Skip to content

vm: fix leak in vm.compileFunction when importModuleDynamically is used

Rodrigo Muino Tomonari requested to merge github/fork/joyeecheung/fix-compile-function-leak into main

Previously in the implementation there was a cycle that V8 could not detect:

Strong global reference to CompiledFnEntry (JS wrapper)
    -> strong reference to callback setting (through the
       callbackMap key-value pair)
    -> importModuleDynamically (wrapper in internalCompileFunction())
    -> Strong reference to the compiled function (through closure in
       internalCompileFunction())

The CompiledFnEntry only gets GC'ed when the compiled function is GC'ed. Since the compiled function is always reachable as described above, there is a leak.

We only needed the first strong global reference because we didn't want the function to outlive the CompiledFnEntry. In this case it can be solved by using a private symbol instead of going with the global reference + destruction in the weak callback, which V8's GC is not going to understand.

Fixes: https://github.com/nodejs/node/issues/42080

Merge request reports