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1.1 root 1: .\" Copyright (c) 1980 Regents of the University of California.
2: .\" All rights reserved. The Berkeley software License Agreement
3: .\" specifies the terms and conditions for redistribution.
4: .\"
5: .\" @(#)ld.1 6.2 (Berkeley) 5/8/86
6: .\"
7: .TH LD 1 "May 8, 1986"
8: .UC 4
9: .SH NAME
10: ld \- link editor
11: .SH SYNOPSIS
12: .B ld
13: [ option ] ... file ...
14: .SH DESCRIPTION
15: .I Ld
16: combines several
17: object programs into one, resolves external
18: references, and searches libraries.
19: In the simplest case several object
20: .I files
21: are given, and
22: .I ld
23: combines them, producing
24: an object module which can be either executed or
25: become the input for a further
26: .I ld
27: run.
28: (In the latter case, the
29: .B \-r
30: option must be given
31: to preserve the relocation bits.)\
32: The output of
33: .I ld
34: is left on
35: .BR a.out .
36: This file is made executable
37: only if no errors occurred during the load.
38: .PP
39: The argument routines are concatenated in the order
40: specified. The entry point of the output is the
41: beginning of the first routine (unless the \fB\-e\fP option is specified).
42: .PP
43: If any argument is a library, it is searched exactly once
44: at the point it is encountered in the argument list.
45: Only those routines defining an unresolved external
46: reference are loaded.
47: If a routine from a library
48: references another routine in the library,
49: and the library has not been processed by
50: .IR ranlib (1),
51: the referenced routine must appear after the
52: referencing routine in the library.
53: Thus the order of programs within libraries
54: may be important.
55: The first member of a library
56: should be a file named `\_\^\_.SYMDEF',
57: which is understood to be a dictionary for the library as produced by
58: .IR ranlib (1);
59: the dictionary is searched iteratively to satisfy as many references as
60: possible.
61: .PP
62: The symbols `\_etext', `\_edata' and `\_end'
63: (`etext', `edata' and `end' in C)
64: are reserved, and if referred to,
65: are set to the first location above the program,
66: the first location above initialized data,
67: and the first location above all data respectively.
68: It is erroneous to define these symbols.
69: .PP
70: .I Ld
71: understands several options.
72: Except for
73: .BR \-l ,
74: they should appear before the file names.
75: .TP
76: .B \-A
77: This option specifies incremental loading, i.e.
78: linking is to be done in a manner so that the resulting object
79: may be read into an already executing program.
80: The next argument is the name of a file whose symbol table will be
81: taken as a basis on which to define additional symbols.
82: Only newly linked material will be entered into the text and
83: data portions of
84: .BR a.out,
85: but the new symbol table will reflect
86: every symbol defined before and after the incremental load.
87: This argument must appear before any other object file in the argument list.
88: The
89: .B \-T
90: option may be used as well, and will be taken to mean that the
91: newly linked segment will commence at the corresponding address
92: (which must be a multiple of 1024).
93: The default value is the old value of _end.
94: .TP
95: .B \-D
96: Take the next argument as a hexadecimal number and pad the data segment
97: with zero bytes to the indicated length.
98: .TP
99: .B \-d
100: Force definition of common storage
101: even if the
102: .B \-r
103: flag is present.
104: .TP
105: .B \-e
106: The following argument is taken to be the
107: name of the entry point of the loaded
108: program; location 0 is the default.
109: .TP
110: .BI \-L dir
111: Add
112: .I dir
113: to the list of directories in which libraries are searched for.
114: Directories specified with
115: .B \-L
116: are searched before the standard directories.
117: .TP
118: .BI \-l x
119: This
120: option is an abbreviation for the library name
121: .RI `lib x .a',
122: where
123: .I x
124: is a string.
125: .I Ld
126: searches for libraries first in any directories
127: specified with
128: .B \-L
129: options, then in the standard directories `/lib', `/usr/lib', and
130: `/usr/local/lib'.
131: A library is searched when its name is encountered,
132: so the placement of a
133: .B \-l
134: is significant.
135: .TP
136: .B \-M
137: produce a primitive load map, listing the names of the files
138: which will be loaded.
139: .TP
140: .B \-N
141: Do not make the text portion read only or sharable. (Use "magic number" 0407.)
142: .TP
143: .B \-n
144: Arrange (by giving the output file a 0410 "magic number") that
145: when the output file is executed,
146: the text portion will be read-only and shared
147: among all users executing the file.
148: This involves moving the data areas up to the first
149: possible 1024 byte boundary following the
150: end of the text.
151: .TP
152: .B \-o
153: The
154: .I name
155: argument after
156: .B \-o
157: is used as the name of the
158: .I ld
159: output file, instead of
160: .BR a.out .
161: .TP
162: .B \-r
163: Generate relocation bits in the output file
164: so that it can be the subject of another
165: .I ld
166: run.
167: This flag also prevents final definitions from being
168: given to common symbols,
169: and suppresses the `undefined symbol' diagnostics.
170: .TP
171: .B \-S
172: `Strip' the output by removing all symbols except locals and globals.
173: .TP
174: .B \-s
175: `Strip' the output, that is, remove the symbol table
176: and relocation bits to save space (but impair the
177: usefulness of the debuggers).
178: This information can also be removed by
179: .IR strip (1).
180: .TP
181: .B \-T
182: The next argument is a hexadecimal number which sets the text segment origin.
183: The default origin is 0.
184: .TP
185: .B \-t
186: ("trace") Print the name of each file as it is processed.
187: .TP
188: .B \-u
189: Take the following argument as a symbol and enter
190: it as undefined in the symbol table. This is useful
191: for loading wholly from a library, since initially the symbol
192: table is empty and an unresolved reference is needed
193: to force the loading of the first routine.
194: .TP
195: .B \-X
196: Save local symbols
197: except for those whose names begin with `L'.
198: This option is used by
199: .IR cc (1)
200: to discard internally-generated labels while
201: retaining symbols local to routines.
202: .TP
203: .B \-x
204: Do not preserve local
205: (non-.globl) symbols in the output symbol table; only enter
206: external symbols.
207: This option saves some space in the output file.
208: .TP
209: \fB\-y\fIsym\fR
210: Indicate each file in which
211: .I sym
212: appears, its type and whether the file defines or references it.
213: Many such options may be given to trace many symbols.
214: (It is usually necessary to begin
215: .I sym
216: with an `_', as external C, FORTRAN and Pascal variables begin
217: with underscores.)
218: .TP
219: .B \-z
220: Arrange for the process to be loaded on
221: demand from the resulting executable file (413 format)
222: rather than preloaded.
223: This is the default.
224: Results in a 1024 byte header on the output file followed by
225: a text and data segment each of which have size a multiple of 1024 bytes
226: (being padded out with nulls in the file if necessary).
227: With this format the first few BSS segment symbols may actually appear
228: (from the output of
229: .IR size (1))
230: to live in the data segment;
231: this to avoid wasting the space resulting from data segment size roundup.
232: .SH FILES
233: .ta \w'/usr/local/lib/lib*.a\ \ 'u
234: /lib/lib*.a libraries
235: .br
236: /usr/lib/lib*.a more libraries
237: .br
238: /usr/local/lib/lib*.a still more libraries
239: .br
240: a.out output file
241: .SH "SEE ALSO"
242: as(1), ar(1), cc(1), ranlib(1)
243: .SH BUGS
244: There is no way to force data to be page aligned.
245: .I Ld
246: pads images which are to be demand loaded from
247: the file system to the next
248: page boundary to avoid a bug in the system.
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