term% cat index.txt LD(1) General Commands Manual LD(1)
NAME
ld - link editor
SYNOPSIS
ld [ option ] ... file ...
DESCRIPTION
Ld combines several object programs into one, resolves external refer‐
ences, and searches libraries. In the simplest case several object
files are given, and ld combines them, producing an object module which
can be either executed or become the input for a further ld run. (In
the latter case, the -r option must be given to preserve the relocation
bits.) The output of ld is left on a.out. This file is made exe‐
cutable only if no errors occurred during the load.
The argument routines are concatenated in the order specified. The en‐
try point of the output is the beginning of the first routine (unless
the -e option is specified).
If any argument is a library, it is searched exactly once at the point
it is encountered in the argument list. Only those routines defining
an unresolved external reference are loaded. If a routine from a li‐
brary references another routine in the library, and the library has
not been processed by ranlib (see ar(1)), the referenced routine must
appear after the referencing routine in the library. Thus the order of
programs within libraries may be important. The first member of a li‐
brary should be a file named `__.SYMDEF', which is understood to be a
dictionary for the library as produced by ranlib(1); the dictionary is
searched iteratively to satisfy as many references as possible.
The symbols `_etext', `_edata' and `_end' (`etext', `edata' and `end'
in C) are reserved, and if referred to, are set to the first location
above the program, the first location above initialized data, and the
first location above all data respectively. It is erroneous to define
these symbols.
Ld understands several options. Except for -l, they should appear be‐
fore the file names.
-A This option specifies incremental loading, i.e. linking is to
be done in a manner so that the resulting object may be read
into an already executing program. The next argument is the
name of a file whose symbol table will be taken as a basis on
which to define additional symbols. Only newly linked material
will be entered into the text and data portions of a.out, but
the new symbol table will reflect every symbol defined before
and after the incremental load. This argument must appear be‐
fore any other object file in the argument list. The -T option
may be used as well, and will be taken to mean that the newly
linked segment will commence at the corresponding address (which
must be a multiple of 1024). The default value is the old value
of _end.
-D Take the next argument as a hexadecimal number and pad the data
segment with zero bytes to the indicated length.
-d Force definition of common storage even if the -r flag is
present.
-e The following argument is taken to be the name of the entry
point of the loaded program; location 0 is the default.
-lx This option is an abbreviation for the library name
`/lib/libx.a', where x is a string. If that does not exist, ld
tries `/usr/lib/libx.a' A library is searched when its name is
encountered, so the placement of a -l is significant.
-M produce a primitive load map, listing the names of the files
which will be loaded.
-N Do not make the text portion read only or sharable. (Use "magic
number" 0407.)
-n Arrange (by giving the output file a 0410 "magic number") that
when the output file is executed, the text portion will be read-
only and shared among all users executing the file. This in‐
volves moving the data areas up to the first possible 1024 byte
boundary following the end of the text.
-o The name argument after -o is used as the name of the ld output
file, instead of a.out.
-r Generate relocation bits in the output file so that it can be
the subject of another ld run. This flag also prevents final
definitions from being given to common symbols, and suppresses
the `undefined symbol' diagnostics.
-S `Strip' the output by removing all symbols except locals and
globals.
-s `Strip' the output, that is, remove the symbol table and reloca‐
tion bits to save space (but impair the usefulness of the debug‐
gers). This information can also be removed by strip(1).
-T The next argument is a hexadecimal number which sets the text
segment origin. The default origin is 0.
-t (`trace') Print the name of each file as it is processed.
-u Take the following argument as a symbol and enter it as unde‐
fined in the symbol table. This is useful for loading wholly
from a library, since initially the symbol table is empty and an
unresolved reference is needed to force the loading of the first
routine.
-X Save local symbols except for those whose names begin with `L'.
This option is used by cc(1) to discard internally-generated la‐
bels while retaining symbols local to routines.
-x Do not preserve local (non-.globl) symbols in the output symbol
table; only enter external symbols. This option saves some
space in the output file.
-ysym Indicate each file in which sym appears, its type and whether
the file defines or references it. Many such options may be
given to trace many symbols. (It is usually necessary to begin
sym with an `_', as external C, FORTRAN and Pascal variables be‐
gin with underscores.)
-z Arrange for the process to be loaded on demand from the result‐
ing executable file (413 format) rather than preloaded. This is
the default. Results in a 1024 byte header on the output file
followed by a text and data segment each of which have size a
multiple of 1024 bytes (being padded out with nulls in the file
if necessary). With this format the first few BSS segment sym‐
bols may actually appear (from the output of size(1)) to live in
the data segment; this to avoid wasting the space resulting from
data segment size roundup.
FILES
/lib/lib*.a libraries
/usr/lib/lib*.a more libraries
/usr/local/lib/lib*.a still more libraries
a.out output file
SEE ALSO
as(1), ar(1), cc(1), ranlib(1), size(1), nm(1)
BUGS
There is no way to force data to be page aligned.
LD(1)