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add perlnumber.pod (from Ilya Zakharevich); substantially edited
[perl5.git] / ext / DynaLoader / DynaLoader_pm.PL
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1
2use Config;
3
4sub to_string {
5 my ($value) = @_;
146174a9 6 $value =~ s/\\/\\\\/g;
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7 $value =~ s/'/\\'/g;
8 return "'$value'";
9}
10
11unlink "DynaLoader.pm" if -f "DynaLoader.pm";
12open OUT, ">DynaLoader.pm" or die $!;
13print OUT <<'EOT';
14
15# Generated from DynaLoader.pm.PL (resolved %Config::Config values)
16
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17package DynaLoader;
18
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19# And Gandalf said: 'Many folk like to know beforehand what is to
20# be set on the table; but those who have laboured to prepare the
21# feast like to keep their secret; for wonder makes the words of
22# praise louder.'
23
24# (Quote from Tolkien sugested by Anno Siegel.)
25#
26# See pod text at end of file for documentation.
27# See also ext/DynaLoader/README in source tree for other information.
28#
29# Tim.Bunce@ig.co.uk, August 1994
30
146174a9 31$VERSION = "1.03"; # avoid typo warning
dc848c6f 32
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33require AutoLoader;
34*AUTOLOAD = \&AutoLoader::AUTOLOAD;
8e07c86e 35
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36# The following require can't be removed during maintenance
37# releases, sadly, because of the risk of buggy code that does
38# require Carp; Carp::croak "..."; without brackets dying
39# if Carp hasn't been loaded in earlier compile time. :-(
40# We'll let those bugs get found on the development track.
41require Carp if $] < 5.00450;
42
43
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44# enable debug/trace messages from DynaLoader perl code
45$dl_debug = $ENV{PERL_DL_DEBUG} || 0 unless defined $dl_debug;
46
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47#
48# Flags to alter dl_load_file behaviour. Assigned bits:
49# 0x01 make symbols available for linking later dl_load_file's.
50# (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
f86702cc 51# (ignored under VMS; effect is built-in to image linking)
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52#
53# This is called as a class method $module->dl_load_flags. The
54# definition here will be inherited and result on "default" loading
55# behaviour unless a sub-class of DynaLoader defines its own version.
56#
57
58sub dl_load_flags { 0x00 }
59
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60# ($dl_dlext, $dlsrc)
61# = @Config::Config{'dlext', 'dlsrc'};
62EOT
63
64print OUT " (\$dl_dlext, \$dlsrc) = (",
65 to_string($Config::Config{'dlext'}), ",",
66 to_string($Config::Config{'dlsrc'}), ")\n;" ;
ff7f3c60 67
03c9e98c 68print OUT <<'EOT';
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69
70# Some systems need special handling to expand file specifications
71# (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
72# See dl_expandspec() for more details. Should be harmless but
73# inefficient to define on systems that don't need it.
d404d5bf 74$do_expand = $Is_VMS = $^O eq 'VMS';
146174a9 75$Is_MacOS = $^O eq 'MacOS';
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76
77@dl_require_symbols = (); # names of symbols we need
78@dl_resolve_using = (); # names of files to link with
79@dl_library_path = (); # path to look for files
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80@dl_librefs = (); # things we have loaded
81@dl_modules = (); # Modules we have loaded
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82
83# This is a fix to support DLD's unfortunate desire to relink -lc
84@dl_resolve_using = dl_findfile('-lc') if $dlsrc eq "dl_dld.xs";
85
86# Initialise @dl_library_path with the 'standard' library path
87# for this platform as determined by Configure
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88
89# push(@dl_library_path, split(' ', $Config::Config{'libpth'});
90EOT
91
92print OUT "push(\@dl_library_path, split(' ', ",
93 to_string($Config::Config{'libpth'}), "));\n";
94
95print OUT <<'EOT';
8e07c86e 96
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97# Add to @dl_library_path any extra directories we can gather
98# from environment variables.
