DynaLoader::Functions(User Contributed Perl DocumentDynaLoader::Functions(3pm)
NAME
DynaLoader::Functions - deconstructed dynamic C library loading
SYNOPSIS
use DynaLoader::Functions qw(
loadable_for_module
linkable_for_loadable linkable_for_module);
$loadable = loadable_for_module("Acme::Widget");
@linkable = linkable_for_loadable($loadable);
@linkable = linkable_for_module("Acme::Widget");
use DynaLoader::Functions qw(dyna_load dyna_resolve dyna_unload);
$libh = dyna_load($loadable, {
require_symbols => ["boot_Acme__Widget"],
});
my $bootfunc = dyna_resolve($libh, "boot_Acme__Widget");
dyna_unload($libh);
DESCRIPTION
This module provides a function-based interface to dynamic loading as
used by Perl. Some details of dynamic loading are very platform-
dependent, so correct use of these functions requires the programmer to
be mindful of the space of platform variations.
FUNCTIONS
File finding
loadable_for_module(MODULE_NAME)
MODULE_NAME must be the name of a Perl module, in bareword syntax
with "::" separators. The named module is presumed to be an XS
extension following standard conventions, and its runtime-loadable
C library file is searched for. If found, the name of the library
file is returned. If it cannot be found, the function "die"s with
an informative error message.
If the named module is actually not an XS extension, or is not
installed, or stores its C library in a non-standard place, there
is a non-trivial danger that this function will find some other
library file and believe it to be the right one. This function
should therefore only be used when there is an expectation that the
module is installed and would in normal operation load its
corresponding C library.
linkable_for_loadable(LOADABLE_FILENAME)
If symbols in one runtime-loadable C library are to be made
available to another runtime-loadable C library, depending on the
platform it may be necessary to refer to the exporting library when
linking the importing library. Generally this is not required on
Unix, but it is required on Windows. Where it is required to refer
to the exporting library at link time, the file used may be the
loadable library file itself, or may be a separate file used only
for this purpose. Given the loadable form of an exporting library,
this function determines what is required at link time for an
importing library.
LOADABLE_FILENAME must be the name of a runtime-loadable C library
file. The function checks what is required to link a library that
will at runtime import symbols from this library. It returns a
list (which will be empty on many platforms) of names of files that
must be used as additional objects when linking the importing
library.
linkable_for_module(MODULE_NAME)
Performs the job of "linkable_for_loadable" (which see for
explanation), but based on a module name instead of a loadable
library filename.
MODULE_NAME must be the name of a Perl module, in bareword syntax
with "::" separators. The function checks what is required to link
a library that will at runtime import symbols from the loadable C
library associated with the module. It returns a list (which will
be empty on many platforms) of names of files that must be used as
additional objects when linking the importing library.
Low-level dynamic loading
dyna_load(LOADABLE_FILENAME[, OPTIONS])
Dynamically load the runtime-loadable C library in the file named
LOADABLE_FILENAME. The process is influenced by optional
information supplied in the hash referenced by OPTIONS. On the
platforms that make dynamic loading easiest it is not necessary to
supply any options (in which case the parameter may be omitted),
but if wide portability is required then some options are required.
The permitted keys in the OPTIONS hash are:
resolve_using
Reference to an array, default empty, of names of additional
library files required to supply symbols used by the library
being loaded. On most platforms this is not used. On those
platforms where it is required, the need for this will be known
by whatever generated the library to be loaded, and it will
normally be set by a bootstrap file (see use_bootstrap_options
below).
require_symbols
Reference to an array, default empty, of names of symbols
expected to be found in the library being loaded. On most
platforms this is not used, but on some a library cannot be
loaded without naming at least one symbol for which a need can
be satisfied by the library.
use_bootstrap_options
Truth value, default false, controlling whether a "bootstrap"
file will be consulted as an additional source of options to
control loading. The "bootstrap" file, if it exists, is
located in the same directory as the loadable library file, and
has a similar name differing only in its ".bs" ending.
symbols_global
Truth value, default false, indicating whether symbols found in
the library being loaded must be made available to
subsequently-loaded libraries. Depending on platform, symbols
may be so available even if it is not requested. Some
platforms, on the other hand, can't provide this facility.
On platforms incapable of making loaded symbols globally
available, currently loading is liable to claim success while
leaving the symbols de facto unavailable. It is intended that
in the future such platforms will instead generate an exception
when this facility is requested.
unresolved_action
String keyword indicating what should be done if unresolved
symbols are detected while loading the library. It may be
"ERROR" (default) to treat it as an error, "WARN" to emit a
warning, or "IGNORE" to ignore the situation. Some platforms
can't detect this problem, so passing this check doesn't
guarantee that there won't be any runtime problems due to
unresolved symbols.
On success, returns a handle that can be used to refer to the
loaded library for subsequent calls to "dyna_resolve" and
"dyna_unload". On failure, "die"s.
dyna_resolve(LIBRARY_HANDLE, SYMBOL_NAME[, OPTIONS])
Resolve the symbol SYMBOL in the previously-loaded library
identified by the LIBRARY_HANDLE. The process is influenced by
optional information supplied in the hash referenced by OPTIONS.
The permitted keys in the OPTIONS hash are:
unresolved_action
String keyword indicating what should be done if the symbol
cannot be resolved. It may be "ERROR" (default) to treat it as
an error, "WARN" to emit a warning and return "undef", or
"IGNORE" to return "undef" without a warning.
On success, returns the value of the specified symbol, in a
platform-dependent format. Returns "undef" if the symbol could not
be resolved and this is not being treated as an error.
dyna_unload(LIBRARY_HANDLE[, OPTIONS])
Unload the previously-loaded library identified by the
LIBRARY_HANDLE. The process is influenced by optional information
supplied in the hash referenced by OPTIONS. The permitted keys in
the OPTIONS hash are:
fail_action
String keyword indicating what should be done if unloading
detectably fails. It may be "ERROR" (default) to treat it as
an error, "WARN" to emit a warning, or "IGNORE" to ignore the
situation.
On some platforms unloading is not possible. On any platform,
unloading can be expected to cause mayhem if any code from the
library is currently executing, if there are any live references to
data in the library, or if any symbols provided by the library are
referenced by any subsequently-loaded library.
SEE ALSO
DynaLoader, ExtUtils::CBuilder, XSLoader
AUTHOR
Andrew Main (Zefram) <zefram@fysh.org>
COPYRIGHT
Copyright (C) 2011, 2012, 2013, 2017 Andrew Main (Zefram)
<zefram@fysh.org>
LICENSE
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.34.0 2022-10-13 DynaLoader::Functions(3pm)
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