Trait mmtk::vm::scanning::ObjectTracerContext

source · 
pub trait ObjectTracerContext<VM: VMBinding>: Clone + Send + 'static {
    type TracerType: ObjectTracer;

    // Required method
    fn with_tracer<R, F>(&self, worker: &mut GCWorker<VM>, func: F) -> R
       where F: FnOnce(&mut Self::TracerType) -> R;
}
Expand description

An ObjectTracerContext gives a GC worker temporary access to an ObjectTracer, allowing the GC worker to trace objects. This trait is intended to abstract out the implementation details of tracing objects, enqueuing objects, and creating work packets that expand the transitive closure, allowing the VM binding to focus on VM-specific parts.

This trait is used during root scanning and binding-side weak reference processing.

Required Associated Types§

source

type TracerType: ObjectTracer

The concrete ObjectTracer type.

FIXME: The current code works because of the unsafe method ProcessEdgesWork::set_worker. The tracer should borrow the worker passed to with_queuing_tracer during its lifetime. For this reason, TracerType should have a <'w> lifetime parameter. Generic Associated Types (GAT) is already stablized in Rust 1.65. We should update our toolchain version, too.

Required Methods§

source

fn with_tracer<R, F>(&self, worker: &mut GCWorker<VM>, func: F) -> R
where F: FnOnce(&mut Self::TracerType) -> R,

Create a temporary ObjectTracer and provide access in the scope of func.

When the ObjectTracer::trace_object is called, if the traced object is first visited in this transitive closure, it will be enqueued. After func returns, the implememtation will create work packets to continue computing the transitive closure from the newly enqueued objects.

API functions that provide QueuingTracerFactory should document

  1. on which fields the user is supposed to call ObjectTracer::trace_object, and
  2. which work bucket the generated work packet will be added to. Sometimes the user needs to know when the computing of transitive closure finishes.

Arguments:

  • worker: The current GC worker.
  • func: A caller-supplied closure in which the created ObjectTracer can be used.

Returns: The return value of func.

Object Safety§

This trait is not object safe.

Implementors§