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> Values that are forgotten without being dropped can leak resources or even cause undefined behavior! I thought that Rust had given up on considering mem::for

• saghm 6y ago
  Yes, you're correct. From the documentation on std::mem::forget[1]: "forget is not marked as unsafe, because Rust's safety guarantees do not include a guarantee that destructors will always run. For example, a program can create a reference cycle using Rc, or call process::exit to exit without running destructors. Thus, allowing mem::forget from safe code does not fundamentally change Rust's safety guarantees. That said, leaking resources such as memory or I/O objects is usually undesirable. The need comes up in some specialized use cases for FFI or unsafe code, but even then, ManuallyDrop is typically preferred. Because forgetting a value is allowed, any unsafe code you write must allow for this possibility. You cannot return a value and expect that the caller will necessarily run the value's destructor." [1]: https://doc.rust-lang.org/std/mem/fn.forget.html#safety https://doc.rust-lang.org/std/mem/fn.forget.html#safety
  • kzrdude 6y ago
    It hasn't officially been formulated this way, but whatever owns a value will have the power to decide if its destructor should run or not.