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8.61. DynaLoader

The standard Perl interface to the
dynamic linking mechanisms available on many platforms.

8.61.1. Using DynaLoader

Use DynaLoader like this:

package Module;
require DynaLoader;
@ISA = qw(... DynaLoader ...);
bootstrap Module;

The bootstrap method calls your
module''''s bootstrap routine directly if the module is
statically linked into Perl. Otherwise, the module inherits the
bootstrap method from DynaLoader, which loads in
your module and calls its bootstrap method.

8.61.2. Extending to New Architectures

If you want to extend DynaLoader to a new architecture, you need to
know about its internal interface. The variables it uses are:

$dl_debug

Enables internal debugging messages on the Perl side of the
DynaLoader; by default, is set to
$ENV{''''PERL_DL_DEBUG''''} if that is defined. A
similar debugging variable is added to the C code (see
dlutils.c) and enabled if Perl was built with
the -DDEBUGGING flag, or it can be set via the
PERL_DL_DEBUG environment variable. Set to 1 for
minimal information or higher for more detail.

@dl_library_path

Default list of directories to search for libraries; initialized to
hold the list of directories in $Config{''''libpth''''}.
Should also be initialized with other directories that can be
determined from the environment at runtime.

@dl_resolve_using

List of additional libraries or other shared objects for resolving
undefined symbols. Required only on platforms without automatic
handling for dependent libraries.

@dl_require_symbols

List of one or more symbol names in the library/object file to be
dynamically loaded. Only required on some platforms.

Of the following subroutines, bootstrap and
dl_findfile are standard across all platforms and
are defined in DynaLoader.pm. The others are
defined in the .xs file that supplies the
implementation for the platform.

bootstrap (modulename)

Normal entry point for automatic dynamic loading in Perl.

dl_error

Gets error message text from the last failed DynaLoader function:

$message = dl_error(  );

dl_expandspec (spec)

Used for systems that require special filename handling to deal with
symbolic names for files. spec specifies
the filenames that need the special handling.

dl_findfile (names)

Determines the full paths to one or more loadable files, given their
generic names and optionally one or more directories. Searches
directories in @dl_library_path by default and
returns an empty list if no files are found.

dl_find_symbol (libref, symbol)

Looks in libref for the address of symbol
symbol. Returns the address, or
undef if not found.

dl_install_xsub (perl_name, symref[, filename])

Creates a new Perl external subroutine. Takes the following arguments:

perl_name

Name of the new subroutine.

symref

Pointer to the function that implements the routine.

filename

The source file for the function. If not defined, DynaLoader is used.

dl_load_file (filename)

Dynamically loads filename, which must be
the path to a shared object or library; returns
undef on error.

dl_undef_symbols

Returns list of symbol names that remain undefined after
dl_load_file, or ( ) if the
names are unknown.