| // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT |
| |
| // Copyright 2022 The Fuchsia Authors |
| // |
| // Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0 |
| // <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT |
| // license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option. |
| // This file may not be copied, modified, or distributed except according to |
| // those terms. |
| |
| //! Utilities used by macros and by `zerocopy-derive`. |
| //! |
| //! These are defined here `zerocopy` rather than in code generated by macros or |
| //! by `zerocopy-derive` so that they can be compiled once rather than |
| //! recompiled for every invocation (e.g., if they were defined in generated |
| //! code, then deriving `IntoBytes` and `FromBytes` on three different types |
| //! would result in the code in question being emitted and compiled six |
| //! different times). |
| |
| #![allow(missing_debug_implementations)] |
| |
| // FIXME(#29), FIXME(https://github.com/rust-lang/rust/issues/69835): Remove |
| // this `cfg` when `size_of_val_raw` is stabilized. |
| #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)] |
| #[cfg(not(target_pointer_width = "16"))] |
| use core::ptr::{self, NonNull}; |
| use core::{marker::PhantomData, mem, num::Wrapping}; |
| |
| use crate::{ |
| pointer::{ |
| cast::CastSized, |
| invariant::{Aligned, Initialized, Valid}, |
| BecauseImmutable, |
| }, |
| FromBytes, Immutable, IntoBytes, KnownLayout, Ptr, ReadOnly, TryFromBytes, ValidityError, |
| }; |
| |
| /// Projects the type of the field at `Index` in `Self` without regard for field |
| /// privacy. |
| /// |
| /// The `Index` parameter is any sort of handle that identifies the field; its |
| /// definition is the obligation of the implementer. |
| /// |
| /// # Safety |
| /// |
| /// Unsafe code may assume that this accurately reflects the definition of |
| /// `Self`. |
| pub unsafe trait Field<Index> { |
| /// The type of the field at `Index`. |
| type Type: ?Sized; |
| } |
| |
| #[cfg_attr( |
| not(no_zerocopy_diagnostic_on_unimplemented_1_78_0), |
| diagnostic::on_unimplemented( |
| message = "`{T}` has {PADDING_BYTES} total byte(s) of padding", |
| label = "types with padding cannot implement `IntoBytes`", |
| note = "consider using `zerocopy::Unalign` to lower the alignment of individual fields", |
| note = "consider adding explicit fields where padding would be", |
| note = "consider using `#[repr(packed)]` to remove padding" |
| ) |
| )] |
| pub trait PaddingFree<T: ?Sized, const PADDING_BYTES: usize> {} |
| impl<T: ?Sized> PaddingFree<T, 0> for () {} |
| |
| // FIXME(#1112): In the slice DST case, we should delegate to *both* |
| // `PaddingFree` *and* `DynamicPaddingFree` (and probably rename `PaddingFree` |
| // to `StaticPaddingFree` or something - or introduce a third trait with that |
| // name) so that we can have more clear error messages. |
| |
| #[cfg_attr( |
| not(no_zerocopy_diagnostic_on_unimplemented_1_78_0), |
| diagnostic::on_unimplemented( |
| message = "`{T}` has one or more padding bytes", |
| label = "types with padding cannot implement `IntoBytes`", |
| note = "consider using `zerocopy::Unalign` to lower the alignment of individual fields", |
| note = "consider adding explicit fields where padding would be", |
| note = "consider using `#[repr(packed)]` to remove padding" |
| ) |
| )] |
| pub trait DynamicPaddingFree<T: ?Sized, const HAS_PADDING: bool> {} |
| impl<T: ?Sized> DynamicPaddingFree<T, false> for () {} |
| |
| #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)] |
| #[cfg(not(target_pointer_width = "16"))] |
| const _64K: usize = 1 << 16; |
| |
| // FIXME(#29), FIXME(https://github.com/rust-lang/rust/issues/69835): Remove |
| // this `cfg` when `size_of_val_raw` is stabilized. |
| #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)] |
| #[cfg(not(target_pointer_width = "16"))] |
| #[repr(C, align(65536))] |
| struct Aligned64kAllocation([u8; _64K]); |
| |
| /// A pointer to an aligned allocation of size 2^16. |
| /// |
| /// # Safety |
| /// |
| /// `ALIGNED_64K_ALLOCATION` is guaranteed to point to the entirety of an |
| /// allocation with size and alignment 2^16, and to have valid provenance. |
| // FIXME(#29), FIXME(https://github.com/rust-lang/rust/issues/69835): Remove |
| // this `cfg` when `size_of_val_raw` is stabilized. |
| #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)] |
| #[cfg(not(target_pointer_width = "16"))] |
| pub const ALIGNED_64K_ALLOCATION: NonNull<[u8]> = { |
| const REF: &Aligned64kAllocation = &Aligned64kAllocation([0; _64K]); |
| let ptr: *const Aligned64kAllocation = REF; |
| let ptr: *const [u8] = ptr::slice_from_raw_parts(ptr.cast(), _64K); |
| // SAFETY: |
| // - `ptr` is derived from a Rust reference, which is guaranteed to be |
| // non-null. |
| // - `ptr` is derived from an `&Aligned64kAllocation`, which has size and |
| // alignment `_64K` as promised. Its length is initialized to `_64K`, |
| // which means that it refers to the entire allocation. |
| // - `ptr` is derived from a Rust reference, which is guaranteed to have |
| // valid provenance. |
| // |
| // FIXME(#429): Once `NonNull::new_unchecked` docs document that it |
| // preserves provenance, cite those docs. |
| // FIXME: Replace this `as` with `ptr.cast_mut()` once our MSRV >= 1.65 |
| #[allow(clippy::as_conversions)] |
| unsafe { |
| NonNull::new_unchecked(ptr as *mut _) |
| } |
| }; |
| |
| /// Computes the offset of the base of the field `$trailing_field_name` within |
| /// the type `$ty`. |
| /// |
| /// `trailing_field_offset!` produces code which is valid in a `const` context. |
| // FIXME(#29), FIXME(https://github.com/rust-lang/rust/issues/69835): Remove |
| // this `cfg` when `size_of_val_raw` is stabilized. |
| #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)] |
| #[doc(hidden)] // `#[macro_export]` bypasses this module's `#[doc(hidden)]`. |
| #[macro_export] |
| macro_rules! trailing_field_offset { |
| ($ty:ty, $trailing_field_name:tt) => {{ |
| let min_size = { |
| let zero_elems: *const [()] = |
| $crate::util::macro_util::core_reexport::ptr::slice_from_raw_parts( |
| $crate::util::macro_util::core_reexport::ptr::NonNull::<()>::dangling() |
| .as_ptr() |
| .cast_const(), |
| 0, |
| ); |
| // SAFETY: |
| // - If `$ty` is `Sized`, `size_of_val_raw` is always safe to call. |
| // - Otherwise: |
| // - If `$ty` is not a slice DST, this pointer conversion will |
| // fail due to "mismatched vtable kinds", and compilation will |
