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32 .\" @(#) dlopen.3 1.6 90/01/31 SMI
33 .\" $FreeBSD: head/lib/libc/gen/dlopen.3 211397 2010-08-16 15:18:30Z joel $
40 .Nd returns handle to dynamically loaded shared object
42 This function is not in a library. It is included in every dynamically linked
43 program automatically.
47 .Fn dlopen "const char *name" "int mode"
52 provides access to the shared object in
54 returning a descriptor that can be used for later
55 references to the object in calls to other dl functions.
58 was not in the address space prior to the call to
60 it is placed in the address space.
61 When an object is first loaded into the address space in this way, its
64 if any, is called by the dynamic linker.
67 has already been placed in the address space in a previous call to
69 it is not added a second time, although a reference count of
74 A null pointer supplied for
76 is interpreted as a reference to the main
77 executable of the process.
81 controls the way in which external function references from the
82 loaded object are bound to their referents.
83 It must contain one of the following values, possibly ORed with
84 additional flags which will be described subsequently:
85 .Bl -tag -width RTLD_LAZYX
87 Each external function reference is resolved when the function is first
90 All external function references are bound immediately by
95 is normally preferred, for reasons of efficiency.
98 is useful to ensure that any undefined symbols are discovered during the
102 One of the following flags may be ORed into the
105 .Bl -tag -width RTLD_NODELETE
107 Symbols from this shared object and its directed acyclic graph (DAG)
108 of needed objects will be available for resolving undefined references
109 from all other shared objects.
111 Symbols in this shared object and its DAG of needed objects will be
112 available for resolving undefined references only from other objects
114 This is the default, but it may be specified
115 explicitly with this flag.
117 When set, causes dynamic linker to exit after loading all objects
118 needed by this shared object and printing a summary which includes
119 the absolute pathnames of all objects, to standard output.
122 will return to the caller only in the case of error.
124 Prevents unload of the loaded object on
126 The same behaviour may be requested by
128 option of the static linker
131 Ony return valid handle for the object if it is already loaded in
132 the process address space, otherwise
135 Other mode flags may be specified, which will be applied for promotion
136 for the found object.
142 returns a null pointer in the event of an error.
144 Whenever an error has been detected, a message detailing it can be
145 retrieved via a call to
148 The following program will open any shared gcc library found
149 and display the directory in which it was found using the
157 main (int argc, char *argv[])
163 /* open shared gcc library */
164 handle = dlopen("libgcc_s.so", RTLD_LAZY);
166 fprintf (stderr, "%s\n", dlerror ());
170 /* get information about the library origin */
171 result = dlinfo (handle, RTLD_DI_ORIGIN, (void *)&origin);
173 fprintf (stderr, "%s\n", dlerror ());
178 /* Display the origin */
179 printf ("libgcc_s origin is %s\\n", &origin[0]);