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Revert adding Atomic::from_mut.
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This made too many assumptions about platforms, breaking some things.

Will need to be added later with a better way of gating on proper
alignment, without hardcoding cfg(target_arch)s.
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@m-ou-se
m-ou-se committed Sep 20, 2020
1 parent 10b3595 commit 5ef1db3
Showing 1 changed file with 0 additions and 90 deletions.
90 changes: 0 additions & 90 deletions library/core/src/sync/atomic.rs
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Expand Up @@ -110,7 +110,6 @@ use self::Ordering::*;
use crate::cell::UnsafeCell;
use crate::fmt;
use crate::intrinsics;
use crate::mem::align_of;

use crate::hint::spin_loop;

Expand Down Expand Up @@ -328,27 +327,6 @@ impl AtomicBool {
unsafe { &mut *(self.v.get() as *mut bool) }
}

/// Get atomic access to a `&mut bool`.
///
/// # Examples
///
/// ```
/// #![feature(atomic_from_mut)]
/// use std::sync::atomic::{AtomicBool, Ordering};
///
/// let mut some_bool = true;
/// let a = AtomicBool::from_mut(&mut some_bool);
/// a.store(false, Ordering::Relaxed);
/// assert_eq!(some_bool, false);
/// ```
#[inline]
#[unstable(feature = "atomic_from_mut", issue = "76314")]
pub fn from_mut(v: &mut bool) -> &Self {
// SAFETY: the mutable reference guarantees unique ownership, and
// alignment of both `bool` and `Self` is 1.
unsafe { &*(v as *mut bool as *mut Self) }
}

/// Consumes the atomic and returns the contained value.
///
/// This is safe because passing `self` by value guarantees that no other threads are
Expand Down Expand Up @@ -842,30 +820,6 @@ impl<T> AtomicPtr<T> {
unsafe { &mut *self.p.get() }
}

/// Get atomic access to a pointer.
///
/// # Examples
///
/// ```
/// #![feature(atomic_from_mut)]
/// use std::sync::atomic::{AtomicPtr, Ordering};
///
/// let mut some_ptr = &mut 123 as *mut i32;
/// let a = AtomicPtr::from_mut(&mut some_ptr);
/// a.store(&mut 456, Ordering::Relaxed);
/// assert_eq!(unsafe { *some_ptr }, 456);
/// ```
#[inline]
#[unstable(feature = "atomic_from_mut", issue = "76314")]
pub fn from_mut(v: &mut *mut T) -> &Self {
let [] = [(); align_of::<AtomicPtr<()>>() - align_of::<*mut ()>()];
// SAFETY:
// - the mutable reference guarantees unique ownership.
// - the alignment of `*mut T` and `Self` is the same on all platforms
// supported by rust, as verified above.
unsafe { &*(v as *mut *mut T as *mut Self) }
}

/// Consumes the atomic and returns the contained value.
///
/// This is safe because passing `self` by value guarantees that no other threads are
Expand Down Expand Up @@ -1168,7 +1122,6 @@ macro_rules! atomic_int {
$stable_nand:meta,
$const_stable:meta,
$stable_init_const:meta,
$(from_mut: cfg($from_mut_cfg:meta),)?
$s_int_type:literal, $int_ref:expr,
$extra_feature:expr,
$min_fn:ident, $max_fn:ident,
Expand Down Expand Up @@ -1280,45 +1233,6 @@ assert_eq!(some_var.load(Ordering::SeqCst), 5);
}
}

doc_comment! {
concat!("Get atomic access to a `&mut ", stringify!($int_type), "`.
",
if_not_8_bit! {
$int_type,
concat!(
"**Note:** This function is only available on targets where `",
stringify!($int_type), "` has an alignment of ", $align, " bytes."
)
},
"
# Examples
```
#![feature(atomic_from_mut)]
", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
let mut some_int = 123;
let a = ", stringify!($atomic_type), "::from_mut(&mut some_int);
a.store(100, Ordering::Relaxed);
assert_eq!(some_int, 100);
```
"),
#[inline]
$(#[cfg($from_mut_cfg)])?
#[unstable(feature = "atomic_from_mut", issue = "76314")]
pub fn from_mut(v: &mut $int_type) -> &Self {
let [] = [(); align_of::<Self>() - align_of::<$int_type>()];
// SAFETY:
// - the mutable reference guarantees unique ownership.
// - the alignment of `$int_type` and `Self` is the
// same on all platforms enabled by `$from_mut_cfg`
// as verified above.
unsafe { &*(v as *mut $int_type as *mut Self) }
}
}

doc_comment! {
concat!("Consumes the atomic and returns the contained value.
Expand Down Expand Up @@ -2077,7 +1991,6 @@ atomic_int! {
stable(feature = "integer_atomics_stable", since = "1.34.0"),
rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
unstable(feature = "integer_atomics", issue = "32976"),
from_mut: cfg(not(target_arch = "x86")),
"i64", "../../../std/primitive.i64.html",
"",
atomic_min, atomic_max,
Expand All @@ -2096,7 +2009,6 @@ atomic_int! {
stable(feature = "integer_atomics_stable", since = "1.34.0"),
rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
unstable(feature = "integer_atomics", issue = "32976"),
from_mut: cfg(not(target_arch = "x86")),
"u64", "../../../std/primitive.u64.html",
"",
atomic_umin, atomic_umax,
Expand All @@ -2115,7 +2027,6 @@ atomic_int! {
unstable(feature = "integer_atomics", issue = "32976"),
rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
unstable(feature = "integer_atomics", issue = "32976"),
from_mut: cfg(not(target_arch = "x86_64")),
"i128", "../../../std/primitive.i128.html",
"#![feature(integer_atomics)]\n\n",
atomic_min, atomic_max,
Expand All @@ -2134,7 +2045,6 @@ atomic_int! {
unstable(feature = "integer_atomics", issue = "32976"),
rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
unstable(feature = "integer_atomics", issue = "32976"),
from_mut: cfg(not(target_arch = "x86_64")),
"u128", "../../../std/primitive.u128.html",
"#![feature(integer_atomics)]\n\n",
atomic_umin, atomic_umax,
Expand Down

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