| // fail. |
| // - If `$ty` is a slice DST, we have constructed `zero_elems` to |
| // have zero trailing slice elements. Per the `size_of_val_raw` |
| // docs, "For the special case where the dynamic tail length is |
| // 0, this function is safe to call." [1] |
| // |
| // [1] https://doc.rust-lang.org/nightly/std/mem/fn.size_of_val_raw.html |
| unsafe { |
| #[allow(clippy::as_conversions)] |
| $crate::util::macro_util::core_reexport::mem::size_of_val_raw( |
| zero_elems as *const $ty, |
| ) |
| } |
| }; |
| |
| assert!(min_size <= _64K); |
| |
| #[allow(clippy::as_conversions)] |
| let ptr = ALIGNED_64K_ALLOCATION.as_ptr() as *const $ty; |
| |
| // SAFETY: |
| // - Thanks to the preceding `assert!`, we know that the value with zero |
| // elements fits in `_64K` bytes, and thus in the allocation addressed |
| // by `ALIGNED_64K_ALLOCATION`. The offset of the trailing field is |
| // guaranteed to be no larger than this size, so this field projection |
| // is guaranteed to remain in-bounds of its allocation. |
| // - Because the minimum size is no larger than `_64K` bytes, and |
| // because an object's size must always be a multiple of its alignment |
| // [1], we know that `$ty`'s alignment is no larger than `_64K`. The |
| // allocation addressed by `ALIGNED_64K_ALLOCATION` is guaranteed to |
| // be aligned to `_64K`, so `ptr` is guaranteed to satisfy `$ty`'s |
| // alignment. |
| // - As required by `addr_of!`, we do not write through `field`. |
| // |
| // Note that, as of [2], this requirement is technically unnecessary |
| // for Rust versions >= 1.75.0, but no harm in guaranteeing it anyway |
| // until we bump our MSRV. |
| // |
| // [1] Per https://doc.rust-lang.org/reference/type-layout.html: |
| // |
| // The size of a value is always a multiple of its alignment. |
| // |
| // [2] https://github.com/rust-lang/reference/pull/1387 |
| let field = unsafe { |
| $crate::util::macro_util::core_reexport::ptr::addr_of!((*ptr).$trailing_field_name) |
| }; |
| // SAFETY: |
| // - Both `ptr` and `field` are derived from the same allocated object. |
| // - By the preceding safety comment, `field` is in bounds of that |
| // allocated object. |
| // - The distance, in bytes, between `ptr` and `field` is required to be |
| // a multiple of the size of `u8`, which is trivially true because |
| // `u8`'s size is 1. |
| // - The distance, in bytes, cannot overflow `isize`. This is guaranteed |
| // because no allocated object can have a size larger than can fit in |
| // `isize`. [1] |
| // - The distance being in-bounds cannot rely on wrapping around the |
| // address space. This is guaranteed because the same is guaranteed of |
| // allocated objects. [1] |
| // |
| // [1] FIXME(#429), FIXME(https://github.com/rust-lang/rust/pull/116675): |
| // Once these are guaranteed in the Reference, cite it. |
| let offset = unsafe { field.cast::<u8>().offset_from(ptr.cast::<u8>()) }; |
| // Guaranteed not to be lossy: `field` comes after `ptr`, so the offset |
| // from `ptr` to `field` is guaranteed to be positive. |
| assert!(offset >= 0); |
| Some( |
| #[allow(clippy::as_conversions)] |
| { |
| offset as usize |
| }, |
| ) |
| }}; |
| } |
| |
| /// Computes alignment of `$ty: ?Sized`. |
| /// |
| /// `align_of!` produces code which is valid in a `const` context. |
| // FIXME(#29), FIXME(https://github.com/rust-lang/rust/issues/69835): Remove |
| // this `cfg` when `size_of_val_raw` is stabilized. |
| #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)] |
| #[doc(hidden)] // `#[macro_export]` bypasses this module's `#[doc(hidden)]`. |
| #[macro_export] |
| macro_rules! align_of { |
| ($ty:ty) => {{ |
| // SAFETY: `OffsetOfTrailingIsAlignment` is `repr(C)`, and its layout is |
| // guaranteed [1] to begin with the single-byte layout for `_byte`, |
| // followed by the padding needed to align `_trailing`, then the layout |
| // for `_trailing`, and finally any trailing padding bytes needed to |
| // correctly-align the entire struct. |
| // |
| // This macro computes the alignment of `$ty` by counting the number of |
| // bytes preceding `_trailing`. For instance, if the alignment of `$ty` |
| // is `1`, then no padding is required align `_trailing` and it will be |
| // located immediately after `_byte` at offset 1. If the alignment of |
| // `$ty` is 2, then a single padding byte is required before |
| // `_trailing`, and `_trailing` will be located at offset 2. |
| |
| // This correspondence between offset and alignment holds for all valid |
| // Rust alignments, and we confirm this exhaustively (or, at least up to |
| // the maximum alignment supported by `trailing_field_offset!`) in |
| // `test_align_of_dst`. |
| // |
| // [1]: https://doc.rust-lang.org/nomicon/other-reprs.html#reprc |
| |
| #[repr(C)] |
| struct OffsetOfTrailingIsAlignment { |
| _byte: u8, |
| _trailing: $ty, |
| } |
| |
| trailing_field_offset!(OffsetOfTrailingIsAlignment, _trailing) |
| }}; |
| } |
| |
| mod size_to_tag { |
| pub trait SizeToTag<const SIZE: usize> { |
| type Tag; |
| } |
| |
| impl SizeToTag<1> for () { |
| type Tag = u8; |
| } |
| impl SizeToTag<2> for () { |
| type Tag = u16; |
| } |
| impl SizeToTag<4> for () { |
| type Tag = u32; |
| } |
| impl SizeToTag<8> for () { |
| type Tag = u64; |
| } |
| impl SizeToTag<16> for () { |
| type Tag = u128; |
| } |
| } |
| |
| /// An alias for the unsigned integer of the given size in bytes. |
| #[doc(hidden)] |
| pub type SizeToTag<const SIZE: usize> = <() as size_to_tag::SizeToTag<SIZE>>::Tag; |
| |
| // We put `Sized` in its own module so it can have the same name as the standard |
| // library `Sized` without shadowing it in the parent module. |
| #[cfg(not(no_zerocopy_diagnostic_on_unimplemented_1_78_0))] |
| mod __size_of { |
| #[diagnostic::on_unimplemented( |
| message = "`{Self}` is unsized", |
| label = "`IntoBytes` needs all field types to be `Sized` in order to determine whether there is padding", |
| note = "consider using `#[repr(packed)]` to remove padding", |
| note = "`IntoBytes` does not require the fields of `#[repr(packed)]` types to be `Sized`" |
| )] |
| pub trait Sized: core::marker::Sized {} |
| impl<T: core::marker::Sized> Sized for T {} |
| |
| #[inline(always)] |
| #[must_use] |
| #[allow(clippy::needless_maybe_sized)] |
| pub const fn size_of<T: Sized + ?core::marker::Sized>() -> usize { |
| core::mem::size_of::<T>() |
| } |
| } |
| |
| #[cfg(no_zerocopy_diagnostic_on_unimplemented_1_78_0)] |
| pub use core::mem::size_of; |
| |
