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Allow reallocation to different alignment

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This commit is contained in:
Tim Diekmann 2020-08-18 22:39:33 +02:00
parent be97d13ffc
commit 438c40efa1
5 changed files with 180 additions and 163 deletions
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89
library/alloc/src/alloc.rs
View File

@ -3,7 +3,7 @@
#![stable(feature = "alloc_module", since = "1.28.0")]
use core::intrinsics::{self, min_align_of_val, size_of_val};
use core::ptr::{NonNull, Unique};
use core::ptr::{self, NonNull, Unique};
#[stable(feature = "alloc_module", since = "1.28.0")]
#[doc(inline)]
@ -180,36 +180,45 @@ impl Global {
unsafe fn grow_impl(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
zeroed: bool,
) -> Result<NonNull<[u8]>, AllocErr> {
debug_assert!(
new_size >= layout.size(),
"`new_size` must be greater than or equal to `layout.size()`"
new_layout.size() >= old_layout.size(),
"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
);
match layout.size() {
// SAFETY: the caller must ensure that the `new_size` does not overflow.
// `layout.align()` comes from a `Layout` and is thus guaranteed to be valid for a Layout.
0 => unsafe {
let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
self.alloc_impl(new_layout, zeroed)
},
match old_layout.size() {
0 => self.alloc_impl(new_layout, zeroed),
// SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`
// as required by safety conditions. Other conditions must be upheld by the caller
old_size => unsafe {
// `realloc` probably checks for `new_size >= size` or something similar.
intrinsics::assume(new_size >= layout.size());
old_size if old_layout.align() == new_layout.align() => unsafe {
let new_size = new_layout.size();
let raw_ptr = realloc(ptr.as_ptr(), layout, new_size);
// `realloc` probably checks for `new_size >= old_layout.size()` or something similar.
intrinsics::assume(new_size >= old_layout.size());
let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
let ptr = NonNull::new(raw_ptr).ok_or(AllocErr)?;
if zeroed {
raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
}
Ok(NonNull::slice_from_raw_parts(ptr, new_size))
},
// SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
// both the old and new memory allocation are valid for reads and writes for `old_size`
// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
// for `dealloc` must be upheld by the caller.
old_size => unsafe {
let new_ptr = self.alloc_impl(new_layout, zeroed)?;
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
self.dealloc(ptr, old_layout);
Ok(new_ptr)
},
}
}
}
@ -239,52 +248,64 @@ unsafe impl AllocRef for Global {
unsafe fn grow(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
// SAFETY: all conditions must be upheld by the caller
unsafe { self.grow_impl(ptr, layout, new_size, false) }
unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
}
#[inline]
unsafe fn grow_zeroed(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
// SAFETY: all conditions must be upheld by the caller
unsafe { self.grow_impl(ptr, layout, new_size, true) }
unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
}
#[inline]
unsafe fn shrink(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
debug_assert!(
new_size <= layout.size(),
"`new_size` must be smaller than or equal to `layout.size()`"
new_layout.size() <= old_layout.size(),
"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
);
match new_size {
match new_layout.size() {
// SAFETY: conditions must be upheld by the caller
0 => unsafe {
self.dealloc(ptr, layout);
Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0))
self.dealloc(ptr, old_layout);
Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
},
// SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
new_size => unsafe {
// `realloc` probably checks for `new_size <= size` or something similar.
intrinsics::assume(new_size <= layout.size());
new_size if old_layout.align() == new_layout.align() => unsafe {
// `realloc` probably checks for `new_size <= old_layout.size()` or something similar.
intrinsics::assume(new_size <= old_layout.size());
let raw_ptr = realloc(ptr.as_ptr(), layout, new_size);
let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
let ptr = NonNull::new(raw_ptr).ok_or(AllocErr)?;
Ok(NonNull::slice_from_raw_parts(ptr, new_size))
},
// SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
// both the old and new memory allocation are valid for reads and writes for `new_size`
// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
// for `dealloc` must be upheld by the caller.
new_size => unsafe {
let new_ptr = self.alloc(new_layout)?;
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
self.dealloc(ptr, old_layout);
Ok(new_ptr)
},
}
}
}
@ -297,7 +318,7 @@ unsafe impl AllocRef for Global {
unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
match Global.alloc(layout) {
Ok(ptr) => ptr.as_non_null_ptr().as_ptr(),
Ok(ptr) => ptr.as_mut_ptr(),
Err(_) => handle_alloc_error(layout),
}
}

