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Diffstat (limited to '')
-rw-r--r-- | src/test/ui/consts/offset_from.rs | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/src/test/ui/consts/offset_from.rs b/src/test/ui/consts/offset_from.rs new file mode 100644 index 000000000..b53718316 --- /dev/null +++ b/src/test/ui/consts/offset_from.rs @@ -0,0 +1,60 @@ +// run-pass + +#![feature(const_ptr_offset_from)] +#![feature(const_ptr_sub_ptr)] +#![feature(ptr_sub_ptr)] + +struct Struct { + field: (), +} + +#[repr(C)] +struct Struct2 { + data: u8, + field: u8, +} + +pub const OFFSET: usize = { + let uninit = std::mem::MaybeUninit::<Struct>::uninit(); + let base_ptr: *const Struct = &uninit as *const _ as *const Struct; + // The following statement is UB (taking the address of an uninitialized field). + // Const eval doesn't detect this right now, but it may stop compiling at some point + // in the future. + let field_ptr = unsafe { &(*base_ptr).field as *const () as *const u8 }; + let offset = unsafe { field_ptr.offset_from(base_ptr as *const u8) }; + offset as usize +}; + +pub const OFFSET_2: usize = { + let uninit = std::mem::MaybeUninit::<Struct2>::uninit(); + let base_ptr: *const Struct2 = &uninit as *const _ as *const Struct2; + let field_ptr = unsafe { &(*base_ptr).field as *const u8 }; + let offset = unsafe { field_ptr.offset_from(base_ptr as *const u8) }; + offset as usize +}; + +pub const OVERFLOW: isize = { + let uninit = std::mem::MaybeUninit::<Struct2>::uninit(); + let base_ptr: *const Struct2 = &uninit as *const _ as *const Struct2; + let field_ptr = unsafe { &(*base_ptr).field as *const u8 }; + unsafe { (base_ptr as *const u8).offset_from(field_ptr) } +}; + +pub const OFFSET_EQUAL_INTS: isize = { + let ptr = 1 as *const u8; + unsafe { ptr.offset_from(ptr) } +}; + +pub const OFFSET_UNSIGNED: usize = { + let a = ['a', 'b', 'c']; + let ptr = a.as_ptr(); + unsafe { ptr.add(2).sub_ptr(ptr) } +}; + +fn main() { + assert_eq!(OFFSET, 0); + assert_eq!(OFFSET_2, 1); + assert_eq!(OVERFLOW, -1); + assert_eq!(OFFSET_EQUAL_INTS, 0); + assert_eq!(OFFSET_UNSIGNED, 2); +} |