term% cat index.txt LD(1) General Commands Manual LD(1)
NAME
ld - loader
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.
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(1), the referenced routine must appear af‐
ter the referencing routine in the library. Thus the order of programs
within libraries may be important. If the first member of a library is
named ‘__.SYMDEF', then it is understood to be a dictionary for the li‐
brary such as produced by ranlib; the dictionary is searched itera‐
tively 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.
-s ‘Strip' the output, that is, remove the symbol table and reloca‐
tion bits to save space (but impair the usefulness of the debug‐
ger). This information can also be removed by strip(1).
-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.
-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.
-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.
-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.
-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.
-d Force definition of common storage even if the -r flag is
present.
-n Arrange 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 4K
word boundary following the end of the text.
-i When the output file is executed, the program text and data ar‐
eas will live in separate address spaces. The only difference
between this option and -n is that here the data starts at loca‐
tion 0.
-o The name argument after -o is used as the name of the ld output
file, instead of a.out.
-e The following argument is taken to be the name of the entry
point of the loaded program; location 0 is the default.
-O This is an overlay file, only the text segment will be replaced
by exec(2). Shared data must have the same layout as in the
program overlaid.
-D The next argument is a decimal number that sets the size of the
data segment.
FILES
/lib/lib*.a libraries
/usr/lib/lib*.a more libraries
a.out output file
SEE ALSO
as(1), ar(1), cc(1), ranlib(1)
BUGS
LD(1)