13
library/alloc/src/raw_vec.rs
View File

@ -465,8 +465,9 @@ impl<T, A: AllocRef> RawVec<T, A> {
let new_size = amount * mem::size_of::<T>();
let ptr = unsafe {
self.alloc.shrink(ptr, layout, new_size).map_err(|_| TryReserveError::AllocError {
layout: Layout::from_size_align_unchecked(new_size, layout.align()),
let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
self.alloc.shrink(ptr, layout, new_layout).map_err(|_| TryReserveError::AllocError {
layout: new_layout,
non_exhaustive: (),
})?
};
@ -493,14 +494,12 @@ where
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 { alloc.grow(ptr, old_layout, new_layout.size()) }
unsafe { alloc.grow(ptr, old_layout, new_layout) }
} else {
alloc.alloc(new_layout)
}
.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })?;
};
Ok(memory)
memory.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })
}
unsafe impl<#[may_dangle] T, A: AllocRef> Drop for RawVec<T, A> {

140
library/core/src/alloc/mod.rs
View File

@ -147,9 +147,8 @@ pub unsafe trait AllocRef {
/// Attempts to extend the memory block.
///
/// Returns a new [`NonNull<[u8]>`] containing a pointer and the actual size of the allocated
/// memory. The pointer is suitable for holding data described by a new layout with `layout`’s
/// alignment and a size given by `new_size`. To accomplish this, the allocator may extend the
/// allocation referenced by `ptr` to fit the new layout.
/// memory. The pointer is suitable for holding data described by `new_layout`. To accomplish
/// this, the allocator may extend the allocation referenced by `ptr` to fit the new layout.
///
/// If this returns `Ok`, then ownership of the memory block referenced by `ptr` has been
/// transferred to this allocator. The memory may or may not have been freed, and should be
@ -163,11 +162,9 @@ pub unsafe trait AllocRef {
///
/// # Safety
///
/// * `ptr` must denote a block of memory [*currently allocated*] via this allocator,
/// * `layout` must [*fit*] that block of memory (The `new_size` argument need not fit it.),
/// * `new_size` must be greater than or equal to `layout.size()`, and
/// * `new_size`, when rounded up to the nearest multiple of `layout.align()`, must not overflow
/// (i.e., the rounded value must be less than or equal to `usize::MAX`).
/// * `ptr` must denote a block of memory [*currently allocated*] via this allocator.
/// * `old_layout` must [*fit*] that block of memory (The `new_layout` argument need not fit it.).
/// * `new_layout.size()` must be greater than or equal to `old_layout.size()`.
///
/// [*currently allocated*]: #currently-allocated-memory
/// [*fit*]: #memory-fitting
@ -188,28 +185,24 @@ pub unsafe trait AllocRef {
unsafe fn grow(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
let size = layout.size();
debug_assert!(
new_size >= size,
"`new_size` must be greater than or equal to `layout.size()`"
new_layout.size() >= old_layout.size(),
"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
);
// SAFETY: the caller must ensure that the `new_size` does not overflow.
// `layout.align()` comes from a `Layout` and is thus guaranteed to be valid for a Layout.
let new_layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
let new_ptr = self.alloc(new_layout)?;
// SAFETY: because `new_size` must be greater than or equal to `size`, both the old and new
// memory allocation are valid for reads and writes for `size` bytes. Also, because the old
// allocation wasn't yet deallocated, it cannot overlap `new_ptr`. Thus, the call to
// `copy_nonoverlapping` is safe.
// The safety contract for `dealloc` must be upheld by the caller.
// SAFETY: because `new_layout.size()` must be greater than or equal to
// `old_layout.size()`, both the old and new memory allocation are valid for reads and
// writes for `old_layout.size()` bytes. Also, because the old allocation wasn't yet