| #[cfg(not(no_zerocopy_diagnostic_on_unimplemented_1_78_0))] |
| pub use __size_of::size_of; |
| |
| /// How many padding bytes does the struct type `$t` have? |
| /// |
| /// `$ts` is the list of the type of every field in `$t`. `$t` must be a struct |
| /// type, or else `struct_padding!`'s result may be meaningless. |
| /// |
| /// Note that `struct_padding!`'s results are independent of `repcr` since they |
| /// only consider the size of the type and the sizes of the fields. Whatever the |
| /// repr, the size of the type already takes into account any padding that the |
| /// compiler has decided to add. Structs with well-defined representations (such |
| /// as `repr(C)`) can use this macro to check for padding. Note that while this |
| /// may yield some consistent value for some `repr(Rust)` structs, it is not |
| /// guaranteed across platforms or compilations. |
| #[doc(hidden)] // `#[macro_export]` bypasses this module's `#[doc(hidden)]`. |
| #[macro_export] |
| macro_rules! struct_padding { |
| ($t:ty, $_align:expr, $_packed:expr, [$($ts:ty),*]) => {{ |
| // The `align` and `packed` directives can be ignored here. Regardless |
| // of if and how they are set, comparing the size of `$t` to the sum of |
| // its field sizes is a reliable indicator of the presence of padding. |
| $crate::util::macro_util::size_of::<$t>() - (0 $(+ $crate::util::macro_util::size_of::<$ts>())*) |
| }}; |
| } |
| |
| /// Does the `repr(C)` struct type `$t` have padding? |
| /// |
| /// `$ts` is the list of the type of every field in `$t`. `$t` must be a |
| /// `repr(C)` struct type, or else `struct_has_padding!`'s result may be |
| /// meaningless. |
| #[doc(hidden)] // `#[macro_export]` bypasses this module's `#[doc(hidden)]`. |
| #[macro_export] |
| macro_rules! repr_c_struct_has_padding { |
| ($t:ty, $align:expr, $packed:expr, [$($ts:tt),*]) => {{ |
| let layout = $crate::DstLayout::for_repr_c_struct( |
| $align, |
| $packed, |
| &[$($crate::repr_c_struct_has_padding!(@field $ts),)*] |
| ); |
| layout.requires_static_padding() || layout.requires_dynamic_padding() |
| }}; |
| (@field ([$t:ty])) => { |
| <[$t] as $crate::KnownLayout>::LAYOUT |
| }; |
| (@field ($t:ty)) => { |
| $crate::DstLayout::for_unpadded_type::<$t>() |
| }; |
| (@field [$t:ty]) => { |
| <[$t] as $crate::KnownLayout>::LAYOUT |
| }; |
| (@field $t:ty) => { |
| $crate::DstLayout::for_unpadded_type::<$t>() |
| }; |
| } |
| |
| /// Does the union type `$t` have padding? |
| /// |
| /// `$ts` is the list of the type of every field in `$t`. `$t` must be a union |
| /// type, or else `union_padding!`'s result may be meaningless. |
| /// |
| /// Note that `union_padding!`'s results are independent of `repr` since they |
| /// only consider the size of the type and the sizes of the fields. Whatever the |
| /// repr, the size of the type already takes into account any padding that the |
| /// compiler has decided to add. Unions with well-defined representations (such |
| /// as `repr(C)`) can use this macro to check for padding. Note that while this |
| /// may yield some consistent value for some `repr(Rust)` unions, it is not |
| /// guaranteed across platforms or compilations. |
| #[doc(hidden)] // `#[macro_export]` bypasses this module's `#[doc(hidden)]`. |
| #[macro_export] |
| macro_rules! union_padding { |
| ($t:ty, $_align:expr, $_packed:expr, [$($ts:ty),*]) => {{ |
| // The `align` and `packed` directives can be ignored here. Regardless |
| // of if and how they are set, comparing the size of `$t` to each of its |
| // field sizes is a reliable indicator of the presence of padding. |
| let mut max = 0; |
| $({ |
| let padding = $crate::util::macro_util::size_of::<$t>() - $crate::util::macro_util::size_of::<$ts>(); |
| if padding > max { |
| max = padding; |
| } |
| })* |
| max |
| }}; |
| } |
| |
| /// How many padding bytes does the enum type `$t` have? |
| /// |
| /// `$disc` is the type of the enum tag, and `$ts` is a list of fields in each |
| /// square-bracket-delimited variant. `$t` must be an enum, or else |
| /// `enum_padding!`'s result may be meaningless. An enum has padding if any of |
| /// its variant structs [1][2] contain padding, and so all of the variants of an |
| /// enum must be "full" in order for the enum to not have padding. |
| /// |
| /// The results of `enum_padding!` require that the enum is not `repr(Rust)`, as |
| /// `repr(Rust)` enums may niche the enum's tag and reduce the total number of |
| /// bytes required to represent the enum as a result. As long as the enum is |
| /// `repr(C)`, `repr(int)`, or `repr(C, int)`, this will consistently return |
| /// whether the enum contains any padding bytes. |
| /// |
| /// [1]: https://doc.rust-lang.org/1.81.0/reference/type-layout.html#reprc-enums-with-fields |
| /// [2]: https://doc.rust-lang.org/1.81.0/reference/type-layout.html#primitive-representation-of-enums-with-fields |
| #[doc(hidden)] // `#[macro_export]` bypasses this module's `#[doc(hidden)]`. |
| #[macro_export] |
| macro_rules! enum_padding { |
| ($t:ty, $_align:expr, $packed:expr, $disc:ty, $([$($ts:ty),*]),*) => {{ |
| // The `align` and `packed` directives are irrelevant. `$align` can be |
| // ignored because regardless of if and how it is set, comparing the |
| // size of `$t` to each of its field sizes is a reliable indicator of |
| // the presence of padding. `$packed` is irrelevant because it is |
| // forbidden on enums. |
| #[allow(clippy::as_conversions)] |
| const _: [(); 1] = [(); $packed.is_none() as usize]; |
| let mut max = 0; |
| $({ |
| let padding = $crate::util::macro_util::size_of::<$t>() |
| - ( |
| $crate::util::macro_util::size_of::<$disc>() |
| $(+ $crate::util::macro_util::size_of::<$ts>())* |
| ); |
| if padding > max { |
| max = padding; |
| } |
| })* |
| max |
| }}; |
| } |
| |
| /// Unwraps an infallible `Result`. |
| #[doc(hidden)] |
| #[macro_export] |
| macro_rules! into_inner { |
| ($e:expr) => { |
| match $e { |
| $crate::util::macro_util::core_reexport::result::Result::Ok(e) => e, |
| $crate::util::macro_util::core_reexport::result::Result::Err(i) => match i {}, |
| } |
| }; |
| } |
| |
| /// Translates an identifier or tuple index into a numeric identifier. |
| #[doc(hidden)] // `#[macro_export]` bypasses this module's `#[doc(hidden)]`. |
| #[macro_export] |
| macro_rules! ident_id { |
| ($field:ident) => { |
| $crate::util::macro_util::hash_name(stringify!($field)) |
| }; |
| ($field:literal) => { |
| $field |
| }; |
| } |
| |
| /// Computes the hash of a string. |
| /// |
