LD(1) LD(1)
NAME
ld - link editor or loader
SYNOPSIS
ld [ option ... ] file ...
DESCRIPTION
Ld combines several object programs into one, resolves
external references, and searches libraries. In the sim-
plest case several object files are given, and ld combines
them, producing an object module which can be either exe-
cuted 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 This file is
made executable only if no errors occurred during the load.
The argument routines are concatenated in the order speci-
fied. The entry 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 library references another rou-
tine 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; see
lorder(1). The first member of a library should be a file
named __.SYMDEF, which is understood to be a dictionary for
the library as produced by ranlib; the dictionary is
searched iteratively to satisfy as many references as possi-
ble.
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 and -o, they
should appear before the file names.
-A Load incrementally, so that the resulting object code
may be read into an already executing program. The
next argument names an object file whose symbol table
will be added to. Only newly linked material will be
entered into the text and data portions of but the new
symbol table will reflect every symbol defined before
LD(1) LD(1)
and after the incremental load. -A must not follow any
object file names.
-D Take the next argument as a hexadecimal number and pad
the data segment with zeros 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 the
option 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 that when the output file is executed, the text
portion will be read-only and shared among all users
executing the file. (Use magic number 0410 and move
the data segment to a 1024 byte boundary.)
-o The name argument after -o is used as the name of the
ld output file, instead of
-r Generate relocation bits in the output file so that it
can be the subject of another ld run. This flag also
prevents final fixing of `common' symbols (uninitial-
ized C variables or Fortran common variables), and sup-
presses `undefined symbol' diagnostics.
-s Strip the output, that is, remove the symbol table and
relocation bits to save space (but impair the useful-
ness of the debuggers). This information can also be
removed by strip(1).
-S Partially strip; remove all symbols that were not in
the source.
-T The next argument is a hexadecimal number which sets
the text segment origin. With option -A this origin
must be a multiple of 1024. The default is 0, or _end
with -A.
LD(1) LD(1)
-t (trace) Print the name of each file as it is pro-
cessed.
-u Take the following argument as a symbol and enter it as
undefined in the symbol table. This is useful for
loading wholly from a library, since initially the sym-
bol 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 labels while retaining symbols
local to routines.
-x Do not preserve local 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 underscore `_',
as external C, Fortran, and Pascal variables begin with
underscores.)
-z Arrange for the process to be loaded on demand from the
resulting executable file (magic number 413) rather
than preloaded. This (default) output format has a
1024-byte header followed by a text and data segment
each of which have size a multiple of 1024 bytes (being
padded out with zeros if necessary). The first few BSS
segment symbols may appear in the data segment to avoid
wasting space at the end of that segment.
FILES
libraries
more libraries
output file
SEE ALSO
as(1), ar(1), cc(1), f77(1), size(1), nm(1), lorder(1),
a.out(5)
BUGS
There is no way to force data to be page aligned.