MirBSD manpage: XSLoader(3p)

XSLoader(3p)    Perl Programmers Reference Guide     XSLoader(3p)


     XSLoader - Dynamically load C libraries into Perl code


     Version 0.06


         package YourPackage;
         use XSLoader;

         XSLoader::load 'YourPackage', $YourPackage::VERSION;


     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".

     Migration from "DynaLoader"

     A typical module using DynaLoader starts like this:

         package YourPackage;
         require DynaLoader;

         our @ISA = qw( OnePackage OtherPackage DynaLoader );
         our $VERSION = '0.01';
         bootstrap YourPackage $VERSION;

     Change this to

         package YourPackage;
         use XSLoader;

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

     In other words: replace "require DynaLoader" by "use
     XSLoader", remove "DynaLoader" from @ISA, change "bootstrap"
     by "XSLoader::load".  Do not forget to quote the name of
     your package on the "XSLoader::load" line, and add comma
     (",") before the arguments ($VERSION above).

     Of course, if @ISA contained only "DynaLoader", there is no
     need to have the @ISA assignment at all; moreover, if
     instead of "our" one uses the more backward-compatible

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         use vars qw($VERSION @ISA);

     one can remove this reference to @ISA together with the @ISA

     If no $VERSION was specified on the "bootstrap" line, the
     last line becomes

         XSLoader::load 'YourPackage';

     Backward compatible boilerplate

     If you want to have your cake and eat it too, you need a
     more complicated boilerplate.

         package YourPackage;
         use vars qw($VERSION @ISA);

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

     The parentheses about "XSLoader::load()" arguments are
     needed since we replaced "use XSLoader" by "require", so the
     compiler does not know that a function "XSLoader::load()" is

     This boilerplate uses the low-overhead "XSLoader" if
     present; if used with an antic Perl which has no "XSLoader",
     it falls back to using "DynaLoader".

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.

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     The call to "XSLoader::load()" (or "bootstrap()") has three
     side effects:

     +   if $VERSION was specified, a sanity check is done to
         ensure that the versions of the .pm and the (compiled)
         .xs parts are compatible;

     +   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;
         use vars qw($VERSION @ISA);

         BEGIN {
            @ISA = qw( OnePackage OtherPackage );
            $VERSION = '0.01';

            # Put Perl code used in the BOOT: section here

            XSLoader::load 'YourPackage', $VERSION;

         # Put Perl code making calls into XSUBs here

     The most hairy case

     If the interdependence of your "BOOT:" section and Perl code
     is more complicated than this (e.g., the "BOOT:" section
     makes calls to Perl functions which make calls to XSUBs with
     prototypes), get rid of the "BOOT:" section altogether.
     Replace it with a function "onBOOT()", and call it like

         package YourPackage;
         use XSLoader;
         use vars qw($VERSION @ISA);

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         BEGIN {
            @ISA = qw( OnePackage OtherPackage );
            $VERSION = '0.01';
            XSLoader::load 'YourPackage', $VERSION;

         # Put Perl code used in onBOOT() function here; calls to XSUBs are
         # prototype-checked.


         # Put Perl initialization code assuming that XS is initialized here


     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.

     XSLoader::load('Your::Module', $Your::Module::VERSION)
         (F) You tried to invoke "load()" without any argument.
         You must supply a module name, and optionally its ver-


     To reduce the overhead as much as possible, only one possi-
     ble 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 over-
     head than running the same extensions after "make install".


     Please report any bugs or feature requests via the perl-
     bug(1) utility.



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     Ilya Zakharevich originally extracted "XSLoader" from

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

     Previous maintainer was Michael G Schwern


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

perl v5.8.8                2005-02-05                           5

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