HP UX Software Transition Kit (STK) Dladdr Routine, Using dlclose to unload a shared library

Table 29 Parameters

Parameter	Definition
handle	Value returned by a previous invocation of dlopen.

Return Values

If the referenced shared library was successfully closed, dlclose returns 0. If the shared library cannot be closed or if the handle does not refer to an open shared library, the dlclose routine returns a non-0 value. For more detailed diagnostic information you can use the dlerror routine.

Description

The dlclose routine disassociates a shared library previously opened by the dlopen routine from the current process. Once a shared library has been closed using the dlclose routine, the dlsym routine no longer has access to its symbols. All shared libraries loaded automatically as a result of invoking dlopen on the referenced shared library [see dlopen(3C)] are also closed.

A successful invocation of dlclose does not guarantee that the shared libraries associated with handle have actually been removed from the address space of the process. shared libraries loaded by one invocation of dlopen may also be loaded by another invocation of dlopen. The same shared library may also be opened multiple times. A shared library is not removed from the address space until all references to that shared library through an explicit dlopen invocation have been closed and all other shared libraries implicitly referencing that shared library have also been closed. Once a shared library is closed by dlclose, referencing symbols contained in that shared library can cause undefined behavior.

Using dlclose to unload a shared library

The following example shows how to use dlclose to unload a shared library:

void*	handle;
int	ret_value;

handle = dlopen("./lib1.so", RTLD_GLOBAL RTLD_LAZY);if (handle == NULL) { printf("%s\n", dlerror());

}

ret_value = dlclose(handle);

if (ret_value != 0) { printf("%s\n", dlerror());

}

The dladdr Routine

The dladdr routine gets the symbolic information for an address.

Syntax

int dladdr(void *address, D1_info *dlip); Table 30 Parameter

Parameter	Description
address
dlip	A pointer to a D1_info structure. The structure must be allocated by the user.

The dlopen Shared Library Management Routines 163