In my ObjC->Mono bridge I have been using the Boehm collector and pinned memory
(as an expedient).
I now want to move to SGEN and moveable memory.
As a first step I have switched to SGEN and left pinning enabled.
My ObjC code wraps a MonoObject * in an NSObject.
When the MonoObject is set it is pinned.
A simple monoObjectTrace property watches to see if the MonoObject moves.
Under the Boehm collector objects seem to stay pinned as requested.
Under SGEN they don’t i.e.: the exception in the second method below raises
i.e.: self.monoObjectTrace != (NSUInteger)monoObject)
What am I doing wrong?
I do want to migrate to moveable memory support ASAP but a step wise approach
seems best.
#define DB_TRACE_MONO_OBJECT_ADDRESS
- (void)setMonoObject:(MonoObject *)monoObject
{
if (_mono_gchandle) {
NSLog(@"calling mono_gchandle_free!");
mono_gchandle_free(_mono_gchandle);
_mono_gchandle = 0;
}
// we don't want to persist the monoObject in an ivar or on the heap in
general as it would
// require always pinning the pointed to MonoObject
if (monoObject) {
_mono_gchandle = mono_gchandle_new(monoObject,
self.monoEnvironment.pinGCHandles);
}
#ifdef DB_TRACE_MONO_OBJECT_ADDRESS
self.monoObjectTrace = (NSUInteger)monoObject;
#endif
}
- (MonoObject *)monoObject
{
// This pointer should be valid while it is visible on the unmanaged stack.
// Dont save it into the heap as it may become invalid if the MonoObject is
not pinned
// and the managed instance gets moved in memory.
MonoObject *monoObject = mono_gchandle_get_target(_mono_gchandle);
#ifdef DB_TRACE_MONO_OBJECT_ADDRESS
if (self.monoObjectTrace != (NSUInteger)monoObject) {
[NSException raise:@"Managed object has moved" format:@"Support for
moved managed objects is pending."];
}
#endif
return monoObject;
}
Jonathan
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