87 lines
2.2 KiB
Rust
87 lines
2.2 KiB
Rust
use std::usize;
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fn one_line_ref() -> i16 {
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*&1
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}
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fn basic_ref() -> i16 {
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let x = &1;
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*x
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}
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fn basic_ref_mut() -> i16 {
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let x = &mut 1;
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*x += 2;
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*x
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}
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fn basic_ref_mut_var() -> i16 {
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let mut a = 1;
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{
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let x = &mut a;
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*x += 2;
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}
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a
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}
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fn tuple_ref_mut() -> (i8, i8) {
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let mut t = (10, 20);
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{
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let x = &mut t.1;
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*x += 2;
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}
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t
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}
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fn match_ref_mut() -> i8 {
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let mut t = (20, 22);
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{
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let opt = Some(&mut t);
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match opt {
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Some(&mut (ref mut x, ref mut y)) => *x += *y,
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None => {},
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}
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}
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t.0
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}
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fn dangling_pointer() -> *const i32 {
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let b = Box::new((42, 42)); // make it bigger than the alignment, so that there is some "room" after this pointer
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&b.0 as *const i32
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}
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fn main() {
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assert_eq!(one_line_ref(), 1);
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assert_eq!(basic_ref(), 1);
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assert_eq!(basic_ref_mut(), 3);
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assert_eq!(basic_ref_mut_var(), 3);
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assert_eq!(tuple_ref_mut(), (10, 22));
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assert_eq!(match_ref_mut(), 42);
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// Compare even dangling pointers with NULL, and with others in the same allocation, including
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// out-of-bounds.
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assert!(dangling_pointer() != std::ptr::null());
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assert!(match dangling_pointer() as usize { 0 => false, _ => true });
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let dangling = dangling_pointer();
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assert!(dangling == dangling);
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assert!(dangling.wrapping_add(1) != dangling);
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assert!(dangling.wrapping_sub(1) != dangling);
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// Compare pointer with BIG integers
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let dangling = dangling as usize;
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assert!(dangling != usize::MAX);
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assert!(dangling != usize::MAX - 1);
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assert!(dangling != usize::MAX - 2);
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assert!(dangling != usize::MAX - 3); // this is even 4-aligned, but it still cannot be equal because of the extra "room" after this pointer
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assert_eq!((usize::MAX - 3) % 4, 0); // just to be sure we got this right
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// Compare pointer with unaligned integers
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assert!(dangling != 1usize);
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assert!(dangling != 2usize);
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assert!(dangling != 3usize);
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// 4 is a possible choice! So we cannot compare with that.
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assert!(dangling != 5usize);
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assert!(dangling != 6usize);
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assert!(dangling != 7usize);
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}
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