// deallocated, it cannot overlap `new_ptr`. Thus, the call to `copy_nonoverlapping` is
// safe. The safety contract for `dealloc` must be upheld by the caller.
unsafe {
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), size);
self.dealloc(ptr, layout);
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_layout.size());
self.dealloc(ptr, old_layout);
}
Ok(new_ptr)
@ -220,21 +213,19 @@ pub unsafe trait AllocRef {
///
/// The memory block will contain the following contents after a successful call to
/// `grow_zeroed`:
/// * Bytes `0..layout.size()` are preserved from the original allocation.
/// * Bytes `layout.size()..old_size` will either be preserved or zeroed, depending on the
/// allocator implementation. `old_size` refers to the size of the memory block prior to
/// the `grow_zeroed` call, which may be larger than the size that was originally requested
/// when it was allocated.
/// * Bytes `0..old_layout.size()` are preserved from the original allocation.
/// * Bytes `old_layout.size()..old_size` will either be preserved or zeroed, depending on
/// the allocator implementation. `old_size` refers to the size of the memory block prior
/// to the `grow_zeroed` call, which may be larger than the size that was originally
/// requested when it was allocated.
/// * Bytes `old_size..new_size` are zeroed. `new_size` refers to the size of the memory
/// block returned by the `grow` call.
/// block returned by the `grow_zeroed` call.
///
/// # Safety
///
/// * `ptr` must denote a block of memory [*currently allocated*] via this allocator,
/// * `layout` must [*fit*] that block of memory (The `new_size` argument need not fit it.),
/// * `new_size` must be greater than or equal to `layout.size()`, and
/// * `new_size`, when rounded up to the nearest multiple of `layout.align()`, must not overflow
/// (i.e., the rounded value must be less than or equal to `usize::MAX`).
/// * `ptr` must denote a block of memory [*currently allocated*] via this allocator.
/// * `old_layout` must [*fit*] that block of memory (The `new_layout` argument need not fit it.).
/// * `new_layout.size()` must be greater than or equal to `old_layout.size()`.
///
/// [*currently allocated*]: #currently-allocated-memory
/// [*fit*]: #memory-fitting
@ -255,28 +246,24 @@ pub unsafe trait AllocRef {
unsafe fn grow_zeroed(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
let size = layout.size();
debug_assert!(
new_size >= size,
"`new_size` must be greater than or equal to `layout.size()`"
new_layout.size() >= old_layout.size(),
"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
);
// SAFETY: the caller must ensure that the `new_size` does not overflow.
// `layout.align()` comes from a `Layout` and is thus guaranteed to be valid for a Layout.
let new_layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
let new_ptr = self.alloc_zeroed(new_layout)?;
// SAFETY: because `new_size` must be greater than or equal to `size`, both the old and new
// memory allocation are valid for reads and writes for `size` bytes. Also, because the old
// allocation wasn't yet deallocated, it cannot overlap `new_ptr`. Thus, the call to
// `copy_nonoverlapping` is safe.
// The safety contract for `dealloc` must be upheld by the caller.
// SAFETY: because `new_layout.size()` must be greater than or equal to
// `old_layout.size()`, both the old and new memory allocation are valid for reads and
// writes for `old_layout.size()` bytes. Also, because the old allocation wasn't yet
// deallocated, it cannot overlap `new_ptr`. Thus, the call to `copy_nonoverlapping` is
// safe. The safety contract for `dealloc` must be upheld by the caller.
unsafe {
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), size);
self.dealloc(ptr, layout);
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_layout.size());
self.dealloc(ptr, old_layout);
}
Ok(new_ptr)
