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 implementation,
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 referenced 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()
referencing 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 Technology
-- 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 .