Vendor things

third-party/vendor/zerocopy-derive/tests/struct_as_bytes.rs

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+// Copyright 2019 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.
+
+#![allow(warnings)]
+
+mod util;
+
+use std::{marker::PhantomData, mem::ManuallyDrop, option::IntoIter};
+
+use {static_assertions::assert_impl_all, zerocopy::AsBytes};
+
+use self::util::AU16;
+
+// A struct is `AsBytes` if:
+// - all fields are `AsBytes`
+// - `repr(C)` or `repr(transparent)` and
+//   - no padding (size of struct equals sum of size of field types)
+// - `repr(packed)`
+
+#[derive(AsBytes)]
+#[repr(C)]
+struct CZst;
+
+assert_impl_all!(CZst: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(C)]
+struct C {
+    a: u8,
+    b: u8,
+    c: AU16,
+}
+
+assert_impl_all!(C: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(transparent)]
+struct Transparent {
+    a: u8,
+    b: CZst,
+}
+
+assert_impl_all!(Transparent: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(transparent)]
+struct TransparentGeneric<T: ?Sized> {
+    a: CZst,
+    b: T,
+}
+
+assert_impl_all!(TransparentGeneric<u64>: AsBytes);
+assert_impl_all!(TransparentGeneric<[u64]>: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(C, packed)]
+struct CZstPacked;
+
+assert_impl_all!(CZstPacked: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(C, packed)]
+struct CPacked {
+    a: u8,
+    // NOTE: The `u16` type is not guaranteed to have alignment 2, although it
+    // does on many platforms. However, to fix this would require a custom type
+    // with a `#[repr(align(2))]` attribute, and `#[repr(packed)]` types are not
+    // allowed to transitively contain `#[repr(align(...))]` types. Thus, we
+    // have no choice but to use `u16` here. Luckily, these tests run in CI on
+    // platforms on which `u16` has alignment 2, so this isn't that big of a
+    // deal.
+    b: u16,
+}
+
+assert_impl_all!(CPacked: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(C, packed(2))]
+// The same caveats as for CPacked apply - we're assuming u64 is at least
+// 4-byte aligned by default. Without packed(2), this should fail, as there
+// would be padding between a/b assuming u64 is 4+ byte aligned.
+struct CPacked2 {
+    a: u16,
+    b: u64,
+}
+
+assert_impl_all!(CPacked2: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(C, packed)]
+struct CPackedGeneric<T, U: ?Sized> {
+    t: T,
+    // Unsized types stored in `repr(packed)` structs must not be dropped
+    // because dropping them in-place might be unsound depending on the
+    // alignment of the outer struct. Sized types can be dropped by first being
+    // moved to an aligned stack variable, but this isn't possible with unsized
+    // types.
+    u: ManuallyDrop<U>,
+}
+
+assert_impl_all!(CPackedGeneric<u8, AU16>: AsBytes);
+assert_impl_all!(CPackedGeneric<u8, [AU16]>: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(packed)]
+struct Packed {
+    a: u8,
+    // NOTE: The `u16` type is not guaranteed to have alignment 2, although it
+    // does on many platforms. However, to fix this would require a custom type
+    // with a `#[repr(align(2))]` attribute, and `#[repr(packed)]` types are not
+    // allowed to transitively contain `#[repr(align(...))]` types. Thus, we
+    // have no choice but to use `u16` here. Luckily, these tests run in CI on
+    // platforms on which `u16` has alignment 2, so this isn't that big of a
+    // deal.
+    b: u16,
+}
+
+assert_impl_all!(Packed: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(packed)]
+struct PackedGeneric<T, U: ?Sized> {
+    t: T,
+    // Unsized types stored in `repr(packed)` structs must not be dropped
+    // because dropping them in-place might be unsound depending on the
+    // alignment of the outer struct. Sized types can be dropped by first being
+    // moved to an aligned stack variable, but this isn't possible with unsized
+    // types.
+    u: ManuallyDrop<U>,
+}
+
+assert_impl_all!(PackedGeneric<u8, AU16>: AsBytes);
+assert_impl_all!(PackedGeneric<u8, [AU16]>: AsBytes);
+
+#[derive(AsBytes)]
+#[repr(transparent)]
+struct Unsized {
+    a: [u8],
+}
+
+assert_impl_all!(Unsized: AsBytes);
+
+// Deriving `AsBytes` should work if the struct has bounded parameters.
+
+#[derive(AsBytes)]
+#[repr(transparent)]
+struct WithParams<'a: 'b, 'b: 'a, const N: usize, T: 'a + 'b + AsBytes>(
+    [T; N],
+    PhantomData<&'a &'b ()>,
+)
+where
+    'a: 'b,
+    'b: 'a,
+    T: 'a + 'b + AsBytes;
+
+assert_impl_all!(WithParams<'static, 'static, 42, u8>: AsBytes);