LD(1) COMMAND REFERENCE LD(1)
NAME
ld - link editor
SYNOPSIS
ld [ -d ] [ -e ] [ -n ] [ -o ] [ -r ] [ -s ] [ -t ] [ -u ] [
-x ] [ -y sym ] [ -z ] [ -A ] [ -D ] [ -G ] [ -M ] [ -N ] [
-P pagesize ] [ -S ] [ -T ] [ -X ] filename... [ -lx ]
DESCRIPTION
Ld combines several object programs into one, resolves
external references, 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 executable only if no errors occurred
during the load.
The argument routines are concatenated in the order
specified. 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
routine in the library, and the library has not been
processed by ranlib(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 library 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.
OPTIONS
Ld understands several options. Except for -l, they should
appear before the file names.
-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.
Printed 10/17/86 1
LD(1) COMMAND REFERENCE LD(1)
-lx This option is an abbreviation for the library name
"libx.a", where x is a string. Ld finds this library by
looking in the directories named in the environment
variable LIBPATH. If LIBPATH has not been set, it takes
the default value of "/lib /usr/lib /usr/local/lib". A
library is searched when its name is encountered, so the
placement of a -l is significant.
-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 involves moving the data areas
up to the first possible "page size" 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, that is, remove the symbol table and
relocation bits to save space (but impair the usefulness
of the debuggers). This information can also be removed
by strip(1).
-t execution trace. Probably only useful for debugging the
loader.
-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
symbol table is empty and an unresolved reference is
needed to force the loading of the first routine.
-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 begin with underscores.)
-z Arrange for the process to be loaded on demand from the
resulting executable file (413 format) rather than
preloading by default. Results in a "page size" byte
Printed 10/17/86 2
LD(1) COMMAND REFERENCE LD(1)
header on the output file followed by a text and data
segment each of which have size a multiple of "page
size" (being padded out with nulls in the file if
necessary). With this format the first few BSS segment
symbols 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.
-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 before 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 "page size"). 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.
-G Take the next argument as a hexadecimal number and use
it as the base address of the bss segment. (Useful for
ROM based code).
-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.)
-P The next argument is a decimal number which sets the
page size of target system. If this flag is not used,
the page size will be set to that of the host system,
normally 1024.
-S `Strip' the output by removing all symbols except locals
and globals.
-T The next argument is a hexadecimal number which sets the
text segment origin. The default origin is 0.
-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
Printed 10/17/86 3
LD(1) COMMAND REFERENCE LD(1)
local to routines.
VARIABLES
LIBPATH The -l search path, an ordered list of
directories, separated by colons and/or
whitespace.
FILES
/lib/lib*.a libraries
/usr/lib/lib*.a more libraries
/usr/local/lib/lib*.a still more libraries
a.out output file
CAVEATS
There is no way to force data to be page aligned.
SEE ALSO
as(1), ar(1), cc(1), ranlib(1).
Printed 10/17/86 4
%%index%%
na:72,52;
sy:124,553;
de:677,1976;
op:2653,440;3237,2795;6176,2614;8934,29;
fi:9192,296;
va:8963,229;
ca:9488,106;
se:9594,151;
%%index%%000000000161