vm.SourceTextModule memory leak

@legendecas

The OOM can be reproduced even without link and evaluate:

// Flags: --max-heap-size=16 --experimental-vm-modules
import {SourceTextModule, createContext} from 'vm';

globalThis.iter = 0;
setInterval(() => {
   // Do not capture any variables.
   globalThis.iter++;
   console.log("iterations", globalThis.iter);
   const context = createContext();
   for (let i = 0; i < 100; i++) {
     new SourceTextModule(`
       export default function() { }
     `, {
       identifier: 'foo',
       context,
     });
   }
}, 1);

This crashes after around tens of iterations deterministically.

Originally posted by @legendecas in #50113

@addaleax

It looks like @addaleax might have noticed something 4 years ago that could be related:

bool IsNotIndicativeOfMemoryLeakAtExit() const override {
  // XXX: The garbage collection rules for ModuleWrap are *super* unclear.
  // Do these objects ever get GC'd? Are we just okay with leaking them?
  return true;
}

(this is from #35490)

That said, my C++ is seriously rusty, so I'm really not sure.

This comment in lib/internal/modules/esm/utils.js originally made me think the issue was here, but callbackReferrer doesn't seem to be leaking if I know how to correctly interpret the heaps (which I might not!).

I've uploaded my heaps and the script I'm using to analyze the leak here: https://github.com/KernelDeimos/node-59118 - let me know if I'm on the right track or not; I've never contributed to node before but I really want to be able to use vm.Module without worrying that it will be experimental forever.

I think this was fixed by #59117 - at least, it no longer reproduces on main. Closing.

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`vm.SourceTextModule` memory leak #59118

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vm.SourceTextModule memory leak #59118

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KernelDeimos commented on Sep 9, 2025

joyeecheung commented on Jan 29, 2026

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`vm.SourceTextModule` memory leak #59118