zlib: fix memory leak for unused zlib instances

addaleax · addaleax · commit 6e16ad7a63ba · 2018-07-03T19:22:34.000+02:00
An oversight in an earlier commit led to a memory leak in the untypical situation that zlib instances are created but never used, because zlib handles no longer started out their life as weak handles. The bug was introduced in bd20110. Refs: #20455 PR-URL: #21607 Reviewed-By: Tobias Nießen <tniessen@tnie.de>
diff --git a/src/node_zlib.cc b/src/node_zlib.cc
@@ -90,6 +90,7 @@ class ZCtx : public AsyncWrap, public ThreadPoolWork {
         refs_(0),
         gzip_id_bytes_read_(0),
         write_result_(nullptr) {
+    MakeWeak();
   }
 
 
diff --git a/test/parallel/test-zlib-unused-weak.js b/test/parallel/test-zlib-unused-weak.js
@@ -0,0 +1,18 @@
+'use strict';
+// Flags: --expose-gc
+require('../common');
+const assert = require('assert');
+const zlib = require('zlib');
+
+// Tests that native zlib handles start out their life as weak handles.
+
+const before = process.memoryUsage().external;
+for (let i = 0; i < 100; ++i)
+  zlib.createGzip();
+const afterCreation = process.memoryUsage().external;
+global.gc();
+const afterGC = process.memoryUsage().external;
+
+assert((afterGC - before) / (afterCreation - before) <= 0.05,
+       `Expected after-GC delta ${afterGC - before} to be less than 5 %` +
+       ` of before-GC delta ${afterCreation - before}`);

Original file line number	Diff line number	Diff line change
`@@ -90,6 +90,7 @@ class ZCtx : public AsyncWrap, public ThreadPoolWork {`
`90`	`90`	`refs_(0),`
`91`	`91`	`gzip_id_bytes_read_(0),`
`92`	`92`	`write_result_(nullptr) {`
	`93`	`+ MakeWeak();`
`93`	`94`	`}`
`94`	`95`
`95`	`96`