1ExtUtils::Liblist(3)  User Contributed Perl Documentation ExtUtils::Liblist(3)
2
3
4

NAME

6       ExtUtils::Liblist - determine libraries to use and how to use them
7

SYNOPSIS

9         require ExtUtils::Liblist;
10
11         $MM->ext($potential_libs, $verbose, $need_names);
12
13         # Usually you can get away with:
14         ExtUtils::Liblist->ext($potential_libs, $verbose, $need_names)
15

DESCRIPTION

17       This utility takes a list of libraries in the form "-llib1 -llib2
18       -llib3" and returns lines suitable for inclusion in an extension
19       Makefile.  Extra library paths may be included with the form
20       "-L/another/path" this will affect the searches for all subsequent
21       libraries.
22
23       It returns an array of four or five scalar values: EXTRALIBS,
24       BSLOADLIBS, LDLOADLIBS, LD_RUN_PATH, and, optionally, a reference to
25       the array of the filenames of actual libraries.  Some of these don't
26       mean anything unless on Unix.  See the details about those platform
27       specifics below.  The list of the filenames is returned only if
28       $need_names argument is true.
29
30       Dependent libraries can be linked in one of three ways:
31
32       · For static extensions
33
34         by the ld command when the perl binary is linked with the extension
35         library. See EXTRALIBS below.
36
37       · For dynamic extensions at build/link time
38
39         by the ld command when the shared object is built/linked. See
40         LDLOADLIBS below.
41
42       · For dynamic extensions at load time
43
44         by the DynaLoader when the shared object is loaded. See BSLOADLIBS
45         below.
46
47   EXTRALIBS
48       List of libraries that need to be linked with when linking a perl
49       binary which includes this extension. Only those libraries that
50       actually exist are included.  These are written to a file and used when
51       linking perl.
52
53   LDLOADLIBS and LD_RUN_PATH
54       List of those libraries which can or must be linked into the shared
55       library when created using ld. These may be static or dynamic
56       libraries.  LD_RUN_PATH is a colon separated list of the directories in
57       LDLOADLIBS. It is passed as an environment variable to the process that
58       links the shared library.
59
60       Fedora extension: This generation of LD_RUN_PATH is disabled by
61       default.  To use the generated LD_RUN_PATH for all links, set the
62       USE_MM_LD_RUN_PATH MakeMaker object attribute / argument, (or set the
63       $USE_MM_LD_RUN_PATH environment variable).
64
65   BSLOADLIBS
66       List of those libraries that are needed but can be linked in
67       dynamically at run time on this platform.  SunOS/Solaris does not need
68       this because ld records the information (from LDLOADLIBS) into the
69       object file.  This list is used to create a .bs (bootstrap) file.
70

