#![feature(rustc_attrs, const_transmute)] #![allow(const_err, invalid_value)] // make sure we cannot allow away the errors tested here use std::mem; use std::ptr::NonNull; use std::num::{NonZeroU8, NonZeroUsize}; const NON_NULL: NonNull = unsafe { mem::transmute(1usize) }; const NON_NULL_PTR: NonNull = unsafe { mem::transmute(&1) }; const NULL_PTR: NonNull = unsafe { mem::transmute(0usize) }; //~^ ERROR it is undefined behavior to use this value #[deny(const_err)] // this triggers a `const_err` so validation does not even happen const OUT_OF_BOUNDS_PTR: NonNull = { unsafe { let ptr: &[u8; 256] = mem::transmute(&0u8); // &0 gets promoted so it does not dangle // Use address-of-element for pointer arithmetic. This could wrap around to NULL! let out_of_bounds_ptr = &ptr[255]; //~ ERROR any use of this value will cause an error mem::transmute(out_of_bounds_ptr) } }; const NULL_U8: NonZeroU8 = unsafe { mem::transmute(0u8) }; //~^ ERROR it is undefined behavior to use this value const NULL_USIZE: NonZeroUsize = unsafe { mem::transmute(0usize) }; //~^ ERROR it is undefined behavior to use this value union Transmute { uninit: (), out: NonZeroU8, } const UNINIT: NonZeroU8 = unsafe { Transmute { uninit: () }.out }; //~^ ERROR it is undefined behavior to use this value // Also test other uses of rustc_layout_scalar_valid_range_start #[rustc_layout_scalar_valid_range_start(10)] #[rustc_layout_scalar_valid_range_end(30)] struct RestrictedRange1(u32); const BAD_RANGE1: RestrictedRange1 = unsafe { RestrictedRange1(42) }; //~^ ERROR it is undefined behavior to use this value #[rustc_layout_scalar_valid_range_start(30)] #[rustc_layout_scalar_valid_range_end(10)] struct RestrictedRange2(u32); const BAD_RANGE2: RestrictedRange2 = unsafe { RestrictedRange2(20) }; //~^ ERROR it is undefined behavior to use this value fn main() {}