LD
Section: User Commands (1)
Updated: 17 July 1986
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NAME
ld - link editor
SYNOPSIS
ld
[
-align datum
]
[
-A name
]
[ -d ]
[ -D hex ]
[ -e entry ]
[ -lx ]
[ -Ldir ]
[ -M ]
[ -n ]
[ -N ]
[
-o name
]
[
-r
]
[
-s
]
[
-S
]
[
-t
]
[
-T[text]hex
]
[
-Tdata hex
]
[
-u name
]
[
-x
]
[
-X
]
[
-ysym
]
[
-z
]
filename...
DESCRIPTION
ld
combines several object programs into one, resolves external references,
and searches libraries. In the simplest case several object
filenames
are given, and
ld
combines them, producing an object module which can either be executed or
become the input for a subsequent
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 file called
a.out
if not otherwise specified. The output file
is made executable only if no errors occurred during link editing.
Files specified by the argument
filename ...
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 a
named file
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 same library, and the library has not been
processed by
ranlib,
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;
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
Options should appear before the
filenames,
except abbreviated library
names specified by the
-l
option, which can appear anywhere.
- -align datum
-
datum
(usually a
FORTRAN
common block) is increased in length
to be a multiple of the page size; its beginning
is set at a page boundary.
- -A name
-
Incremental loading: linking is to be done in a manner so that the
resulting object may be read into an already executing program.
name
is the name of a file whose symbol table is taken as a basis
on which to define additional symbols. Only newly linked material is
entered into the text and data portions of
a.out,
but the new symbol table will reflect all symbols defined before and after
the incremental load. This argument must appear before any other object
file in the argument list. One or both of the
-T
options may be used as well, and will be taken to mean that the newly linked
segment will commence at the corresponding addresses (which must be a multiple
of the page size). The default value is the old value of
_end.
- -d
-
Force definition of common storage even if the
-r
flag is present.
- -D hex
-
Pad the data segment with zero-valued bytes to make it hex
bytes long.
- -e entry
-
Define the entry point: the entry argument is made the
name of the entry point of the loaded program.
- -lx
-
This option is an abbreviation for the library name
libx.a,
where
x
is a string.
ld
searches for libraries first in any directories specified with
-L
options, then in the standard directory /sprite/lib/tm.md,
where tm is the target machine on which the linked program
is intended to execute. Tm defaults to the value of the
MACHINE environment variable, but may be overridden with
the -m switch.
A library is searched when its name is encountered,
so the placement of a
-l
is significant.
- -Ldir
-
Add
dir
to the list of directories in which libraries are searched for.
Directories specified with
-L
are searched before the standard directory.
- -mtm
-
Use tm as the target machine for this link, rather than the
MACHINE environment variable. This switch determines where
the linker looks for libraries (see the -l switch above).
- -M
-
Produce a primitive load map, listing the names of the files
which will be loaded.
- -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
processes executing the file. This involves moving the data areas up to the first
possible segment boundary following the end of the text.
- -N
-
Do not make the text portion read-only or sharable. (Use `magic number' 0407.)
- -o name
-
Name
is made 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).
- -S
-
Strip the output by removing all symbols except locals and globals.
- -t
-
Trace: display the name of each file as it is processed.
- -T[text]hex
-
Start the text segment at location hex. Specifying
-T
is the same as using the
-Ttext
option.
- -Tdata hex
-
Start the data segment at location hex. This option is only of use
to programmers wishing to write code for
PROMs,
since the resulting code cannot be executed by the
UNIX
system.
- -u name
-
Enter name as an undefined symbol. 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
-
Preserve only global (non-.globl) symbols in the output symbol
table; only enter external symbols.
This option saves some space in the output file.
- -X
-
Record local symbols, except for those whose names begin with `L'.
This option is used by
cc
to discard internally generated labels while
retaining symbols local to routines.
- -ysym
-
Display 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 (0413 `magic number') rather than preloaded. This is the default.
Results in a (32-byte) header on the output file followed by
text and data segments, each of which has a multiple of page-size
bytes (being padded out with nulls in the file if necessary).
With this format the first few BSS segment symbols may actually end up
in the data segment;
this is to avoid wasting the space resulting from rounding the data
segment size.
The text is read-only and shared among all processes executing the file.
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(1V), ranlib(1), strip(1)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- FILES
-
- SEE ALSO
-
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