|
|
| |
FFI::CheckLib(3) |
User Contributed Perl Documentation |
FFI::CheckLib(3) |
FFI::CheckLib - Check that a library is available for FFI
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 );
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.
All of these take the same named parameters and are exported by default.
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.
[version 0.28]
In 0.28 and later, if the Alien is not installed then it will
be ignored and this module will search in system or specified
directories only. This module will still throw an exception, if
the Alien doesn't look like a module name or if it does not provide a
"dynamic_libs" method (which is
implemented by all Alien::Base subclasses).
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(%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"
[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.
[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.
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.
[version 0.17]
my $path = where($name);
Return the path to the first library that matches the given
name.
Not exported by default.
[version 0.17]
my @paths = where($name);
Return the paths to all the libraries that match the given
name.
Not exported by default.
[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.
[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.
- 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.
- FFI::Platypus
- Call library functions dynamically without a compiler.
- Dist::Zilla::Plugin::FFI::CheckLib
- Dist::Zilla plugin for this module.
Author: Graham Ollis <plicease@cpan.org>
Contributors:
Bakkiaraj Murugesan (bakkiaraj)
Dan Book (grinnz, DBOOK)
Ilya Pavlov (Ilya, ILUX)
Shawn Laffan (SLAFFAN)
Petr Pisar (ppisar)
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.
Visit the GSP FreeBSD Man Page Interface. Output converted with ManDoc. |