NAME¶

XSLoader - Dynamically load C libraries into Perl code

VERSION¶

Version 0.32

SYNOPSIS¶

    package YourPackage;
    require XSLoader;
    XSLoader::load(__PACKAGE__, $VERSION);

DESCRIPTION¶

This module defines a standard simplified interface to the dynamic linking mechanisms available on many platforms. Its primary purpose is to implement cheap automatic dynamic loading of Perl modules.

For a more complicated interface, see DynaLoader. Many (most) features of "DynaLoader" are not implemented in "XSLoader", like for example the "dl_load_flags", not honored by "XSLoader".

    package YourPackage;
    require DynaLoader;
    our @ISA = qw( OnePackage OtherPackage DynaLoader );
    our $VERSION = '0.01';
    __PACKAGE__->bootstrap($VERSION);

    package YourPackage;
    use XSLoader;
    our @ISA = qw( OnePackage OtherPackage );
    our $VERSION = '0.01';
    XSLoader::load(__PACKAGE__, $VERSION);

    use vars qw($VERSION @ISA);

    XSLoader::load(__PACKAGE__);

    XSLoader::load();

    package YourPackage;
    our @ISA = qw( OnePackage OtherPackage );
    our $VERSION = '0.01';
    eval {
       require XSLoader;
        XSLoader::load(__PACKAGE__, $VERSION);
       1;
    } or do {
       require DynaLoader;
       push @ISA, 'DynaLoader';
       __PACKAGE__->bootstrap($VERSION);
    };

Order of initialization: early load()¶

Skip this section if the XSUB functions are supposed to be called from other modules only; read it only if you call your XSUBs from the code in your module, or have a "BOOT:" section in your XS file (see "The BOOT: Keyword" in perlxs). What is described here is equally applicable to the DynaLoader interface.

A sufficiently complicated module using XS would have both Perl code (defined in YourPackage.pm) and XS code (defined in YourPackage.xs). If this Perl code makes calls into this XS code, and/or this XS code makes calls to the Perl code, one should be careful with the order of initialization.

The call to XSLoader::load() (or bootstrap()) calls the module's bootstrap code. For modules build by xsubpp (nearly all modules) this has three side effects:

• A sanity check is done to ensure that the versions of the .pm and the (compiled) .xs parts are compatible. If $VERSION was specified, this is used for the check. If not specified, it defaults to "$XS_VERSION // $VERSION" (in the module's namespace)
• the XSUBs are made accessible from Perl
• if a "BOOT:" section was present in the .xs file, the code there is called.

Consequently, if the code in the .pm file makes calls to these XSUBs, it is convenient to have XSUBs installed before the Perl code is defined; for example, this makes prototypes for XSUBs visible to this Perl code. Alternatively, if the "BOOT:" section makes calls to Perl functions (or uses Perl variables) defined in the .pm file, they must be defined prior to the call to XSLoader::load() (or bootstrap()).

The first situation being much more frequent, it makes sense to rewrite the boilerplate as

    package YourPackage;
    use XSLoader;
    our ($VERSION, @ISA);
    BEGIN {
       @ISA = qw( OnePackage OtherPackage );
       $VERSION = '0.01';
       # Put Perl code used in the BOOT: section here
       XSLoader::load(__PACKAGE__, $VERSION);
    }
    # Put Perl code making calls into XSUBs here

    package YourPackage;
    use XSLoader;
    our ($VERSION, @ISA);
    BEGIN {
       @ISA = qw( OnePackage OtherPackage );
       $VERSION = '0.01';
       XSLoader::load(__PACKAGE__, $VERSION);
    }
    # Put Perl code used in onBOOT() function here; calls to XSUBs are
    # prototype-checked.
    onBOOT;
    # Put Perl initialization code assuming that XS is initialized here

DIAGNOSTICS¶

"Can't find '%s' symbol in %s"

(F) The bootstrap symbol could not be found in the extension module.

"Can't load '%s' for module %s: %s"

(F) The loading or initialisation of the extension module failed. The detailed error follows.

"Undefined symbols present after loading %s: %s"

(W) As the message says, some symbols stay undefined although the extension module was correctly loaded and initialised. The list of undefined symbols follows.

LIMITATIONS¶

To reduce the overhead as much as possible, only one possible location is checked to find the extension DLL (this location is where "make install" would put the DLL). If not found, the search for the DLL is transparently delegated to "DynaLoader", which looks for the DLL along the @INC list.

In particular, this is applicable to the structure of @INC used for testing not-yet-installed extensions. This means that running uninstalled extensions may have much more overhead than running the same extensions after "make install".

KNOWN BUGS¶

The new simpler way to call XSLoader::load() with no arguments at all does not work on Perl 5.8.4 and 5.8.5.

BUGS¶

Please report any bugs or feature requests via the perlbug(1) utility.

SEE ALSO¶

DynaLoader

AUTHORS¶

Ilya Zakharevich originally extracted "XSLoader" from "DynaLoader".

CPAN version is currently maintained by Sébastien Aperghis-Tramoni <sebastien@aperghis.net>.

Previous maintainer was Michael G Schwern <schwern@pobox.com>.

COPYRIGHT & LICENSE¶

Copyright (C) 1990-2011 by Larry Wall and others.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.