NAME
FFI::CheckLib - Check that a library is available for FFI
VERSION
version 0.27
SYNOPSIS
use FFI::CheckLib;
check_lib_or_exit( lib => 'jpeg', symbol => 'jinit_memory_mgr' );
check_lib_or_exit( lib => [ 'iconv', 'jpeg' ] );
# or prompt for path to library and then:
print "where to find jpeg library: ";
my $path = <STDIN>;
check_lib_or_exit( lib => 'jpeg', libpath => $path );
DESCRIPTION
This module checks whether a particular dynamic library is available
for FFI to use. It is modeled heavily on Devel::CheckLib, but will find
dynamic libraries even when development packages are not installed. It
also provides a find_lib function that will return the full path to the
found dynamic library, which can be feed directly into FFI::Platypus or
another FFI system.
Although intended mainly for FFI modules via FFI::Platypus and similar,
this module does not actually use any FFI to do its detection and
probing. This module does not have any non-core runtime dependencies.
The test suite does depend on Test2::Suite.
FUNCTIONS
All of these take the same named parameters and are exported by
default.
find_lib
my(@libs) = find_lib(%args);
This will return a list of dynamic libraries, or empty list if none
were found.
[version 0.05]
If called in scalar context it will return the first library found.
Arguments are key value pairs with these keys:
lib
Must be either a string with the name of a single library or a
reference to an array of strings of library names. Depending on your
platform, CheckLib will prepend lib or append .dll or .so when
searching.
[version 0.11]
As a special case, if * is specified then any libs found will match.
libpath
A string or array of additional paths to search for libraries.
systempath
[version 0.11]
A string or array of system paths to search for instead of letting
FFI::CheckLib determine the system path. You can set this to [] in
order to not search any system paths.
symbol
A string or a list of symbol names that must be found.
verify
A code reference used to verify a library really is the one that you
want. It should take two arguments, which is the name of the library
and the full path to the library pathname. It should return true if
it is acceptable, and false otherwise. You can use this in
conjunction with FFI::Platypus to determine if it is going to meet
your needs. Example:
use FFI::CheckLib;
use FFI::Platypus;
my($lib) = find_lib(
lib => 'foo',
verify => sub {
my($name, $libpath) = @_;
my $ffi = FFI::Platypus->new;
$ffi->lib($libpath);
my $f = $ffi->function('foo_version', [] => 'int');
return $f->call() >= 500; # we accept version 500 or better
},
);
recursive
[version 0.11]
Recursively search for libraries in any non-system paths (those
provided via libpath above).
try_linker_script
[version 0.24]
Some vendors provide .so files that are linker scripts that point to
the real binary shared library. These linker scripts can be used by
gcc or clang, but are not directly usable by FFI::Platypus and
friends. On select platforms, this options will use the linker
command (ld) to attempt to resolve the real .so for non-binary files.
Since there is extra overhead this is off by default.
An example is libyaml on Red Hat based Linux distributions. On Debian
these are handled with symlinks and no trickery is required.
alien
[version 0.25]
If no libraries can be found, try the given aliens instead. The Alien
classes specified must provide the Alien::Base interface for dynamic
libraries, which is to say they should provide a method called
dynamic_libs that returns a list of dynamic libraries.
assert_lib
assert_lib(%args);
This behaves exactly the same as find_lib, except that instead of
returning empty list of failure it throws an exception.
check_lib_or_exit
check_lib_or_exit(%args);
This behaves exactly the same as assert_lib, except that instead of
dying, it warns (with exactly the same error message) and exists. This
is intended for use in Makefile.PL or Build.PL
find_lib_or_exit
[version 0.05]
my(@libs) = find_lib_or_exit(%args);
This behaves exactly the same as find_lib, except that if the library
is not found, it will call exit with an appropriate diagnostic.
find_lib_or_die
[version 0.06]
my(@libs) = find_lib_or_die(%args);
This behaves exactly the same as find_lib, except that if the library
is not found, it will die with an appropriate diagnostic.
check_lib
my $bool = check_lib(%args);
This behaves exactly the same as find_lib, except that it returns true
(1) on finding the appropriate libraries or false (0) otherwise.
which
[version 0.17]
my $path = where($name);
Return the path to the first library that matches the given name.
Not exported by default.
where
[version 0.17]
my @paths = where($name);
Return the paths to all the libraries that match the given name.
Not exported by default.
has_symbols
[version 0.17]
my $bool = has_symbols($path, @symbol_names);
Returns true if all of the symbols can be found in the dynamic library
located at the given path. Can be useful in conjunction with verify
with find_lib above.
Not exported by default.
system_path
[version 0.20]
my $path = FFI::CheckLib::system_path;
Returns the system path as a list reference. On some systems, this is
PATH on others it might be LD_LIBRARY_PATH on still others it could be
something completely different. So although you may add items to this
list, you should probably do some careful consideration before you do
so.
This function is not exportable, even on request.
FAQ
Why not just use dlopen?
Calling dlopen on a library name and then dlclose immediately can
tell you if you have the exact name of a library available on a
system. It does have a number of drawbacks as well.
No absolute or relative path
It only tells you that the library is somewhere on the system, not
having the absolute or relative path makes it harder to generate
useful diagnostics.
POSIX only
This doesn't work on non-POSIX systems like Microsoft Windows. If
you are using a POSIX emulation layer on Windows that provides
dlopen, like Cygwin, there are a number of gotchas there as well.
Having a layer written in Perl handles this means that developers
on Unix can develop FFI that will more likely work on these
platforms without special casing them.
inconsistent implementations
Even on POSIX systems you have inconsistent implementations.
OpenBSD for example don't usually include symlinks for .so files
meaning you need to know the exact .so version.
non-system directories
By default dlopen only works for libraries in the system paths.
Most platforms have a way of configuring the search for different
non-system paths, but none of them are portable, and are usually
discouraged anyway. Alien and friends need to do searches for
dynamic libraries in non-system directories for share installs.
My 64-bit Perl is misconfigured and has 32-bit libraries in its search
path. Is that a bug in FFI::CheckLib?
Nope.
The way FFI::CheckLib is implemented it won't work on AIX, HP-UX,
OpenVMS or Plan 9.
I know for a fact that it doesn't work on AIX as currently
implemented because I used to develop on AIX in the early 2000s, and
I am aware of some of the technical challenges. There are probably
other systems that it won't work on. I would love to add support for
these platforms. Realistically these platforms have a tiny market
share, and absent patches from users or the companies that own these
operating systems (patches welcome), or hardware / CPU time
donations, these platforms are unsupportable anyway.
SEE ALSO
FFI::Platypus
Call library functions dynamically without a compiler.
Dist::Zilla::Plugin::FFI::CheckLib
Dist::Zilla plugin for this module.
AUTHOR
Author: Graham Ollis <plicease@cpan.org>
Contributors:
Bakkiaraj Murugesan (bakkiaraj)
Dan Book (grinnz, DBOOK)
Ilya Pavlov (Ilya, ILUX)
Shawn Laffan (SLAFFAN)
Petr Pisar (ppisar)
COPYRIGHT AND LICENSE
This software is copyright (c) 2014-2018 by Graham Ollis.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.