@ -285,9 +272,8 @@ pub unsafe trait AllocRef {
/// Attempts to shrink the memory block.
///
/// Returns a new [`NonNull<[u8]>`] containing a pointer and the actual size of the allocated
/// memory. The pointer is suitable for holding data described by a new layout with `layout`’s
/// alignment and a size given by `new_size`. To accomplish this, the allocator may shrink the
/// allocation referenced by `ptr` to fit the new layout.
/// memory. The pointer is suitable for holding data described by `new_layout`. To accomplish
/// this, the allocator may shrink the allocation referenced by `ptr` to fit the new layout.
///
/// If this returns `Ok`, then ownership of the memory block referenced by `ptr` has been
/// transferred to this allocator. The memory may or may not have been freed, and should be
@ -301,9 +287,9 @@ pub unsafe trait AllocRef {
///
/// # Safety
///
/// * `ptr` must denote a block of memory [*currently allocated*] via this allocator,
/// * `layout` must [*fit*] that block of memory (The `new_size` argument need not fit it.), and
/// * `new_size` must be smaller than or equal to `layout.size()`.
/// * `ptr` must denote a block of memory [*currently allocated*] via this allocator.
/// * `old_layout` must [*fit*] that block of memory (The `new_layout` argument need not fit it.).
/// * `new_layout.size()` must be smaller than or equal to `old_layout.size()`.
///
/// [*currently allocated*]: #currently-allocated-memory
/// [*fit*]: #memory-fitting
@ -324,28 +310,24 @@ pub unsafe trait AllocRef {
unsafe fn shrink(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
let size = layout.size();
debug_assert!(
new_size <= size,
"`new_size` must be smaller than or equal to `layout.size()`"
new_layout.size() <= old_layout.size(),
"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
);
// SAFETY: the caller must ensure that the `new_size` does not overflow.
// `layout.align()` comes from a `Layout` and is thus guaranteed to be valid for a Layout.
let new_layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
let new_ptr = self.alloc(new_layout)?;
// SAFETY: because `new_size` must be lower than or equal to `size`, both the old and new
// memory allocation are valid for reads and writes for `new_size` bytes. Also, because the
// old allocation wasn't yet deallocated, it cannot overlap `new_ptr`. Thus, the call to
// `copy_nonoverlapping` is safe.
// The safety contract for `dealloc` must be upheld by the caller.
// SAFETY: because `new_layout.size()` must be lower than or equal to
// `old_layout.size()`, both the old and new memory allocation are valid for reads and
// writes for `new_layout.size()` bytes. Also, because the old allocation wasn't yet
// deallocated, it cannot overlap `new_ptr`. Thus, the call to `copy_nonoverlapping` is
// safe. The safety contract for `dealloc` must be upheld by the caller.
unsafe {
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), size);
self.dealloc(ptr, layout);
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_layout.size());
self.dealloc(ptr, old_layout);
}
Ok(new_ptr)
@ -385,32 +367,32 @@ where
unsafe fn grow(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
// SAFETY: the safety contract must be upheld by the caller
unsafe { (**self).grow(ptr, layout, new_size) }
unsafe { (**self).grow(ptr, old_layout, new_layout) }
}
#[inline]
unsafe fn grow_zeroed(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
// SAFETY: the safety contract must be upheld by the caller
unsafe { (**self).grow_zeroed(ptr, layout, new_size) }
unsafe { (**self).grow_zeroed(ptr, old_layout, new_layout) }
}
#[inline]
unsafe fn shrink(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
// SAFETY: the safety contract must be upheld by the caller
unsafe { (**self).shrink(ptr, layout, new_size) }
unsafe { (**self).shrink(ptr, old_layout, new_layout) }
}
}

