1XSLoader(3pm)          Perl Programmers Reference Guide          XSLoader(3pm)
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NAME

6       XSLoader - Dynamically load C libraries into Perl code
7

VERSION

9       Version 0.30
10

SYNOPSIS

12           package YourPackage;
13           require XSLoader;
14
15           XSLoader::load(__PACKAGE__, $VERSION);
16

DESCRIPTION

18       This module defines a standard simplified interface to the dynamic
19       linking mechanisms available on many platforms.  Its primary purpose is
20       to implement cheap automatic dynamic loading of Perl modules.
21
22       For a more complicated interface, see DynaLoader.  Many (most) features
23       of "DynaLoader" are not implemented in "XSLoader", like for example the
24       "dl_load_flags", not honored by "XSLoader".
25
26   Migration from "DynaLoader"
27       A typical module using DynaLoader starts like this:
28
29           package YourPackage;
30           require DynaLoader;
31
32           our @ISA = qw( OnePackage OtherPackage DynaLoader );
33           our $VERSION = '0.01';
34           __PACKAGE__->bootstrap($VERSION);
35
36       Change this to
37
38           package YourPackage;
39           use XSLoader;
40
41           our @ISA = qw( OnePackage OtherPackage );
42           our $VERSION = '0.01';
43           XSLoader::load(__PACKAGE__, $VERSION);
44
45       In other words: replace "require DynaLoader" by "use XSLoader", remove
46       "DynaLoader" from @ISA, change "bootstrap" by "XSLoader::load".  Do not
47       forget to quote the name of your package on the "XSLoader::load" line,
48       and add comma (",") before the arguments ($VERSION above).
49
50       Of course, if @ISA contained only "DynaLoader", there is no need to
51       have the @ISA assignment at all; moreover, if instead of "our" one uses
52       the more backward-compatible
53
54           use vars qw($VERSION @ISA);
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56       one can remove this reference to @ISA together with the @ISA
57       assignment.
58
59       If no $VERSION was specified on the "bootstrap" line, the last line
60       becomes
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62           XSLoader::load(__PACKAGE__);
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64       in which case it can be further simplified to
65
66           XSLoader::load();
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68       as "load" will use "caller" to determine the package.
69
70   Backward compatible boilerplate
71       If you want to have your cake and eat it too, you need a more
72       complicated boilerplate.
73
74           package YourPackage;
75
76           our @ISA = qw( OnePackage OtherPackage );
77           our $VERSION = '0.01';
78           eval {
79              require XSLoader;
80               XSLoader::load(__PACKAGE__, $VERSION);
81              1;
82           } or do {
83              require DynaLoader;
84              push @ISA, 'DynaLoader';
85              __PACKAGE__->bootstrap($VERSION);
86           };
87
88       The parentheses about "XSLoader::load()" arguments are needed since we
89       replaced "use XSLoader" by "require", so the compiler does not know
90       that a function "XSLoader::load()" is present.
91
92       This boilerplate uses the low-overhead "XSLoader" if present; if used
93       with an antique Perl which has no "XSLoader", it falls back to using
94       "DynaLoader".
95

Order of initialization: early load()

