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// Copyright (c) 2020 Gilad Naaman, Ralf Jung
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
/// `raw_const!`, or just ref-then-cast when that is not available.
#[cfg(feature = "unstable_raw")]
#[macro_export]
#[doc(hidden)]
macro_rules! _memoffset__raw_const {
($path:expr) => {{
$crate::ptr::raw_const!($path)
}};
}
#[cfg(not(feature = "unstable_raw"))]
#[macro_export]
#[doc(hidden)]
macro_rules! _memoffset__raw_const {
($path:expr) => {{
// This is UB because we create an intermediate reference to uninitialized memory.
// Nothing we can do about that without `raw_const!` though.
&$path as *const _
}};
}
/// Deref-coercion protection macro.
#[cfg(allow_clippy)]
#[macro_export]
#[doc(hidden)]
macro_rules! _memoffset__field_check {
($type:path, $field:tt) => {
// Make sure the field actually exists. This line ensures that a
// compile-time error is generated if $field is accessed through a
// Deref impl.
#[allow(clippy::unneeded_field_pattern)]
let $type { $field: _, .. };
};
}
#[cfg(not(allow_clippy))]
#[macro_export]
#[doc(hidden)]
macro_rules! _memoffset__field_check {
($type:path, $field:tt) => {
// Make sure the field actually exists. This line ensures that a
// compile-time error is generated if $field is accessed through a
// Deref impl.
let $type { $field: _, .. };
};
}
/// Computes a const raw pointer to the given field of the given base pointer
/// to the given parent type.
///
/// The `base` pointer *must not* be dangling, but it *may* point to
/// uninitialized memory.
#[macro_export(local_inner_macros)]
macro_rules! raw_field {
($base:expr, $parent:path, $field:tt) => {{
_memoffset__field_check!($parent, $field);
// Get the field address.
// Crucially, we know that this will not trigger a deref coercion because
// of the field check we did above.
#[allow(unused_unsafe)] // for when the macro is used in an unsafe block
unsafe {
_memoffset__raw_const!((*($base as *const $parent)).$field)
}
}};
}
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