Function enter_vm

crates/vm/src/vm/thread.rs:78–105

(vm: &VirtualMachine, f: impl FnOnce() -> R)

}

pub fn enter_vm<R>(vm: &VirtualMachine, f: impl FnOnce() -> R) -> R {
    VM_STACK.with(|vms| {
        // Outermost enter_vm: transition DETACHED → ATTACHED
        #[cfg(all(unix, feature = "threading"))]
        let was_outermost = vms.borrow().is_empty();

        vms.borrow_mut().push(vm.into());

        // Initialize thread slot for this thread if not already done
        #[cfg(feature = "threading")]
        init_thread_slot_if_needed(vm);

        #[cfg(all(unix, feature = "threading"))]
        if was_outermost {
            attach_thread(vm);
        }

        scopeguard::defer! {
            // Outermost exit: transition ATTACHED → DETACHED
            #[cfg(all(unix, feature = "threading"))]
            if vms.borrow().len() == 1 {
                detach_thread();
            }
            vms.borrow_mut().pop();
        }
        VM_CURRENT.set(vm, f)
    })
}

/// Initialize thread slot for current thread if not already initialized.
/// Called automatically by enter_vm().