Implement reference counting (#592)

lib/rtrace/index.js

@@ -0,0 +1,73 @@
+function rtrace(onerror, oninfo) {
+  if (!onerror) onerror = function() {};
+  if (!oninfo) oninfo = function() {};
+  var blocks = new Map();
+  var rtrace = {
+
+    allocCount: 0,
+    freeCount: 0,
+    incrementCount: 0,
+    decrementCount: 0,
+
+    onalloc: function(block) {
+      ++rtrace.allocCount;
+      if (blocks.has(block)) {
+        onerror(Error("duplicate alloc: " + block));
+      } else {
+        oninfo("ALLOC " + block);
+        blocks.set(block, 0);
+      }
+    },
+
+    onfree: function(block) {
+      ++rtrace.freeCount;
+      if (!blocks.has(block)) {
+        onerror(Error("orphaned free: " + block));
+      } else {
+        oninfo("FREE " + block + " @ " + blocks.get(block));
+        blocks.delete(block);
+      }
+    },
+
+    onincrement: function(block) {
+      ++rtrace.incrementCount;
+      if (!blocks.has(block)) {
+        onerror(Error("orphaned increment: " + block));
+      } else {
+        let rc = blocks.get(block);
+        oninfo("++ " + block + " @ " + rc + "->" + (rc + 1));
+        blocks.set(block, rc + 1);
+      }
+    },
+
+    ondecrement: function(block) {
+      ++rtrace.decrementCount;
+      if (!blocks.has(block)) {
+        onerror(Error("orphaned decrement: " + block));
+      } else {
+        let rc = blocks.get(block);
+        if (rc < 1) {
+          onerror(Error("invalid decrement: " + block));
+        } else {
+          oninfo("-- " + block + " @ " + rc + "->" + (rc - 1));
+          blocks.set(block, rc - 1);
+        }
+      }
+    },
+
+    get active() {
+      return Boolean(rtrace.allocCount || rtrace.freeCount || rtrace.incrementCount || rtrace.decrementCount);
+    },
+
+    check() {
+      if (oninfo) {
+        for (let [block, rc ] of blocks) {
+          oninfo("LEAKING " + block + " @ " + rc);
+        }
+      }
+      return blocks.size;
+    }
+  };
+  return rtrace;
+}
+module.exports = rtrace;