| /// NOTE(#2749) on hash collisions: This function's output only needs to be |
| /// deterministic within a particular compilation. Thus, if a user ever reports |
| /// a hash collision (very unlikely given the <= 16-byte special case), we can |
| /// strengthen the hash function at that point and publish a new version. Since |
| /// this is computed at compile time on small strings, we can easily use more |
| /// expensive and higher-quality hash functions if need be. |
| #[inline(always)] |
| #[must_use] |
| #[allow(clippy::as_conversions, clippy::indexing_slicing, clippy::arithmetic_side_effects)] |
| pub const fn hash_name(name: &str) -> i128 { |
| let name = name.as_bytes(); |
| |
| // We guarantee freedom from hash collisions between any two strings of |
| // length 16 or less by having the hashes of such strings be equal to |
| // their value. There is still a possibility that such strings will have |
| // the same value as the hash of a string of length > 16. |
| if name.len() <= size_of::<u128>() { |
| let mut bytes = [0u8; 16]; |
| |
| let mut i = 0; |
| while i < name.len() { |
| bytes[i] = name[i]; |
| i += 1; |
| } |
| |
| return i128::from_ne_bytes(bytes); |
| }; |
| |
| // An implementation of FxHasher, although returning a u128. Probably |
| // not as strong as it could be, but probably more collision resistant |
| // than normal 64-bit FxHasher. |
| let mut hash = 0u128; |
| let mut i = 0; |
| while i < name.len() { |
| // This is just FxHasher's `0x517cc1b727220a95` constant |
| // concatenated back-to-back. |
| const K: u128 = 0x517cc1b727220a95517cc1b727220a95; |
| hash = (hash.rotate_left(5) ^ (name[i] as u128)).wrapping_mul(K); |
| i += 1; |
| } |
| i128::from_ne_bytes(hash.to_ne_bytes()) |
| } |
| |
| /// Attempts to transmute `Src` into `Dst`. |
| /// |
| /// A helper for `try_transmute!`. |
| /// |
| /// # Panics |
| /// |
| /// `try_transmute` may either produce a post-monomorphization error or a panic |
| /// if `Dst` is bigger than `Src`. Otherwise, `try_transmute` panics under the |
| /// same circumstances as [`is_bit_valid`]. |
| /// |
| /// [`is_bit_valid`]: TryFromBytes::is_bit_valid |
| #[inline(always)] |
| pub fn try_transmute<Src, Dst>(src: Src) -> Result<Dst, ValidityError<Src, Dst>> |
| where |
| Src: IntoBytes, |
| Dst: TryFromBytes, |
| { |
| static_assert!(Src, Dst => mem::size_of::<Dst>() == mem::size_of::<Src>()); |
| |
| let mu_src = mem::MaybeUninit::new(src); |
| // SAFETY: `MaybeUninit` has no validity requirements. |
| let mu_dst: mem::MaybeUninit<ReadOnly<Dst>> = |
| unsafe { crate::util::transmute_unchecked(mu_src) }; |
| |
| let ptr = Ptr::from_ref(&mu_dst); |
| |
| // SAFETY: Since `Src: IntoBytes`, and since `size_of::<Src>() == |
| // size_of::<Dst>()` by the preceding assertion, all of `mu_dst`'s bytes are |
| // initialized. `MaybeUninit` has no validity requirements, so even if |
| // `ptr` is used to mutate its referent (which it actually can't be - it's |
| // a shared `ReadOnly` pointer), that won't violate its referent's validity. |
| let ptr = unsafe { ptr.assume_validity::<Initialized>() }; |
| if Dst::is_bit_valid(ptr.cast::<_, CastSized, _>()) { |
| // SAFETY: Since `Dst::is_bit_valid`, we know that `ptr`'s referent is |
| // bit-valid for `Dst`. `ptr` points to `mu_dst`, and no intervening |
| // operations have mutated it, so it is a bit-valid `Dst`. |
| Ok(ReadOnly::into_inner(unsafe { mu_dst.assume_init() })) |
| } else { |
| // SAFETY: `MaybeUninit` has no validity requirements. |
| let mu_src: mem::MaybeUninit<Src> = unsafe { crate::util::transmute_unchecked(mu_dst) }; |
| // SAFETY: `mu_dst`/`mu_src` was constructed from `src` and never |
| // modified, so it is still bit-valid. |
| Err(ValidityError::new(unsafe { mu_src.assume_init() })) |
| } |
| } |
| |
| /// See `try_transmute_ref!` documentation. |
| pub trait TryTransmuteRefDst<'a> { |
| type Dst: ?Sized; |
| |
| /// See `try_transmute_ref!` documentation. |
| fn try_transmute_ref(self) -> Result<&'a Self::Dst, ValidityError<&'a Self::Src, Self::Dst>> |
| where |
| Self: TryTransmuteRefSrc<'a>, |
| Self::Src: IntoBytes + Immutable + KnownLayout, |
| Self::Dst: TryFromBytes + Immutable + KnownLayout; |
| } |
| |
| pub trait TryTransmuteRefSrc<'a> { |
| type Src: ?Sized; |
| } |
| |
| impl<'a, Src, Dst> TryTransmuteRefSrc<'a> for Wrap<&'a Src, &'a Dst> |
| where |
| Src: ?Sized, |
| Dst: ?Sized, |
| { |
| type Src = Src; |
| } |
| |
| impl<'a, Src, Dst> TryTransmuteRefDst<'a> for Wrap<&'a Src, &'a Dst> |
| where |
| Src: IntoBytes + Immutable + KnownLayout + ?Sized, |
| Dst: TryFromBytes + Immutable + KnownLayout + ?Sized, |
| { |
| type Dst = Dst; |
| |
| #[inline(always)] |
| fn try_transmute_ref( |
| self, |
| ) -> Result< |
| &'a Dst, |
| ValidityError<&'a <Wrap<&'a Src, &'a Dst> as TryTransmuteRefSrc<'a>>::Src, Dst>, |
| > { |
| let ptr = Ptr::from_ref(self.0); |
| #[rustfmt::skip] |
| let res = ptr.try_with(#[inline(always)] |ptr| { |
| let ptr = ptr.recall_validity::<Initialized, _>(); |
| let ptr = ptr.cast::<_, crate::layout::CastFrom<Dst>, _>(); |
| ptr.try_into_valid() |
| }); |
| match res { |
| Ok(ptr) => { |
| static_assert!(Src: ?Sized + KnownLayout, Dst: ?Sized + KnownLayout => { |
| Src::LAYOUT.align.get() >= Dst::LAYOUT.align.get() |
| }, "cannot transmute reference when destination type has higher alignment than source type"); |
| // SAFETY: We have checked that `Dst` does not have a stricter |
| // alignment requirement than `Src`. |
| let ptr = unsafe { ptr.assume_alignment::<Aligned>() }; |
| Ok(ptr.as_ref()) |
| } |
| Err(err) => Err(err.map_src(Ptr::as_ref)), |
| } |
| } |
| } |
| |
| pub trait TryTransmuteMutDst<'a> { |
| type Dst: ?Sized; |
| |
| /// See `try_transmute_mut!` documentation. |
| fn try_transmute_mut( |
| self, |
| ) -> Result<&'a mut Self::Dst, ValidityError<&'a mut Self::Src, Self::Dst>> |
| where |
| Self: TryTransmuteMutSrc<'a>, |
| Self::Src: IntoBytes, |
| Self::Dst: TryFromBytes; |
| } |
| |
| pub trait TryTransmuteMutSrc<'a> { |
| type Src: ?Sized; |
| } |
| |
| impl<'a, Src, Dst> TryTransmuteMutSrc<'a> for Wrap<&'a mut Src, &'a mut Dst> |
| where |
| Src: ?Sized, |
| Dst: ?Sized, |
| { |
| type Src = Src; |
| } |
| |
| impl<'a, Src, Dst> TryTransmuteMutDst<'a> for Wrap<&'a mut Src, &'a mut Dst> |
| where |
| Src: FromBytes + IntoBytes + KnownLayout + ?Sized, |
| Dst: TryFromBytes + IntoBytes + KnownLayout + ?Sized, |
| { |
| type Dst = Dst; |
| |
| #[inline(always)] |
| fn try_transmute_mut( |
| self, |
| ) -> Result< |
| &'a mut Dst, |
