dlclose(3posix) [linux man page]
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)
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 symbol table handle SYNOPSIS
#include <dlfcn.h> int dlclose(void *handle); DESCRIPTION
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 process. 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 target for dynamic relocations performed in the processing of other relocatable 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. RETURN VALUE
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(). ERRORS
No errors are defined. The following sections are informative. EXAMPLES
The following example illustrates use of dlopen() and dlclose(): #include <dlfcn.h> int eret; void *mylib; ... /* Open a dynamic library and then close it ... */ mylib = dlopen("mylib.so", RTLD_LOCAL | RTLD_LAZY); ... eret = dlclose(mylib); ... APPLICATION USAGE
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. Implementations 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 ta- ble handle. 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(). RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
dlerror(), dlopen(), dlsym() The Base Definitions volume of POSIX.1-2008, <dlfcn.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical 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 Stan- dard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE
/The Open Group 2013 DLCLOSE(3P)