rt: Free all outstanding boxes at task death

mk/rt.mk

@@ -67,6 +67,7 @@ RUNTIME_CS_$(1) := \
               rt/rust_abi.cpp \
               rt/rust_cc.cpp \
               rt/rust_debug.cpp \
+              rt/rust_box_annihilator.cpp \
               rt/memory_region.cpp \
               rt/boxed_region.cpp \
               rt/arch/$$(HOST_$(1))/context.cpp

src/rt/rust_box_annihilator.cpp

@@ -0,0 +1,15 @@
+#include "rust_internal.h"
+#include "rust_shape.h"
+
+void
+annihilate_boxes(rust_task *task) {
+    LOG(task, gc, "annihilating boxes for task %p", task);
+
+    boxed_region *boxed = &task->boxed;
+    rust_opaque_box *box = boxed->first_live_alloc();
+    while (box != NULL) {
+        rust_opaque_box *tmp = box;
+        box = box->next;
+        boxed->free(tmp);
+    }
+}

src/rt/rust_task.cpp

@@ -87,12 +87,17 @@ struct cleanup_args {
     bool threw_exception;
 };
 
+void
+annihilate_boxes(rust_task *task);
+
 void
 cleanup_task(cleanup_args *args) {
     spawn_args *a = args->spargs;
     bool threw_exception = args->threw_exception;
     rust_task *task = a->task;
 
+    cc::do_cc(task);
+    annihilate_boxes(task);
     cc::do_final_cc(task);
 
     task->die();