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use &dl_error rather than &dl_load_file as the guard for calling
[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 $!;
13print OUT <<'EOT';
14
15# Generated from DynaLoader.pm.PL (resolved %Config::Config values)
16
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17package DynaLoader;
18
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19# And Gandalf said: 'Many folk like to know beforehand what is to
20# be set on the table; but those who have laboured to prepare the
21# feast like to keep their secret; for wonder makes the words of
22# praise louder.'
23
24# (Quote from Tolkien sugested by Anno Siegel.)
25#
26# See pod text at end of file for documentation.
27# See also ext/DynaLoader/README in source tree for other information.
28#
29# Tim.Bunce@ig.co.uk, August 1994
30
abb9e9dc 31$VERSION = "1.04"; # 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 $module->dl_load_flags. The
54# definition here will be inherited and result on "default" loading
55# behaviour unless a sub-class of DynaLoader defines its own version.
56#
57
58sub dl_load_flags { 0x00 }
59
03c9e98c
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60# ($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
5cf1d1f1
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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 $ENV{LD_LIBRARY_PATH};
146174a9 114}
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115
116# No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
b4cea227 117# NOTE: All dl_*.xs (including dl_none.xs) define a dl_error() XSUB
bb3913c7 118boot_DynaLoader('DynaLoader') if defined(&boot_DynaLoader) &&
b4cea227 119 !defined(&dl_error);
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120
121if ($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 $dl_debug;
276
277 # accumulate directories but process files as they appear
278 arg: foreach(@args) {
279 # Special fast case: full filepath requires no search
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PP
280 if ($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
abb9e9dc 414dl_error(), dl_findfile(), dl_expandspec(), dl_load_file(), dl_unload_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
c2960299
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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
c2960299
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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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NIS
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
abb9e9dc 466 $status = dl_unload_file($libref) C
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467 $symref = dl_find_symbol($libref, $symbol) C
468 @symbols = dl_undef_symbols() C
469 dl_install_xsub($name, $symref [, $filename]) C
470 $message = dl_error C
471
472=over 4
473
474=item @dl_library_path
475
476The standard/default list of directories in which dl_findfile() will
477search for libraries etc. Directories are searched in order:
478$dl_library_path[0], [1], ... etc
479
480@dl_library_path is initialised to hold the list of 'normal' directories
481(F</usr/lib>, etc) determined by B<Configure> (C<$Config{'libpth'}>). This should
482ensure portability across a wide range of platforms.
483
484@dl_library_path should also be initialised with any other directories
485that can be determined from the environment at runtime (such as
486LD_LIBRARY_PATH for SunOS).
487
488After initialisation @dl_library_path can be manipulated by an
489application using push and unshift before calling dl_findfile().
490Unshift can be used to add directories to the front of the search order
491either to save search time or to override libraries with the same name
492in the 'normal' directories.
493
494The load function that dl_load_file() calls may require an absolute
495pathname. The dl_findfile() function and @dl_library_path can be
496used to search for and return the absolute pathname for the
497library/object that you wish to load.
498
499=item @dl_resolve_using
500
501A list of additional libraries or other shared objects which can be
502used to resolve any undefined symbols that might be generated by a
503later call to load_file().
504
505This is only required on some platforms which do not handle dependent
7a2e2cd6
PP
506libraries automatically. For example the Socket Perl extension
507library (F<auto/Socket/Socket.so>) contains references to many socket
508functions which need to be resolved when it's loaded. Most platforms
509will automatically know where to find the 'dependent' library (e.g.,
510F</usr/lib/libsocket.so>). A few platforms need to be told the
511location of the dependent library explicitly. Use @dl_resolve_using
512for this.
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513
514Example usage:
515
516 @dl_resolve_using = dl_findfile('-lsocket');
517
518=item @dl_require_symbols
519
520A list of one or more symbol names that are in the library/object file
521to be dynamically loaded. This is only required on some platforms.
522
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523=item @dl_librefs
524
525An array of the handles returned by successful calls to dl_load_file(),
526made by bootstrap, in the order in which they were loaded.
527Can be used with dl_find_symbol() to look for a symbol in any of
528the loaded files.
529
530=item @dl_modules
531
532An array of module (package) names that have been bootstrap'ed.
533
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534=item dl_error()
535
536Syntax:
537
538 $message = dl_error();
539
540Error message text from the last failed DynaLoader function. Note
541that, similar to errno in unix, a successful function call does not
542reset this message.
543
544Implementations should detect the error as soon as it occurs in any of
545the other functions and save the corresponding message for later
546retrieval. This will avoid problems on some platforms (such as SunOS)
547where the error message is very temporary (e.g., dlerror()).
