02-01-2002
Ok. Apparently I understood you correctly in the first post. First of all, when you create an object containing a virtual function, you do not create a virtual function table. At compile time, a pointer to the virtual function is created and placed into a module wide virtual function table which is a table of pointers to virtual functions defined within the compiled object. If you can get the value of the pointer pointing to the virtual function table, it will only have meaning in the executable that contains the instantiation of Class1, in this case object Obj1.
Secondly, if you create a shared memory segment and place a pointer to the virtual function, the virtual function table, or a pointer to anything inside the address space of ProcessA, you are NOT "sharing the object". You are passing a virtual memory address with meaning in ProcessA, to ProcessB where it has no meaning. When ProcessB dereferences the pointer, you will more than likely get a SIGSEGV.
Shared memory is used for passing DATA objects, not executable text (i.e. a virtual function) or a pointer.
Obviously, I don't know why ProcessB needs to access the Obj1 object defined in ProcessA. If the Class1 template (with virtual functions and all) is declared inside both source modules (or more likely in a header file and included in the source), then you could have separate instantiations of the template in both processes. If you need to share data values between the instantiated objects, then you could pass the data values using shared memory, but you cannot pass a pointer to the executable text of the virtual function. You don't need to as you would have the same executable text in each process.
Now, that said, you should look at the load() system call in AIX. I've used this to dynamically create modules and load them into the process address space of a running process. Realize that this is a non-portable system call. Since I don't know what your ultimate goal is here, this is the only possible option I can come up with.
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LEARN ABOUT DEBIAN
dispatch_resume
dispatch_object(3) BSD Library Functions Manual dispatch_object(3)
NAME
dispatch_object -- General manipulation of dispatch objects
SYNOPSIS
#include <dispatch/dispatch.h>
void
dispatch_retain(dispatch_object_t object);
void
dispatch_release(dispatch_object_t object);
void
dispatch_suspend(dispatch_object_t object);
void
dispatch_resume(dispatch_object_t object);
void *
dispatch_get_context(dispatch_object_t object);
void
dispatch_set_context(dispatch_object_t object, void *context);
void
dispatch_set_finalizer_f(dispatch_object_t object, dispatch_function_t finalizer);
DESCRIPTION
Dispatch objects share functions for coordinating memory management, suspension, cancellation and context pointers. While all dispatch
objects are retainable, not all objects support suspension, context pointers or finalizers (currently only queues and sources support these
additional interfaces).
MEMORY MANGEMENT
Objects returned by creation functions in the dispatch framework may be uniformly retained and released with the functions dispatch_retain()
and dispatch_release() respectively.
The dispatch framework does not guarantee that any given client has the last or only reference to a given object. Objects may be retained
internally by the system.
SUSPENSION
The invocation of blocks on dispatch queues or dispatch sources may be suspended or resumed with the functions dispatch_suspend() and
dispatch_resume() respectively. The dispatch framework always checks the suspension status before executing a block, but such changes never
affect a block during execution (non-preemptive). Therefore the suspension of an object is asynchronous, unless it is performed from the
context of the target queue for the given object. The result of suspending or resuming an object that is not a dispatch queue or a dispatch
source is undefined.
Important: suspension applies to all aspects of the dispatch object life cycle, including the finalizer function and cancellation handler.
Therefore it is important to balance calls to dispatch_suspend() and dispatch_resume() such that the dispatch object is fully resumed when
the last reference is released. The result of releasing all references to a dispatch object while in a suspended state is undefined.
CONTEXT POINTERS
Dispatch queues and sources support supplemental context pointers. The value of the context pointer may be retrieved and updated with
dispatch_get_context() and dispatch_set_context() respectively. The dispatch_set_finalizer_f() specifies an optional per-object finalizer
function that is invoked asynchronously if the context pointer is not NULL when the last reference to the object is released. This gives the
application an opportunity to free the context data associated with the object.
The result of getting or setting the context of an object that is not a dispatch queue or a dispatch source is undefined.
SEE ALSO
dispatch(3), dispatch_group_create(3), dispatch_queue_create(3), dispatch_semaphore_create(3), dispatch_source_create(3)
Darwin May 1, 2009 Darwin