compiler: add munmap finalizer on cache hits to avoid memory leak

[valpackett]

Not sure how this was never noticed, trying to run the same thing over and over in response to request with cache enabled would OOM very quickly…

[ncruces]

Thanks for the report. I don't think this is the correct/best place to fix?

I think this should be added somewhere to this function:

wazero/internal/engine/compiler/engine_cache.go

Line 133 in 610fdbd

func deserializeCompiledModule(wazeroVersion string, reader io.ReadCloser, module *wasm.Module) (cm *compiledModule, staleCache bool, err error) {

cc: @mathetake

[valpackett]

Seemed like the place with least duplication and seemed good that it's the same function as the non-cached path. Inside getCompiledModule I thought in some way does make sense too, but there would need to be duplicated for the memory hit and disk hit paths.

[ncruces]

The memory cache hit doesn't create a new instance, so it doesn't need one?

You're actually replacing the finalizer that's already there, which probably causes no harm, but is unnecessary.

[valpackett]

Oh, makes sense. I see wazevo actually does set the finalizer and it's in getCompiledModule for the disk branch, so this should match that now.

[mathetake]

Thanks! I actually noticed this before but yeah completely it slipped my mind