DLCLOSE(3C)							   DLCLOSE(3C)

NAME    [Toc]    [Back]

     dlclose - close a shared object

SYNOPSIS    [Toc]    [Back]

     cc	[flag ...] file	...  -lc [library ...]

     #include <dlfcn.h>

     int dlclose(void *handle);

DESCRIPTION    [Toc]    [Back]

     dlclose disassociates a shared object previously opened by	dlopen,
     sgidladd, or sgidlopen_version from the current process. Once an object
     has been closed using dlclose, its	symbols	are no longer available	to
     dlsym or to the program.  All objects loaded automatically	as a result of
     invoking dlopen, on the referenced	object [see dlopen(3) sgidladd,	or
     sgidlopen_version]	are also closed	(however no object still open via any
     dlopen, sgidladd, or sgidlopen_version is closed till the last open
     handle is dlclosed).

     handle is the value returned by a previous	invocation of dlopen.

SEE ALSO    [Toc]    [Back]

     dlerror(3), dlopen(3), sgidlopen_version(3), sgidladd(3), dlsym(3),
     dso(5).

DIAGNOSTICS    [Toc]    [Back]

     If	the referenced object was successfully closed, dlclose returns 0. If
     the object	could not be closed, or	if handle does not refer to an open
     object, dlclose returns a non-0 value.  More detailed diagnostic
     information is available through dlerror.

NOTES    [Toc]    [Back]

     A successful invocation of	dlclose	does not guarantee that	the objects
     associated	with handle are	actually removed from the address space	of the
     process.  Objects loaded by one invocation	of dlopen may also be loaded
     by	another	invocation of dlopen.  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 dlopen invocation have
     been closed and all other objects implicitly referencing that object have
     also been closed.

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

     Use of dlclose on a DSO can cause surprising side effects because dlclose
     forces many symbol's GOT entries to be reset for re-lazy-evaluation.  A
     result of this is that previously-saved (by the program or	a DSO)
     function pointers may hold	obsolete or incorrect values.






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DLCLOSE(3C)							   DLCLOSE(3C)



     Symbol lookups proceed in order on	a linear list, and a DSO is not	opened
     twice with	the same version number	(unless	different dlopen paths make
     the DSO name appear different to rld).  When multiple sgidladds are done
     and an earlier DSO	is dlclosed this can change what symbol	a call is
     resolved to and even result in unintentionally calling different routines
     (with the same name) from a single	place in the program at	different
     times.  See the discussion	of this	in the dlopen description under
     "NAMESPACE	ISSUES".


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