548
549=item $dl_debug
550
551Internal debugging messages are enabled when $dl_debug is set true.
552Currently setting $dl_debug only affects the Perl side of the
553DynaLoader. These messages should help an application developer to
554resolve any DynaLoader usage problems.
555
556$dl_debug is set to C<$ENV{'PERL_DL_DEBUG'}> if defined.
557
558For the DynaLoader developer/porter there is a similar debugging
559variable added to the C code (see dlutils.c) and enabled if Perl was
560built with the B<-DDEBUGGING> flag. This can also be set via the
561PERL_DL_DEBUG environment variable. Set to 1 for minimal information or
562higher for more.
563
564=item dl_findfile()
565
566Syntax:
567
568 @filepaths = dl_findfile(@names)
569
570Determine the full paths (including file suffix) of one or more
571loadable files given their generic names and optionally one or more
572directories. Searches directories in @dl_library_path by default and
573returns an empty list if no files were found.
574
575Names can be specified in a variety of platform independent forms. Any
576names in the form B<-lname> are converted into F<libname.*>, where F<.*> is
577an appropriate suffix for the platform.
578
579If a name does not already have a suitable prefix and/or suffix then
580the corresponding file will be searched for by trying combinations of
581prefix and suffix appropriate to the platform: "$name.o", "lib$name.*"
582and "$name".
583
584If any directories are included in @names they are searched before
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585@dl_library_path. Directories may be specified as B<-Ldir>. Any other
586names are treated as filenames to be searched for.
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587
588Using arguments of the form C<-Ldir> and C<-lname> is recommended.
589
590Example:
591
592 @dl_resolve_using = dl_findfile(qw(-L/usr/5lib -lposix));
593
594
595=item dl_expandspec()
596
597Syntax:
598
599 $filepath = dl_expandspec($spec)
600
601Some unusual systems, such as VMS, require special filename handling in
602order to deal with symbolic names for files (i.e., VMS's Logical Names).
603
604To support these systems a dl_expandspec() function can be implemented
605either in the F<dl_*.xs> file or code can be added to the autoloadable
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606dl_expandspec() function in F<DynaLoader.pm>. See F<DynaLoader.pm> for
607more information.
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608
609=item dl_load_file()
610
611Syntax:
612
ff7f3c60 613 $libref = dl_load_file($filename, $flags)
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614
615Dynamically load $filename, which must be the path to a shared object
616or library. An opaque 'library reference' is returned as a handle for
617the loaded object. Returns undef on error.
618
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619The $flags argument to alters dl_load_file behaviour.
620Assigned bits:
621
622 0x01 make symbols available for linking later dl_load_file's.
623 (only known to work on Solaris 2 using dlopen(RTLD_GLOBAL))
f86702cc 624 (ignored under VMS; this is a normal part of image linking)
ff7f3c60 625
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626(On systems that provide a handle for the loaded object such as SunOS
627and HPUX, $libref will be that handle. On other systems $libref will
628typically be $filename or a pointer to a buffer containing $filename.
629The application should not examine or alter $libref in any way.)
630
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631This is the function that does the real work. It should use the
632current values of @dl_require_symbols and @dl_resolve_using if required.
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633
634 SunOS: dlopen($filename)
635 HP-UX: shl_load($filename)
636 Linux: dld_create_reference(@dl_require_symbols); dld_link($filename)
637 NeXT: rld_load($filename, @dl_resolve_using)
638 VMS: lib$find_image_symbol($filename,$dl_require_symbols[0])
639
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640(The dlopen() function is also used by Solaris and some versions of
641Linux, and is a common choice when providing a "wrapper" on other
642mechanisms as is done in the OS/2 port.)
643
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644=item dl_unload_file()
645
646Syntax:
647
648 $status = dl_unload_file($libref)
649
650Dynamically unload $libref, which must be an opaque 'library reference' as
651returned from dl_load_file. Returns one on success and zero on failure.
652
653This function is optional and may not necessarily be provided on all platforms.
654If it is defined, it is called automatically when the interpreter exits for
655every shared object or library loaded by DynaLoader::bootstrap. All such
656library references are stored in @dl_librefs by DynaLoader::Bootstrap as it
22851543 657loads the libraries. The files are unloaded in last-in, first-out order.
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658
659This unloading is usually necessary when embedding a shared-object perl (e.g.
660one configured with -Duseshrplib) within a larger application, and the perl
661interpreter is created and destroyed several times within the lifetime of the
662application. In this case it is possible that the system dynamic linker will
663unload and then subsequently reload the shared libperl without relocating any
664references to it from any files DynaLoaded by the previous incarnation of the
665interpreter. As a result, any shared objects opened by DynaLoader may point to
666a now invalid 'ghost' of the libperl shared object, causing apparently random
667memory corruption and crashes. This behaviour is most commonly seen when using
668Apache and mod_perl built with the APXS mechanism.
