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(7) 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(7),
standards(7) Linker and Libraries GuideNOTES
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).
March 1, 2004 DLCLOSE(3C)
