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Stabilize `const_mem_zeroed` 

Make `core::mem::zeroed` const stable. Newly stable API:

    // core::mem
    pub const unsafe fn zeroed<T>() -> T;

This is stabilized with `const_maybe_uninit_zeroed` since it is a simple
wrapper.

In order to make this possible, intrinsics `assert_zero_valid` was made
const stable under `const_assert_type2`.
`assert_mem_uninitialized_valid` was also made const stable since it is
under the same gate.
This commit is contained in:
Trevor Gross 2023-09-29 02:40:30 -04:00
parent f6ce646d3f
commit 5e5f3341e3
4 changed files with 10 additions and 10 deletions
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4
library/core/src/intrinsics.rs
View File

@ -1072,7 +1072,7 @@ extern "rust-intrinsic" {
/// zero-initialization: This will statically either panic, or do nothing.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
#[rustc_const_stable(feature = "const_assert_type2", since = "CURRENT_RUSTC_VERSION")]
#[rustc_safe_intrinsic]
#[rustc_nounwind]
pub fn assert_zero_valid<T>();
@ -1080,7 +1080,7 @@ extern "rust-intrinsic" {
/// A guard for `std::mem::uninitialized`. This will statically either panic, or do nothing.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
#[rustc_const_stable(feature = "const_assert_type2", since = "CURRENT_RUSTC_VERSION")]
#[rustc_safe_intrinsic]
#[rustc_nounwind]
pub fn assert_mem_uninitialized_valid<T>();

3
library/core/src/mem/mod.rs
View File

@ -647,7 +647,8 @@ pub const fn needs_drop<T: ?Sized>() -> bool {
#[allow(deprecated)]
#[rustc_diagnostic_item = "mem_zeroed"]
#[track_caller]
pub unsafe fn zeroed<T>() -> T {
#[rustc_const_stable(feature = "const_mem_zeroed", since = "CURRENT_RUSTC_VERSION")]
pub const unsafe fn zeroed<T>() -> T {
// SAFETY: the caller must guarantee that an all-zero value is valid for `T`.
unsafe {
intrinsics::assert_zero_valid::<T>();

1
tests/ui/consts/assert-type-intrinsics.rs
View File

@ -1,5 +1,4 @@
#![feature(never_type)]
#![feature(const_assert_type2)]
#![feature(core_intrinsics)]
use std::intrinsics;

12
tests/ui/consts/assert-type-intrinsics.stderr
View File

@ -1,20 +1,20 @@
error[E0080]: evaluation of constant value failed
--> $DIR/assert-type-intrinsics.rs:12:9
--> $DIR/assert-type-intrinsics.rs:11:9
|
LL | MaybeUninit::<!>::uninit().assume_init();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'aborted execution: attempted to instantiate uninhabited type `!`', $DIR/assert-type-intrinsics.rs:12:36
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'aborted execution: attempted to instantiate uninhabited type `!`', $DIR/assert-type-intrinsics.rs:11:36
error[E0080]: evaluation of constant value failed
--> $DIR/assert-type-intrinsics.rs:16:9
--> $DIR/assert-type-intrinsics.rs:15:9
|
LL | intrinsics::assert_mem_uninitialized_valid::<&'static i32>();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'aborted execution: attempted to leave type `&i32` uninitialized, which is invalid', $DIR/assert-type-intrinsics.rs:16:9
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'aborted execution: attempted to leave type `&i32` uninitialized, which is invalid', $DIR/assert-type-intrinsics.rs:15:9
error[E0080]: evaluation of constant value failed
--> $DIR/assert-type-intrinsics.rs:20:9
--> $DIR/assert-type-intrinsics.rs:19:9
|
LL | intrinsics::assert_zero_valid::<&'static i32>();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'aborted execution: attempted to zero-initialize type `&i32`, which is invalid', $DIR/assert-type-intrinsics.rs:20:9
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'aborted execution: attempted to zero-initialize type `&i32`, which is invalid', $DIR/assert-type-intrinsics.rs:19:9
error: aborting due to 3 previous errors