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raw_vec.rs: Remove superfluous fn alloc_guard #145750

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Merged
merged 1 commit into from
Sep 4, 2025
+2 −25
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raw_vec.rs: Remove superfluous fn alloc_guard #145750

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27 changes: 2 additions & 25 deletions library/alloc/src/raw_vec/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -468,10 +468,6 @@ impl<A: Allocator> RawVecInner<A> {
return Ok(Self::new_in(alloc, elem_layout.alignment()));
}

if let Err(err) = alloc_guard(layout.size()) {
return Err(err);
}

let result = match init {
AllocInit::Uninitialized => alloc.allocate(layout),
#[cfg(not(no_global_oom_handling))]
Expand Down Expand Up @@ -662,7 +658,7 @@ impl<A: Allocator> RawVecInner<A> {
let new_layout = layout_array(cap, elem_layout)?;

let ptr = finish_grow(new_layout, self.current_memory(elem_layout), &mut self.alloc)?;
// SAFETY: finish_grow would have resulted in a capacity overflow if we tried to allocate more than `isize::MAX` items
// SAFETY: layout_array would have resulted in a capacity overflow if we tried to allocate more than `isize::MAX` items

unsafe { self.set_ptr_and_cap(ptr, cap) };
Ok(())
Expand All @@ -684,7 +680,7 @@ impl<A: Allocator> RawVecInner<A> {
let new_layout = layout_array(cap, elem_layout)?;

let ptr = finish_grow(new_layout, self.current_memory(elem_layout), &mut self.alloc)?;
// SAFETY: finish_grow would have resulted in a capacity overflow if we tried to allocate more than `isize::MAX` items
// SAFETY: layout_array would have resulted in a capacity overflow if we tried to allocate more than `isize::MAX` items
unsafe {
self.set_ptr_and_cap(ptr, cap);
}
Expand Down Expand Up @@ -771,8 +767,6 @@ fn finish_grow<A>(
where
A: Allocator,
{
alloc_guard(new_layout.size())?;

let memory = if let Some((ptr, old_layout)) = current_memory {
debug_assert_eq!(old_layout.align(), new_layout.align());
unsafe {
Expand All @@ -799,23 +793,6 @@ fn handle_error(e: TryReserveError) -> ! {
}
}

// We need to guarantee the following:
// * We don't ever allocate `> isize::MAX` byte-size objects.
// * We don't overflow `usize::MAX` and actually allocate too little.
//
// On 64-bit we just need to check for overflow since trying to allocate
// `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add
// an extra guard for this in case we're running on a platform which can use
// all 4GB in user-space, e.g., PAE or x32.
#[inline]
fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> {
if usize::BITS < 64 && alloc_size > isize::MAX as usize {
Err(CapacityOverflow.into())
} else {
Ok(())
}
}

#[inline]
fn layout_array(cap: usize, elem_layout: Layout) -> Result<Layout, TryReserveError> {
elem_layout.repeat(cap).map(|(layout, _pad)| layout).map_err(|_| CapacityOverflow.into())
Expand Down
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