ld(1)ld(1)Nameld - link editor
Syntaxld [option...] file...
Description
The command combines several object programs into one, resolves exter‐
nal references, and searches libraries. In the simplest case, several
object files are given, and combines them, producing an object module
which can either be executed or can become the input for a further run.
(In the latter case, the -r option must be given to preserve the relo‐
cation bits.) The output of is left on a.out. This file is only made
executable if no errors occurred during the load.
The argument routines are linked together in the order specified. The
entry point of the output is the beginning of the first routine, unless
the -e option is specified.
If the argument is a library, it is searched only 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 the referenced routine must appear after the referencing
routine in the library. Thus, the order of programs within libraries
is important. The first member of a library should be a file named
__.SYMDEF, which is a dictionary for the library that is produced by
The dictionary is searched repeatedly 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 loca‐
tion above all data, in that order. It is an error to define these
symbols.
Options
The command has several options. Except for the -l option, they should
appear before the file names.
-A Specifies incremental loading. Linking is done so that the
resulting object may be read into an already executing pro‐
gram. The next argument is the name of a file whose symbol
table is used to define additional symbols. Only newly
linked material is entered into the text and data portions of
a.out, but the new symbol table reflects 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 is taken to mean that
the newly linked segment commences at the corresponding
address (which must be a multiple of 1024). The default
value is the old value of _end.
-D Takes the next argument as a hexadecimal number and pads the
data segment with zero bytes to the indicated length.
-d Forces definition of common storage even if the -r flag is
present.
-e Takes the next argument as the name of the entry point of the
loaded program; location 0 is the default.
-Ldir Adds dir to the list of directories that are searched for
libraries. Directories specified with -L are searched before
the standard directories.
-lx Abbreviates the library name libx.a, where x is a string.
The command searches for libraries first in any directories
specified with -L options, then in the standard directories
/lib, /usr/lib, and /usr/local/lib. A library is searched
when its name is encountered, so the placement of a -l is
significant.
-H Takes the next argument as a decimal integer, adds it to the
end of text, and causes the data section to start at a higher
address.
-M Produces a primitive load map, listing the names of the files
that are loaded.
-N Indicates a portion of text to not make read-only or
sharable. (Use magic number 0407.)
-n Arranges (by giving the output file a 0410 magic number) that
the text portion is read-only and shared among all users exe‐
cuting the file when the output file is executed. This
involves moving the data areas up to the first possible 1024
byte boundary following the end of the text.
-o Takes the name argument after -o as the name of the output
file, instead of a.out.
-r Generates relocation bits in the output file so that it can
be the subject of another run. This flag also prevents final
definitions from being given to common symbols and suppresses
the undefined symbol diagnostics.
-S Strips the output by removing all symbols except locals and
globals.
-s Removes the symbol table and relocation bits to save space
(this impairs the usefulness of the debuggers). This infor‐
mation can also be removed by
-T Takes the next argument as a hexadecimal number which sets
the text segment origin. The default origin is 0.
-t(trace) Prints the name of each file as it is processed.
-u Takes the next argument as a symbol and enters it as unde‐
fined in the symbol table. This is useful for loading 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 Saves local symbols except for those whose names begin with a
capital L. This option is used by to discard internally-gen‐
erated labels while retaining symbols local to routines.
-x Discards local (non-global) symbols in the output symbol ta‐
ble; only enters external symbols. This option saves some
space in the output file.
-Yenvironment
Adjusts the magic number in the output file so that the pro‐
gram runs in the specified environment . The parameter can
be POSIX, SYSTEM_FIVE, or BSD . The parameter sets the pro‐
gram's execution environment to conform with one of the three
standards. If it is present, this parameter overrides the
PROG_ENV environment variable. If no environment is given,
SYSTEM_FIVE is assumed. If neither this parameter nor the
PROG_ENV variable is present, -YBSD is assumed.
-ysym Indicates 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 (_), because external C, FOR‐
TRAN and Pascal variables begin with underscores.
-z Arranges for the process to be loaded on demand from the
resulting executable file (413 format) rather than preloaded.
This is the default. It results in a 1024 byte header on the
output file followed by a text and data segment whose size is
a multiple of 1024 bytes (being padded out with nulls in the
file if necessary). With this format the first few BSS seg‐
ment symbols may, from the output of appear to reside in the
data segment. This avoids wasting the space which results
from the roundup of the data segment size.
Restrictions
There is no way to force data to be page aligned. The command pads the
images which are to be demand loaded from the file system to the next
page boundary.
When linking code contains GFLOAT instructions, the GFLOAT versions of
libc and/or the math library must be used rather than the normal DFLOAT
versions. Link to these by using -lcg and/or -lmg.
The compiler and the linker cannot detect the use of mixed double
floating point types, and your program may produce erroneous results.
Files
/lib/lib*.a libraries.
/usr/lib/lib*.a libraries
/usr/local/lib/lib*.a
libraries
a.out output file
See Alsoar(1), as(1), cc(1), ranlib(1)
VAX ld(1)
