Manual Pages for UNIX Darwin command on man ExtUtils::Liblist

ExtUtils::Liblist(3pm) Perl Programmers Reference Guide ExtUtils::Liblist(3pm)

NAME

ExtUtils::Liblist - determine libraries to use and how to use them

SYNOPSIS

require ExtUtils::Liblist;

$MM->ext($potentiallibs, $verbose, $neednames);

# Usually you can get away with:

ExtUtils::Liblist->ext($potentiallibs, $verbose, $neednames)

DESCRIPTION

This utility takes a list of libraries in the form "-llib1 -llib2

-llib3" and returns lines suitable for inclusion in an extension Make-

file. Extra library paths may be included with the form

"-L/another/path" this will affect the searches for all subsequent

libraries.

It returns an array of four or five scalar values: EXTRALIBS, BSLOAD-

LIBS, LDLOADLIBS, LDRUNPATH, and, optionally, a reference to the array of the filenames of actual libraries. Some of these don't mean anything unless on Unix. See the details about those platform specifics below. The list of the filenames is returned only if

$neednames argument is true.

Dependent libraries can be linked in one of three ways: * For static extensions by the ld command when the perl binary is linked with the extension library. See EXTRALIBS below. * For dynamic extensions at build/link time

by the ld command when the shared object is built/linked. See LDLOAD-

LIBS below. * For dynamic extensions at load time by the DynaLoader when the shared object is loaded. See BSLOADLIBS below. EEXXTTRRAALLIIBBSS List of libraries that need to be linked with when linking a perl

binary which includes this extension. Only those libraries that actu-

ally exist are included. These are written to a file and used when linking perl. LLDDLLOOAADDLLIIBBSS aanndd LLDDRRUUNNPPAATTHH List of those libraries which can or must be linked into the shared library when created using ld. These may be static or dynamic libraries. LDRUNPATH is a colon separated list of the directories in LDLOADLIBS. It is passed as an environment variable to the process that links the shared library. BBSSLLOOAADDLLIIBBSS

List of those libraries that are needed but can be linked in dynami-

cally at run time on this platform. SunOS/Solaris does not need this because ld records the information (from LDLOADLIBS) into the object file. This list is used to create a .bs (bootstrap) file. PPOORRTTAABBIILLIITTYY This module deals with a lot of system dependencies and has quite a few architecture specific "if"s in the code. VVMMSS iimmpplleemmeennttaattiioonn The version of ext() which is executed under VMS differs from the

Unix-OS/2 version in several respects:

+o Input library and path specifications are accepted with or without

the "-l" and "-L" prefixes used by Unix linkers. If neither prefix

is present, a token is considered a directory to search if it is in fact a directory, and a library to search for otherwise. Authors who wish their extensions to be portable to Unix or OS/2 should use the

Unix prefixes, since the Unix-OS/2 version of ext() requires them.

+o Wherever possible, shareable images are preferred to object libraries, and object libraries to plain object files. In accordance with VMS naming conventions, ext() looks for files named libshr and

librtl; it also looks for liblib and liblib to accommodate Unix con-

ventions used in some ported software. +o For each library that is found, an appropriate directive for a linker

options file is generated. The return values are space-separated

strings of these directives, rather than elements used on the linker command line.

+o LDLOADLIBS contains both the libraries found based on $potentiallibs

and the CRTLs, if any, specified in Config.pm. EXTRALIBS contains

just those libraries found based on $potentiallibs. BSLOADLIBS and

LDRUNPATH are always empty. In addition, an attempt is made to recognize several common Unix

library names, and filter them out or convert them to their VMS equiva-

lents, as appropriate. In general, the VMS version of ext() should properly handle input from extensions originally designed for a Unix or VMS environment. If you encounter problems, or discover cases where the search could be improved, please let us know. WWiinn3322 iimmpplleemmeennttaattiioonn The version of ext() which is executed under Win32 differs from the

Unix-OS/2 version in several respects:

+o If $potentiallibs is empty, the return value will be empty. Other-

wise, the libraries specified by $Config{perllibs} (see Config.pm)

will be appended to the list of $potentiallibs. The libraries will

be searched for in the directories specified in $potentiallibs,

$Config{libpth}, and in "$Config{installarchlib}/CORE". For each

library that is found, a space-separated list of fully qualified

library pathnames is generated. +o Input library and path specifications are accepted with or without

the "-l" and "-L" prefixes used by Unix linkers.

