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Auto merge of #25300 - kballard:core-slice-overflow, r=Gankro
core::slice was originally written to tolerate overflow (notably, with slices of zero-sized elements), but it was never updated to use wrapping arithmetic when overflow traps were added. Also correctly handle the case of calling .nth() on an Iter with a zero-sized element type. The iterator was assuming that the pointer value of the returned reference was meaningful, but that's not true for zero-sized elements. Fixes #25016.
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| // Copyright 2015 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // http://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
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| // compile-flags: -C debug-assertions | ||
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| #![feature(core)] | ||
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| use std::slice; | ||
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| fn foo<T>(v: &[T]) -> Option<&[T]> { | ||
| let mut it = v.iter(); | ||
| for _ in 0..5 { | ||
| let _ = it.next(); | ||
| } | ||
| Some(it.as_slice()) | ||
| } | ||
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| fn foo_mut<T>(v: &mut [T]) -> Option<&mut [T]> { | ||
| let mut it = v.iter_mut(); | ||
| for _ in 0..5 { | ||
| let _ = it.next(); | ||
| } | ||
| Some(it.into_slice()) | ||
| } | ||
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| pub fn main() { | ||
| // In a slice of zero-size elements the pointer is meaningless. | ||
| // Ensure iteration still works even if the pointer is at the end of the address space. | ||
| let slice: &[()] = unsafe { slice::from_raw_parts(-5isize as *const (), 10) }; | ||
| assert_eq!(slice.len(), 10); | ||
| assert_eq!(slice.iter().count(), 10); | ||
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| // .nth() on the iterator should also behave correctly | ||
| let mut it = slice.iter(); | ||
| assert!(it.nth(5).is_some()); | ||
| assert_eq!(it.count(), 4); | ||
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| // Converting Iter to a slice should never have a null pointer | ||
| assert!(foo(slice).is_some()); | ||
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| // Test mutable iterators as well | ||
| let slice: &mut [()] = unsafe { slice::from_raw_parts_mut(-5isize as *mut (), 10) }; | ||
| assert_eq!(slice.len(), 10); | ||
| assert_eq!(slice.iter_mut().count(), 10); | ||
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| { | ||
| let mut it = slice.iter_mut(); | ||
| assert!(it.nth(5).is_some()); | ||
| assert_eq!(it.count(), 4); | ||
| } | ||
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| assert!(foo_mut(slice).is_some()) | ||
| } |