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DynaLoader
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1996-02-09
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9KB
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250 lines
package DynaLoader;
#
# And Gandalf said: 'Many folk like to know beforehand what is to
# be set on the table; but those who have laboured to prepare the
# feast like to keep their secret; for wonder makes the words of
# praise louder.'
#
# Quote from Tolkien sugested by Anno Siegel.
#
# Read ext/DynaLoader/README and DynaLoader.doc for
# detailed information.
#
# Tim.Bunce@ig.co.uk, August 1994
use Config;
use Carp;
use AutoLoader;
@ISA=qw(AutoLoader);
# enable messages from DynaLoader perl code
$dl_debug = 0 unless $dl_debug;
$dl_debug = $ENV{'PERL_DL_DEBUG'} if $ENV{'PERL_DL_DEBUG'};
$dl_so = $dl_dlext = ""; # avoid typo warnings
$dl_so = $Config{'so'}; # suffix for shared libraries
$dl_dlext = $Config{'dlext'}; # suffix for dynamic modules
# Some systems need special handling to expand file specifications
# (VMS support by Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>)
# See dl_expandspec() for more details. Should be harmless but
# inefficient to define on systems that don't need it.
$do_expand = ($Config{'osname'} eq 'VMS');
@dl_require_symbols = (); # names of symbols we need
@dl_resolve_using = (); # names of files to link with
@dl_library_path = (); # path to look for files
# This is a fix to support DLD's unfortunate desire to relink -lc
@dl_resolve_using = dl_findfile('-lc') if $Config{'dlsrc'} eq "dl_dld.xs";
# Initialise @dl_library_path with the 'standard' library path
# for this platform as determined by Configure
push(@dl_library_path, split(' ',$Config{'libpth'}));
# Add to @dl_library_path any extra directories we can gather from
# environment variables. So far LD_LIBRARY_PATH is the only known
# variable used for this purpose. Others may be added later.
push(@dl_library_path, split(/:/, $ENV{'LD_LIBRARY_PATH'}))
if $ENV{'LD_LIBRARY_PATH'};
# No prizes for guessing why we don't say 'bootstrap DynaLoader;' here.
boot_DynaLoader() if defined(&boot_DynaLoader);
if ($dl_debug){
print STDERR "DynaLoader.pm loaded (@dl_library_path)\n";
print STDERR "DynaLoader not linked into this perl\n"
unless defined(&boot_DynaLoader);
}
1; # End of main code
# The bootstrap function cannot be autoloaded (without complications)
# so we define it here:
sub bootstrap {
# use local vars to enable $module.bs script to edit values
local(@args) = @_;
local($module) = $args[0];
local(@dirs, $file);
croak "Usage: DynaLoader::bootstrap(module)"
unless ($module);
croak "Can't load module $module, dynamic loading not available in this perl"
unless defined(&dl_load_file);
print STDERR "DynaLoader::bootstrap($module)\n" if $dl_debug;
my(@modparts) = split(/::/,$module);
my($modfname) = $modparts[-1];
my($modpname) = join('/',@modparts);
foreach (@INC) {
my $dir = "$_/auto/$modpname";
next unless -d $dir; # skip over uninteresting directories
# check for common cases to avoid autoload of dl_findfile
last if ($file=_check_file("$dir/$modfname.$dl_dlext"));
# no luck here, save dir for possible later dl_findfile search
push(@dirs, "-L$dir");
}
# last resort, let dl_findfile have a go in all known locations
$file = dl_findfile(@dirs, map("-L$_",@INC), $modfname) unless $file;
croak "Can't find loadable object for module $module in \@INC"
unless $file;
my($bootname) = "boot_$module";
$bootname =~ s/\W/_/g;
@dl_require_symbols = ($bootname);
# Execute optional '.bootstrap' perl script for this module.
# The .bs file can be used to configure @dl_resolve_using etc to
# match the needs of the individual module on this architecture.
my $bs = $file;
$bs =~ s/(\.\w+)?$/\.bs/; # look for .bs 'beside' the library
if (-s $bs) { # only read file if it's not empty
local($osname, $dlsrc) = @Config{'osname','dlsrc'};
print STDERR "BS: $bs ($osname, $dlsrc)\n" if $dl_debug;
eval { do $bs; };
warn "$bs: $@\n" if $@;
