Add a function to print object info from the space for debugging

src/mmtk.rs

@@ -597,3 +597,8 @@ impl<VM: VMBinding> MMTK<VM> {
             .initialize_object_metadata(object, false)
     }
 }
+
+#[no_mangle]
+pub fn mmtk_debug_print_object_info(object: crate::util::ObjectReference) {
+    println!("{}", SFT_MAP.get_checked(object.to_raw_address()).debug_get_object_info(object))
+}

src/policy/copyspace.rs

@@ -100,6 +100,10 @@ impl<VM: VMBinding> SFT for CopySpace<VM> {
         let worker = worker.into_mut::<VM>();
         self.trace_object(queue, object, self.common.copy, worker)
     }
+
+    fn debug_get_object_info(&self, object: ObjectReference) -> String {
+        format!("{}: {:?}, {:?}", self.name(), object_forwarding::debug_get_object_forwarding_info::<VM>(object), crate::policy::sft::debug_get_object_global_info(object))
+    }
 }
 
 impl<VM: VMBinding> Space<VM> for CopySpace<VM> {

src/policy/immix/immixspace.rs

@@ -163,6 +163,12 @@ impl<VM: VMBinding> SFT for ImmixSpace<VM> {
     ) -> ObjectReference {
         panic!("We do not use SFT to trace objects for Immix. sft_trace_object() cannot be used.")
     }
+
+    fn debug_get_object_info(&self, object: ObjectReference) -> String {
+        let line = Line::from_unaligned_address(object.to_raw_address());
+        let block = Block::from_unaligned_address(object.to_raw_address());
+        format!("{}: marked = {}, line marked = {}, block state = {:?}, {}, {}", self.name(), self.is_marked(object), line.is_marked(self.mark_state), block.get_state(), object_forwarding::debug_get_object_forwarding_info::<VM>(object), crate::policy::sft::debug_get_object_global_info(object))
+    }
 }
 
 impl<VM: VMBinding> Space<VM> for ImmixSpace<VM> {

src/policy/markcompactspace.rs

@@ -102,6 +102,10 @@ impl<VM: VMBinding> SFT for MarkCompactSpace<VM> {
         // Depending on which trace it is, we should manually call either trace_mark or trace_forward.
         panic!("sft_trace_object() cannot be used with mark compact space")
     }
+
+    fn debug_get_object_info(&self, object: ObjectReference) -> String {
+        format!("{}: marked = {:?}, head forwarding pointer = {:?}. {}", self.name(), MarkCompactSpace::<VM>::is_marked(object), MarkCompactSpace::<VM>::get_header_forwarding_pointer(object), crate::policy::sft::debug_get_object_global_info(object))
+    }
 }
 
 impl<VM: VMBinding> Space<VM> for MarkCompactSpace<VM> {

src/policy/sft.rs

@@ -101,6 +101,19 @@ pub trait SFT {
         object: ObjectReference,
         worker: GCWorkerMutRef,
     ) -> ObjectReference;
+
+    fn debug_get_object_info(&self, object: ObjectReference) -> String {
+        crate::policy::sft::debug_get_object_global_info(object)
+    }
+}
+
+pub(crate) fn debug_get_object_global_info(object: ObjectReference) -> String {
+    let mut ret = String::new();
+    #[cfg(feature = "vo_bit")]
+    {
+        ret += &format!("vo bit = {}", crate::util::metadata::vo_bit::is_vo_bit_set(object));
+    }
+    ret
 }
 
 // Create erased VM refs for these types that will be used in `sft_trace_object()`.

src/util/object_forwarding.rs

@@ -233,3 +233,8 @@ pub(super) fn forwarding_bits_offset_in_forwarding_pointer<VM: VMBinding>() -> O
 pub(super) fn forwarding_bits_offset_in_forwarding_pointer<VM: VMBinding>() -> Option<isize> {
     unimplemented!()
 }
+
+pub(crate) fn debug_get_object_forwarding_info<VM: VMBinding>(object: ObjectReference) -> String {
+    let forwarding_bits = get_forwarding_status::<VM>(object);
+    format!("forwarding bits = {:?}, forwarding pointer = {:?}", forwarding_bits, if state_is_forwarded_or_being_forwarded(forwarding_bits) { Some(read_forwarding_pointer::<VM>(object)) } else { None })
+}