dlclose(3c) [opensolaris man page]

dlclose(3C)						   Standard C Library Functions 					       dlclose(3C)

NAME

       dlclose - close a shared object

SYNOPSIS

       #include <dlfcn.h>

       int dlclose(void *handle);

DESCRIPTION

       The  dlclose()  function  decrements  the  reference count of the supplied handle. This handle represents an executable object file and its
       dependencies, acquired from a previous call to dlopen(). A handle that is no longer referenced is processed in an  attempt  to  unload  any
       objects that are associated with the handle from the current process. An unreferenced handle is no longer available to dlsym().

       Any  finalization  code	within	an  object  is	executed  prior  to that object being unloaded. Any routines registered by an object using
       atexit(3C) are called prior to that object being unloaded. See NOTES.

RETURN VALUES

       If the handle was successfully unreferenced, dlclose() returns 0. If the handle is invalid, or an error occurred as a result  of  unloading
       an object, dlclose() returns a non-zero value. Additional diagnostic information is available through dlerror().

USAGE

       The dlclose() function is one of a family of functions that give the user direct access to the dynamic linking facilities. These facilities
       are available to dynamically-linked processes only. See the Linker and Libraries Guide.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       ld(1), ld.so.1(1), atexit(3C), dladdr(3C), dldump(3C), dlerror(3C), dlopen(3C), dlsym(3C), attributes(5), standards(5)

       Linker and Libraries Guide

NOTES

       A successful invocation of  dlclose() does not guarantee that the objects associated with the handle are removed from the address space	of
       the current process. Objects can be referenced by multiple handles, or by other objects. An object is not removed from the address space of
       the current process until all references to that object are removed.

       Once an object has been closed by dlclose(), referencing symbols contained in that object can cause undefined behavior.

       As part of unloading an object, finalization code within the object is called before the dlclose() returns. This finalization is user code,
       and  as such, can produce errors that can not be caught by dlclose(). For example, an object loaded using RTLD_LAZY that attempts to call a
       function that can not be located, results in process termination. Erroneous programming practices within the  finalization  code  can  also
       result  in  process  termination.  The runtime linkers debugging facility can offer help identifying these types of error. See the LD_DEBUG
       environment variable of ld.so.1(1).

SunOS 5.11							   1 March 2004 						       dlclose(3C)

DLCLOSE(P)						     POSIX Programmer's Manual							DLCLOSE(P)

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(P)