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Support custom allocators in Box #77187

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merged 5 commits into from
Oct 26, 2020
Merged

Support custom allocators in Box #77187

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f288cd2
Support custom allocators in `Box`
TimDiekmann Oct 6, 2020
d5720bb
Fix mir-opt output for 32 bit
TimDiekmann Oct 7, 2020
955b37b
Merge branch 'master' into box-alloc
TimDiekmann Oct 16, 2020
693a2bf
Rename `Box::alloc` to `Box::alloc_ref`
TimDiekmann Oct 23, 2020
06e4497
Merge remote-tracking branch 'upstream/master' into box-alloc
TimDiekmann Oct 25, 2020
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19 changes: 15 additions & 4 deletions library/alloc/src/alloc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,13 @@

#![stable(feature = "alloc_module", since = "1.28.0")]

use core::intrinsics::{self, min_align_of_val, size_of_val};
use core::ptr::{self, NonNull, Unique};
#[cfg(not(test))]
use core::intrinsics;
use core::intrinsics::{min_align_of_val, size_of_val};

use core::ptr::Unique;
#[cfg(not(test))]
use core::ptr::{self, NonNull};

#[stable(feature = "alloc_module", since = "1.28.0")]
#[doc(inline)]
Expand Down Expand Up @@ -39,8 +44,12 @@ extern "Rust" {
/// accessed through the [free functions in `alloc`](self#functions).
#[unstable(feature = "allocator_api", issue = "32838")]
#[derive(Copy, Clone, Default, Debug)]
#[cfg(not(test))]
pub struct Global;

#[cfg(test)]
pub use std::alloc::Global;

/// Allocate memory with the global allocator.
///
/// This function forwards calls to the [`GlobalAlloc::alloc`] method
Expand Down Expand Up @@ -144,6 +153,7 @@ pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
}

#[cfg(not(test))]
impl Global {
#[inline]
fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
Expand Down Expand Up @@ -207,6 +217,7 @@ impl Global {
}

#[unstable(feature = "allocator_api", issue = "32838")]
#[cfg(not(test))]
unsafe impl AllocRef for Global {
#[inline]
fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
Expand Down Expand Up @@ -313,12 +324,12 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
// well.
// For example if `Box` is changed to `struct Box<T: ?Sized, A: AllocRef>(Unique<T>, A)`,
// this function has to be changed to `fn box_free<T: ?Sized, A: AllocRef>(Unique<T>, A)` as well.
pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
pub(crate) unsafe fn box_free<T: ?Sized, A: AllocRef>(ptr: Unique<T>, alloc: A) {
unsafe {
let size = size_of_val(ptr.as_ref());
let align = min_align_of_val(ptr.as_ref());
let layout = Layout::from_size_align_unchecked(size, align);
Global.dealloc(ptr.cast().into(), layout)
alloc.dealloc(ptr.cast().into(), layout)
}
}

Expand Down
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