dlclose(3C)dlclose(3C)NAME
dlclose() - close a shared library
SYNOPSIS
[flag ... ] file ... [library]...
Multithread Usage
This routine is thread-safe.
NOTE: The dynamic loader serializes the loading and unloading of shared libraries in multithreaded applications using a recursive pthread
mutex lock. See the for more information.
DESCRIPTION
is one of a family of routines that give the user direct access to the dynamic linking facilities (using the option on the compiler or com-
mand line). disassociates a shared object previously opened by from the current process. Once an object has been closed using its symbols
are no longer available to All objects loaded automatically as a result of invoking on the referenced object (see dlopen(3C)) are also
closed. handle is the value returned by a previous invocation of
RETURN VALUE
If the referenced object was successfully closed, returns If the object could not be closed, or if handle does not refer to an open object,
returns a non-0 value. More detailed diagnostic information is available through
ERRORS
If fails, a subsequent call to returns one of the following values.
Cannot apply relocation in library.
Cannot close library due to remaining dependencies.
Invalid handle.
Out of memory.
failed on entry to or exit from
failed on exit from
failed on entry to
Unknown handle.
WARNINGS
A successful invocation of does not guarantee that the objects associated with handle have actually been removed from the address space of
the process. Objects loaded by one invocation of may also be loaded by another invocation of The same object may also be opened multiple
times. An object is not removed from the address space until all references to that object through an explicit invocation have been closed
and all other objects implicitly referencing that object have also been closed.
Once an object has been closed by referencing symbols contained in that object can cause undefined behavior.
SEE ALSO dlerrno(3C), dlerror(3C), dlopen(3C), dlsym(3C).
Texts and Tutorials
(See the option)
(See manuals(5) for ordering information)
dlclose(3C)
Check Out this Related Man Page
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 correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
NAME
dlclose - close a dlopen object
SYNOPSIS
#include <dlfcn.h>
int dlclose(void *handle);
DESCRIPTION
The dlclose() function shall inform the system that the object referenced by a handle returned from a previous dlopen() invocation is no
longer needed by the application.
The use of dlclose() reflects a statement of intent on the part of the process, but does not create any requirement upon the implementa-
tion, such as removal of the code or symbols referenced by handle. Once an object has been closed using dlclose() an application should
assume that its symbols are no longer available to dlsym(). All objects loaded automatically as a result of invoking dlopen() on the refer-
enced object shall also be closed if this is the last reference to it.
Although a dlclose() operation is not required to remove structures from an address space, neither is an implementation prohibited from
doing so. The only restriction on such a removal is that no object shall be removed to which references have been relocated, until or
unless all such references are removed. For instance, an object that had been loaded with a dlopen() operation specifying the RTLD_GLOBAL
flag might provide a target for dynamic relocations performed in the processing of other objects-in such environments, an application may
assume that no relocation, once made, shall be undone or remade unless the object requiring the relocation has itself been removed.
RETURN VALUE
If the referenced object was successfully closed, dlclose() shall return 0. If the object could not be closed, or if handle does not refer
to an open object, dlclose() shall return a non-zero value. More detailed diagnostic information shall be available through dlerror().
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
The following example illustrates use of dlopen() and dlclose():
...
/* Open a dynamic library and then close it ... */
#include <dlfcn.h>
void *mylib;
int eret;
mylib = dlopen("mylib.so", RTLD_LOCAL | RTLD_LAZY);
...
eret = dlclose(mylib);
...
APPLICATION USAGE
A conforming application should employ a handle returned from a dlopen() invocation only within a given scope bracketed by the dlopen() and
dlclose() operations. Implementations are free to use reference counting or other techniques such that multiple calls to dlopen() referenc-
ing the same object may return the same object for handle. Implementations are also free to reuse a handle. For these reasons, the value
of a handle must be treated as an opaque object by the application, used only in calls to dlsym() and dlclose().
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
dlerror(), dlopen(), dlsym(), the Base Definitions volume of IEEE Std 1003.1-2001, <dlfcn.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .
IEEE /The Open Group 2003 DLCLOSE(3P)