From 526d29865c3956ab0dcfba62df7a1933e1f1520d Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sat, 21 Dec 2024 08:32:47 +0100 Subject: [PATCH] ptr::copy: fix docs for the overlapping case --- compiler/rustc_const_eval/src/interpret/memory.rs | 2 ++ library/core/src/intrinsics/mod.rs | 8 +++----- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs index 027ba9644cba9..0790db984e345 100644 --- a/compiler/rustc_const_eval/src/interpret/memory.rs +++ b/compiler/rustc_const_eval/src/interpret/memory.rs @@ -1359,6 +1359,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { let src_alloc = self.get_alloc_raw(src_alloc_id)?; let src_range = alloc_range(src_offset, size); assert!(!self.memory.validation_in_progress, "we can't be copying during validation"); + // For the overlapping case, it is crucial that we trigger the read hook + // before the write hook -- the aliasing model cares about the order. M::before_memory_read( tcx, &self.machine, diff --git a/library/core/src/intrinsics/mod.rs b/library/core/src/intrinsics/mod.rs index 3e53c0497cc78..61a142b459ac8 100644 --- a/library/core/src/intrinsics/mod.rs +++ b/library/core/src/intrinsics/mod.rs @@ -4364,13 +4364,11 @@ pub const unsafe fn copy_nonoverlapping(src: *const T, dst: *mut T, count: us /// /// Behavior is undefined if any of the following conditions are violated: /// -/// * `src` must be [valid] for reads of `count * size_of::()` bytes, and must remain valid even -/// when `dst` is written for `count * size_of::()` bytes. (This means if the memory ranges -/// overlap, the two pointers must not be subject to aliasing restrictions relative to each -/// other.) +/// * `src` must be [valid] for reads of `count * size_of::()` bytes. /// /// * `dst` must be [valid] for writes of `count * size_of::()` bytes, and must remain valid even -/// when `src` is read for `count * size_of::()` bytes. +/// when `src` is read for `count * size_of::()` bytes. (This means if the memory ranges +/// overlap, the `dst` pointer must not be invalidated by `src` reads.) /// /// * Both `src` and `dst` must be properly aligned. ///