85
library/std/src/alloc.rs
View File

@ -154,36 +154,45 @@ impl System {
unsafe fn grow_impl(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
zeroed: bool,
) -> Result<NonNull<[u8]>, AllocErr> {
debug_assert!(
new_size >= layout.size(),
"`new_size` must be greater than or equal to `layout.size()`"
new_layout.size() >= old_layout.size(),
"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
);
match layout.size() {
// SAFETY: the caller must ensure that the `new_size` does not overflow.
// `layout.align()` comes from a `Layout` and is thus guaranteed to be valid for a Layout.
0 => unsafe {
let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
self.alloc_impl(new_layout, zeroed)
},
match old_layout.size() {
0 => self.alloc_impl(new_layout, zeroed),
// SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`
// as required by safety conditions. Other conditions must be upheld by the caller
old_size => unsafe {
// `realloc` probably checks for `new_size >= size` or something similar.
intrinsics::assume(new_size >= layout.size());
old_size if old_layout.align() == new_layout.align() => unsafe {
let new_size = new_layout.size();
let raw_ptr = GlobalAlloc::realloc(self, ptr.as_ptr(), layout, new_size);
// `realloc` probably checks for `new_size >= old_layout.size()` or something similar.
intrinsics::assume(new_size >= old_layout.size());
let raw_ptr = GlobalAlloc::realloc(self, ptr.as_ptr(), old_layout, new_size);
let ptr = NonNull::new(raw_ptr).ok_or(AllocErr)?;
if zeroed {
raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
}
Ok(NonNull::slice_from_raw_parts(ptr, new_size))
},
// SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
// both the old and new memory allocation are valid for reads and writes for `old_size`
// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
// for `dealloc` must be upheld by the caller.
old_size => unsafe {
let new_ptr = self.alloc_impl(new_layout, zeroed)?;
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
self.dealloc(ptr, old_layout);
Ok(new_ptr)
},
}
}
}
@ -215,52 +224,64 @@ unsafe impl AllocRef for System {
unsafe fn grow(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
// SAFETY: all conditions must be upheld by the caller
unsafe { self.grow_impl(ptr, layout, new_size, false) }
unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
}
#[inline]
unsafe fn grow_zeroed(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
// SAFETY: all conditions must be upheld by the caller
unsafe { self.grow_impl(ptr, layout, new_size, true) }
unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
}
#[inline]
unsafe fn shrink(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocErr> {
debug_assert!(
new_size <= layout.size(),
"`new_size` must be smaller than or equal to `layout.size()`"
new_layout.size() <= old_layout.size(),
"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
);
match new_size {
match new_layout.size() {
// SAFETY: conditions must be upheld by the caller
0 => unsafe {
self.dealloc(ptr, layout);
Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0))
self.dealloc(ptr, old_layout);
Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
},
// SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
new_size => unsafe {
// `realloc` probably checks for `new_size <= size` or something similar.
intrinsics::assume(new_size <= layout.size());
new_size if old_layout.align() == new_layout.align() => unsafe {
// `realloc` probably checks for `new_size <= old_layout.size()` or something similar.
intrinsics::assume(new_size <= old_layout.size());
let raw_ptr = GlobalAlloc::realloc(self, ptr.as_ptr(), layout, new_size);
let raw_ptr = GlobalAlloc::realloc(self, ptr.as_ptr(), old_layout, new_size);
let ptr = NonNull::new(raw_ptr).ok_or(AllocErr)?;
Ok(NonNull::slice_from_raw_parts(ptr, new_size))
},
// SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
// both the old and new memory allocation are valid for reads and writes for `new_size`
// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
// for `dealloc` must be upheld by the caller.
new_size => unsafe {
let new_ptr = self.alloc(new_layout)?;
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
self.dealloc(ptr, old_layout);
Ok(new_ptr)
},
}
}
}

16
src/test/ui/realloc-16687.rs
View File

@ -48,7 +48,7 @@ unsafe fn test_triangle() -> bool {
println!("allocate({:?}) = {:?}", layout, ptr);
}
ptr.as_non_null_ptr().as_ptr()
ptr.as_mut_ptr()
}
unsafe fn deallocate(ptr: *mut u8, layout: Layout) {
@ -65,23 +65,17 @@ unsafe fn test_triangle() -> bool {
}
let memory = if new.size() > old.size() {
Global.grow(
NonNull::new_unchecked(ptr),
old,
new.size(),
)
Global.grow(NonNull::new_unchecked(ptr), old, new)
} else {
Global.shrink(NonNull::new_unchecked(ptr), old, new.size())
Global.shrink(NonNull::new_unchecked(ptr), old, new)
};
let ptr = memory.unwrap_or_else(|_| {
handle_alloc_error(Layout::from_size_align_unchecked(new.size(), old.align()))
});
let ptr = memory.unwrap_or_else(|_| handle_alloc_error(new));
if PRINT {
println!("reallocate({:?}, old={:?}, new={:?}) = {:?}", ptr, old, new, ptr);
}
ptr.as_non_null_ptr().as_ptr()
ptr.as_mut_ptr()
}
fn idx_to_size(i: usize) -> usize {