zlib: fix memory leak for unused zlib instances

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 <[email protected]>
nodejs · Jul 4, 2018 · 96dae83 · 96dae83
1 parent 9cd5c0e
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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}`);