1DynaLoader::Functions(3U)ser Contributed Perl DocumentatiDoynnaLoader::Functions(3)
2
6 DynaLoader::Functions - deconstructed dynamic C library loading
7
9 use DynaLoader::Functions qw(
10 loadable_for_module
11 linkable_for_loadable linkable_for_module);
12 $loadable = loadable_for_module("Acme::Widget");
14 @linkable = linkable_for_loadable($loadable);
15 @linkable = linkable_for_module("Acme::Widget");
16 use DynaLoader::Functions qw(dyna_load dyna_resolve dyna_unload);
18 $libh = dyna_load($loadable, {
20 require_symbols => ["boot_Acme__Widget"],
21 });
22 my $bootfunc = dyna_resolve($libh, "boot_Acme__Widget");
23 dyna_unload($libh);
24
26 This module provides a function-based interface to dynamic loading as
27 used by Perl. Some details of dynamic loading are very platform-
28 dependent, so correct use of these functions requires the programmer to
29 be mindful of the space of platform variations.
30
32 File finding
33 loadable_for_module(MODULE_NAME)
34 MODULE_NAME must be the name of a Perl module, in bareword syntax
35 with "::" separators. The named module is presumed to be an XS
36 extension following standard conventions, and its runtime-loadable
37 C library file is searched for. If found, the name of the library
38 file is returned. If it cannot be found, the function "die"s with
39 an informative error message.
40 If the named module is actually not an XS extension, or is not
42 installed, or stores its C library in a non-standard place, there
43 is a non-trivial danger that this function will find some other
44 library file and believe it to be the right one. This function
45 should therefore only be used when there is an expectation that the
46 module is installed and would in normal operation load its
47 corresponding C library.
48 linkable_for_loadable(LOADABLE_FILENAME)
50 If symbols in one runtime-loadable C library are to be made
51 available to another runtime-loadable C library, depending on the
52 platform it may be necessary to refer to the exporting library when
53 linking the importing library. Generally this is not required on
54 Unix, but it is required on Windows. Where it is required to refer
55 to the exporting library at link time, the file used may be the
56 loadable library file itself, or may be a separate file used only
57 for this purpose. Given the loadable form of an exporting library,
58 this function determines what is required at link time for an
59 importing library.
60 LOADABLE_FILENAME must be the name of a runtime-loadable C library
62 file. The function checks what is required to link a library that
63 will at runtime import symbols from this library. It returns a
64 list (which will be empty on many platforms) of names of files that
65 must be used as additional objects when linking the importing
66 library.
67 linkable_for_module(MODULE_NAME)
69 Performs the job of "linkable_for_loadable" (which see for
70 explanation), but based on a module name instead of a loadable
71 library filename.
72 MODULE_NAME must be the name of a Perl module, in bareword syntax
74 with "::" separators. The function checks what is required to link
75 a library that will at runtime import symbols from the loadable C
76 library associated with the module. It returns a list (which will
77 be empty on many platforms) of names of files that must be used as
78 additional objects when linking the importing library.
79 Low-level dynamic loading
81 dyna_load(LOADABLE_FILENAME[, OPTIONS])
82 Dynamically load the runtime-loadable C library in the file named
83 LOADABLE_FILENAME. The process is influenced by optional
84 information supplied in the hash referenced by OPTIONS. On the
85 platforms that make dynamic loading easiest it is not necessary to
86 supply any options (in which case the parameter may be omitted),
87 but if wide portability is required then some options are required.
88 The permitted keys in the OPTIONS hash are:
89 resolve_using
91 Reference to an array, default empty, of names of additional
92 library files required to supply symbols used by the library
93 being loaded. On most platforms this is not used. On those
94 platforms where it is required, the need for this will be known
95 by whatever generated the library to be loaded, and it will
96 normally be set by a bootstrap file (see use_bootstrap_options
97 below).
98 require_symbols
100 Reference to an array, default empty, of names of symbols
101 expected to be found in the library being loaded. On most
102 platforms this is not used, but on some a library cannot be
103 loaded without naming at least one symbol for which a need can
104 be satisfied by the library.
105 use_bootstrap_options
107 Truth value, default false, controlling whether a "bootstrap"
108 file will be consulted as an additional source of options to
109 control loading. The "bootstrap" file, if it exists, is
110 located in the same directory as the loadable library file, and
111 has a similar name differing only in its ".bs" ending.
112 symbols_global
114 Truth value, default false, indicating whether symbols found in
115 the library being loaded must be made available to
116 subsequently-loaded libraries. Depending on platform, symbols
117 may be so available even if it is not requested. Some
118 platforms, on the other hand, can't provide this facility.
119 On platforms incapable of making loaded symbols globally
121 available, currently loading is liable to claim success while
122 leaving the symbols de facto unavailable. It is intended that
123 in the future such platforms will instead generate an exception
124 when this facility is requested.
125 unresolved_action
127 String keyword indicating what should be done if unresolved
128 symbols are detected while loading the library. It may be
129 "ERROR" (default) to treat it as an error, "WARN" to emit a
130 warning, or "IGNORE" to ignore the situation. Some platforms
131 can't detect this problem, so passing this check doesn't
132 guarantee that there won't be any runtime problems due to
133 unresolved symbols.
134 On success, returns a handle that can be used to refer to the
136 loaded library for subsequent calls to "dyna_resolve" and
137 "dyna_unload". On failure, "die"s.
138 dyna_resolve(LIBRARY_HANDLE, SYMBOL_NAME[, OPTIONS])
140 Resolve the symbol SYMBOL in the previously-loaded library
141 identified by the LIBRARY_HANDLE. The process is influenced by
142 optional information supplied in the hash referenced by OPTIONS.
143 The permitted keys in the OPTIONS hash are:
144 unresolved_action
146 String keyword indicating what should be done if the symbol
147 cannot be resolved. It may be "ERROR" (default) to treat it as
148 an error, "WARN" to emit a warning and return "undef", or
149 "IGNORE" to return "undef" without a warning.
150 On success, returns the value of the specified symbol, in a
152 platform-dependent format. Returns "undef" if the symbol could not
153 be resolved and this is not being treated as an error.
154 dyna_unload(LIBRARY_HANDLE[, OPTIONS])
156 Unload the previously-loaded library identified by the
157 LIBRARY_HANDLE. The process is influenced by optional information
158 supplied in the hash referenced by OPTIONS. The permitted keys in
159 the OPTIONS hash are:
160 fail_action
162 String keyword indicating what should be done if unloading
163 detectably fails. It may be "ERROR" (default) to treat it as
164 an error, "WARN" to emit a warning, or "IGNORE" to ignore the
165 situation.
166 On some platforms unloading is not possible. On any platform,
168 unloading can be expected to cause mayhem if any code from the
169 library is currently executing, if there are any live references to
170 data in the library, or if any symbols provided by the library are
171 referenced by any subsequently-loaded library.
172
174 DynaLoader, ExtUtils::CBuilder, XSLoader
175
177 Andrew Main (Zefram) <zefram@fysh.org>
178
180 Copyright (C) 2011, 2012, 2013, 2017 Andrew Main (Zefram)
181 <zefram@fysh.org>
182
184 This module is free software; you can redistribute it and/or modify it
185 under the same terms as Perl itself.
186perl v5.30.0 2019-07-26 DynaLoader::Functions(3)