An entry of the form "-La:\foo" specifies the "a:\foo" directory to

look for the libraries that follow.

An entry of the form "-lfoo" specifies the library "foo", which may

be spelled differently depending on what kind of compiler you are using. If you are using GCC, it gets translated to "libfoo.a", but for other win32 compilers, it becomes "foo.lib". If no files are found by those translated names, one more attempt is made to find them using either "foo.a" or "libfoo.lib", depending on whether GCC or some other win32 compiler is being used, respectively.

If neither the "-L" or "-l" prefix is present in an entry, the entry

is considered a directory to search if it is in fact a directory, and

a library to search for otherwise. The $Config{libext} suffix will

be appended to any entries that are not directories and don't already have the suffix.

Note that the "-L" and "-l" prefixes are nnoott rreeqquuiirreedd, but authors

who wish their extensions to be portable to Unix or OS/2 should use

the prefixes, since the Unix-OS/2 version of ext() requires them.

+o Entries cannot be plain object files, as many Win32 compilers will not handle object files in the place of libraries.

+o Entries in $potentiallibs beginning with a colon and followed by

alphanumeric characters are treated as flags. Unknown flags will be ignored. An entry that matches "/:nodefault/i" disables the appending of

default libraries found in $Config{perllibs} (this should be only

needed very rarely). An entry that matches "/:nosearch/i" disables all searching for the

libraries specified after it. Translation of "-Lfoo" and "-lfoo"

still happens as appropriate (depending on compiler being used, as

reflected by $Config{cc}), but the entries are not verified to be

valid files or directories. An entry that matches "/:search/i" reenables searching for the libraries specified after it. You can put it at the end to enable

searching for default libraries specified by $Config{perllibs}.

+o The libraries specified may be a mixture of static libraries and import libraries (to link with DLLs). Since both kinds are used

pretty transparently on the Win32 platform, we do not attempt to dis-

tinguish between them. +o LDLOADLIBS and EXTRALIBS are always identical under Win32, and BSLOADLIBS and LDRUNPATH are always empty (this may change in future). +o You must make sure that any paths and path components are properly

surrounded with double-quotes if they contain spaces. For example,

$potentiallibs could be (literally):

"-Lc:\Program Files\vc\lib" msvcrt.lib "la test\foo bar.lib"

Note how the first and last entries are protected by quotes in order to protect the spaces. +o Since this module is most often used only indirectly from extension "Makefile.PL" files, here is an example "Makefile.PL" entry to add a library to the build process for an extension:

LIBS => ['-lgl']

When using GCC, that entry specifies that MakeMaker should first look for "libgl.a" (followed by "gl.a") in all the locations specified by

$Config{libpth}.

When using a compiler other than GCC, the above entry will search for "gl.lib" (followed by "libgl.lib").

If the library happens to be in a location not in $Config{libpth},

you need:

LIBS => ['-Lc:\gllibs -lgl']

Here is a less often used example:

LIBS => ['-lgl', ':nosearch -Ld:\mesalibs -lmesa -luser32']

This specifies a search for library "gl" as before. If that search fails to find the library, it looks at the next item in the list. The

":nosearch" flag will prevent searching for the libraries that fol-

low, so it simply returns the value as "-Ld:\mesalibs -lmesa

-luser32", since GCC can use that value as is with its linker.

When using the Visual C compiler, the second item is returned as

"-libpath:d:\mesalibs mesa.lib user32.lib".

When using the Borland compiler, the second item is returned as

"-Ld:\mesalibs mesa.lib user32.lib", and MakeMaker takes care of mov-

ing the "-Ld:\mesalibs" to the correct place in the linker command

line.