refactor: move crate::utils::{alloc:: → }{vec, freeze}, remove r3_kernel::utils::alloc

`cfg_phaseN!` will need `ConstAllocator`, and they can't produce
`ConstAllocator` to be used by themselves because, if the constructed
`ConstAllocator` is stored in a local variable of a user-controlled
`async` closure, there exists no way to guarantee that its destructor is
called before the control exits the scope (a concrete example of the
exploitation of this caveat can be found in [1]).

`vec` and `freeze` are kept out of `r3_core::utils::alloc` to minimize
the stable API surface to maintain.

[1]: https://github.com/yvt/cryo/blob/3cd529a8665063e98961e08b4df25d398d9bd4b5/src/lib.rs#L565-L662

Author: yvt

src/r3_core/src/utils/alloc/allocator.rs

@@ -24,6 +24,10 @@ macro_rules! const_try_result {
 /// `ConstAllocator`. This is accomplished by, instead of making a call to
 /// `const_allocate` for each allocation request, slicing out each allocated
 /// region from larger blocks using a dynamic storage allocation algorithm.
+///
+/// # Stability
+///
+/// This type is subject to the kernel-side API stability guarantee.
 pub struct ConstAllocator {
     // We very much want to put these in `core::cell::*`, but they aren't very
     // useful in `const fn`, unfortunately.
@@ -192,6 +196,10 @@ impl const Drop for ConstAllocator {
 /// that may be due to resource exhaustion or to
 /// something wrong when combining the given input arguments with this
 /// allocator.
+///
+/// # Stability
+///
+/// This trait is subject to the kernel-side API stability guarantee.
 #[derive(Clone, Copy)]
 pub struct AllocError;
 
@@ -200,6 +208,10 @@ pub struct AllocError;
 /// # Safety
 ///
 /// See [`core::alloc::Allocator`]'s documentation.
+///
+/// # Stability
+///
+/// This trait is subject to the kernel-side API stability guarantee.
 pub unsafe trait Allocator {
     fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>;
 

src/r3_core/src/utils/alloc/mod.rs

@@ -1,7 +1,4 @@
 //! Compile-time memory allocation
-#[macro_use]
-mod vec;
 mod allocator;
-mod freeze;
 mod rlsf;
-pub use {allocator::*, freeze::*, vec::*};
+pub use allocator::*;

src/r3_core/src/utils/alloc/freeze.rs renamed to src/r3_core/src/utils/freeze.rs

@@ -1,4 +1,7 @@
 //! Utility
+//!
+//! **This module is exempt from the API stability guarantee** unless specified
+//! otherwise. It's exposed mostly because it's needed by macros.
 use core::marker::PhantomData;
 
 /// Conditional type
@@ -45,6 +48,10 @@ mod binary_search;
 mod sort;
 pub(crate) use sort::*;
 #[macro_use]
+mod vec;
+pub use vec::*;
+mod freeze;
+pub use freeze::*;
 mod alloc;
 pub use alloc::*;
 #[macro_use]

src/r3_core/src/utils/mod.rs

@@ -0,0 +1 @@
+../../../r3_core/src/utils/freeze.rs

src/r3_core/src/utils/alloc/vec.rs renamed to src/r3_core/src/utils/vec.rs

@@ -1,7 +1,7 @@
 //! Utility
 //!
 //! **This module is exempt from the API stability guarantee** unless specified
-//! otherwise. It's exposed only because it's needed by macros.
+//! otherwise. It's exposed mostly because it's needed by macros.
 use core::marker::PhantomData;
 
 /// Conditional type
@@ -46,15 +46,16 @@ mod aligned_storage;
 pub mod binary_heap;
 pub(crate) mod convert;
 mod ctz;
+mod freeze;
 mod int;
 pub(crate) mod intrusive_list;
 pub mod mem;
 pub(crate) mod pin;
 mod prio_bitmap;
 mod rawcell;
 #[macro_use]
-mod alloc;
-pub use self::{aligned_storage::*, alloc::*, int::*, prio_bitmap::*, rawcell::*};
+mod vec;
+pub use self::{aligned_storage::*, freeze::*, int::*, prio_bitmap::*, rawcell::*, vec::*};
 pub use r3_core::utils::{Init, ZeroInit};
 
 /// A "type function" producing a type.

src/r3_kernel/src/utils/alloc

@@ -0,0 +1 @@
+../../../r3_core/src/utils/vec.rs