Description

The __commonJS runtime helper retains a reference to the factory function (cb) after the module has been initialized. In long-lived Node.js processes (e.g. SSR servers), the executed factory can never be garbage collected, causing memory to grow monotonically.

Context

When loading a Rolldown-built CJS bundle via vm.createContext + vm.runInContext (a common SSR pattern), module exports are cached in memory for request reuse. Because the __commonJS closure keeps holding the factory reference even after execution, the factory cannot be GC'd. This means each time a new version of the bundle is loaded, memory only increases and never drops back.

Reproduction

A runnable demo is available at:
https://stackblitz.com/edit/vitejs-vite-pn1msfza?file=rolldown-issue.md

Run node --expose-gc demo.mjs to reproduce.

Expected Behavior

After the module factory has been executed and exports cached, the factory reference should be released (e.g. set cb = null) so it becomes eligible for garbage collection.

Suggested Fix

In the __commonJS helper, null out the cb reference after the factory has been called:

// After calling the factory and caching the result:
cb = null;

This is a one-line fix but has significant impact for SSR and other long-lived process use cases where bundles are loaded/unloaded over time.