I tried this code (playground):

static mut FLAG: bool = false; fn main() { let p = std::ptr::addr_of!(FLAG); println!("{p:p}") }

I expected this to compile without adding an unsafe block, since the act of getting the address of the static on its own cannot(?) cause Undefined Behavior. Making addr_of! and addr_of_mut! safe when used on a static mut would make the behavior consistent with UnsafeCell::get, which has identical safety concerns in a multithreaded environment.

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Exists on stable and the nightly version used by playground (2024-05-30).