}
# Many dynamic extension loading problems will appear to come from
# this section of code: XYZ failed at line 123 of DynaLoader.pm.
# Often these errors are actually occurring in the initialisation
# C code of the extension XS file. Perl reports the error as being
# in this perl code simply because this was the last perl code
# it executed.
my $libref = dl_load_file($file) or
croak "Can't load '$file' for module $module: ".dl_error()."\n";
my(@unresolved) = dl_undef_symbols();
carp "Undefined symbols present after loading $file: @unresolved\n"
if (@unresolved);
my $boot_symbol_ref = dl_find_symbol($libref, $bootname) or
croak "Can't find '$bootname' symbol in $file\n";
dl_install_xsub("${module}::bootstrap", $boot_symbol_ref, $file);
# See comment block above
&{"${module}::bootstrap"}(@args);
}
sub _check_file{ # private utility to handle dl_expandspec vs -f tests
my($file) = @_;
return $file if (!$do_expand && -f $file); # the common case
return $file if ( $do_expand && ($file=dl_expandspec($file)));
return undef;
}
# Let autosplit and the autoloader deal with these functions:
__END__
sub dl_findfile {
# Read ext/DynaLoader/DynaLoader.doc for detailed information.
# This function does not automatically consider the architecture
# or the perl library auto directories.
my (@args) = @_;
my (@dirs, $dir); # which directories to search
my (@found); # full paths to real files we have found
my ($vms) = ($Config{'osname'} eq 'VMS');
print STDERR "dl_findfile(@args)\n" if $dl_debug;
# accumulate directories but process files as they appear
arg: foreach(@args) {
# Special fast case: full filepath requires no search
if (m:/: && -f $_ && !$do_expand){
push(@found,$_);
last arg unless wantarray;
next;
}
# Deal with directories first:
# Using a -L prefix is the preferred option (faster and more robust)
if (m:^-L:){ s/^-L//; push(@dirs, $_); next; }
# Otherwise we try to try to spot directories by a heuristic
# (this is a more complicated issue than it first appears)
if (m:/: && -d $_){ push(@dirs, $_); next; }
# VMS: we may be using native VMS directry syntax instead of
# Unix emulation, so check this as well
if ($vms && /[:>\]]/ && -d $_){ push(@dirs, $_); next; }
# Only files should get this far...
my(@names, $name); # what filenames to look for
if (m:-l: ){ # convert -lname to appropriate library name
s/-l//;
push(@names,"lib$_.$dl_so");
push(@names,"lib$_.a");
}else{ # Umm, a bare name. Try various alternatives:
# these should be ordered with the most likely first
push(@names,"$_.$dl_so") unless m/\.$dl_so$/o;
push(@names,"lib$_.$dl_so") unless m:/:;
push(@names,"$_.o") unless m/\.(o|$dl_so)$/o;
push(@names,"$_.a") unless m/\.a$/;
push(@names, $_);
}
foreach $dir (@dirs, @dl_library_path) {
next unless -d $dir;
foreach $name (@names) {
my($file) = "$dir/$name";
print STDERR " checking in $dir for $name\n" if $dl_debug;
$file = _check_file($file);
if ($file){
push(@found, $file);
next arg; # no need to look any further
}
}
}
}
if ($dl_debug) {
foreach(@dirs) {
print STDERR " dl_findfile ignored non-existent directory: $_\n" unless -d $_;
}
print STDERR "dl_findfile found: @found\n";
}
return $found[0] unless wantarray;
@found;
}
sub dl_expandspec{
my($spec) = @_;
# Optional function invoked if DynaLoader.pm sets $do_expand.
# Most systems do not require or use this function.
# Some systems may implement it in the dl_*.xs file in which case
# this autoload version will not be called but is harmless.
# This function is designed to deal with systems which treat some
# 'filenames' in a special way. For example VMS 'Logical Names'
# (something like unix environment variables - but different).
# This function should recognise such names and expand them into
# full file paths.
# Must return undef if $spec is invalid or file does not exist.
my($file) = $spec; # default output to input
my($osname) = $Config{'osname'};
if ($osname eq 'VMS'){ # dl_expandspec should be defined in dl_vms.xs
croak "dl_expandspec: should be defined in XS file!\n";
}else{
return undef unless -f $file;
}
print STDERR "dl_expandspec($spec) => $file\n" if $dl_debug;
$file;
}