1LD(1) General Commands Manual LD(1)
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6 ld - loader
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9 ld [ option ] file ...
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12 Ld combines several object programs into one, resolves external refer‐
13 ences, and searches libraries. In the simplest case several object
14 files are given, and ld combines them, producing an object module which
15 can be either executed or become the input for a further ld run. (In
16 the latter case, the -r option must be given to preserve the relocation
17 bits.) The output of ld is left on a.out. This file is made exe‐
18 cutable only if no errors occurred during the load.
19 The argument routines are concatenated in the order specified. The
21 entry point of the output is the beginning of the first routine.
22 If any argument is a library, it is searched exactly once at the point
24 it is encountered in the argument list. Only those routines defining
25 an unresolved external reference are loaded. If a routine from a
26 library references another routine in the library, and the library has
27 not been processed by ranlib(1), the referenced routine must appear
28 after the referencing routine in the library. Thus the order of pro‐
29 grams within libraries may be important. If the first member of a
30 library is named `__.SYMDEF', then it is understood to be a dictionary
31 for the library such as produced by ranlib; the dictionary is searched
32 iteratively to satisfy as many references as possible.
33 The symbols `_etext', `_edata' and `_end' (`etext', `edata' and `end'
35 in C) are reserved, and if referred to, are set to the first location
36 above the program, the first location above initialized data, and the
37 first location above all data respectively. It is erroneous to define
38 these symbols.
39 Ld understands several options. Except for -l, they should appear
41 before the file names.
42 -s `Strip' the output, that is, remove the symbol table and reloca‐
44 tion bits to save space (but impair the usefulness of the debug‐
45 ger). This information can also be removed by strip(1).
46 -u Take the following argument as a symbol and enter it as unde‐
48 fined in the symbol table. This is useful for loading wholly
49 from a library, since initially the symbol table is empty and an
50 unresolved reference is needed to force the loading of the first
51 routine.
52 -lx This option is an abbreviation for the library name
54 `/lib/libx.a', where x is a string. If that does not exist, ld
55 tries `/usr/lib/libx.a'. A library is searched when its name is
56 encountered, so the placement of a -l is significant.
57 -x Do not preserve local (non-.globl) symbols in the output symbol
59 table; only enter external symbols. This option saves some
60 space in the output file.
61 -X Save local symbols except for those whose names begin with `L'.
63 This option is used by cc(1) to discard internally generated
64 labels while retaining symbols local to routines.
65 -r Generate relocation bits in the output file so that it can be
67 the subject of another ld run. This flag also prevents final
68 definitions from being given to common symbols, and suppresses
69 the `undefined symbol' diagnostics.
70 -d Force definition of common storage even if the -r flag is
72 present.
73 -n Arrange that when the output file is executed, the text portion
75 will be read-only and shared among all users executing the file.
76 This involves moving the data areas up to the first possible 4K
77 word boundary following the end of the text.
78 -i When the output file is executed, the program text and data
80 areas will live in separate address spaces. The only difference
81 between this option and -n is that here the data starts at loca‐
82 tion 0.
83 -o The name argument after -o is used as the name of the ld output
85 file, instead of a.out.
86 -e The following argument is taken to be the name of the entry
88 point of the loaded program; location 0 is the default.
89 -O This is an overlay file, only the text segment will be replaced
91 by exec(2). Shared data must have the same layout as in the
92 program overlaid.
93 -D The next argument is a decimal number that sets the size of the
95 data segment.
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98 /lib/lib*.a libraries
99 /usr/lib/lib*.a more libraries
100 a.out output file
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103 as(1), ar(1), cc(1), ranlib(1)
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106 LD(1)