From c46e803aaf5a0bfc5dfcd1570349eee71ce81634 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sun, 28 Aug 2022 13:01:56 -0400 Subject: [PATCH] improve OFFSET_IS_ADDR docs --- compiler/rustc_middle/src/mir/interpret/pointer.rs | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/compiler/rustc_middle/src/mir/interpret/pointer.rs b/compiler/rustc_middle/src/mir/interpret/pointer.rs index 5fa802236edd..95e52e391d8f 100644 --- a/compiler/rustc_middle/src/mir/interpret/pointer.rs +++ b/compiler/rustc_middle/src/mir/interpret/pointer.rs @@ -107,8 +107,12 @@ impl PointerArithmetic for T {} /// pointer), but `derive` adds some unnecessary bounds. pub trait Provenance: Copy + fmt::Debug { /// Says whether the `offset` field of `Pointer`s with this provenance is the actual physical address. - /// If `true, ptr-to-int casts work by simply discarding the provenance. - /// If `false`, ptr-to-int casts are not supported. The offset *must* be relative in that case. + /// - If `false`, the offset *must* be relative. This means the bytes representing a pointer are + /// different from what the Abstract Machine prescribes, so the interpreter must prevent any + /// operation that would inspect the underlying bytes of a pointer, such as ptr-to-int + /// transmutation. A `ReadPointerAsBytes` error will be raised in such situations. + /// - If `true`, the interpreter will permit operations to inspect the underlying bytes of a + /// pointer, and implement ptr-to-int transmutation by stripping provenance. const OFFSET_IS_ADDR: bool; /// We also use this trait to control whether to abort execution when a pointer is being partially overwritten