vm: clear stack memory moved to heap.

* vm.c (vm_make_closure): When a display frame is captured by
a closure and moves into the heap object, the original should
be cleared to all nil values, otherwise it can cause spurious
retention of garbage.

1 files changed, 3 insertions, 1 deletions

diff --git a/vm.c b/vm.c
index d06c2ee2..25a7b713 100644
--- a/vm.c
+++ b/vm.c
@@ -245,9 +245,11 @@ static val vm_make_closure(struct vm *vm, int frsz)
     case NUM:
       {
         val heap_vec = vector(vec, nil);
+        size_t size = sizeof *cdi->mem * c_num(vec);
         cdi->vec = heap_vec;
         cdi->mem = heap_vec->v.vec;
-        memcpy(cdi->mem, mem, sizeof *cdi->mem * c_num(vec));
+        memcpy(cdi->mem, mem, size);
+        memset(mem, 0, size);
         mut(closure);
         *sdi = *cdi;
         break;