly in an application.
295
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296The DynaLoader is designed to be a very simple high-level
297interface that is sufficiently general to cover the requirements
298of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
299
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300It is also hoped that the interface will cover the needs of OS/2, NT
301etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
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302
303It must be stressed that the DynaLoader, by itself, is practically
304useless for accessing non-Perl libraries because it provides almost no
305Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
306library function or supplying arguments. It is anticipated that any
307glue that may be developed in the future will be implemented in a
308separate dynamically loaded module.
309
310DynaLoader Interface Summary
311
312 @dl_library_path
313 @dl_resolve_using
314 @dl_require_symbols
315 $dl_debug
316 Implemented in:
317 bootstrap($modulename) Perl
318 @filepaths = dl_findfile(@names) Perl
319
320 $libref = dl_load_file($filename) C
321 $symref = dl_find_symbol($libref, $symbol) C
322 @symbols = dl_undef_symbols() C
323 dl_install_xsub($name, $symref [, $filename]) C
324 $message = dl_error C
325
326=over 4
327
328=item @dl_library_path
329
330The standard/default list of directories in which dl_findfile() will
331search for libraries etc. Directories are searched in order:
332$dl_library_path[0], [1], ... etc
333
334@dl_library_path is initialised to hold the list of 'normal' directories
335(F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
336ensure portability across a wide range of platforms.
337
338@dl_library_path should also be initialised with any other directories
339that can be determined from the environment at runtime (such as
340LD_LIBRARY_PATH for SunOS).
341
342After initialisation @dl_library_path can be manipulated by an
343application using push and unshift before calling dl_findfile().
344Unshift can be used to add directories to the front of the search order
345either to save search time or to override libraries with the same name
346in the 'normal' directories.
347
348The load function that dl_load_file() calls may require an absolute
349pathname. The dl_findfile() function and @dl_library_path can be
350used to search for and return the absolute pathname for the
351library/object that you wish to load.
352
353=item @dl_resolve_using
354
355A list of additional libraries or other shared objects which can be
356used to resolve any undefined symbols that might be generated by a
357later call to load_file().
358
359This is only required on some platforms which do not handle dependent
360libraries automatically. For example the Socket Perl extension library
361(F<auto/Socket/Socket.so>) contains references to many socket functions
362which need to be resolved when it's loaded. Most platforms will
363automatically know where to find the 'dependent' library (e.g.,
364F</usr/lib/libsocket.so>). A few platforms need to to be told the location
365of the dependent library explicitly. Use @dl_resolve_using for this.
366
367Example usage:
368
369 @dl_resolve_using = dl_findfile('-lsocket');
370
371=item @dl_require_symbols
372
373A list of one or more symbol names that are in the library/object file
374to be dynamically loaded. This is only required on some platforms.
375
376=item dl_error()
377
378Syntax:
379
380 $message = dl_error();
381
382Error message text from the last failed DynaLoader function. Note
383that, similar to errno in unix, a successful function call does not
384reset this message.
385
386Implementations should detect the error as soon as it occurs in any of
387the other functions and save the corresponding message for later
388retrieval. This will avoid problems on some platforms (such as SunOS)
389where the error message is very temporary (e.g., dlerror()).
390
391=item $dl_debug
392
393Internal debugging messages are enabled when $dl_debug is set true.
394Currently setting $dl_debug only affects the Perl side of the
395DynaLoader. These messages should help an application developer to
396resolve any DynaLoader usage problems.
397
398$dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
399
400For the DynaLoader developer/porter there is a similar debugging
401variable added to the C code (see dlutils.c) and enabled if Perl was
402built with the B<-DDEBUGGING> flag. This can also be set via the
403PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
404higher for more.
405
406=item dl_findfile()
407
408Syntax:
409
410 @filepaths = dl_findfile(@names)
411
412Determine the full paths (including file suffix) of one or more
413loadable files given their generic names and optionally one or more
414directories. Searches directories in @dl_library_path by default and
415returns an empty list if no files were found.
416
417Names can be specified in a variety of platform independent forms. Any
418names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
419an appropriate suffix for the platform.
420
421If a name does not already have a suitable prefix and/or suffix then
422the corresponding file will be searched for by trying combinations of
423prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
424and "$name".
425
426If any directories are included in @names they are searched before
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427@dl_library_path. Directories may be specified as B<-Ldir>. Any other
428names are treated as filenames to be searched for.
