GC handles are wrappers that are used to keep references to managed objects in the unmanaged space and preventing the object from being disposed.
These are the C equivalents of the System.GCHandle structure.
There are two kinds of GCHandles that can be created:
To retrieve the target address of an object pointed to by a GCHandle you should use mono_gchandle_get_target.
For example, consider the following C code:
The object in `o' will *NOT* be scanned.
If you need to store an object in a C variable and prevent it from being collected, you need to acquire a GC handle for it.
TRUE means the object will be pinned, so it won't move in memory when we'll use a moving GC. You can access the MonoObject* referenced by a handle with:
When you don't need the handle anymore you need to call:
Note that if you assign a new object to the C var, you need to get a new handle, it's not enough to store a new object in the C var.
So code that looked like this:
should now be changed to:
mono_gchandle_new
obj | managed object to get a handle for |
pinned | whether the object should be pinned |
This returns a handle that wraps the object, this is used to keep a reference to a managed object from the unmanaged world and preventing the object from being disposed.
If pinned is false the address of the object can not be obtained, if it is true the address of the object can be obtained. This will also pin the object so it will not be possible by a moving garbage collector to move the object.
mono_gchandle_new_weakref
obj | managed object to get a handle for |
track_resurrection | Determines how long to track the object, if this is set to TRUE , the object is tracked after finalization, if FALSE , the object is only tracked up until the point of finalization. |
This returns a weak handle that wraps the object, this is used to
keep a reference to a managed object from the unmanaged world.
Unlike the mono_gchandle_new_internal
the object can be reclaimed by the
garbage collector. In this case the value of the GCHandle will be
set to zero.
If track_resurrection is TRUE
the object will be tracked through
finalization and if the object is resurrected during the execution
of the finalizer, then the returned weakref will continue to hold
a reference to the object. If track_resurrection is FALSE
, then
the weak reference's target will become NULL
as soon as the object
is passed on to the finalizer.
mono_gchandle_get_target
gchandle | a GCHandle's handle. |
MonoObject*
represented by the handle or
NULL
for a collected object if using a weakref handle.
The handle was previously created by calling mono_gchandle_new_internal
or
mono_gchandle_new_weakref
.