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Rollup merge of #110635 - scottmcm:zst-checks, r=the8472

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More `IS_ZST` in `library`

I noticed that `post_inc_start` and `pre_dec_end` were doing this check in different ways

d19b64fb54/library/core/src/slice/iter/macros.rs (L76-L93)

so started making this PR, then added a few more I found since I was already making changes anyway.
This commit is contained in:
Yuki Okushi 2023-04-22 10:33:57 +09:00 committed by GitHub
commit 581e7417ce
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 7 additions and 15 deletions
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10
library/alloc/src/boxed/thin.rs
View File

@ -7,7 +7,7 @@ use core::fmt::{self, Debug, Display, Formatter};
use core::marker::PhantomData;
#[cfg(not(no_global_oom_handling))]
use core::marker::Unsize;
use core::mem;
use core::mem::{self, SizedTypeProperties};
use core::ops::{Deref, DerefMut};
use core::ptr::Pointee;
use core::ptr::{self, NonNull};
@ -202,9 +202,7 @@ impl<H> WithHeader<H> {
let ptr = if layout.size() == 0 {
// Some paranoia checking, mostly so that the ThinBox tests are
// more able to catch issues.
debug_assert!(
value_offset == 0 && mem::size_of::<T>() == 0 && mem::size_of::<H>() == 0
);
debug_assert!(value_offset == 0 && T::IS_ZST && H::IS_ZST);
layout.dangling()
} else {
let ptr = alloc::alloc(layout);
@ -249,9 +247,7 @@ impl<H> WithHeader<H> {
alloc::dealloc(self.ptr.as_ptr().sub(value_offset), layout);
} else {
debug_assert!(
value_offset == 0
&& mem::size_of::<H>() == 0
&& self.value_layout.size() == 0
value_offset == 0 && H::IS_ZST && self.value_layout.size() == 0
);
}
}

4
library/alloc/src/vec/drain.rs
View File

@ -112,9 +112,7 @@ impl<'a, T, A: Allocator> Drain<'a, T, A> {
let unyielded_ptr = this.iter.as_slice().as_ptr();
// ZSTs have no identity, so we don't need to move them around.
let needs_move = mem::size_of::<T>() != 0;
if needs_move {
if !T::IS_ZST {
let start_ptr = source_vec.as_mut_ptr().add(start);
// memmove back unyielded elements

6
library/alloc/src/vec/drain_filter.rs
View File

@ -1,5 +1,5 @@
use crate::alloc::{Allocator, Global};
use core::mem::{self, ManuallyDrop};
use core::mem::{ManuallyDrop, SizedTypeProperties};
use core::ptr;
use core::slice;
@ -96,9 +96,7 @@ where
unsafe {
// ZSTs have no identity, so we don't need to move them around.
let needs_move = mem::size_of::<T>() != 0;
if needs_move && this.idx < this.old_len && this.del > 0 {
if !T::IS_ZST && this.idx < this.old_len && this.del > 0 {
let ptr = this.vec.as_mut_ptr();
let src = ptr.add(this.idx);
let dst = src.sub(this.del);

2
library/core/src/slice/iter/macros.rs
View File

@ -73,7 +73,7 @@ macro_rules! iterator {
// Unsafe because the offset must not exceed `self.len()`.
#[inline(always)]
unsafe fn post_inc_start(&mut self, offset: usize) -> * $raw_mut T {
if mem::size_of::<T>() == 0 {
if T::IS_ZST {
zst_shrink!(self, offset);
self.ptr.as_ptr()
} else {