| ValidityError<&'a mut <Wrap<&'a mut Src, &'a mut Dst> as TryTransmuteMutSrc<'a>>::Src, Dst>, |
| > { |
| let ptr = Ptr::from_mut(self.0); |
| // SAFETY: The provided closure returns the only copy of `ptr`. |
| #[rustfmt::skip] |
| let res = unsafe { |
| ptr.try_with_unchecked(#[inline(always)] |ptr| { |
| let ptr = ptr.recall_validity::<Initialized, (_, (_, _))>(); |
| let ptr = ptr.cast::<_, crate::layout::CastFrom<Dst>, _>(); |
| ptr.try_into_valid() |
| }) |
| }; |
| match res { |
| Ok(ptr) => { |
| static_assert!(Src: ?Sized + KnownLayout, Dst: ?Sized + KnownLayout => { |
| Src::LAYOUT.align.get() >= Dst::LAYOUT.align.get() |
| }, "cannot transmute reference when destination type has higher alignment than source type"); |
| // SAFETY: We have checked that `Dst` does not have a stricter |
| // alignment requirement than `Src`. |
| let ptr = unsafe { ptr.assume_alignment::<Aligned>() }; |
| Ok(ptr.as_mut()) |
| } |
| Err(err) => Err(err.map_src(Ptr::as_mut)), |
| } |
| } |
| } |
| |
| // Used in `transmute_ref!` and friends. |
| // |
| // This permits us to use the autoref specialization trick to dispatch to |
| // associated functions for `transmute_ref` and `transmute_mut` when both `Src` |
| // and `Dst` are `Sized`, and to trait methods otherwise. The associated |
| // functions, unlike the trait methods, do not require a `KnownLayout` bound. |
| // This permits us to add support for transmuting references to unsized types |
| // without breaking backwards-compatibility (on v0.8.x) with the old |
| // implementation, which did not require a `KnownLayout` bound to transmute |
| // sized types. |
| #[derive(Copy, Clone)] |
| pub struct Wrap<Src, Dst>(pub Src, pub PhantomData<Dst>); |
| |
| impl<Src, Dst> Wrap<Src, Dst> { |
| #[inline(always)] |
| pub const fn new(src: Src) -> Self { |
| Wrap(src, PhantomData) |
| } |
| } |
| |
| impl<'a, Src, Dst> Wrap<&'a Src, &'a Dst> |
| where |
| Src: ?Sized, |
| Dst: ?Sized, |
| { |
| #[allow(clippy::must_use_candidate, clippy::missing_inline_in_public_items, clippy::empty_loop)] |
| pub const fn transmute_ref_inference_helper(self) -> &'a Dst { |
| loop {} |
| } |
| } |
| |
| impl<'a, Src, Dst> Wrap<&'a Src, &'a Dst> { |
| /// # Safety |
| /// The caller must guarantee that: |
| /// - `Src: IntoBytes + Immutable` |
| /// - `Dst: FromBytes + Immutable` |
| /// |
| /// # PME |
| /// |
| /// Instantiating this method PMEs unless both: |
| /// - `mem::size_of::<Dst>() == mem::size_of::<Src>()` |
| /// - `mem::align_of::<Dst>() <= mem::align_of::<Src>()` |
| #[inline(always)] |
| #[must_use] |
| pub const unsafe fn transmute_ref(self) -> &'a Dst { |
| static_assert!(Src, Dst => mem::size_of::<Dst>() == mem::size_of::<Src>()); |
| static_assert!(Src, Dst => mem::align_of::<Dst>() <= mem::align_of::<Src>()); |
| |
| let src: *const Src = self.0; |
| let dst = src.cast::<Dst>(); |
| // SAFETY: |
| // - We know that it is sound to view the target type of the input |
| // reference (`Src`) as the target type of the output reference |
| // (`Dst`) because the caller has guaranteed that `Src: IntoBytes`, |
| // `Dst: FromBytes`, and `size_of::<Src>() == size_of::<Dst>()`. |
| // - We know that there are no `UnsafeCell`s, and thus we don't have to |
| // worry about `UnsafeCell` overlap, because `Src: Immutable` and |
| // `Dst: Immutable`. |
| // - The caller has guaranteed that alignment is not increased. |
| // - We know that the returned lifetime will not outlive the input |
| // lifetime thanks to the lifetime bounds on this function. |
| // |
| // FIXME(#67): Once our MSRV is 1.58, replace this `transmute` with |
| // `&*dst`. |
| #[allow(clippy::transmute_ptr_to_ref)] |
| unsafe { |
| mem::transmute(dst) |
| } |
| } |
| |
| #[inline(always)] |
| pub fn try_transmute_ref(self) -> Result<&'a Dst, ValidityError<&'a Src, Dst>> |
| where |
| Src: IntoBytes + Immutable, |
| Dst: TryFromBytes + Immutable, |
| { |
| static_assert!(Src => mem::align_of::<Src>() == mem::align_of::<Wrapping<Src>>()); |
| static_assert!(Dst => mem::align_of::<Dst>() == mem::align_of::<Wrapping<Dst>>()); |
| |
| // SAFETY: By the preceding assert, `Src` and `Wrapping<Src>` have the |
| // same alignment. |
| let src: &Wrapping<Src> = |
| unsafe { crate::util::transmute_ref::<_, _, BecauseImmutable>(self.0) }; |
| let src = Wrap::new(src); |
| <Wrap<&'a Wrapping<Src>, &'a Wrapping<Dst>> as TryTransmuteRefDst<'a>>::try_transmute_ref( |
| src, |
| ) |
| .map( |
| // SAFETY: By the preceding assert, `Dst` and `Wrapping<Dst>` have |
| // the same alignment. |
| #[inline(always)] |
| |dst| unsafe { crate::util::transmute_ref::<_, _, BecauseImmutable>(dst) }, |
| ) |
| .map_err( |
| #[inline(always)] |
| |err| { |
| // SAFETY: By the preceding assert, `Src` and `Wrapping<Src>` have the |
| // same alignment. |
| ValidityError::new(unsafe { |
| crate::util::transmute_ref::<_, _, BecauseImmutable>(err.into_src()) |
| }) |
| }, |
| ) |
| } |
| } |
| |
| impl<'a, Src, Dst> Wrap<&'a mut Src, &'a mut Dst> |
| where |
| Src: ?Sized, |
| Dst: ?Sized, |
| { |
| #[allow(clippy::must_use_candidate, clippy::missing_inline_in_public_items, clippy::empty_loop)] |
| pub fn transmute_mut_inference_helper(self) -> &'a mut Dst { |
| loop {} |
| } |
| } |
| |
| impl<'a, Src, Dst> Wrap<&'a mut Src, &'a mut Dst> { |
| /// Transmutes a mutable reference of one type to a mutable reference of |
| /// another type. |
| /// |
| /// # PME |
| /// |
| /// Instantiating this method PMEs unless both: |
| /// - `mem::size_of::<Dst>() == mem::size_of::<Src>()` |
| /// - `mem::align_of::<Dst>() <= mem::align_of::<Src>()` |
| #[inline(always)] |
| #[must_use] |
| pub fn transmute_mut(self) -> &'a mut Dst |
| where |
| Src: FromBytes + IntoBytes, |
| Dst: FromBytes + IntoBytes, |
| { |
| static_assert!(Src, Dst => mem::size_of::<Dst>() == mem::size_of::<Src>()); |
| static_assert!(Src, Dst => mem::align_of::<Dst>() <= mem::align_of::<Src>()); |
| |
| let src: *mut Src = self.0; |
| let dst = src.cast::<Dst>(); |
| // SAFETY: |
| // - We know that it is sound to view the target type of the input |
| // reference (`Src`) as the target type of the output reference |
| // (`Dst`) and vice-versa because `Src: FromBytes + IntoBytes`, `Dst: |
| // FromBytes + IntoBytes`, and (as asserted above) `size_of::<Src>() |
| // == size_of::<Dst>()`. |
| // - We asserted above that alignment will not increase. |
| // - We know that the returned lifetime will not outlive the input |
| // lifetime thanks to the lifetime bounds on this function. |
