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Mac OS X / Darwin man pages : libtool (1)
libtool (1)

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Name

libtool - create libraries
ranlib - add or update the table of contents of archive libraries

Synopsis

libtool -static -o output [ -sacLT ] [ - ] [ -arch_only arch_type ] file... [-filelist listfile[,dirname]]

libtool -dynamic -o output [ -install_name name ] [ -compatibility_version number ] [ -current_version number ] [ link editor flags ] [ -v ] [ -noall_load ] [ - ] [ -arch_only arch_type ] file... [-filelist listfile[,dirname]]

ranlib [ -sactfLT ] [ - ] archive...

Description

The libtool command takes the specified input object files and creates a library for use with the link editor, ld(1) . The library's name is specified by output (the argument to the -o flag). The input object files may be in any correct format that contains object files (``fat'' files, archives, object files). Libtool will not put any non-object input file into the output library (unlike ranlib, which allows this in the archives it operates on).

When producing a ``fat'' file from objects of the same CPU type and differing CPU subtypes, libtool and ranlib create at most one library for each CPU type, rather than a separate library in a fat file for each of the unique pairings of CPU type and CPU subtype. Thus, the resulting CPU subtype for each library is the _ALL CPU subtype for that CPU type. This strategy strongly encourages the implementor of a library to create one library that chooses optimum code to run at run time, rather than at link time.

Libtool can create either dynamically linked shared libraries, with -dynamic, or statically linked (archive) libraries, with -static.

Dynamically Linked Shared Libraries

Dynamically linked libraries, unlike statically linked libraries, are Mach-O format files and not ar(5) format files. Dynamically linked libraries have two restrictions: No symbol may be defined in more than one object file and no common symbol can be used. To maximize sharing of a dynamically linked shared library the objects should be compiled with the -dynamic flag of cc(1) to produce indirect undefined references and position-independent code. To build a dynamically linked library, libtool, runs the link editor, ld(1) , with -dylib once for each architecutre present in the input objects and then lipo(1) to create a fat file if needed.

ARCHIVE (or statically linked) LIBRARIES

Libtool with -static is intended to replace ar(5) and ranlib. For backward compatibility, ranlib is still available, and it supports fat files. Ranlib adds or updates the table of contents to each archive so it can be linked by the link editor, ld(1) . The table of contents is an archive member at the beginning of the archive that indicates which symbols are defined in which library members. Because ranlib rewrites the archive, sufficient temporary file space must be available in the file system that contains the current directory. Ranlib takes all correct forms of libraries (fat files containing archives, and simple archives) and updates the table of contents for all archives in the file. Ranlib also takes one common incorrect form of archive, an archive whose members are fat object files, adding or updating the table of contents and producing the library in correct form (a fat file containing multiple archives).

The archive member name for a table of contents begins with ``__.SYMDEF''. Currently, there are two types of table of contents produced by libtool -static and ranlib and understood by the link editor, ld(1) . These are explained below, under the -s and -a options.

Options

The following options pertain to libtool only.

-static
Produce a statically linked (archive) library from the input files. This is the default.

-dynamic
Produce a dynamically linked shared library from the input files.

-install_name name
ror a dynamic shared library this specifies the file name the library will be installed in for programs that use it. If this is not specified the name specified by the -o output option will be used.

-compatibility_version number
For a dynamic shared library this specifies the compatibility version number of the library. When a library is used the compatibility version is checked and if the user's version is greater that the library's version, an error message is printed and the using program exits. The format of number is X[.Y[.Z]] where X must be a positive non-zero number less than or equal to 65535, and .Y and .Z are optional and if present must be nonnegative numbers less than or equal to 255. If this is not specified then it has a value of 0 and no checking is done when the library is used.

-current_version number
For dynamic shared library files this specifies the current version number of the library. The program using the library can obtain the current version of the library programmatically to determine exactly which version of the library it is using. The format of number is X[.Y[.Z]] where X must be a positive nonzero number less than or equal to 65535, and .Y and .Z are optional and if present must be non-negative numbers less than or equal to 255. If this is not specified then it has a value of 0.