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99if ($Is_MacOS) {
100 push(@dl_library_path, split(/,/, $ENV{LD_LIBRARY_PATH}))
101 if exists $ENV{LD_LIBRARY_PATH};
102} else {
103 push(@dl_library_path, split(/:/, $ENV{$Config::Config{ldlibpthname}}))
104 if exists $Config::Config{ldlibpthname} &&
105 $Config::Config{ldlibpthname} ne '' &&
106 exists $ENV{$Config::Config{ldlibpthname}} ;;
107 push(@dl_library_path, split(/:/, $ENV{$Config::Config{ldlibpthname}}))
108 if exists $Config::Config{ldlibpthname} &&
109 $Config::Config{ldlibpthname} ne '' &&
110 exists $ENV{$Config::Config{ldlibpthname}} ;;
5cf1d1f1 111# E.g. HP-UX supports both its native SHLIB_PATH *and* LD_LIBRARY_PATH.
8e07c86e 112push(@dl_library_path, split(/:/, $ENV{LD_LIBRARY_PATH}))
5cf1d1f1 113 if exists $ENV{LD_LIBRARY_PATH};
146174a9 114}
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115
116# No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
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117boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
118 !defined(&dl_load_file);
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119
120
121if ($dl_debug) {
122 print STDERR "DynaLoader.pm loaded (@INC, @dl_library_path)\n";
123 print STDERR "DynaLoader not linked into this perl\n"
124 unless defined(&boot_DynaLoader);
125}
126
1271; # End of main code
128
129
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130sub croak { require Carp; Carp::croak(@_) }
131
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132sub bootstrap_inherit {
133 my $module = $_[0];
134 local *isa = *{"$module\::ISA"};
135 local @isa = (@isa, 'DynaLoader');
136 # Cannot goto due to delocalization. Will report errors on a wrong line?
137 bootstrap(@_);
138}
139
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140# The bootstrap function cannot be autoloaded (without complications)
141# so we define it here:
142
143sub bootstrap {
144 # use local vars to enable $module.bs script to edit values
145 local(@args) = @_;
146 local($module) = $args[0];
147 local(@dirs, $file);
148
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149 unless ($module) {
150 require Carp;
151 Carp::confess("Usage: DynaLoader::bootstrap(module)");
152 }
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153
154 # A common error on platforms which don't support dynamic loading.
155 # Since it's fatal and potentially confusing we give a detailed message.
fb73857a 156 croak("Can't load module $module, dynamic loading not available in this perl.\n".
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157 " (You may need to build a new perl executable which either supports\n".
158 " dynamic loading or has the $module module statically linked into it.)\n")
159 unless defined(&dl_load_file);
160
161 my @modparts = split(/::/,$module);
162 my $modfname = $modparts[-1];
163
164 # Some systems have restrictions on files names for DLL's etc.
165 # mod2fname returns appropriate file base name (typically truncated)
166 # It may also edit @modparts if required.
167 $modfname = &mod2fname(\@modparts) if defined &mod2fname;
168
146174a9 169 my $modpname = join(($Is_MacOS ? ':' : '/'),@modparts);
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170
171 print STDERR "DynaLoader::bootstrap for $module ",
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172 ($Is_MacOS
173 ? "(auto/$modpname/$modfname.$dl_dlext)\n" :
174 "(:auto:$modpname:$modfname.$dl_dlext)\n")
175 if $dl_debug;
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176
177 foreach (@INC) {
54d6a3b3 178 chop($_ = VMS::Filespec::unixpath($_)) if $Is_VMS;
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179 my $dir;
180 if ($Is_MacOS) {
181 chop $_ if /:$/;
182 $dir = "$_:auto:$modpname";
183 } else {
184 $dir = "$_/auto/$modpname";
185 }
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186 next unless -d $dir; # skip over uninteresting directories
187
188 # check for common cases to avoid autoload of dl_findfile
146174a9 189 my $try = $Is_MacOS ? "$dir:$modfname.$dl_dlext" : "$dir/$modfname.$dl_dlext";
fb73857a 190 last if $file = ($do_expand) ? dl_expandspec($try) : (-f $try && $try);
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191
192 # no luck here, save dir for possible later dl_findfile search
fb73857a 193 push @dirs, $dir;
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194 }
195 # last resort, let dl_findfile have a go in all known locations
fb73857a 196 $file = dl_findfile(map("-L$_",@dirs,@INC), $modfname) unless $file;
8e07c86e 197
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198 croak("Can't locate loadable object for module $module in \@INC (\@INC contains: @INC)")
199 unless $file; # wording similar to error from 'require'
8e07c86e 200
b6837a3b 201 $file = uc($file) if $Is_VMS && $Config{d_vms_case_sensitive_symbols};
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202 my $bootname = "boot_$module";
203 $bootname =~ s/\W/_/g;
204 @dl_require_symbols = ($bootname);
205
206 # Execute optional '.bootstrap' perl script for this module.
