fix memory leak on cursor iteration (#24). (#25)

benchmarks/memory_leak_check.jl

@@ -0,0 +1,26 @@
+
+#
+# Stress test to check for memory leaks (#24)
+#
+
+using Mongoc
+
+client = Mongoc.Client() # default locahost:27017
+db = client["testDB"]
+collection=db["testCollection"]
+
+document = Mongoc.BSON()
+document["name"] = "Felipe"
+document["age"] = 35
+document["preferences"] = [ "Music", "Computer", "Photography" ]
+
+# generate some entries
+for i in 1:100000
+    push!(collection, document)
+end
+
+# read bson documents from collection
+for i in 1:10000
+    for entry in collection
+    end
+end

src/api.jl

@@ -336,16 +336,13 @@ end
 #
 
 function _iterate(cursor::Cursor, state::Nothing=nothing)
-    next = BSON()
-    handle = next.handle
-    handle_ref = Ref{Ptr{Cvoid}}(handle)
-    has_next = mongoc_cursor_next(cursor.handle, handle_ref)
-    next.handle = handle_ref[]
+    bson_handle_ref = Ref{Ptr{Cvoid}}()
+    has_next = mongoc_cursor_next(cursor.handle, bson_handle_ref)
 
     if has_next
         # The bson document is valid only until the next call to mongoc_cursor_next.
         # So we should return a deepcopy.
-        return deepcopy(next), nothing
+        return deepcopy(BSON(bson_handle_ref[], enable_finalizer=false)), nothing
     else
         err = BSONError()
         if mongoc_cursor_error(cursor.handle, err)