227 lines
7.5 KiB
Rust
227 lines
7.5 KiB
Rust
// Copyright (c) 2020 Gilad Naaman, Ralf Jung
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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/// `addr_of!`, or just ref-then-cast when that is not available.
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#[cfg(raw_ref_macros)]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__addr_of {
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($path:expr) => {{
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$crate::__priv::ptr::addr_of!($path)
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}};
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}
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#[cfg(not(raw_ref_macros))]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__addr_of {
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($path:expr) => {{
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// This is UB because we create an intermediate reference to uninitialized memory.
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// Nothing we can do about that without `addr_of!` though.
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&$path as *const _
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}};
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}
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/// Deref-coercion protection macro.
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///
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/// Prevents complilation if the specified field name is not a part of the
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/// struct definition.
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///
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/// ```compile_fail
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/// use memoffset::_memoffset__field_check;
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///
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/// struct Foo {
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/// foo: i32,
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/// }
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///
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/// type BoxedFoo = Box<Foo>;
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///
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/// _memoffset__field_check!(BoxedFoo, foo);
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/// ```
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#[cfg(allow_clippy)]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__field_check {
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($type:path, $field:tt) => {
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// Make sure the field actually exists. This line ensures that a
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// compile-time error is generated if $field is accessed through a
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// Deref impl.
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#[allow(clippy::unneeded_field_pattern)]
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let $type { $field: _, .. };
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};
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}
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#[cfg(not(allow_clippy))]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__field_check {
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($type:path, $field:tt) => {
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// Make sure the field actually exists. This line ensures that a
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// compile-time error is generated if $field is accessed through a
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// Deref impl.
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let $type { $field: _, .. };
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};
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}
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/// Deref-coercion protection macro.
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///
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/// Prevents complilation if the specified type is not a tuple.
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///
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/// ```compile_fail
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/// use memoffset::_memoffset__field_check_tuple;
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///
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/// _memoffset__field_check_tuple!(i32, 0);
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/// ```
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#[cfg(allow_clippy)]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__field_check_tuple {
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($type:ty, $field:tt) => {
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// Make sure the type argument is a tuple
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#[allow(clippy::unneeded_wildcard_pattern)]
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let (_, ..): $type;
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};
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}
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#[cfg(not(allow_clippy))]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__field_check_tuple {
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($type:ty, $field:tt) => {
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// Make sure the type argument is a tuple
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let (_, ..): $type;
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};
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}
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/// Deref-coercion protection macro for unions.
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/// Unfortunately accepts single-field structs as well, which is not ideal,
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/// but ultimately pretty harmless.
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///
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/// ```compile_fail
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/// use memoffset::_memoffset__field_check_union;
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///
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/// union Foo {
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/// variant_a: i32,
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/// }
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///
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/// type BoxedFoo = Box<Foo>;
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///
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/// _memoffset__field_check_union!(BoxedFoo, variant_a);
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/// ```
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#[cfg(allow_clippy)]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__field_check_union {
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($type:path, $field:tt) => {
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// Make sure the field actually exists. This line ensures that a
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// compile-time error is generated if $field is accessed through a
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// Deref impl.
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#[allow(clippy::unneeded_wildcard_pattern)]
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// rustc1.19 requires unsafe here for the pattern; not needed in newer versions
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#[allow(unused_unsafe)]
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unsafe {
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let $type { $field: _ };
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}
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};
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}
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#[cfg(not(allow_clippy))]
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#[macro_export]
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#[doc(hidden)]
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macro_rules! _memoffset__field_check_union {
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($type:path, $field:tt) => {
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// Make sure the field actually exists. This line ensures that a
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// compile-time error is generated if $field is accessed through a
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// Deref impl.
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// rustc1.19 requires unsafe here for the pattern; not needed in newer versions
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#[allow(unused_unsafe)]
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unsafe {
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let $type { $field: _ };
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}
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};
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}
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/// Computes a const raw pointer to the given field of the given base pointer
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/// to the given parent type.
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///
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/// The `base` pointer *must not* be dangling, but it *may* point to
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/// uninitialized memory.
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#[macro_export(local_inner_macros)]
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macro_rules! raw_field {
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($base:expr, $parent:path, $field:tt) => {{
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_memoffset__field_check!($parent, $field);
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let base = $base; // evaluate $base outside the `unsafe` block
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// Get the field address.
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// Crucially, we know that this will not trigger a deref coercion because
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// of the field check we did above.
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#[allow(unused_unsafe)] // for when the macro is used in an unsafe block
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unsafe {
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_memoffset__addr_of!((*(base as *const $parent)).$field)
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}
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}};
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}
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/// Computes a const raw pointer to the given field of the given base pointer
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/// to the given parent tuple typle.
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///
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/// The `base` pointer *must not* be dangling, but it *may* point to
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/// uninitialized memory.
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#[cfg(tuple_ty)]
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#[macro_export(local_inner_macros)]
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macro_rules! raw_field_tuple {
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($base:expr, $parent:ty, $field:tt) => {{
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_memoffset__field_check_tuple!($parent, $field);
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let base = $base; // evaluate $base outside the `unsafe` block
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// Get the field address.
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// Crucially, we know that this will not trigger a deref coercion because
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// of the field check we did above.
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#[allow(unused_unsafe)] // for when the macro is used in an unsafe block
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unsafe {
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_memoffset__addr_of!((*(base as *const $parent)).$field)
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}
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}};
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}
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/// Computes a const raw pointer to the given field of the given base pointer
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/// to the given parent tuple typle.
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///
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/// The `base` pointer *must not* be dangling, but it *may* point to
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/// uninitialized memory.
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///
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/// ## Note
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/// This macro is the same as `raw_field`, except for a different Deref-coercion check that
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/// supports unions.
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/// Due to macro_rules limitations, this check will accept structs with a single field as well as unions.
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/// This is not a stable guarantee, and future versions of this crate might fail
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/// on any use of this macro with a struct, without a semver bump.
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#[macro_export(local_inner_macros)]
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macro_rules! raw_field_union {
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($base:expr, $parent:path, $field:tt) => {{
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_memoffset__field_check_union!($parent, $field);
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let base = $base; // evaluate $base outside the `unsafe` block
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// Get the field address.
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// Crucially, we know that this will not trigger a deref coercion because
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// of the field check we did above.
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#[allow(unused_unsafe)] // for when the macro is used in an unsafe block
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unsafe {
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_memoffset__addr_of!((*(base as *const $parent)).$field)
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}
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}};
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}
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