-noall_load
For dynamic shared library files this specifies the the default behavior of loading all members of archives on the command line is not to be done. This option is used by the GNU compiler driver, cc(1) , when used with it's -dynamiclib option. This is done to allow selective loading of the GNU's compiler's runtime support library, libcc_dynamic.a .

link editor flags
For a dynamic shared library the following ld(1) flags are accepted and passed through: -lx, -weak-lx, -search_paths_first -weak_library, -Ldir, -ysym, -usym, -initsym, -idefinition:indi_rect, -seg1addr, -segs_read_only_addr, -segs_read_write_addr, -seg_addr_table, -seg_addr_table_filename, -segprot, -segalign, -sectcreate, -sectorder, -sectorder_detail, -sectalign, -undefined, -read_only_relocs, -prebind, -prebind_all_twolevel_modules, -noprebind, -framework, -weak_framework, -umbrella, -allowable_client, -sub_umbrella, -sub_library, -F, -U, -Y, -Sn, -Si, -S, -X, -x, -whyload, -all_load. -arch_errors_fatal, -dylib_file, -run_init_lazily, -final_output, -multiply_defined, -multiply_defined_unused, -twolevel_namespace, -twolevel_namespace_hints, -flat_namespace, -nomultidefs, -headerpad, -headerpad_max_install_names,

-weak_reference_mismatches,
-M, -no_arch_warnings, -single_module, -multi_module, -exported_symbols_list, -unexported_symbols_list, -m. See the ld(1) man page for details on these flags. The flag -image_base is a synonym for -seg1addr.

-v
Verbose mode, which prints the ld(1) commands and lipo(1) commands executed.

-filelist listfile[,dirname]
The listfile contains a list of file names and is an alternative way of specifiying file names on the command line. The file names are listed one per line separated only by newlines (spaces and tabs are assumed to be part of the file name). If the optional directory name, dirname is specified then it is prepended to each name in the list file.

-arch_only arch_type
This option causes libtool to build a library only for the specified arch_type and ignores all other architectures in the input files. When building a dynamic library, if this is specified with a specific cpusubtype other than the family cpusubtype then libtool it does not use the ld(1) -force_cpusubtype_ALL flag and passes the -arch_only argument to ld(1) as the -arch flag so that the output is tagged with that cpusubtype.

The following options pertain to the table of contents for an archive library, and apply to both libtool -static and ranlib:

-s
Produce the preferred type of table of contents, which results in faster link editing when linking with the archive. The order of the table of contents is sorted by symbol name. The library member name of this type of table of contents is ``__.SYMDEF SORTED''. This type of table of contents can only be produced when the library does not have multiple members that define the same symbol. This is the default.

-a
Produce the original type of table of contents, whose order is based on the order of the members in the archive. The library member name of this type of table of contents is ``__.SYMDEF''. This type of table of contents must be used when the library has multiple members that define the same symbol.

-c
Include common symbols as definitions with respect to the table of contents. This is seldom the intended behavior for linking from a library, as it forces the linking of a library member just because it uses an uninitialized global that is undefined at that point in the linking. This option is included only because this was the original behavior of ranlib. This option is not the default.

-L
Use the 4.4bsd archive extended format #1, which allows archive member names to be longer than 16 characters and have spaces in their names. This option is the default.

-T
Truncate archive member names to 16 characters and don't use the 4.4bsd extended format #1. This option is not the default.

-f
Warns when the output archive is fat and ar(1) will no longer be able to operate on it.

For compatibility, the following ranlib option is accepted (but ignored):

-t
This option used to request that ranlib only ``touch'' the archives instead of modifying them. The option is now ignored, and the table of contents is rebuilt.

One other option applies to both libtool and ranlib:

-
Treat all remaining arguments as names of files (or archives) and not as options.

See Also

ld(1) , ar(1) , otool(1) , make(1) , redo_prebinding(1) , ar(5)

Bugs

With the way libraries used to be created, errors were possible if the library was modified with ar(1) and the table of contents was not updated by rerunning ranlib(1) . Thus the link editor, ld, warns when the modification date of a library is more recent than the creation date of its table of contents. Unfortunately, this means that you get the warning even if you only copy the library.


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