ld - loader
ld [ option ] file ...
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.
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. If the first member of a library is named `__.SYMDEF', then it is understood
to be a dictionary for the library such 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 erro-
neous to define these symbols.
Ld understands several options. Except for -l, they should appear before the file names.
-s `Strip' the output, that is, remove the symbol table and relocation bits to save
space (but impair the usefulness of the debugger). This information can also be
removed by strip(1).
-u Take the following argument as a symbol and enter it as undefined in the symbol ta-
ble. 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
-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 labels while retaining symbols local
-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 com-
mon 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 areas will live in sep-
arate address spaces. The only difference between this option and -n is that here
the data starts at location 0.
-o The name argument after -o is used as the name of the ld output file, instead of
-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.
/usr/lib/lib*.a more libraries
a.out output file
as(1), ar(1), cc(1), ranlib(1)