207 # The .bs file can be used to configure @dl_resolve_using etc to
208 # match the needs of the individual module on this architecture.
209 my $bs = $file;
3f45a6dd 210 $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
8e07c86e 211 if (-s $bs) { # only read file if it's not empty
d404d5bf 212 print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
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213 eval { do $bs; };
214 warn "$bs: $@\n" if $@;
215 }
216
217 # Many dynamic extension loading problems will appear to come from
218 # this section of code: XYZ failed at line 123 of DynaLoader.pm.
219 # Often these errors are actually occurring in the initialisation
220 # C code of the extension XS file. Perl reports the error as being
221 # in this perl code simply because this was the last perl code
222 # it executed.
223
ff7f3c60 224 my $libref = dl_load_file($file, $module->dl_load_flags) or
549a6b10 225 croak("Can't load '$file' for module $module: ".dl_error());
8e07c86e 226
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227 push(@dl_librefs,$libref); # record loaded object
228
8e07c86e 229 my @unresolved = dl_undef_symbols();
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230 if (@unresolved) {
231 require Carp;
232 Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
233 }
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234
235 my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
fb73857a 236 croak("Can't find '$bootname' symbol in $file\n");
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237
238 my $xs = dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
239
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240 push(@dl_modules, $module); # record loaded module
241
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242 # See comment block above
243 &$xs(@args);
244}
245
246
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247#sub _check_file { # private utility to handle dl_expandspec vs -f tests
248# my($file) = @_;
249# return $file if (!$do_expand && -f $file); # the common case
250# return $file if ( $do_expand && ($file=dl_expandspec($file)));
251# return undef;
252#}
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253
254
255# Let autosplit and the autoloader deal with these functions:
256__END__
257
258
259sub dl_findfile {
260 # Read ext/DynaLoader/DynaLoader.doc for detailed information.
261 # This function does not automatically consider the architecture
262 # or the perl library auto directories.
263 my (@args) = @_;
264 my (@dirs, $dir); # which directories to search
265 my (@found); # full paths to real files we have found
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266EOT
267
268print OUT ' my $dl_ext= ' . to_string($Config::Config{'dlext'}) .
269 "; # \$Config::Config{'dlext'} suffix for perl extensions\n";
270print OUT ' my $dl_so = ' . to_string($Config::Config{'so'}) .
271 "; # \$Config::Config{'so'} suffix for shared libraries\n";
272
273print OUT <<'EOT';
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274
275 print STDERR "dl_findfile(@args)\n" if $dl_debug;
276
277 # accumulate directories but process files as they appear
278 arg: foreach(@args) {
279 # Special fast case: full filepath requires no search
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280 if ($Is_VMS && m%[:>/\]]% && -f $_) {
281 push(@found,dl_expandspec(VMS::Filespec::vmsify($_)));
282 last arg unless wantarray;
283 next;
284 }
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285 elsif ($Is_MacOS) {
286 if (m/:/ && -f $_) {
287 push(@found,$_);
288 last arg unless wantarray;
289 }
290 }
54d6a3b3 291 elsif (m:/: && -f $_ && !$do_expand) {
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292 push(@found,$_);
293 last arg unless wantarray;
294 next;
295 }
296
297 # Deal with directories first:
298 # Using a -L prefix is the preferred option (faster and more robust)
299 if (m:^-L:) { s/^-L//; push(@dirs, $_); next; }
300
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301 if ($Is_MacOS) {
302 # Otherwise we try to try to spot directories by a heuristic
303 # (this is a more complicated issue than it first appears)
304 if (m/:/ && -d $_) { push(@dirs, $_); next; }
305 # Only files should get this far...