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429
430Using arguments of the form C<-Ldir> and C<-lname> is recommended.
431
432Example:
433
434 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
435
436
437=item dl_expandspec()
438
439Syntax:
440
441 $filepath = dl_expandspec($spec)
442
443Some unusual systems, such as VMS, require special filename handling in
444order to deal with symbolic names for files (i.e., VMS's Logical Names).
445
446To support these systems a dl_expandspec() function can be implemented
447either in the F<dl_*.xs> file or code can be added to the autoloadable
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448dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
449more information.
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450
451=item dl_load_file()
452
453Syntax:
454
455 $libref = dl_load_file($filename)
456
457Dynamically load $filename, which must be the path to a shared object
458or library. An opaque 'library reference' is returned as a handle for
459the loaded object. Returns undef on error.
460
461(On systems that provide a handle for the loaded object such as SunOS
462and HPUX, $libref will be that handle. On other systems $libref will
463typically be $filename or a pointer to a buffer containing $filename.
464The application should not examine or alter $libref in any way.)
465
466This is function that does the real work. It should use the current
467values of @dl_require_symbols and @dl_resolve_using if required.
468
469 SunOS: dlopen($filename)
470 HP-UX: shl_load($filename)
471 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
472 NeXT: rld_load($filename, @dl_resolve_using)
473 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
474
475
476=item dl_find_symbol()
477
478Syntax:
479
480 $symref = dl_find_symbol($libref, $symbol)
481
482Return the address of the symbol $symbol or C<undef> if not found. If the
483target system has separate functions to search for symbols of different
484types then dl_find_symbol() should search for function symbols first and
485then other types.
486
487The exact manner in which the address is returned in $symref is not
488currently defined. The only initial requirement is that $symref can
489be passed to, and understood by, dl_install_xsub().
490
491 SunOS: dlsym($libref, $symbol)
492 HP-UX: shl_findsym($libref, $symbol)
493 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
494 NeXT: rld_lookup("_$symbol")
495 VMS: lib$find_image_symbol($libref,$symbol)
496
497
498=item dl_undef_symbols()
499
500Example
501
502 @symbols = dl_undef_symbols()
503
504Return a list of symbol names which remain undefined after load_file().
505Returns C<()> if not known. Don't worry if your platform does not provide
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506a mechanism for this. Most do not need it and hence do not provide it,
507they just return an empty list.
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508
509
510=item dl_install_xsub()
511
512Syntax:
513
514 dl_install_xsub($perl_name, $symref [, $filename])
515
516Create a new Perl external subroutine named $perl_name using $symref as
517a pointer to the function which implements the routine. This is simply
518a direct call to newXSUB(). Returns a reference to the installed
519function.
520
521The $filename parameter is used by Perl to identify the source file for
522the function if required by die(), caller() or the debugger. If
523$filename is not defined then "DynaLoader" will be used.
524
525
1fef88e7 526=item bootstrap()
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527
528Syntax:
529
530bootstrap($module)
531
532This is the normal entry point for automatic dynamic loading in Perl.
533
534It performs the following actions:
535
536=over 8
537
538=item *
539
540locates an auto/$module directory by searching @INC
541
542=item *
543
544uses dl_findfile() to determine the filename to load
545
546=item *
547
548sets @dl_require_symbols to C<("boot_$module")>
549
550=item *
551
552executes an F<auto/$module/$module.bs> file if it exists
553(typically used to add to @dl_resolve_using any files which
554are required to load the module on the current platform)
555
556=item *
557
558calls dl_load_file() to load the file
559
560=item *
561
562calls dl_undef_symbols() and warns if any symbols are undefined
563
564=item *
565
566calls dl_find_symbol() for "boot_$module"
567
568=item *
569
570calls dl_install_xsub() to install it as "${module}::bootstrap"
571
572=item *
573
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574calls &{"${module}::bootstrap"} to bootstrap the module (actually
575it uses the function reference returned by dl_install_xsub for speed)
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576
577=back
578
579=back
580
581
582=head1 AUTHOR
583
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584Tim Bunce, 11 August 1994.
585
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586This interface is based on the work and comments of (in no particular
587order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
c2960299 588Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
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589
590Larry Wall designed the elegant inherited bootstrap mechanism and
591implemented the first Perl 5 dynamic loader using it.
592
3b35bae3 593=cut