1XSLoader(3pm) Perl Programmers Reference Guide XSLoader(3pm)
2
6 XSLoader - Dynamically load C libraries into Perl code
7
9 Version 0.15
10
12 package YourPackage;
13 require XSLoader;
14 XSLoader::load();
16
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 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 Migration from "DynaLoader"
27 A typical module using DynaLoader starts like this:
28 package YourPackage;
30 require DynaLoader;
31 our @ISA = qw( OnePackage OtherPackage DynaLoader );
33 our $VERSION = '0.01';
34 bootstrap YourPackage $VERSION;
35 Change this to
37 package YourPackage;
39 use XSLoader;
40 our @ISA = qw( OnePackage OtherPackage );
42 our $VERSION = '0.01';
43 XSLoader::load 'YourPackage', $VERSION;
44 In other words: replace "require DynaLoader" by "use XSLoader", remove
46 "DynaLoader" from @ISA, change "bootstrap" by "XSLoader::load". Do not
47 forget to quote the name of your package on the "XSLoader::load" line,
48 and add comma (",") before the arguments ($VERSION above).
49 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 use vars qw($VERSION @ISA);
55 one can remove this reference to @ISA together with the @ISA
57 assignment.
58 If no $VERSION was specified on the "bootstrap" line, the last line
60 becomes
61 XSLoader::load 'YourPackage';
63 If the call to "load" is from the YourPackage, then that can be further
65 simplified to
66 XSLoader::load();
68 as "load" will use "caller" to determine the package.
70 Backward compatible boilerplate
72 If you want to have your cake and eat it too, you need a more
73 complicated boilerplate.
74 package YourPackage;
76 use vars qw($VERSION @ISA);
77 @ISA = qw( OnePackage OtherPackage );
79 $VERSION = '0.01';
80 eval {
81 require XSLoader;
82 XSLoader::load('YourPackage', $VERSION);
83 1;
84 } or do {
85 require DynaLoader;
86 push @ISA, 'DynaLoader';
87 bootstrap YourPackage $VERSION;
88 };
89 The parentheses about "XSLoader::load()" arguments are needed since we
91 replaced "use XSLoader" by "require", so the compiler does not know
92 that a function "XSLoader::load()" is present.
93 This boilerplate uses the low-overhead "XSLoader" if present; if used
95 with an antic Perl which has no "XSLoader", it falls back to using
96 "DynaLoader".
97
99 Skip this section if the XSUB functions are supposed to be called from
100 other modules only; read it only if you call your XSUBs from the code
101 in your module, or have a "BOOT:" section in your XS file (see "The
102 BOOT: Keyword" in perlxs). What is described here is equally
103 applicable to the DynaLoader interface.
104 A sufficiently complicated module using XS would have both Perl code
106 (defined in YourPackage.pm) and XS code (defined in YourPackage.xs).
107 If this Perl code makes calls into this XS code, and/or this XS code
108 makes calls to the Perl code, one should be careful with the order of
109 initialization.
110 The call to "XSLoader::load()" (or "bootstrap()") calls the module's
112 bootstrap code. For modules build by xsubpp (nearly all modules) this
113 has three side effects:
114 · A sanity check is done to ensure that the versions of the .pm and
116 the (compiled) .xs parts are compatible. If $VERSION was specified,
117 this is used for the check. If not specified, it defaults to
118 "$XS_VERSION // $VERSION" (in the module's namespace)
119 · the XSUBs are made accessible from Perl
121 · if a "BOOT:" section was present in the .xs file, the code there is
123 called.
124 Consequently, if the code in the .pm file makes calls to these XSUBs,
126 it is convenient to have XSUBs installed before the Perl code is
127 defined; for example, this makes prototypes for XSUBs visible to this
128 Perl code. Alternatively, if the "BOOT:" section makes calls to Perl
129 functions (or uses Perl variables) defined in the .pm file, they must
130 be defined prior to the call to "XSLoader::load()" (or "bootstrap()").
131 The first situation being much more frequent, it makes sense to rewrite
133 the boilerplate as
134 package YourPackage;
136 use XSLoader;
137 use vars qw($VERSION @ISA);
138 BEGIN {
140 @ISA = qw( OnePackage OtherPackage );
141 $VERSION = '0.01';
142 # Put Perl code used in the BOOT: section here
144 XSLoader::load 'YourPackage', $VERSION;
146 }
147 # Put Perl code making calls into XSUBs here
149 The most hairy case
151 If the interdependence of your "BOOT:" section and Perl code is more
152 complicated than this (e.g., the "BOOT:" section makes calls to Perl
153 functions which make calls to XSUBs with prototypes), get rid of the
154 "BOOT:" section altogether. Replace it with a function "onBOOT()", and
155 call it like this:
156 package YourPackage;
158 use XSLoader;
159 use vars qw($VERSION @ISA);
160 BEGIN {
162 @ISA = qw( OnePackage OtherPackage );
163 $VERSION = '0.01';
164 XSLoader::load 'YourPackage', $VERSION;
165 }
166 # Put Perl code used in onBOOT() function here; calls to XSUBs are
168 # prototype-checked.
169 onBOOT;
171 # Put Perl initialization code assuming that XS is initialized here
173
175 "Can't find '%s' symbol in %s"
176 (F) The bootstrap symbol could not be found in the extension
177 module.
178 "Can't load '%s' for module %s: %s"
180 (F) The loading or initialisation of the extension module failed.
181 The detailed error follows.
182 "Undefined symbols present after loading %s: %s"
184 (W) As the message says, some symbols stay undefined although the
185 extension module was correctly loaded and initialised. The list of
186 undefined symbols follows.
187
189 To reduce the overhead as much as possible, only one possible location
190 is checked to find the extension DLL (this location is where "make
191 install" would put the DLL). If not found, the search for the DLL is
192 transparently delegated to "DynaLoader", which looks for the DLL along
193 the @INC list.
194 In particular, this is applicable to the structure of @INC used for
196 testing not-yet-installed extensions. This means that running
197 uninstalled extensions may have much more overhead than running the
198 same extensions after "make install".
199
201 The new simpler way to call "XSLoader::load()" with no arguments at all
202 does not work on Perl 5.8.4 and 5.8.5.
203
205 Please report any bugs or feature requests via the perlbug(1) utility.
206
208 DynaLoader
209
211 Ilya Zakharevich originally extracted "XSLoader" from "DynaLoader".
212 CPAN version is currently maintained by Sebastien Aperghis-Tramoni
214 <sebastien@aperghis.net>.
215 Previous maintainer was Michael G Schwern <schwern@pobox.com>.
217
219 Copyright (C) 1990-2011 by Larry Wall and others.
220 This program is free software; you can redistribute it and/or modify it
222 under the same terms as Perl itself.
223perl v5.16.3 2019-01-21 XSLoader(3pm)