306 my(@names, $name); # what filenames to look for
307 s/^-l//;
308 push(@names, $_);
309 foreach $dir (@dirs, @dl_library_path) {
310 next unless -d $dir;
311 $dir =~ s/^([^:]+)$/:$1/;
312 $dir =~ s/:$//;
313 foreach $name (@names) {
314 my($file) = "$dir:$name";
315 print STDERR " checking in $dir for $name\n" if $dl_debug;
316 if (-f $file) {
317 push(@found, $file);
318 next arg; # no need to look any further
319 }
320 }
321 }
322 next;
323 }
324
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325 # Otherwise we try to try to spot directories by a heuristic
326 # (this is a more complicated issue than it first appears)
327 if (m:/: && -d $_) { push(@dirs, $_); next; }
328
329 # VMS: we may be using native VMS directry syntax instead of
330 # Unix emulation, so check this as well
54d6a3b3 331 if ($Is_VMS && /[:>\]]/ && -d $_) { push(@dirs, $_); next; }
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332
333 # Only files should get this far...
334 my(@names, $name); # what filenames to look for
335 if (m:-l: ) { # convert -lname to appropriate library name
336 s/-l//;
337 push(@names,"lib$_.$dl_so");
338 push(@names,"lib$_.a");
339 } else { # Umm, a bare name. Try various alternatives:
340 # these should be ordered with the most likely first
d404d5bf 341 push(@names,"$_.$dl_ext") unless m/\.$dl_ext$/o;
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342 push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
343 push(@names,"lib$_.$dl_so") unless m:/:;
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344 push(@names,"$_.a") if !m/\.a$/ and $dlsrc eq "dl_dld.xs";
345 push(@names, $_);
346 }
347 foreach $dir (@dirs, @dl_library_path) {
348 next unless -d $dir;
54d6a3b3 349 chop($dir = VMS::Filespec::unixpath($dir)) if $Is_VMS;
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350 foreach $name (@names) {
351 my($file) = "$dir/$name";
352 print STDERR " checking in $dir for $name\n" if $dl_debug;
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353 $file = ($do_expand) ? dl_expandspec($file) : (-f $file && $file);
354 #$file = _check_file($file);
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355 if ($file) {
356 push(@found, $file);
357 next arg; # no need to look any further
358 }
359 }
360 }
361 }
362 if ($dl_debug) {
363 foreach(@dirs) {
364 print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
365 }
366 print STDERR "dl_findfile found: @found\n";
367 }
368 return $found[0] unless wantarray;
369 @found;
370}
371
372
373sub dl_expandspec {
374 my($spec) = @_;
375 # Optional function invoked if DynaLoader.pm sets $do_expand.
376 # Most systems do not require or use this function.
377 # Some systems may implement it in the dl_*.xs file in which case
378 # this autoload version will not be called but is harmless.
379
380 # This function is designed to deal with systems which treat some
381 # 'filenames' in a special way. For example VMS 'Logical Names'
382 # (something like unix environment variables - but different).
383 # This function should recognise such names and expand them into
384 # full file paths.
385 # Must return undef if $spec is invalid or file does not exist.
