create a shared library
mkshlib -s specfil -t target
[-h host] [-n]
[-L dir ...] [-q]
builds both the host and target shared libraries.
A shared library is similar in function to a normal, non-shared
library, except that programs that link with a shared library
share the library code during execution, whereas programs that link
with a non-shared library get their own copy of each library
The host shared library
is an archive that is used to link-edit
user programs with the shared library (see
A host shared library can be treated exactly like a non-shared
library and should be included on
command lines in the usual way (see
Further, all operations that can be done on an archive can also
be done on the host shared library.
The target shared library
is an executable module that is bound
into the user's address space during execution of a program using
the shared library.
The target shared library contains the code for all the routines
in the library and must be fully resolved.
The target is brought into memory during execution of a program
using the shared library, and subsequent processes that use the
shared library share the copy of code already in memory.
The text of the target is always shared, but each process gets
its own copy of the data.
The user interface to mkshlib consists of command
line options and a shared library specification file.
The shared library specification file
describes the contents of the shared library.
The mkshlib command invokes other tools such as the archiver,
and the link editor,
Tools are invoked through the use of
which searches directories in the user's PATH.
Also, prefixes to mkshlib
are passed in the same way as prefixes to the
command, and invoked tools are given the prefix, where appropriate.
For example, i386mkshlib invokes i386ld.
mkshlib recognizes the following command line options:
Specifies the shared library specification file, specfil.
This file contains the information necessary to build a shared library.
Its contents include the branch table specifications for the target,
the path name in which the target should be installed, the start
addresses of text and data for the target, the initialization
specifications for the host, and the list of object files to be
included in the shared library (see details below).
Specifies the output filename of the target shared library being created.
We assume that this file is installed on the target
machine at the location given in the specification file (see the
#target directive below).
If the -n option is used, then a new target shared
library is not generated.
Specifies the output filename of the host shared library being created.
If this option is not given, then the host shared library is not produced.
Do not generate a new target shared library.
This option is useful when producing only a new host shared library.
The -t option must still be supplied since a version
of the target shared library is needed to build the host shared library.
-L dir ...
Change the algorithm of searching for the host shared libraries
specified with the #objects noload directive to look
in dir before looking in the default directories.
The -L option can be specified multiple times on
the command line in which case the directories given with the
-L options are searched in the order given on the
command line before the default directories.
Quiet warning messages.
This option is useful when warning messages are expected but not desired.
The shared library specification file contains all the information
necessary to build both the host and target shared libraries.
The contents and format of the specification file are given by the
directives listed below.
All directives that can be followed by multi-line specifications
are valid until the next directive or the end of the file.
#address sectname address
Specifies the start address, address, of section
sectname for the target.
This directive typically is used to specify the start addresses
of the .text and .data sections.
One #address per section name is valid.
A #address directive must be given exactly once for the
.text section and once for the .data section.
Specifies the absolute path name, pathname, where the
target shared library will be installed on the target machine.
The operating system uses this path name to locate the shared
library when executing a.out files that use this shared library.
This directive must be specified exactly once per specification file.
Specifies the start of the branch table specifications.
The lines following this directive are taken to be branch table
Branch table specification lines have the following format:
funcname <white space> position
where funcname is the name of the symbol given a branch
table entry and position specifies the position of
funcname's branch table entry.
position can be a single integer or a range of integers
of the form position1-position2.
Each position must be greater than or equal to one, the
same position can not be specified more than once, and every position,
from one to the highest given position, must be accounted for.
If a symbol is given more than one branch table entry by
associating a range of positions with the symbol or by specifying
the same symbol on more than one branch table specification line,
then the symbol is defined to have the address of the highest
associated branch table entry.
All other branch table entries for the symbol are ``empty'' slots
and can be replaced by new entries in future versions of the shared library.
Only functions should be given branch table entries, and those
functions must be external symbols.
This directive must be specified exactly once per shared library
The lines following this directive are taken to be the list of
input object files in the order they are to be loaded into the target.
The list simply consists of each path name followed by a newline character.
This list is also used to determine the input object files for the
host shared library, but the order for the host is given by running
the list through
This directive must be specified exactly once per shared library
The #objects noload is followed by a list of host shared libraries.
These libraries are searched in the order listed to resolve
undefined symbols from the library being built.
During the search it is considered an error if a non-shared
version of a symbol is found before a shared version of the symbol.
Each name given is assumed to be a path name to a host or an
argument of the form -lX, where
is the name of a file in LIBDIR or
LLIBDIR. This behavior is identical to
that of ld, and the
-L option can be used on the command line to specify
other directories in which to locate these archives.
If a host shared library is specified using
#objects noload, any cc command that links
to the shared library being built needs to specify that host also.
#hide linker [*]
This directive changes symbols that are normally external
into static symbols, local to the library being created.
A regular expression can be given (see
in which case all external symbols
matching the regular expression are hidden; the #export
directive (see below) can be used to counter this effect for specified symbols.
The optional * is equivalent to the directive
and causes all external symbols to be made into
All symbols specified in #init and #branch
directives are assumed to be external symbols, and
cannot be changed into static symbols using the
#export linker [*]
Symbols given in the #export directive are
external symbols (global among files) that, because
of a regular expression in a #hide directive, would
otherwise have been made static. For example,
causes all symbols except one, two, and
those used in #branch and #init entries to
be tagged as static.
#hide linker *
Specifies that the object file, object, requires initialization code.
The lines following this directive are taken to be initialization
Initialization specification lines have the following format:
ptr <white space> import
ptr is a pointer to the associated imported symbol,
import, and must be defined in the current specified
object file, object.
The initialization code generated for each such line is of the form:
ptr = &import ;
All initializations for a particular object file must be given
once and multiple specifications of the same object file are not allowed.
Specifies a string, string, to be included in the
.comment section of the target shared library.
Specifies a comment.
All information on a line beginning with ## is ignored.
mkshlib returns 0 on success and non-zero on failure.
The -n option cannot be used with the
#objects noload directive.
If mkshlib is asked to create a host library and
a host of that name already exists,
mkshlib updates the host using ar -ru.
Therefore, always remove the host before rebuilding
whenever an object file previously included in the library
is removed or renamed.
If the address specified with the #address directive
is outside user space, the library build may look successful,
but if you try to use it, it might not work.
TEMPDIR is usually /usr/tmp but can be
re-defined by setting the environment variable TMPDIR
``Shared libraries'' in the Programming Tools Guide
is not part of any
currently supported standard;
it is an extension of AT&T System V provided by The Santa Cruz Operation.
© 2003 Caldera International, Inc. All rights reserved.
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