DLCLOSE(3P) POSIX Programmer's Manual DLCLOSE(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEdlclose — close a symbol table handle
int dlclose(void *handle);
The dlclose() function shall inform the system that the symbol table
handle specified by handle is no longer needed by the application.
An application writer may use dlclose() to make a statement of intent
on the part of the process, but this statement does not create any
requirement upon the implementation. When the symbol table handle is
closed, the implementation may unload the executable object files that
were loaded by dlopen() when the symbol table handle was opened and
those that were loaded by dlsym() when using the symbol table handle
identified by handle.
Once a symbol table handle has been closed, an application should
assume that any symbols (function identifiers and data object identi‐
fiers) made visible using handle, are no longer available to the
Although a dlclose() operation is not required to remove any functions
or data objects from the address space, neither is an implementation
prohibited from doing so. The only restriction on such a removal is
that no function nor data object shall be removed to which references
have been relocated, until or unless all such references are removed.
For instance, an executable object file that had been loaded with a
dlopen() operation specifying the RTLD_GLOBAL flag might provide a tar‐
get for dynamic relocations performed in the processing of other relo‐
catable objects—in such environments, an application may assume that no
relocation, once made, shall be undone or remade unless the executable
object file containing the relocated object has itself been removed.
If the referenced symbol table handle was successfully closed,
dlclose() shall return 0. If handle does not refer to an open symbol
table handle or if the symbol table handle could not be closed,
dlclose() shall return a non-zero value. More detailed diagnostic
information shall be available through dlerror().
No errors are defined.
The following sections are informative.
The following example illustrates use of dlopen() and dlclose():
/* Open a dynamic library and then close it ... */
mylib = dlopen("mylib.so", RTLD_LOCAL | RTLD_LAZY);
eret = dlclose(mylib);
A conforming application should employ a symbol table handle returned
from a dlopen() invocation only within a given scope bracketed by a
dlopen() operation and the corresponding dlclose() operation. Implemen‐
tations are free to use reference counting or other techniques such
that multiple calls to dlopen() referencing the same executable object
file may return a pointer to the same data object as the symbol table
Implementations are also free to re-use a handle. For these reasons,
the value of a handle must be treated as an opaque data type by the
application, used only in calls to dlsym() and dlclose().
SEE ALSOdlerror(), dlopen(), dlsym()
The Base Definitions volume of POSIX.1‐2008, <dlfcn.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
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IEEE/The Open Group 2013 DLCLOSE(3P)