XSLoader - Dynamically load C libraries into Perl code
Version 0.06
- package YourPackage;
- use XSLoader;
- XSLoader::load 'YourPackage', $YourPackage::VERSION;
This module defines a standard simplified interface to the dynamic linking mechanisms available on many platforms. Its primary purpose is to implement cheap automatic dynamic loading of Perl modules.
For a more complicated interface, see DynaLoader. Many (most)
features of DynaLoader
are not implemented in XSLoader
, like for
example the dl_load_flags
, not honored by XSLoader
.
DynaLoader
A typical module using DynaLoader starts like this:
Change this to
In other words: replace require DynaLoader
by use XSLoader
, remove
DynaLoader
from @ISA
, change bootstrap
by XSLoader::load
. Do not
forget to quote the name of your package on the XSLoader::load
line,
and add comma (,
) before the arguments ($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
- use vars qw($VERSION @ISA);
one can remove this reference to @ISA
together with the @ISA
assignment.
If no $VERSION
was specified on the bootstrap
line, the last line becomes
- XSLoader::load 'YourPackage';
If you want to have your cake and eat it too, you need a more complicated boilerplate.
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 present.
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
.
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()
) has three side effects:
if $VERSION
was specified, a sanity check is done to ensure that the
versions of the .pm and the (compiled) .xs parts are compatible;
the XSUBs are made accessible from Perl;
if a BOOT:
section was present in the .xs file, the code there is called.
Consequently, if the code in the .pm file makes calls to these XSUBs, it is
convenient to have XSUBs installed before the Perl code is defined; for
example, this makes prototypes for XSUBs visible to this Perl code.
Alternatively, if the BOOT:
section makes calls to Perl functions (or
uses Perl variables) defined in the .pm file, they must be defined prior to
the call to XSLoader::load()
(or bootstrap()
).
The first situation being much more frequent, it makes sense to rewrite the boilerplate as
If the interdependence of your BOOT:
section and Perl code is
more complicated than this (e.g., the BOOT:
section makes calls to Perl
functions which make calls to XSUBs with prototypes), get rid of the BOOT:
section altogether. Replace it with a function onBOOT()
, and call it like
this:
- package YourPackage;
- use XSLoader;
- use vars qw($VERSION @ISA);
- 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.
- onBOOT;
- # Put Perl initialization code assuming that XS is initialized here
(F) The bootstrap symbol could not be found in the extension module.
(F) The loading or initialisation of the extension module failed. The detailed error follows.
(W) As the message says, some symbols stay undefined although the extension module was correctly loaded and initialised. The list of undefined symbols follows.
(F) You tried to invoke load()
without any argument. You must supply
a module name, and optionally its version.
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
.
Please report any bugs or feature requests via the perlbug(1) utility.
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>
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.