386
387 my $file = $spec; # default output to input
388
d404d5bf 389 if ($Is_VMS) { # dl_expandspec should be defined in dl_vms.xs
fb73857a 390 require Carp;
4633a7c4 391 Carp::croak("dl_expandspec: should be defined in XS file!\n");
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392 } else {
393 return undef unless -f $file;
394 }
395 print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
396 $file;
397}
398
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399sub dl_find_symbol_anywhere
400{
401 my $sym = shift;
402 my $libref;
403 foreach $libref (@dl_librefs) {
404 my $symref = dl_find_symbol($libref,$sym);
405 return $symref if $symref;
406 }
407 return undef;
408}
8e07c86e 409
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410=head1 NAME
411
412DynaLoader - Dynamically load C libraries into Perl code
413
ff7f3c60 414dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_find_symbol(), dl_find_symbol_anywhere(), dl_undef_symbols(), dl_install_xsub(), dl_load_flags(), bootstrap() - routines used by DynaLoader modules
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415
416=head1 SYNOPSIS
417
8e07c86e 418 package YourPackage;
3b35bae3 419 require DynaLoader;
c2960299 420 @ISA = qw(... DynaLoader ...);
8e07c86e 421 bootstrap YourPackage;
3b35bae3 422
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423 # optional method for 'global' loading
424 sub dl_load_flags { 0x01 }
425
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426
427=head1 DESCRIPTION
428
c2960299 429This document defines a standard generic interface to the dynamic
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430linking mechanisms available on many platforms. Its primary purpose is
431to implement automatic dynamic loading of Perl modules.
432
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433This document serves as both a specification for anyone wishing to
434implement the DynaLoader for a new platform and as a guide for
435anyone wishing to use the DynaLoader directly in an application.
436
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437The DynaLoader is designed to be a very simple high-level
438interface that is sufficiently general to cover the requirements
439of SunOS, HP-UX, NeXT, Linux, VMS and other platforms.
440
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441It is also hoped that the interface will cover the needs of OS/2, NT
442etc and also allow pseudo-dynamic linking (using C<ld -A> at runtime).
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443
444It must be stressed that the DynaLoader, by itself, is practically
445useless for accessing non-Perl libraries because it provides almost no
446Perl-to-C 'glue'. There is, for example, no mechanism for calling a C
03c9e98c 447library function or supplying arguments. A C::DynaLib module
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448is available from CPAN sites which performs that function for some
449common system types.
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450
451DynaLoader Interface Summary
452
453 @dl_library_path
454 @dl_resolve_using
455 @dl_require_symbols
456 $dl_debug
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457 @dl_librefs
458 @dl_modules
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459 Implemented in:
460 bootstrap($modulename) Perl
461 @filepaths = dl_findfile(@names) Perl
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462 $flags = $modulename->dl_load_flags Perl
463 $symref = dl_find_symbol_anywhere($symbol) Perl
3b35bae3 464
ff7f3c60 465 $libref = dl_load_file($filename, $flags) C
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466 $symref = dl_find_symbol($libref, $symbol) C
467 @symbols = dl_undef_symbols() C
468 dl_install_xsub($name, $symref [, $filename]) C
469 $message = dl_error C
470
471=over 4
472
473=item @dl_library_path
474
475The standard/default list of directories in which dl_findfile() will
476search for libraries etc. Directories are searched in order:
477$dl_library_path[0], [1], ... etc
478
479@dl_library_path is initialised to hold the list of 'normal' directories
480(F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
481ensure portability across a wide range of platforms.
482
483@dl_library_path should also be initialised with any other directories
484that can be determined from the environment at runtime (such as
485LD_LIBRARY_PATH for SunOS).
486
487After initialisation @dl_library_path can be manipulated by an
488application using push and unshift before calling dl_findfile().
489Unshift can be used to add directories to the front of the search order
490either to save search time or to override libraries with the same name
491in the 'normal' directories.
492
493The load function that dl_load_file() calls may require an absolute
494pathname. The dl_findfile() function and @dl_library_path can be
495used to search for and return the absolute pathname for the
496library/object that you wish to load.
497
498=item @dl_resolve_using
499
500A list of additional libraries or other shared objects which can be
501used to resolve any undefined symbols that might be generated by a
502later call to load_file().
