DLCLOSE(P) POSIX Programmer's Manual DLCLOSE(P)
dlclose - close a dlopen object
int dlclose(void *handle);
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 automati-
cally 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.
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 dler-
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 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. Implementa-
tions 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
dlerror() , dlopen() , dlsym() , the Base Definitions volume of IEEE Std 1003.1-2001,
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 DLCLOSE(P)