| unsafe { &mut *dst } |
| } |
| |
| #[inline(always)] |
| pub fn try_transmute_mut(self) -> Result<&'a mut Dst, ValidityError<&'a mut Src, Dst>> |
| where |
| Src: FromBytes + IntoBytes, |
| Dst: TryFromBytes + IntoBytes, |
| { |
| static_assert!(Src => mem::align_of::<Src>() == mem::align_of::<Wrapping<Src>>()); |
| static_assert!(Dst => mem::align_of::<Dst>() == mem::align_of::<Wrapping<Dst>>()); |
| |
| // SAFETY: By the preceding assert, `Src` and `Wrapping<Src>` have the |
| // same alignment. |
| let src: &mut Wrapping<Src> = |
| unsafe { crate::util::transmute_mut::<_, _, (_, (_, _))>(self.0) }; |
| let src = Wrap::new(src); |
| <Wrap<&'a mut Wrapping<Src>, &'a mut Wrapping<Dst>> as TryTransmuteMutDst<'a>> |
| ::try_transmute_mut(src) |
| // SAFETY: By the preceding assert, `Dst` and `Wrapping<Dst>` have the |
| // same alignment. |
| .map(|dst| unsafe { crate::util::transmute_mut::<_, _, (_, (_, _))>(dst) }) |
| .map_err(|err| { |
| // SAFETY: By the preceding assert, `Src` and `Wrapping<Src>` have the |
| // same alignment. |
| ValidityError::new(unsafe { |
| crate::util::transmute_mut::<_, _, (_, (_, _))>(err.into_src()) |
| }) |
| }) |
| } |
| } |
| |
| pub trait TransmuteRefDst<'a> { |
| type Dst: ?Sized; |
| |
| #[must_use] |
| fn transmute_ref(self) -> &'a Self::Dst; |
| } |
| |
| impl<'a, Src: ?Sized, Dst: ?Sized> TransmuteRefDst<'a> for Wrap<&'a Src, &'a Dst> |
| where |
| Src: KnownLayout + IntoBytes + Immutable, |
| Dst: KnownLayout<PointerMetadata = usize> + FromBytes + Immutable, |
| { |
| type Dst = Dst; |
| |
| #[inline(always)] |
| fn transmute_ref(self) -> &'a Dst { |
| let ptr = Ptr::from_ref(self.0) |
| .recall_validity::<Initialized, _>() |
| .transmute_with::<Dst, Initialized, crate::layout::CastFrom<Dst>, (crate::pointer::BecauseMutationCompatible, _)>() |
| .recall_validity::<Valid, _>(); |
| |
| static_assert!(Src: ?Sized + KnownLayout, Dst: ?Sized + KnownLayout => { |
| Src::LAYOUT.align.get() >= Dst::LAYOUT.align.get() |
| }, "cannot transmute reference when destination type has higher alignment than source type"); |
| |
| // SAFETY: The preceding `static_assert!` ensures that |
| // `Src::LAYOUT.align >= Dst::LAYOUT.align`. Since `self` is |
| // validly-aligned for `Src`, it is also validly-aligned for `Dst`. |
| let ptr = unsafe { ptr.assume_alignment() }; |
| |
| ptr.as_ref() |
| } |
| } |
| |
| pub trait TransmuteMutDst<'a> { |
| type Dst: ?Sized; |
| #[must_use] |
| fn transmute_mut(self) -> &'a mut Self::Dst; |
| } |
| |
| impl<'a, Src: ?Sized, Dst: ?Sized> TransmuteMutDst<'a> for Wrap<&'a mut Src, &'a mut Dst> |
| where |
| Src: KnownLayout + FromBytes + IntoBytes, |
| Dst: KnownLayout<PointerMetadata = usize> + FromBytes + IntoBytes, |
| { |
| type Dst = Dst; |
| |
| #[inline(always)] |
| fn transmute_mut(self) -> &'a mut Dst { |
| let ptr = Ptr::from_mut(self.0) |
| .recall_validity::<Initialized, (_, (_, _))>() |
| .transmute_with::<Dst, Initialized, crate::layout::CastFrom<Dst>, _>() |
| .recall_validity::<Valid, (_, (_, _))>(); |
| |
| static_assert!(Src: ?Sized + KnownLayout, Dst: ?Sized + KnownLayout => { |
| Src::LAYOUT.align.get() >= Dst::LAYOUT.align.get() |
| }, "cannot transmute reference when destination type has higher alignment than source type"); |
| |
| // SAFETY: The preceding `static_assert!` ensures that |
| // `Src::LAYOUT.align >= Dst::LAYOUT.align`. Since `self` is |
| // validly-aligned for `Src`, it is also validly-aligned for `Dst`. |
| let ptr = unsafe { ptr.assume_alignment() }; |
| |
| ptr.as_mut() |
| } |
| } |
| |
| /// A function which emits a warning if its return value is not used. |
| #[must_use] |
| #[inline(always)] |
| pub const fn must_use<T>(t: T) -> T { |
| t |
| } |
| |
| // NOTE: We can't change this to a `pub use core as core_reexport` until [1] is |
| // fixed or we update to a semver-breaking version (as of this writing, 0.8.0) |
| // on the `main` branch. |
| // |
| // [1] https://github.com/obi1kenobi/cargo-semver-checks/issues/573 |
| pub mod core_reexport { |
| pub use core::*; |
| |
| pub mod mem { |
| pub use core::mem::*; |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use core::num::NonZeroUsize; |
| |
| use crate::util::testutil::*; |
| |
| #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)] |
| mod nightly { |
| use super::super::*; |
| use crate::util::testutil::*; |
| |
| // FIXME(#29), FIXME(https://github.com/rust-lang/rust/issues/69835): |
| // Remove this `cfg` when `size_of_val_raw` is stabilized. |
| #[allow(clippy::decimal_literal_representation)] |
| #[test] |
| fn test_trailing_field_offset() { |
| assert_eq!(mem::align_of::<Aligned64kAllocation>(), _64K); |
| |
| macro_rules! test { |
| (#[$cfg:meta] ($($ts:ty),* ; $trailing_field_ty:ty) => $expect:expr) => {{ |
| #[$cfg] |
| struct Test($(#[allow(dead_code)] $ts,)* #[allow(dead_code)] $trailing_field_ty); |
| assert_eq!(test!(@offset $($ts),* ; $trailing_field_ty), $expect); |
| }}; |
| (#[$cfg:meta] $(#[$cfgs:meta])* ($($ts:ty),* ; $trailing_field_ty:ty) => $expect:expr) => { |
| test!(#[$cfg] ($($ts),* ; $trailing_field_ty) => $expect); |
| test!($(#[$cfgs])* ($($ts),* ; $trailing_field_ty) => $expect); |
| }; |
| (@offset ; $_trailing:ty) => { trailing_field_offset!(Test, 0) }; |
| (@offset $_t:ty ; $_trailing:ty) => { trailing_field_offset!(Test, 1) }; |
| } |
| |
| test!(#[repr(C)] #[repr(transparent)] #[repr(packed)](; u8) => Some(0)); |
| test!(#[repr(C)] #[repr(transparent)] #[repr(packed)](; [u8]) => Some(0)); |
| test!(#[repr(C)] #[repr(C, packed)] (u8; u8) => Some(1)); |
| test!(#[repr(C)] (; AU64) => Some(0)); |
| test!(#[repr(C)] (; [AU64]) => Some(0)); |
| test!(#[repr(C)] (u8; AU64) => Some(8)); |
| test!(#[repr(C)] (u8; [AU64]) => Some(8)); |
| |
| #[derive( |
| Immutable, FromBytes, Eq, PartialEq, Ord, PartialOrd, Default, Debug, Copy, Clone, |
| )] |
| #[repr(C)] |
| pub(crate) struct Nested<T, U: ?Sized> { |
| _t: T, |
| _u: U, |
| } |
| |
| test!(#[repr(C)] (; Nested<u8, AU64>) => Some(0)); |
| test!(#[repr(C)] (; Nested<u8, [AU64]>) => Some(0)); |
| test!(#[repr(C)] (u8; Nested<u8, AU64>) => Some(8)); |
| test!(#[repr(C)] (u8; Nested<u8, [AU64]>) => Some(8)); |
| |
| // Test that `packed(N)` limits the offset of the trailing field. |
| test!(#[repr(C, packed( 1))] (u8; elain::Align< 2>) => Some( 1)); |
| test!(#[repr(C, packed( 2))] (u8; elain::Align< 4>) => Some( 2)); |
| test!(#[repr(C, packed( 4))] (u8; elain::Align< 8>) => Some( 4)); |
| test!(#[repr(C, packed( 8))] (u8; elain::Align< 16>) => Some( 8)); |
