1 .\" Copyright (c) 1995 Paul Kranenburg
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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38 .Nd run-time link-editor
42 utility is a self-contained shared object providing run-time
43 support for loading and link-editing shared objects into a process'
45 It is also commonly known as the dynamic linker.
46 It uses the data structures
47 contained within dynamically linked programs to determine which shared
48 libraries are needed and loads them using the
52 After all shared libraries have been successfully loaded,
54 proceeds to resolve external references from both the main program and
56 A mechanism is provided for initialization routines
57 to be called on a per-object basis, giving a shared object an opportunity
58 to perform any extra set-up before execution of the program proper begins.
59 This is useful for C++ libraries that contain static constructors.
63 utility itself is loaded by the kernel together with any dynamically-linked
64 program that is to be executed.
65 The kernel transfers control to the
67 After the dynamic linker has finished loading,
68 relocating, and initializing the program and its required shared
69 objects, it transfers control to the entry point of the program.
71 To locate the required shared objects in the file system,
82 recognizes a number of environment variables that can be used to modify
84 On 64-bit architectures, the linker for 32-bit objects recognizes
85 all the environment variables listed below, but is being prefixed with
88 .Ev LD_32_TRACE_LOADED_OBJECTS .
90 .Bl -tag -width ".Ev LD_LIBMAP_DISABLE"
91 .It Ev LD_DUMP_REL_POST
94 will print a table containing all relocations after symbol
95 binding and relocation.
96 .It Ev LD_DUMP_REL_PRE
99 will print a table containing all relocations before symbol
100 binding and relocation.
102 A library replacement list in the same format as
104 For convenience, the characters
108 can be used instead of a space and a newline.
109 This variable is parsed after
111 and will override its entries.
112 .It Ev LD_LIBMAP_DISABLE
113 If set, disables the use of
117 .It Ev LD_LIBRARY_PATH
118 A colon separated list of directories, overriding the default search path
119 for shared libraries.
120 This is ignored for set-user-ID and set-group-ID programs.
122 A list of shared libraries, separated by colons and/or white space,
123 to be linked in before any
124 other shared libraries.
125 If the directory is not specified then
126 the directories specified by
128 will be searched first
129 followed by the set of built-in standard directories.
130 This is ignored for set-user-ID and set-group-ID programs.
132 When set to a nonempty string, causes
134 to relocate all external function calls before starting execution of the
136 Normally, function calls are bound lazily, at the first call
139 increases the start-up time of a program, but it avoids run-time
140 surprises caused by unexpectedly undefined functions.
141 .It Ev LD_TRACE_LOADED_OBJECTS
142 When set to a nonempty string, causes
144 to exit after loading the shared objects and printing a summary which includes
145 the absolute pathnames of all objects, to standard output.
146 .It Ev LD_TRACE_LOADED_OBJECTS_ALL
147 When set to a nonempty string, causes
149 to expand the summary to indicate which objects caused each object to
151 .It Ev LD_TRACE_LOADED_OBJECTS_FMT1
152 .It Ev LD_TRACE_LOADED_OBJECTS_FMT2
153 When set, these variables are interpreted as format strings a la
155 to customize the trace output and are used by
160 to be operated as a filter more conveniently.
161 The following conversions can be used:
164 The main program's name
168 The value of the environment variable
169 .Ev LD_TRACE_LOADED_OBJECTS_PROGNAME
173 The library's major version number.
175 The full pathname as determined by
177 library search rules.
179 The library's load address.
186 are recognized and have their usual meaning.
189 .Bl -tag -width ".Pa /var/run/ld-elf32.so.hints" -compact
190 .It Pa /var/run/ld-elf.so.hints
192 .It Pa /var/run/ld-elf32.so.hints
193 Hints file for 32-bit binaries on 64-bit system.
194 .It Pa /etc/libmap.conf
195 The libmap configuration file.
196 .It Pa /etc/libmap32.conf
197 The libmap configuration file for 32-bit binaries on 64-bit system.