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Created page with " The librarian program, LIBR, has the function of com- bining several object files into a single file known as a library. The purposes of combining several such object module..."
The librarian program, LIBR, has the function of com-
bining several object files into a single file known as a
library. The purposes of combining several such object
modules are several.
a. fewer files to link
b. faster access
c. uses less disk space
In order to make the library concept useful, it is
necessary for the linker to treat modules in a library dif-
ferently from object files. If an object file is specified
to the linker, it will be linked into the final linked
module. A module in a library, however, will only be linked
in if it defines one or more symbols previously known, but
not defined, to the linker. Thus modules in a library will
be linked only if required. Since the choice of modules to
link is made on the first pass of the linker, and the
library is searched in a linear fashion, it is possible to
order the modules in a library to produce special effects
when linking. More will be said about this later.
== The Library Format ==
The modules in a library are basically just con-
catenated, but at the beginning of a library is maintained a
directory of the modules and symbols in the library. Since
this directory is smaller than the sum of the modules, the
linker is speeded up when searching a library since it need
read only the directory and not all the modules on the first
pass. On the second pass it need read only those modules
which are required, seeking over the others. This all minim-
izes disk i/o when linking.
It should be noted that the library format is geared
exclusively toward object modules, and is not a general pur-
pose archiving mechanism as is used by some other compiler
systems. This has the advantage that the format may be
optimized toward speeding up the linkage process.
== Using ==
The librarian program is called LIBR, and the format of
commands to it is as follows:
LIBR k file.lib file.obj ...
Interpreting this, LIBR is the name of the program, k
is a key letter denoting the function requested of the
librarian (replacing, extracting or deleting modules, list-
ing modules or symbols), file.lib is the name of the library
file to be operated on, and file.obj is zero or more object
file names.
The key letters are:
r replace modules
d delete modules
x extract modules
m list module names
s list modules with symbols
When replacing or extracting modules, the file.obj
arguments are the names of the modules to be replaced or
extracted. If no such arguments are supplied, all the
modules in the library will be replaced or extracted respec-
tively. Adding a file to a library is performed by request-
ing the librarian to replace it in the library. Since it is
not present, the module will be appended to the library. If
the r key is used and the library does not exist, it will be
created.
Under the d keyletter, the named object files will be
deleted from the library. In this instance, it is an error
not to give any object file names.
The m and s keyletters will list the named modules and,
in the case of the s keyletter, the symbols defined or
referenced within (global symbols only are handled by the
librarian). As with the r and x keyletters, an empty list of
modules means all the modules in the library.
== Examples ==
Here are some examples of usage of the librarian.
LIBR m file.lib
List all modules in the library file.lib.
LIBR s file.lib a.obj b.obj c.obj
List the global symbols in the modules a.obj, b.obj and
c.obj
LIBR r file.lib 1.obj 2.obj
Replace the module 1.obj in the file file.lib with the
contents of the object file 1.obj, and repeat for
2.obj. If the object module is not already present in
the library, append it to the end.
LIBR x file.lib
Extract, without deletion, all the modules in file.lib
and write them as object files on disk.
LIBR d file.lib a.obj b.obj 2.obj
Delete the object modules a.obj, b.obj and 2.obj from
the library file.lib.
== Supplying Arguments ==
Since it is often necessary to supply many object file
arguments to LIBR, and command lines are restricted to 127
characters by CP/M and MS-DOS, LIBR will accept commands
from standard input if no command line arguments are given.
If the standard input is attached to the console, LIBR will
prompt. Multiple line input may be given by using a
backslash as a continuation character on the end of a line.
If standard input is redirected from a file, LIBR will take
input from the file, without prompting. For example:
LIBR
libr> r file.lib 1.obj 2.obj 3.obj \
libr> 4.obj 5.obj 6.obj
will perform much the same as if the .obj files had been
typed on the command line. The libr> prompts were printed by
LIBR itself, the remainder of the text was typed as input.
LIBR <lib.cmd
Libr will read input from lib.cmd, and execute the com-
mand found therein. This allows a virtually unlimited length
command to be given to LIBR.
== Listing Format ==
A request to LIBR to list module names will simply pro-
duce a list of names, one per line, on standard output. The
s keyletter will produce the same, with a list of symbols
after each module name. Each symbol will be preceded by the
letter D or U, representing a definition or reference to the
symbol respectively. The -W option may be used to determine
the width of the paper for this operation. For example LIBR
-w80 s file.lib will list all modules in file.lib with their
global symbols, with the output formatted for an 80 column
printer or display.
== Ordering of Libraries ==
The librarian creates libraries with the modules in the
order in which they were given on the command line. When
updating a library the order of the modules is preserved.
Any new modules added to a library after it has been created
will be appended to the end.
The ordering of the modules in a library is significant
to the linker. If a library contains a module which refer-
ences a symbol defined in another module in the same
library, the module defining the symbol should come after
the module referencing the symbol.
== Error Messages ==
Libr issues various error messages, most of which
represent a fatal error, while some represent a harmless
occurence which will nonetheless be reported unless the -w
option was used. In this case all warning messages will be
suppressed.