503
504This is only required on some platforms which do not handle dependent
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PP
505libraries automatically. For example the Socket Perl extension
506library (F<auto/Socket/Socket.so>) contains references to many socket
507functions which need to be resolved when it's loaded. Most platforms
508will automatically know where to find the 'dependent' library (e.g.,
509F</usr/lib/libsocket.so>). A few platforms need to be told the
510location of the dependent library explicitly. Use @dl_resolve_using
511for this.
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512
513Example usage:
514
515 @dl_resolve_using = dl_findfile('-lsocket');
516
517=item @dl_require_symbols
518
519A list of one or more symbol names that are in the library/object file
520to be dynamically loaded. This is only required on some platforms.
521
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522=item @dl_librefs
523
524An array of the handles returned by successful calls to dl_load_file(),
525made by bootstrap, in the order in which they were loaded.
526Can be used with dl_find_symbol() to look for a symbol in any of
527the loaded files.
528
529=item @dl_modules
530
531An array of module (package) names that have been bootstrap'ed.
532
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533=item dl_error()
534
535Syntax:
536
537 $message = dl_error();
538
539Error message text from the last failed DynaLoader function. Note
540that, similar to errno in unix, a successful function call does not
541reset this message.
542
543Implementations should detect the error as soon as it occurs in any of
544the other functions and save the corresponding message for later
545retrieval. This will avoid problems on some platforms (such as SunOS)
546where the error message is very temporary (e.g., dlerror()).
547
548=item $dl_debug
549
550Internal debugging messages are enabled when $dl_debug is set true.
551Currently setting $dl_debug only affects the Perl side of the
552DynaLoader. These messages should help an application developer to
553resolve any DynaLoader usage problems.
554
555$dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
556
557For the DynaLoader developer/porter there is a similar debugging
558variable added to the C code (see dlutils.c) and enabled if Perl was
559built with the B<-DDEBUGGING> flag. This can also be set via the
560PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
561higher for more.
562
563=item dl_findfile()
564
565Syntax:
566
567 @filepaths = dl_findfile(@names)
568
569Determine the full paths (including file suffix) of one or more
570loadable files given their generic names and optionally one or more
571directories. Searches directories in @dl_library_path by default and
572returns an empty list if no files were found.
573
574Names can be specified in a variety of platform independent forms. Any
575names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
576an appropriate suffix for the platform.
577
578If a name does not already have a suitable prefix and/or suffix then
579the corresponding file will be searched for by trying combinations of
580prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
581and "$name".
582
583If any directories are included in @names they are searched before
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584@dl_library_path. Directories may be specified as B<-Ldir>. Any other
585names are treated as filenames to be searched for.
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586
587Using arguments of the form C<-Ldir> and C<-lname> is recommended.
588
589Example:
590
591 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
592
593
594=item dl_expandspec()
595
596Syntax:
597
598 $filepath = dl_expandspec($spec)
599
600Some unusual systems, such as VMS, require special filename handling in
601order to deal with symbolic names for files (i.e., VMS's Logical Names).
602
603To support these systems a dl_expandspec() function can be implemented
604either in the F<dl_*.xs> file or code can be added to the autoloadable
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605dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
606more information.
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607
608=item dl_load_file()
609
610Syntax:
611
ff7f3c60 612 $libref = dl_load_file($filename, $flags)
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613
614Dynamically load $filename, which must be the path to a shared object
615or library. An opaque 'library reference' is returned as a handle for
616the loaded object. Returns undef on error.
617
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618The $flags argument to alters dl_load_file behaviour.
619Assigned bits:
620
621 0x01 make symbols available for linking later dl_load_file's.
622 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
f86702cc 623 (ignored under VMS; this is a normal part of image linking)
ff7f3c60 624
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625(On systems that provide a handle for the loaded object such as SunOS
626and HPUX, $libref will be that handle. On other systems $libref will
627typically be $filename or a pointer to a buffer containing $filename.
628The application should not examine or alter $libref in any way.)
629
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630This is the function that does the real work. It should use the
631current values of @dl_require_symbols and @dl_resolve_using if required.
