1 files changed, 57 insertions, 0 deletions
diff --git a/tests/gc/weakrefs.nim b/tests/gc/weakrefs.nim
new file mode 100644
index 000000000..81c048d74
--- /dev/null
+++ b/tests/gc/weakrefs.nim
@@ -0,0 +1,57 @@
+discard """
+  output: "true"
+"""
+
+import intsets
+
+type
+  TMyObject = object
+    id: int
+  StrongObject = ref TMyObject
+  WeakObject = object
+    id: int
+    data: ptr TMyObject
+
+var
+  gid: int # for id generation
+  valid = initIntSet()
+
+proc finalizer(x: StrongObject) =
+  valid.excl(x.id)
+
+when defined(gcDestructors):
+  proc `=destroy`(x: var TMyObject) =
+    valid.excl(x.id)
+
+proc create: StrongObject =
+  when defined(gcDestructors):
+    new(result)
+  else:
+    new(result, finalizer)
+  result.id = gid
+  valid.incl(gid)
+  inc gid
+
+proc register(s: StrongObject): WeakObject =
+  result.data = cast[ptr TMyObject](s)
+  result.id = s.id
+
+proc access(w: WeakObject): StrongObject =
+  ## returns nil if the object doesn't exist anymore
+  if valid.contains(w.id):
+    result = cast[StrongObject](w.data)
+
+proc main =
+  var s: seq[WeakObject]
+  newSeq(s, 10_000)
+  for i in 0 .. s.high:
+    s[i] = register(create())
+  # test that we have at least 80% unreachable weak objects by now:
+  when defined(gcMarkAndSweep):
+    GC_fullcollect()
+  var unreachable = 0
+  for i in 0 .. s.high:
+    if access(s[i]) == nil: inc unreachable
+  echo unreachable > 8_000
+
+main()