ExtUtils::Liblist(3) ExtUtils::Liblist(3)
NAME
ExtUtils::Liblist - determine libraries to use and how to use them
SYNOPSIS
require ExtUtils::Liblist;
ExtUtils::Liblist::ext($self, $potential_libs, $verbose);
DESCRIPTION
This utility takes a list of libraries in the form -llib1 -llib2 -llib3
and prints out lines suitable for inclusion in an extension Makefile.
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 scalar values: EXTRALIBS, BSLOADLIBS,
LDLOADLIBS, and LD_RUN_PATH. Some of these don't mean anything on VMS
and Win32. See the details about those platform specifics below.
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
by the ld command when the shared object is built/linked. See
LDLOADLIBS below.
⊕ For dynamic extensions
by the DynaLoader when the shared object is loaded. See BSLOADLIBS
below.
EXTRALIBS
List of libraries that need to be linked with when linking a perl binary
which includes this extension Only those libraries that actually exist
are included. These are written to a file and used when linking perl.
LDLOADLIBS and LDRUNPATH
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.
LD_RUN_PATH 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.
BSLOADLIBS
List of those libraries that are needed but can be linked in dynamically
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.
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PORTABILITY
This module deals with a lot of system dependencies and has quite a few
architecture specific ifs in the code.
VMS implementation
The version of ext() which is executed under VMS differs from the Unix-
OS/2 version in several respects:
⊕ Input library and path specifications are accepted with or without the
-l and -L prefices 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.
⊕ 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 accomodate Unix conventions used in
some ported software.
⊕ 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.
⊕ LDLOADLIBS and EXTRALIBS are always identical under VMS, and BSLOADLIBS
and LD_RIN_PATH 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 equivalents, 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.
Win32 implementation
The version of ext() which is executed under Win32 differs from the
Unix-OS/2 version in several respects:
⊕ Input library and path specifications are accepted with or without the
-l and -L prefices used by Unix linkers. -lfoo specifies the library
foo.lib and -Ls:ome\dir specifies a directory to look for the libraries
that follow. 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. The $Config{lib_ext} suffix will be appended to
any entries that are not directories and don't already have the suffix.
Authors who wish their extensions to be portable to Unix or OS/2 should
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use the Unix prefixes, since the Unix-OS/2 version of ext() requires
them.
⊕ Entries cannot be plain object files, as many Win32 compilers will not
handle object files in the place of libraries.
⊕ If $potential_libs is empty, the return value will be empty.
Otherwise, the libraries specified by $Config{libs} (see Config.pm)
will be appended to the list of $potential_libs. The libraries will be
searched for in the directories specified in $potential_libs as well as
in $Config{libpth}. For each library that is found, a space-separated
list of fully qualified library pathnames is generated. You may
specify an entry that matches /:nodefault/i in $potential_libs to
disable the appending of default libraries found in $Config{libs} (this
should be only needed very rarely).
⊕ 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 distinguish
between them.
⊕ LDLOADLIBS and EXTRALIBS are always identical under Win32, and
BSLOADLIBS and LD_RUN_PATH are always empty (this may change in
future).
SEE ALSO
the ExtUtils::MakeMaker manpage
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