669
670 SunOS: dlclose($libref)
671 HP-UX: ???
672 Linux: ???
673 NeXT: ???
674 VMS: ???
675
676(The dlclose() function is also used by Solaris and some versions of
677Linux, and is a common choice when providing a "wrapper" on other
678mechanisms as is done in the OS/2 port.)
679
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680=item dl_loadflags()
681
682Syntax:
683
684 $flags = dl_loadflags $modulename;
685
686Designed to be a method call, and to be overridden by a derived class
687(i.e. a class which has DynaLoader in its @ISA). The definition in
688DynaLoader itself returns 0, which produces standard behavior from
689dl_load_file().
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690
691=item dl_find_symbol()
692
693Syntax:
694
695 $symref = dl_find_symbol($libref, $symbol)
696
697Return the address of the symbol $symbol or C<undef> if not found. If the
698target system has separate functions to search for symbols of different
699types then dl_find_symbol() should search for function symbols first and
700then other types.
701
702The exact manner in which the address is returned in $symref is not
703currently defined. The only initial requirement is that $symref can
704be passed to, and understood by, dl_install_xsub().
705
706 SunOS: dlsym($libref, $symbol)
707 HP-UX: shl_findsym($libref, $symbol)
708 Linux: dld_get_func($symbol) and/or dld_get_symbol($symbol)
709 NeXT: rld_lookup("_$symbol")
710 VMS: lib$find_image_symbol($libref,$symbol)
711
712
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713=item dl_find_symbol_anywhere()
714
715Syntax:
716
717 $symref = dl_find_symbol_anywhere($symbol)
718
719Applies dl_find_symbol() to the members of @dl_librefs and returns
720the first match found.
721
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722=item dl_undef_symbols()
723
724Example
725
726 @symbols = dl_undef_symbols()
727
728Return a list of symbol names which remain undefined after load_file().
729Returns C<()> if not known. Don't worry if your platform does not provide
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730a mechanism for this. Most do not need it and hence do not provide it,
731they just return an empty list.
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732
733
734=item dl_install_xsub()
735
736Syntax:
737
738 dl_install_xsub($perl_name, $symref [, $filename])
739
740Create a new Perl external subroutine named $perl_name using $symref as
741a pointer to the function which implements the routine. This is simply
742a direct call to newXSUB(). Returns a reference to the installed
743function.
744
745The $filename parameter is used by Perl to identify the source file for
746the function if required by die(), caller() or the debugger. If
747$filename is not defined then "DynaLoader" will be used.
748
749
1fef88e7 750=item bootstrap()
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751
752Syntax:
753
754bootstrap($module)
755
756This is the normal entry point for automatic dynamic loading in Perl.
757
758It performs the following actions:
759
760=over 8
761
762=item *
763
764locates an auto/$module directory by searching @INC
765
766=item *
767
768uses dl_findfile() to determine the filename to load
769
770=item *
771
772sets @dl_require_symbols to C<("boot_$module")>
773
774=item *
775
776executes an F<auto/$module/$module.bs> file if it exists
777(typically used to add to @dl_resolve_using any files which
778are required to load the module on the current platform)
779
780=item *
781
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782calls dl_load_flags() to determine how to load the file.
783
784=item *
785
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786calls dl_load_file() to load the file
787
788=item *
789
790calls dl_undef_symbols() and warns if any symbols are undefined
791
792=item *
793
794calls dl_find_symbol() for "boot_$module"
795
796=item *
797
798calls dl_install_xsub() to install it as "${module}::bootstrap"
799
800=item *
801
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802calls &{"${module}::bootstrap"} to bootstrap the module (actually
803it uses the function reference returned by dl_install_xsub for speed)
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804
805=back
806
807=back
808
809
810=head1 AUTHOR
811
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812Tim Bunce, 11 August 1994.
813
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814This interface is based on the work and comments of (in no particular
815order): Larry Wall, Robert Sanders, Dean Roehrich, Jeff Okamoto, Anno
c2960299 816Siegel, Thomas Neumann, Paul Marquess, Charles Bailey, myself and others.
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817
818Larry Wall designed the elegant inherited bootstrap mechanism and
819implemented the first Perl 5 dynamic loader using it.
820
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821Solaris global loading added by Nick Ing-Simmons with design/coding
822assistance from Tim Bunce, January 1996.
823
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825EOT
826
827close OUT or die $!;
828