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632
633 SunOS: dlopen($filename)
634 HP-UX: shl_load($filename)
635 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
636 NeXT: rld_load($filename, @dl_resolve_using)
637 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
638
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639(The dlopen() function is also used by Solaris and some versions of
640Linux, and is a common choice when providing a "wrapper" on other
641mechanisms as is done in the OS/2 port.)
642
643=item dl_loadflags()
644
645Syntax:
646
647 $flags = dl_loadflags $modulename;
648
649Designed to be a method call, and to be overridden by a derived class
650(i.e. a class which has DynaLoader in its @ISA). The definition in
651DynaLoader itself returns 0, which produces standard behavior from
652dl_load_file().
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653
654=item dl_find_symbol()
655
656Syntax:
657
658 $symref = dl_find_symbol($libref, $symbol)
659
660Return the address of the symbol $symbol or C<undef> if not found. If the
661target system has separate functions to search for symbols of different
662types then dl_find_symbol() should search for function symbols first and
663then other types.
664
665The exact manner in which the address is returned in $symref is not
666currently defined. The only initial requirement is that $symref can
667be passed to, and understood by, dl_install_xsub().
668
669 SunOS: dlsym($libref, $symbol)
670 HP-UX: shl_findsym($libref, $symbol)
671 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
672 NeXT: rld_lookup("_$symbol")
673 VMS: lib$find_image_symbol($libref,$symbol)
674
675
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676=item dl_find_symbol_anywhere()
677
678Syntax:
679
680 $symref = dl_find_symbol_anywhere($symbol)
681
682Applies dl_find_symbol() to the members of @dl_librefs and returns
683the first match found.
684
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685=item dl_undef_symbols()
686
687Example
688
689 @symbols = dl_undef_symbols()
690
691Return a list of symbol names which remain undefined after load_file().
692Returns C<()> if not known. Don't worry if your platform does not provide
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693a mechanism for this. Most do not need it and hence do not provide it,
694they just return an empty list.
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695
696
697=item dl_install_xsub()
698
699Syntax:
700
701 dl_install_xsub($perl_name, $symref [, $filename])
702
703Create a new Perl external subroutine named $perl_name using $symref as
704a pointer to the function which implements the routine. This is simply
705a direct call to newXSUB(). Returns a reference to the installed
706function.
707
708The $filename parameter is used by Perl to identify the source file for
709the function if required by die(), caller() or the debugger. If
710$filename is not defined then "DynaLoader" will be used.
711
712
1fef88e7 713=item bootstrap()
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714
715Syntax:
716
717bootstrap($module)
718
719This is the normal entry point for automatic dynamic loading in Perl.
720
721It performs the following actions:
722
723=over 8
724
725=item *
726
727locates an auto/$module directory by searching @INC
728
729=item *
730
731uses dl_findfile() to determine the filename to load
732
733=item *
734
735sets @dl_require_symbols to C<("boot_$module")>
736
737=item *
738
739executes an F<auto/$module/$module.bs> file if it exists
740(typically used to add to @dl_resolve_using any files which
741are required to load the module on the current platform)
742
743=item *
744
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745calls dl_load_flags() to determine how to load the file.
746
747=item *
748
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749calls dl_load_file() to load the file
750
751=item *
752
753calls dl_undef_symbols() and warns if any symbols are undefined
754
755=item *
756
757calls dl_find_symbol() for "boot_$module"
758
759=item *
760
761calls dl_install_xsub() to install it as "${module}::bootstrap"
762
763=item *
764
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765calls &{"${module}::bootstrap"} to bootstrap the module (actually
766it uses the function reference returned by dl_install_xsub for speed)
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767
768=back
769
770=back
771
772
773=head1 AUTHOR
774
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775Tim Bunce, 11 August 1994.
776
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777This interface is based on the work and comments of (in no particular
778order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
c2960299 779Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
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780
781Larry Wall designed the elegant inherited bootstrap mechanism and
782implemented the first Perl 5 dynamic loader using it.
783
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784Solaris global loading added by Nick Ing-Simmons with design/coding
785assistance from Tim Bunce, January 1996.
786
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788EOT
789
790close OUT or die $!;
791