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| </pre><pre class="rust"><code><span class="doccomment">/// Asserts that types are equal in size. |
| /// |
| /// When performing operations such as pointer casts or dealing with [`usize`] |
| /// versus [`u64`] versus [`u32`], the size of your types matter. That is where |
| /// this macro comes into play. |
| /// |
| /// # Alternatives |
| /// |
| /// There also exists [`assert_eq_size_val`](macro.assert_eq_size_val.html) and |
| /// [`assert_eq_size_ptr`](macro.assert_eq_size_ptr.html). Instead of specifying |
| /// types to compare, values' sizes can be directly compared against each other. |
| /// |
| /// # Examples |
| /// |
| /// These three types, despite being very different, all have the same size: |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_eq_size!([u8; 4], (u16, u16), u32); |
| /// ``` |
| /// |
| /// The following example fails to compile because `u32` has 4 times the size of |
| /// `u8`: |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// assert_eq_size!(u32, u8); |
| /// ``` |
| /// |
| /// [`usize`]: https://doc.rust-lang.org/std/primitive.usize.html |
| /// [`u64`]: https://doc.rust-lang.org/std/primitive.u64.html |
| /// [`u32`]: https://doc.rust-lang.org/std/primitive.u32.html |
| </span><span class="attribute">#[macro_export] |
| </span><span class="macro">macro_rules! </span>assert_eq_size { |
| (<span class="macro-nonterminal">$x</span>:ty, $(<span class="macro-nonterminal">$xs</span>:ty),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="kw">const _</span>: <span class="kw">fn</span>() = || { |
| $(<span class="kw">let _ </span>= <span class="macro-nonterminal">$crate::_core::mem::transmute</span>::<<span class="macro-nonterminal">$x</span>, <span class="macro-nonterminal">$xs</span>>;)+ |
| }; |
| }; |
| } |
| |
| <span class="doccomment">/// Asserts that values pointed to are equal in size. |
| /// |
| /// # Examples |
| /// |
| /// This especially is useful for when coercing pointers between different types |
| /// and ensuring the underlying values are the same size. |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; fn main() {} |
| /// fn operation(x: &(u32, u32), y: &[u16; 4]) { |
| /// assert_eq_size_ptr!(x, y); |
| /// // ... |
| /// } |
| /// ``` |
| /// |
| /// The following example fails to compile because byte arrays of different |
| /// lengths have different sizes: |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; |
| /// # fn main() { |
| /// static BYTES: &[u8; 4] = &[ |
| /// /* ... */ |
| /// # 0; 4 |
| /// ]; |
| /// |
| /// static TABLE: &[u8; 16] = &[ |
| /// /* ... */ |
| /// # 0; 16 |
| /// ]; |
| /// |
| /// assert_eq_size_ptr!(BYTES, TABLE); |
| /// ``` |
| </span><span class="attribute">#[macro_export] |
| </span><span class="macro">macro_rules! </span>assert_eq_size_ptr { |
| (<span class="macro-nonterminal">$x</span>:expr, $(<span class="macro-nonterminal">$xs</span>:expr),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="attribute">#[allow(unknown_lints, unsafe_code, forget_copy, useless_transmute)] |
| </span><span class="kw">let _ </span>= || <span class="kw">unsafe </span>{ |
| <span class="kw">use </span><span class="macro-nonterminal">$crate::_core</span>::{mem, ptr}; |
| <span class="kw">let </span><span class="kw-2">mut </span>copy = ptr::read(<span class="macro-nonterminal">$x</span>); |
| $(ptr::write(<span class="kw-2">&mut </span>copy, mem::transmute(ptr::read(<span class="macro-nonterminal">$xs</span>)));)+ |
| mem::forget(copy); |
| }; |
| } |
| } |
| |
| <span class="doccomment">/// Asserts that values are equal in size. |
| /// |
| /// This macro doesn't consume its arguments and thus works for |
| /// non-[`Clone`]able values. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # #[macro_use] extern crate static_assertions; |
| /// # fn main() { |
| /// struct Byte(u8); |
| /// |
| /// let x = 10u8; |
| /// let y = Byte(42); // Works for non-cloneable types |
| /// |
| /// assert_eq_size_val!(x, y); |
| /// assert_eq_size_val!(x, y, 0u8); |
| /// # } |
| /// ``` |
| /// |
| /// Even though both values are 0, they are of types with different sizes: |
| /// |
| /// ```compile_fail |
| /// # #[macro_use] extern crate static_assertions; |
| /// # fn main() { |
| /// assert_eq_size_val!(0u8, 0u32); |
| /// # } |
| /// ``` |
| /// |
| /// [`Clone`]: https://doc.rust-lang.org/std/clone/trait.Clone.html |
| </span><span class="attribute">#[macro_export(local_inner_macros)] |
| </span><span class="macro">macro_rules! </span>assert_eq_size_val { |
| (<span class="macro-nonterminal">$x</span>:expr, $(<span class="macro-nonterminal">$xs</span>:expr),+ $(,)<span class="question-mark">?</span>) => { |
| <span class="macro">assert_eq_size_ptr!</span>(<span class="kw-2">&</span><span class="macro-nonterminal">$x</span>, $(<span class="kw-2">&</span><span class="macro-nonterminal">$xs</span>),+); |
| } |
| } |
| </code></pre></div> |
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