| test!(#[repr(C, packed( 16))] (u8; elain::Align< 32>) => Some( 16)); |
| test!(#[repr(C, packed( 32))] (u8; elain::Align< 64>) => Some( 32)); |
| test!(#[repr(C, packed( 64))] (u8; elain::Align< 128>) => Some( 64)); |
| test!(#[repr(C, packed( 128))] (u8; elain::Align< 256>) => Some( 128)); |
| test!(#[repr(C, packed( 256))] (u8; elain::Align< 512>) => Some( 256)); |
| test!(#[repr(C, packed( 512))] (u8; elain::Align< 1024>) => Some( 512)); |
| test!(#[repr(C, packed( 1024))] (u8; elain::Align< 2048>) => Some( 1024)); |
| test!(#[repr(C, packed( 2048))] (u8; elain::Align< 4096>) => Some( 2048)); |
| test!(#[repr(C, packed( 4096))] (u8; elain::Align< 8192>) => Some( 4096)); |
| test!(#[repr(C, packed( 8192))] (u8; elain::Align< 16384>) => Some( 8192)); |
| test!(#[repr(C, packed( 16384))] (u8; elain::Align< 32768>) => Some( 16384)); |
| test!(#[repr(C, packed( 32768))] (u8; elain::Align< 65536>) => Some( 32768)); |
| test!(#[repr(C, packed( 65536))] (u8; elain::Align< 131072>) => Some( 65536)); |
| /* Alignments above 65536 are not yet supported. |
| test!(#[repr(C, packed( 131072))] (u8; elain::Align< 262144>) => Some( 131072)); |
| test!(#[repr(C, packed( 262144))] (u8; elain::Align< 524288>) => Some( 262144)); |
| test!(#[repr(C, packed( 524288))] (u8; elain::Align< 1048576>) => Some( 524288)); |
| test!(#[repr(C, packed( 1048576))] (u8; elain::Align< 2097152>) => Some( 1048576)); |
| test!(#[repr(C, packed( 2097152))] (u8; elain::Align< 4194304>) => Some( 2097152)); |
| test!(#[repr(C, packed( 4194304))] (u8; elain::Align< 8388608>) => Some( 4194304)); |
| test!(#[repr(C, packed( 8388608))] (u8; elain::Align< 16777216>) => Some( 8388608)); |
| test!(#[repr(C, packed( 16777216))] (u8; elain::Align< 33554432>) => Some( 16777216)); |
| test!(#[repr(C, packed( 33554432))] (u8; elain::Align< 67108864>) => Some( 33554432)); |
| test!(#[repr(C, packed( 67108864))] (u8; elain::Align< 33554432>) => Some( 67108864)); |
| test!(#[repr(C, packed( 33554432))] (u8; elain::Align<134217728>) => Some( 33554432)); |
| test!(#[repr(C, packed(134217728))] (u8; elain::Align<268435456>) => Some(134217728)); |
| test!(#[repr(C, packed(268435456))] (u8; elain::Align<268435456>) => Some(268435456)); |
| */ |
| |
| // Test that `align(N)` does not limit the offset of the trailing field. |
| test!(#[repr(C, align( 1))] (u8; elain::Align< 2>) => Some( 2)); |
| test!(#[repr(C, align( 2))] (u8; elain::Align< 4>) => Some( 4)); |
| test!(#[repr(C, align( 4))] (u8; elain::Align< 8>) => Some( 8)); |
| test!(#[repr(C, align( 8))] (u8; elain::Align< 16>) => Some( 16)); |
| test!(#[repr(C, align( 16))] (u8; elain::Align< 32>) => Some( 32)); |
| test!(#[repr(C, align( 32))] (u8; elain::Align< 64>) => Some( 64)); |
| test!(#[repr(C, align( 64))] (u8; elain::Align< 128>) => Some( 128)); |
| test!(#[repr(C, align( 128))] (u8; elain::Align< 256>) => Some( 256)); |
| test!(#[repr(C, align( 256))] (u8; elain::Align< 512>) => Some( 512)); |
| test!(#[repr(C, align( 512))] (u8; elain::Align< 1024>) => Some( 1024)); |
| test!(#[repr(C, align( 1024))] (u8; elain::Align< 2048>) => Some( 2048)); |
| test!(#[repr(C, align( 2048))] (u8; elain::Align< 4096>) => Some( 4096)); |
| test!(#[repr(C, align( 4096))] (u8; elain::Align< 8192>) => Some( 8192)); |
| test!(#[repr(C, align( 8192))] (u8; elain::Align< 16384>) => Some( 16384)); |
| test!(#[repr(C, align( 16384))] (u8; elain::Align< 32768>) => Some( 32768)); |
| test!(#[repr(C, align( 32768))] (u8; elain::Align< 65536>) => Some( 65536)); |
| /* Alignments above 65536 are not yet supported. |
| test!(#[repr(C, align( 65536))] (u8; elain::Align< 131072>) => Some( 131072)); |
| test!(#[repr(C, align( 131072))] (u8; elain::Align< 262144>) => Some( 262144)); |
| test!(#[repr(C, align( 262144))] (u8; elain::Align< 524288>) => Some( 524288)); |
| test!(#[repr(C, align( 524288))] (u8; elain::Align< 1048576>) => Some( 1048576)); |
| test!(#[repr(C, align( 1048576))] (u8; elain::Align< 2097152>) => Some( 2097152)); |
| test!(#[repr(C, align( 2097152))] (u8; elain::Align< 4194304>) => Some( 4194304)); |
| test!(#[repr(C, align( 4194304))] (u8; elain::Align< 8388608>) => Some( 8388608)); |
| test!(#[repr(C, align( 8388608))] (u8; elain::Align< 16777216>) => Some( 16777216)); |
| test!(#[repr(C, align( 16777216))] (u8; elain::Align< 33554432>) => Some( 33554432)); |
| test!(#[repr(C, align( 33554432))] (u8; elain::Align< 67108864>) => Some( 67108864)); |
| test!(#[repr(C, align( 67108864))] (u8; elain::Align< 33554432>) => Some( 33554432)); |
| test!(#[repr(C, align( 33554432))] (u8; elain::Align<134217728>) => Some(134217728)); |
| test!(#[repr(C, align(134217728))] (u8; elain::Align<268435456>) => Some(268435456)); |
| */ |
| } |
| |
| // FIXME(#29), FIXME(https://github.com/rust-lang/rust/issues/69835): |
| // Remove this `cfg` when `size_of_val_raw` is stabilized. |
| #[allow(clippy::decimal_literal_representation)] |
| #[test] |
| fn test_align_of_dst() { |
| // Test that `align_of!` correctly computes the alignment of DSTs. |
| assert_eq!(align_of!([elain::Align<1>]), Some(1)); |
| assert_eq!(align_of!([elain::Align<2>]), Some(2)); |
| assert_eq!(align_of!([elain::Align<4>]), Some(4)); |
| assert_eq!(align_of!([elain::Align<8>]), Some(8)); |
| assert_eq!(align_of!([elain::Align<16>]), Some(16)); |
| assert_eq!(align_of!([elain::Align<32>]), Some(32)); |
| assert_eq!(align_of!([elain::Align<64>]), Some(64)); |
| assert_eq!(align_of!([elain::Align<128>]), Some(128)); |
| assert_eq!(align_of!([elain::Align<256>]), Some(256)); |
| assert_eq!(align_of!([elain::Align<512>]), Some(512)); |
| assert_eq!(align_of!([elain::Align<1024>]), Some(1024)); |
| assert_eq!(align_of!([elain::Align<2048>]), Some(2048)); |
| assert_eq!(align_of!([elain::Align<4096>]), Some(4096)); |
| assert_eq!(align_of!([elain::Align<8192>]), Some(8192)); |
| assert_eq!(align_of!([elain::Align<16384>]), Some(16384)); |
| assert_eq!(align_of!([elain::Align<32768>]), Some(32768)); |
| assert_eq!(align_of!([elain::Align<65536>]), Some(65536)); |
| /* Alignments above 65536 are not yet supported. |
| assert_eq!(align_of!([elain::Align<131072>]), Some(131072)); |
| assert_eq!(align_of!([elain::Align<262144>]), Some(262144)); |
| assert_eq!(align_of!([elain::Align<524288>]), Some(524288)); |
| assert_eq!(align_of!([elain::Align<1048576>]), Some(1048576)); |
| assert_eq!(align_of!([elain::Align<2097152>]), Some(2097152)); |
| assert_eq!(align_of!([elain::Align<4194304>]), Some(4194304)); |
| assert_eq!(align_of!([elain::Align<8388608>]), Some(8388608)); |
