What are the Pitfalls of Go's Default Garbage-Collected Finalization?

Pitfalls of Default Garbage-Collected Finalization in Go

In Go, the runtime.SetFinalizer() function allows developers to associate a finalizer function with specific objects. However, the standard library sets finalizers by default on certain object types, which can have unintended consequences.

Default Finalized Objects

Go automatically finalizes the following object types:

• os.File: Automatically closed upon garbage collection, releasing a file descriptor.
• os.Process: Frees resources associated with the process, including any open handles (no-op on Unix).
• Network connections (only on Windows): Closed automatically by the net package.

Potential Pitfalls

While default finalization can be convenient, it can also lead to issues:

• File descriptor leakage: When an os.File is created using os.NewFile() and its file descriptor is shared with other os.File objects, finalizing any of these objects can render the others unusable. This can be especially problematic when garbage collection is forced, such as when allocating a large amount of memory.

To mitigate these pitfalls, developers should consider carefully which objects they set finalizers on. For example, explicit finalizers can be set on custom types to ensure proper cleanup, while avoiding default finalization on objects that may interact with shared resources.

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