1DLCLOSE(3P) POSIX Programmer's Manual DLCLOSE(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 dlclose — close a symbol table handle
13
15 #include <dlfcn.h>
16 int dlclose(void *handle);
18
20 The dlclose() function shall inform the system that the symbol table
21 handle specified by handle is no longer needed by the application.
22 An application writer may use dlclose() to make a statement of intent
24 on the part of the process, but this statement does not create any
25 requirement upon the implementation. When the symbol table handle is
26 closed, the implementation may unload the executable object files that
27 were loaded by dlopen() when the symbol table handle was opened and
28 those that were loaded by dlsym() when using the symbol table handle
29 identified by handle.
30 Once a symbol table handle has been closed, an application should
32 assume that any symbols (function identifiers and data object identi‐
33 fiers) made visible using handle, are no longer available to the
34 process.
35 Although a dlclose() operation is not required to remove any functions
37 or data objects from the address space, neither is an implementation
38 prohibited from doing so. The only restriction on such a removal is
39 that no function nor data object shall be removed to which references
40 have been relocated, until or unless all such references are removed.
41 For instance, an executable object file that had been loaded with a
42 dlopen() operation specifying the RTLD_GLOBAL flag might provide a tar‐
43 get for dynamic relocations performed in the processing of other relo‐
44 catable objects—in such environments, an application may assume that no
45 relocation, once made, shall be undone or remade unless the executable
46 object file containing the relocated object has itself been removed.
47
49 If the referenced symbol table handle was successfully closed,
50 dlclose() shall return 0. If handle does not refer to an open symbol
51 table handle or if the symbol table handle could not be closed,
52 dlclose() shall return a non-zero value. More detailed diagnostic
53 information shall be available through dlerror().
54
56 No errors are defined.
57 The following sections are informative.
59
61 The following example illustrates use of dlopen() and dlclose():
62 #include <dlfcn.h>
65 int eret;
66 void *mylib;
67 ...
68 /* Open a dynamic library and then close it ... */
69 mylib = dlopen("mylib.so", RTLD_LOCAL | RTLD_LAZY);
70 ...
71 eret = dlclose(mylib);
72 ...
73
75 A conforming application should employ a symbol table handle returned
76 from a dlopen() invocation only within a given scope bracketed by a
77 dlopen() operation and the corresponding dlclose() operation. Implemen‐
78 tations are free to use reference counting or other techniques such
79 that multiple calls to dlopen() referencing the same executable object
80 file may return a pointer to the same data object as the symbol table
81 handle.
82 Implementations are also free to re-use a handle. For these reasons,
84 the value of a handle must be treated as an opaque data type by the
85 application, used only in calls to dlsym() and dlclose().
86
88 None.
89
91 None.
92
94 dlerror(), dlopen(), dlsym()
95 The Base Definitions volume of POSIX.1‐2017, <dlfcn.h>
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99 Portions of this text are reprinted and reproduced in electronic form
100 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
101 table Operating System Interface (POSIX), The Open Group Base Specifi‐
102 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
103 Electrical and Electronics Engineers, Inc and The Open Group. In the
104 event of any discrepancy between this version and the original IEEE and
105 The Open Group Standard, the original IEEE and The Open Group Standard
106 is the referee document. The original Standard can be obtained online
107 at http://www.opengroup.org/unix/online.html .
108 Any typographical or formatting errors that appear in this page are
110 most likely to have been introduced during the conversion of the source
111 files to man page format. To report such errors, see https://www.ker‐
112 nel.org/doc/man-pages/reporting_bugs.html .
113IEEE/The Open Group 2017 DLCLOSE(3P)