| assert_eq!(align_of!([elain::Align<16777216>]), Some(16777216)); |
| assert_eq!(align_of!([elain::Align<33554432>]), Some(33554432)); |
| assert_eq!(align_of!([elain::Align<67108864>]), Some(67108864)); |
| assert_eq!(align_of!([elain::Align<33554432>]), Some(33554432)); |
| assert_eq!(align_of!([elain::Align<134217728>]), Some(134217728)); |
| assert_eq!(align_of!([elain::Align<268435456>]), Some(268435456)); |
| */ |
| } |
| } |
| |
| #[test] |
| fn test_enum_casts() { |
| // Test that casting the variants of enums with signed integer reprs to |
| // unsigned integers obeys expected signed -> unsigned casting rules. |
| |
| #[repr(i8)] |
| enum ReprI8 { |
| MinusOne = -1, |
| Zero = 0, |
| Min = i8::MIN, |
| Max = i8::MAX, |
| } |
| |
| #[allow(clippy::as_conversions)] |
| let x = ReprI8::MinusOne as u8; |
| assert_eq!(x, u8::MAX); |
| |
| #[allow(clippy::as_conversions)] |
| let x = ReprI8::Zero as u8; |
| assert_eq!(x, 0); |
| |
| #[allow(clippy::as_conversions)] |
| let x = ReprI8::Min as u8; |
| assert_eq!(x, 128); |
| |
| #[allow(clippy::as_conversions)] |
| let x = ReprI8::Max as u8; |
| assert_eq!(x, 127); |
| } |
| |
| #[test] |
| fn test_struct_padding() { |
| // Test that, for each provided repr, `struct_padding!` reports the |
| // expected value. |
| macro_rules! test { |
| (#[$cfg:meta] ($($ts:ty),*) => $expect:expr) => {{ |
| #[$cfg] |
| #[allow(dead_code)] |
| struct Test($($ts),*); |
| assert_eq!(struct_padding!(Test, None::<NonZeroUsize>, None::<NonZeroUsize>, [$($ts),*]), $expect); |
| }}; |
| (#[$cfg:meta] $(#[$cfgs:meta])* ($($ts:ty),*) => $expect:expr) => { |
| test!(#[$cfg] ($($ts),*) => $expect); |
| test!($(#[$cfgs])* ($($ts),*) => $expect); |
| }; |
| } |
| |
| test!(#[repr(C)] #[repr(transparent)] #[repr(packed)] () => 0); |
| test!(#[repr(C)] #[repr(transparent)] #[repr(packed)] (u8) => 0); |
| test!(#[repr(C)] #[repr(transparent)] #[repr(packed)] (u8, ()) => 0); |
| test!(#[repr(C)] #[repr(packed)] (u8, u8) => 0); |
| |
| test!(#[repr(C)] (u8, AU64) => 7); |
| // Rust won't let you put `#[repr(packed)]` on a type which contains a |
| // `#[repr(align(n > 1))]` type (`AU64`), so we have to use `u64` here. |
| // It's not ideal, but it definitely has align > 1 on /some/ of our CI |
| // targets, and this isn't a particularly complex macro we're testing |
| // anyway. |
| test!(#[repr(packed)] (u8, u64) => 0); |
| } |
| |
| #[test] |
| fn test_repr_c_struct_padding() { |
| // Test that, for each provided repr, `repr_c_struct_padding!` reports |
| // the expected value. |
| macro_rules! test { |
| (($($ts:tt),*) => $expect:expr) => {{ |
| #[repr(C)] |
| #[allow(dead_code)] |
| struct Test($($ts),*); |
| assert_eq!(repr_c_struct_has_padding!(Test, None::<NonZeroUsize>, None::<NonZeroUsize>, [$($ts),*]), $expect); |
| }}; |
| } |
| |
| // Test static padding |
| test!(() => false); |
| test!(([u8]) => false); |
| test!((u8) => false); |
| test!((u8, [u8]) => false); |
| test!((u8, ()) => false); |
| test!((u8, (), [u8]) => false); |
| test!((u8, u8) => false); |
| test!((u8, u8, [u8]) => false); |
| |
| test!((u8, AU64) => true); |
| test!((u8, AU64, [u8]) => true); |
| |
| // Test dynamic padding |
| test!((AU64, [AU64]) => false); |
| test!((u8, [AU64]) => true); |
| |
| #[repr(align(4))] |
| struct AU32(#[allow(unused)] u32); |
| test!((AU64, [AU64]) => false); |
| test!((AU64, [AU32]) => true); |
| } |
| |
| #[test] |
| fn test_union_padding() { |
| // Test that, for each provided repr, `union_padding!` reports the |
| // expected value. |
| macro_rules! test { |
| (#[$cfg:meta] {$($fs:ident: $ts:ty),*} => $expect:expr) => {{ |
| #[$cfg] |
| #[allow(unused)] // fields are never read |
| union Test{ $($fs: $ts),* } |
| assert_eq!(union_padding!(Test, None::<NonZeroUsize>, None::<usize>, [$($ts),*]), $expect); |
| }}; |
| (#[$cfg:meta] $(#[$cfgs:meta])* {$($fs:ident: $ts:ty),*} => $expect:expr) => { |
| test!(#[$cfg] {$($fs: $ts),*} => $expect); |
| test!($(#[$cfgs])* {$($fs: $ts),*} => $expect); |
| }; |
| } |
| |
| test!(#[repr(C)] #[repr(packed)] {a: u8} => 0); |
| test!(#[repr(C)] #[repr(packed)] {a: u8, b: u8} => 0); |
| |
| // Rust won't let you put `#[repr(packed)]` on a type which contains a |
| // `#[repr(align(n > 1))]` type (`AU64`), so we have to use `u64` here. |
| // It's not ideal, but it definitely has align > 1 on /some/ of our CI |
| // targets, and this isn't a particularly complex macro we're testing |
| // anyway. |
| test!(#[repr(C)] #[repr(packed)] {a: u8, b: u64} => 7); |
| } |
| |
| #[test] |
| fn test_enum_padding() { |
| // Test that, for each provided repr, `enum_has_padding!` reports the |
| // expected value. |
| macro_rules! test { |
| (#[repr($disc:ident $(, $c:ident)?)] { $($vs:ident ($($ts:ty),*),)* } => $expect:expr) => { |
| test!(@case #[repr($disc $(, $c)?)] { $($vs ($($ts),*),)* } => $expect); |
| }; |
| (#[repr($disc:ident $(, $c:ident)?)] #[$cfg:meta] $(#[$cfgs:meta])* { $($vs:ident ($($ts:ty),*),)* } => $expect:expr) => { |
| test!(@case #[repr($disc $(, $c)?)] #[$cfg] { $($vs ($($ts),*),)* } => $expect); |
| test!(#[repr($disc $(, $c)?)] $(#[$cfgs])* { $($vs ($($ts),*),)* } => $expect); |
| }; |
| (@case #[repr($disc:ident $(, $c:ident)?)] $(#[$cfg:meta])? { $($vs:ident ($($ts:ty),*),)* } => $expect:expr) => {{ |
| #[repr($disc $(, $c)?)] |
| $(#[$cfg])? |
| #[allow(unused)] // variants and fields are never used |
| enum Test { |
| $($vs ($($ts),*),)* |
| } |
| assert_eq!( |
| enum_padding!(Test, None::<NonZeroUsize>, None::<NonZeroUsize>, $disc, $([$($ts),*]),*), |
| $expect |
| ); |
| }}; |
| } |
| |
| #[allow(unused)] |
| #[repr(align(2))] |
| struct U16(u16); |
| |
| #[allow(unused)] |
| #[repr(align(4))] |
| struct U32(u32); |
| |
| test!(#[repr(u8)] #[repr(C)] { |
| A(u8), |
| } => 0); |
| test!(#[repr(u16)] #[repr(C)] { |
| A(u8, u8), |
| B(U16), |
| } => 0); |
| test!(#[repr(u32)] #[repr(C)] { |
| A(u8, u8, u8, u8), |
| B(U16, u8, u8), |
| C(u8, u8, U16), |
| D(U16, U16), |
| E(U32), |
| } => 0); |
| |
| // `repr(int)` can pack the discriminant more efficiently |
| test!(#[repr(u8)] { |
| A(u8, U16), |
| } => 0); |
| test!(#[repr(u8)] { |
| A(u8, U16, U32), |
| } => 0); |
| |
| // `repr(C)` cannot |
| test!(#[repr(u8, C)] { |
| A(u8, U16), |
| } => 2); |
| test!(#[repr(u8, C)] { |
| A(u8, u8, u8, U32), |
| } => 4); |
| |
| // And field ordering can always cause problems |
| test!(#[repr(u8)] #[repr(C)] { |
| A(U16, u8), |
| } => 2); |
| test!(#[repr(u8)] #[repr(C)] { |
| A(U32, u8, u8, u8), |
| } => 4); |
| } |
| } |