97       Skip this section if the XSUB functions are supposed to be called from
98       other modules only; read it only if you call your XSUBs from the code
99       in your module, or have a "BOOT:" section in your XS file (see "The
100       BOOT: Keyword" in perlxs).  What is described here is equally
101       applicable to the DynaLoader interface.
102
103       A sufficiently complicated module using XS would have both Perl code
104       (defined in YourPackage.pm) and XS code (defined in YourPackage.xs).
105       If this Perl code makes calls into this XS code, and/or this XS code
106       makes calls to the Perl code, one should be careful with the order of
107       initialization.
108
109       The call to "XSLoader::load()" (or "bootstrap()") calls the module's
110       bootstrap code. For modules build by xsubpp (nearly all modules) this
111       has three side effects:
112
113       •   A sanity check is done to ensure that the versions of the .pm and
114           the (compiled) .xs parts are compatible. If $VERSION was specified,
115           this is used for the check. If not specified, it defaults to
116           "$XS_VERSION // $VERSION" (in the module's namespace)
117
118       •   the XSUBs are made accessible from Perl
119
120       •   if a "BOOT:" section was present in the .xs file, the code there is
121           called.
122
123       Consequently, if the code in the .pm file makes calls to these XSUBs,
124       it is convenient to have XSUBs installed before the Perl code is
125       defined; for example, this makes prototypes for XSUBs visible to this
126       Perl code.  Alternatively, if the "BOOT:" section makes calls to Perl
127       functions (or uses Perl variables) defined in the .pm file, they must
128       be defined prior to the call to "XSLoader::load()" (or "bootstrap()").
129
130       The first situation being much more frequent, it makes sense to rewrite
131       the boilerplate as
132
133           package YourPackage;
134           use XSLoader;
135           our ($VERSION, @ISA);
136
137           BEGIN {
138              @ISA = qw( OnePackage OtherPackage );
139              $VERSION = '0.01';
140
141              # Put Perl code used in the BOOT: section here
142
143              XSLoader::load(__PACKAGE__, $VERSION);
144           }
145
146           # Put Perl code making calls into XSUBs here
147
148   The most hairy case
149       If the interdependence of your "BOOT:" section and Perl code is more
150       complicated than this (e.g., the "BOOT:" section makes calls to Perl
151       functions which make calls to XSUBs with prototypes), get rid of the
152       "BOOT:" section altogether.  Replace it with a function "onBOOT()", and
153       call it like this:
154
155           package YourPackage;
156           use XSLoader;
157           our ($VERSION, @ISA);
158
159           BEGIN {
160              @ISA = qw( OnePackage OtherPackage );
161              $VERSION = '0.01';
162              XSLoader::load(__PACKAGE__, $VERSION);
163           }
164
165           # Put Perl code used in onBOOT() function here; calls to XSUBs are
166           # prototype-checked.
167
168           onBOOT;
169
170           # Put Perl initialization code assuming that XS is initialized here
171

DIAGNOSTICS

173       "Can't find '%s' symbol in %s"
174           (F) The bootstrap symbol could not be found in the extension
175           module.
176
177       "Can't load '%s' for module %s: %s"
178           (F) The loading or initialisation of the extension module failed.
179           The detailed error follows.
180
181       "Undefined symbols present after loading %s: %s"
182           (W) As the message says, some symbols stay undefined although the
183           extension module was correctly loaded and initialised. The list of
184           undefined symbols follows.
185

LIMITATIONS

187       To reduce the overhead as much as possible, only one possible location
188       is checked to find the extension DLL (this location is where "make
189       install" would put the DLL).  If not found, the search for the DLL is
190       transparently delegated to "DynaLoader", which looks for the DLL along
191       the @INC list.
192
193       In particular, this is applicable to the structure of @INC used for
194       testing not-yet-installed extensions.  This means that running
195       uninstalled extensions may have much more overhead than running the
196       same extensions after "make install".
197

KNOWN BUGS

199       The new simpler way to call "XSLoader::load()" with no arguments at all
200       does not work on Perl 5.8.4 and 5.8.5.
201

BUGS

203       Please report any bugs or feature requests via the perlbug(1) utility.
204

SEE ALSO

206       DynaLoader
207

AUTHORS

209       Ilya Zakharevich originally extracted "XSLoader" from "DynaLoader".
210
211       CPAN version is currently maintained by Sebastien Aperghis-Tramoni
212       <sebastien@aperghis.net>.
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214       Previous maintainer was Michael G Schwern <schwern@pobox.com>.
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217       Copyright (C) 1990-2011 by Larry Wall and others.
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219       This program is free software; you can redistribute it and/or modify it
220       under the same terms as Perl itself.
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224perl v5.32.1                      2021-05-31                     XSLoader(3pm)
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