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<h1 id="rust-新版解读--172--feature启用提示"><a class="header" href="#rust-新版解读--172--feature启用提示">Rust 新版解读 | 1.72 | feature启用提示</a></h1>
<blockquote>
<p>Rust 1.72 官方 release doc: <a href="https://blog.rust-lang.org/2023/08/24/Rust-1.72.0.html">Announcing Rust 1.72.0 | Rust Blog</a></p>
</blockquote>
<p>通过 <a href="https://www.rust-lang.org/tools/install">rustup</a> 安装的同学可以使用以下命令升级到 1.72 版本:</p>
<pre><code class="language-shell">$ rustup update stable
</code></pre>
<h2 id="警告可能有用的-cfg-禁用项"><a class="header" href="#警告可能有用的-cfg-禁用项">警告可能有用的 <code>cfg</code> 禁用项</a></h2>
<p>一直以来都支持的通过 <code>cfg</code> 条件编译部分代码,例如在开启特定 feature 时的函数,或者针对特定平台的逻辑。之前编译器会直接无视掉这些代码,现在会记录这些符号名称和对应的 <code>cfg</code> 条件,因此可以警告你正在调用一个特定 feature 下的函数,需要启用 feature</p>
<pre><code class="language-text"> Compiling my-project v0.1.0 (/tmp/my-project)
error[E0432]: unresolved import `rustix::io_uring`
--&gt; src/main.rs:1:5
|
1 | use rustix::io_uring;
| ^^^^^^^^^^^^^^^^ no `io_uring` in the root
|
note: found an item that was configured out
--&gt; /home/username/.cargo/registry/src/index.crates.io-6f17d22bba15001f/rustix-0.38.8/src/lib.rs:213:9
|
213 | pub mod io_uring;
| ^^^^^^^^
= note: the item is gated behind the `io_uring` feature
For more information about this error, try `rustc --explain E0432`.
error: could not compile `my-project` (bin &quot;my-project&quot;) due to previous error
</code></pre>
<h2 id="不受限制的常量计算时间"><a class="header" href="#不受限制的常量计算时间">不受限制的常量计算时间</a></h2>
<p>之前为了避免用户自定义的常量在编译期间进行估算时陷入死循环或占用无限制的时间Rust 之前会限制用作常量计算的语句数目。然而一些特殊的有创造性的 Rust 代码还是会超过这个限制,进而产生编译错误;更糟糕的情况是,是否达到限制的是会随着用户调用库的不同而变化的。</p>
<p>现在,可以在编译时执行无限制的常量计算。而为了避免长时间编译没有反馈,编译器会在编译时代码运行一段时间后发出一条消息,并在每次翻倍的一段时间后重复该消息。默认情况下,编译器还将在捕获无限循环的大量步骤后报错提示 <code>const_eval_long_run</code> ,但可以用 <code>allow(const_eval_long_run)</code> 允许特别长的常量计算。</p>
<h2 id="clippy-lints-上升到-rustc"><a class="header" href="#clippy-lints-上升到-rustc">Clippy lints 上升到 rustc</a></h2>
<p>几个原本由 Clippy 提供的 lints提升到 rustc 里:</p>
<ul>
<li><a href="https://rust-lang.github.io/rust-clippy/rust-1.71.0/index.html#undropped_manually_drops"><code>clippy::undropped_manually_drops</code></a> =&gt; <a href="https://doc.rust-lang.org/1.72.0/rustc/lints/listing/deny-by-default.html#undropped-manually-drops"><code>undropped-manually-drops</code></a> (deny)
<ul>
<li>无作用的 <code>ManullyDrop</code></li>
</ul>
</li>
<li><a href="https://rust-lang.github.io/rust-clippy/rust-1.71.0/index.html#invalid_utf8_in_unchecked"><code>clippy::invalid_utf8_in_unchecked</code></a> =&gt; <a href="https://doc.rust-lang.org/1.72.0/rustc/lints/listing/deny-by-default.html#invalid-from-utf8-unchecked"><code>invalid_from_utf8_unchecked</code></a> (deny) 或 <a href="https://doc.rust-lang.org/1.72.0/rustc/lints/listing/warn-by-default.html#invalid-from-utf8"><code>invalid_from_utf8</code></a> (warn)
<ul>
<li>检查调用 <code>std::str::from_utf8_unchecked</code><code>std::str::from_utf8_unchecked_mut</code> 转换不合法的 UTF-8 字面量,这会违反了 safety 前提,导致未定义行为</li>
<li>检查 <code>std::str::from_utf8</code><code>std::str::from_utf8_mut</code> 转换不合法的 UTF-8 字面量,这会永远返回错误。</li>
</ul>
</li>
<li><a href="https://rust-lang.github.io/rust-clippy/rust-1.71.0/index.html#cmp_nan"><code>clippy::cmp_nan</code></a> =&gt; <a href="https://doc.rust-lang.org/1.72.0/rustc/lints/listing/warn-by-default.html#invalid-nan-comparisons"><code>invalid_nan_comparisons</code></a> (warn)
<ul>
<li>检查使用 <code>f32::NAN</code> 或者 <code>f64::NAN</code> 参与比较,<code>NAN</code> 在比较时无任何意义,即使与自己比较也是无意义行为,建议使用 <code>is_nan()</code> 方法</li>
</ul>
</li>
<li><a href="https://rust-lang.github.io/rust-clippy/rust-1.71.0/index.html#cast_ref_to_mut"><code>clippy::cast_ref_to_mut</code></a> =&gt; <a href="https://doc.rust-lang.org/1.72.0/rustc/lints/listing/allowed-by-default.html#invalid-reference-casting"><code>invalid_reference_casting</code></a> (allow)
<ul>
<li>检查不使用内部可变性的从 <code>&amp;T</code><code>&amp;mut T</code> 的转换这会导致未定义行为。当前这个lint本身还有些问题所以是 <code>allow</code> 级别,预计会在 1.73 版本修正后变为默认 <code>deny</code> </li>
</ul>
</li>
</ul>
<h2 id="未来对-windows-的支持"><a class="header" href="#未来对-windows-的支持">未来对 Windows 的支持</a></h2>
<p>未来的 release 版本里会放弃对 win10 以前的系统的官方支持Rust 1.75 将成为最后一个支持 windows 7,8,8.1的版本2024 年 2 月起的 rust 1.76 将仅支持 win10 及后续版本 target : tier-1 )。详情见提案 <a href="https://github.com/rust-lang/compiler-team/issues/651">MCP 651</a></p>
<h2 id="others"><a class="header" href="#others">Others</a></h2>
<p>其它更新细节和稳定的API列表参考<a href="https://blog.rust-lang.org/2023/08/24/Rust-1.72.0.html#stabilized-apis">原Blog</a></p>
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