XSLoader(3p) Perl Programmers Reference Guide XSLoader(3p) #
XSLoader(3p) Perl Programmers Reference Guide XSLoader(3p)
NNAAMMEE #
XSLoader - Dynamically load C libraries into Perl code
VVEERRSSIIOONN #
Version 0.31
SSYYNNOOPPSSIISS #
package YourPackage;
require XSLoader;
XSLoader::load(__PACKAGE__, $VERSION);
DDEESSCCRRIIPPTTIIOONN #
This module defines a standard _s_i_m_p_l_i_f_i_e_d 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".
MMiiggrraattiioonn ffrroomm “"DDyynnaaLLooaaddeerr"” A typical module using DynaLoader starts like this:
package YourPackage;
require DynaLoader;
our @ISA = qw( OnePackage OtherPackage DynaLoader );
our $VERSION = '0.01';
__PACKAGE__->bootstrap($VERSION);
Change this to
package YourPackage;
use XSLoader;
our @ISA = qw( OnePackage OtherPackage );
our $VERSION = '0.01';
XSLoader::load(__PACKAGE__, $VERSION);
In other words: replace "require DynaLoader" by "use XSLoader", remove
"DynaLoader" from @ISA, change "bootstrap" by "XSLoader::load". Do not
forget to quote the name of your package on the "XSLoader::load" line,
and add comma (",") before the arguments ($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
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(__PACKAGE__);
in which case it can be further simplified to
XSLoader::load();
as "load" will use "caller" to determine the package.
BBaacckkwwaarrdd ccoommppaattiibbllee bbooiilleerrppllaattee If you want to have your cake and eat it too, you need a more complicated boilerplate.
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);
};
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 antique Perl which has no "XSLoader", it falls back to using
"DynaLoader".
OOrrddeerr ooff iinniittiiaalliizzaattiioonn:: eeaarrllyy llooaadd(()) _S_k_i_p _t_h_i_s _s_e_c_t_i_o_n _i_f _t_h_e _X_S_U_B _f_u_n_c_t_i_o_n_s _a_r_e _s_u_p_p_o_s_e_d _t_o _b_e _c_a_l_l_e_d _f_r_o_m _o_t_h_e_r _m_o_d_u_l_e_s _o_n_l_y_; _r_e_a_d _i_t _o_n_l_y _i_f _y_o_u _c_a_l_l _y_o_u_r _X_S_U_B_s _f_r_o_m _t_h_e _c_o_d_e _i_n _y_o_u_r _m_o_d_u_l_e_, _o_r _h_a_v_e _a _"_B_O_O_T_:_" _s_e_c_t_i_o_n _i_n _y_o_u_r _X_S _f_i_l_e _(_s_e_e _"_T_h_e _B_O_O_T_: _K_e_y_w_o_r_d_" _i_n _p_e_r_l_x_s_)_. _W_h_a_t _i_s _d_e_s_c_r_i_b_e_d _h_e_r_e _i_s _e_q_u_a_l_l_y _a_p_p_l_i_c_a_b_l_e _t_o _t_h_e _D_y_n_a_L_o_a_d_e_r _i_n_t_e_r_f_a_c_e_.
A sufficiently complicated module using XS would have both Perl code
(defined in _Y_o_u_r_P_a_c_k_a_g_e_._p_m) and XS code (defined in _Y_o_u_r_P_a_c_k_a_g_e_._x_s). 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 _x_s_u_b_p_p (nearly all modules) this has
three side effects:
• A sanity check is done to ensure that the versions of the _._p_m and the
(compiled) _._x_s parts are compatible. If $VERSION was specified, this
is used for the check. If not specified, it defaults to "$XS_VERSION
// $VERSION" (in the module's namespace)
• the XSUBs are made accessible from Perl
• if a "BOOT:" section was present in the _._x_s file, the code there is
called.
Consequently, if the code in the _._p_m file makes calls to these XSUBs, it
is convenient to have XSUBs installed before the Perl code is defined;
for example, this makes prototypes for XSUBs visible to this Perl code.
Alternatively, if the "BOOT:" section makes calls to Perl functions (or
uses Perl variables) defined in the _._p_m file, they must be defined prior
to the call to "XSLoader::load()" (or "bootstrap()").
The first situation being much more frequent, it makes sense to rewrite
the boilerplate as
package YourPackage;
use XSLoader;
our ($VERSION, @ISA);
BEGIN { #
@ISA = qw( OnePackage OtherPackage );
$VERSION = ‘0.01’; #
# Put Perl code used in the BOOT: section here
XSLoader::load(__PACKAGE__, $VERSION);
}
# Put Perl code making calls into XSUBs here
TThhee mmoosstt hhaaiirryy ccaassee If the interdependence of your “BOOT:” section and Perl code is more complicated than this (e.g., the “BOOT:” section makes calls to Perl functions which make calls to XSUBs with prototypes), get rid of the “BOOT:” section altogether. Replace it with a function “onBOOT()”, and call it like this:
package YourPackage;
use XSLoader;
our ($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
DDIIAAGGNNOOSSTTIICCSS #
"Can't find '%s' symbol in %s"
((FF)) The bootstrap symbol could not be found in the extension module.
"Can't load '%s' for module %s: %s"
((FF)) The loading or initialisation of the extension module failed.
The detailed error follows.
"Undefined symbols present after loading %s: %s"
((WW)) As the message says, some symbols stay undefined although the
extension module was correctly loaded and initialised. The list of
undefined symbols follows.
LLIIMMIITTAATTIIOONNSS #
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".
KKNNOOWWNN BBUUGGSS #
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.
BBUUGGSS #
Please report any bugs or feature requests via the ppeerrllbbuugg(1) utility.
SSEEEE AALLSSOO #
DynaLoader
AAUUTTHHOORRSS #
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>.
CCOOPPYYRRIIGGHHTT && LLIICCEENNSSEE #
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.
perl v5.36.3 2024-03-20 XSLoader(3p)