PORTABILITY

72       This module deals with a lot of system dependencies and has quite a few
73       architecture specific "if"s in the code.
74
75   VMS implementation
76       The version of ext() which is executed under VMS differs from the
77       Unix-OS/2 version in several respects:
78
79       · Input library and path specifications are accepted with or without
80         the "-l" and "-L" prefixes used by Unix linkers.  If neither prefix
81         is present, a token is considered a directory to search if it is in
82         fact a directory, and a library to search for otherwise.  Authors who
83         wish their extensions to be portable to Unix or OS/2 should use the
84         Unix prefixes, since the Unix-OS/2 version of ext() requires them.
85
86       · Wherever possible, shareable images are preferred to object
87         libraries, and object libraries to plain object files.  In accordance
88         with VMS naming conventions, ext() looks for files named libshr and
89         librtl; it also looks for liblib and liblib to accommodate Unix
90         conventions used in some ported software.
91
92       · For each library that is found, an appropriate directive for a linker
93         options file is generated.  The return values are space-separated
94         strings of these directives, rather than elements used on the linker
95         command line.
96
97       · LDLOADLIBS contains both the libraries found based on $potential_libs
98         and the CRTLs, if any, specified in Config.pm.  EXTRALIBS contains
99         just those libraries found based on $potential_libs.  BSLOADLIBS and
100         LD_RUN_PATH are always empty.
101
102       In addition, an attempt is made to recognize several common Unix
103       library names, and filter them out or convert them to their VMS
104       equivalents, as appropriate.
105
106       In general, the VMS version of ext() should properly handle input from
107       extensions originally designed for a Unix or VMS environment.  If you
108       encounter problems, or discover cases where the search could be
109       improved, please let us know.
110
111   Win32 implementation
112       The version of ext() which is executed under Win32 differs from the
113       Unix-OS/2 version in several respects:
114
115       · If $potential_libs is empty, the return value will be empty.
116         Otherwise, the libraries specified by $Config{perllibs} (see
117         Config.pm) will be appended to the list of $potential_libs.  The
118         libraries will be searched for in the directories specified in
119         $potential_libs, $Config{libpth}, and in
120         "$Config{installarchlib}/CORE".  For each library that is found,  a
121         space-separated list of fully qualified library pathnames is
122         generated.
123
124       · Input library and path specifications are accepted with or without
125         the "-l" and "-L" prefixes used by Unix linkers.
126
127         An entry of the form "-La:\foo" specifies the "a:\foo" directory to
128         look for the libraries that follow.
129
130         An entry of the form "-lfoo" specifies the library "foo", which may
131         be spelled differently depending on what kind of compiler you are
132         using.  If you are using GCC, it gets translated to "libfoo.a", but
133         for other win32 compilers, it becomes "foo.lib".  If no files are
134         found by those translated names, one more attempt is made to find
135         them using either "foo.a" or "libfoo.lib", depending on whether GCC
136         or some other win32 compiler is being used, respectively.
137
138         If neither the "-L" or "-l" prefix is present in an entry, the entry
139         is considered a directory to search if it is in fact a directory, and
140         a library to search for otherwise.  The $Config{lib_ext} suffix will
141         be appended to any entries that are not directories and don't already
142         have the suffix.
143
144         Note that the "-L" and "-l" prefixes are not required, but authors
145         who wish their extensions to be portable to Unix or OS/2 should use
146         the prefixes, since the Unix-OS/2 version of ext() requires them.
147
148       · Entries cannot be plain object files, as many Win32 compilers will
149         not handle object files in the place of libraries.
150
151       · Entries in $potential_libs beginning with a colon and followed by
152         alphanumeric characters are treated as flags.  Unknown flags will be
153         ignored.
154
155         An entry that matches "/:nodefault/i" disables the appending of
156         default libraries found in $Config{perllibs} (this should be only
157         needed very rarely).
158
159         An entry that matches "/:nosearch/i" disables all searching for the
160         libraries specified after it.  Translation of "-Lfoo" and "-lfoo"
161         still happens as appropriate (depending on compiler being used, as
162         reflected by $Config{cc}), but the entries are not verified to be
163         valid files or directories.
164
165         An entry that matches "/:search/i" reenables searching for the
166         libraries specified after it.  You can put it at the end to enable
167         searching for default libraries specified by $Config{perllibs}.
168
169       · The libraries specified may be a mixture of static libraries and
170         import libraries (to link with DLLs).  Since both kinds are used
171         pretty transparently on the Win32 platform, we do not attempt to
172         distinguish between them.
173
174       · LDLOADLIBS and EXTRALIBS are always identical under Win32, and
175         BSLOADLIBS and LD_RUN_PATH are always empty (this may change in
176         future).
177
178       · You must make sure that any paths and path components are properly
179         surrounded with double-quotes if they contain spaces. For example,
180         $potential_libs could be (literally):
181
182                 "-Lc:\Program Files\vc\lib" msvcrt.lib "la test\foo bar.lib"
183
184         Note how the first and last entries are protected by quotes in order
185         to protect the spaces.
186
187       · Since this module is most often used only indirectly from extension
188         "Makefile.PL" files, here is an example "Makefile.PL" entry to add a
189         library to the build process for an extension:
190
191                 LIBS => ['-lgl']
192
193         When using GCC, that entry specifies that MakeMaker should first look
194         for "libgl.a" (followed by "gl.a") in all the locations specified by
195         $Config{libpth}.
196
197         When using a compiler other than GCC, the above entry will search for
198         "gl.lib" (followed by "libgl.lib").
199
200         If the library happens to be in a location not in $Config{libpth},
201         you need:
202
203                 LIBS => ['-Lc:\gllibs -lgl']
204
205         Here is a less often used example:
206
207                 LIBS => ['-lgl', ':nosearch -Ld:\mesalibs -lmesa -luser32']
208
209         This specifies a search for library "gl" as before.  If that search
210         fails to find the library, it looks at the next item in the list. The
211         ":nosearch" flag will prevent searching for the libraries that
212         follow, so it simply returns the value as "-Ld:\mesalibs -lmesa
213         -luser32", since GCC can use that value as is with its linker.
214
215         When using the Visual C compiler, the second item is returned as
216         "-libpath:d:\mesalibs mesa.lib user32.lib".
217
218         When using the Borland compiler, the second item is returned as
219         "-Ld:\mesalibs mesa.lib user32.lib", and MakeMaker takes care of
220         moving the "-Ld:\mesalibs" to the correct place in the linker command
221         line.
222

SEE ALSO

224       ExtUtils::MakeMaker
225
226
227
228perl v5.16.3                      2014-06-10              ExtUtils::Liblist(3)
Impressum