| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/cfg-if-1.0.0/src/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../cfg_if/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../cfg_if/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">//! A macro for defining `#[cfg]` if-else statements. |
| //! |
| //! The macro provided by this crate, `cfg_if`, is similar to the `if/elif` C |
| //! preprocessor macro by allowing definition of a cascade of `#[cfg]` cases, |
| //! emitting the implementation which matches first. |
| //! |
| //! This allows you to conveniently provide a long list `#[cfg]`'d blocks of code |
| //! without having to rewrite each clause multiple times. |
| //! |
| //! # Example |
| //! |
| //! ``` |
| //! cfg_if::cfg_if! { |
| //! if #[cfg(unix)] { |
| //! fn foo() { /* unix specific functionality */ } |
| //! } else if #[cfg(target_pointer_width = "32")] { |
| //! fn foo() { /* non-unix, 32-bit functionality */ } |
| //! } else { |
| //! fn foo() { /* fallback implementation */ } |
| //! } |
| //! } |
| //! |
| //! # fn main() {} |
| //! ``` |
| |
| </span><span class="attribute">#![no_std] |
| #![doc(html_root_url = <span class="string">"https://docs.rs/cfg-if"</span>)] |
| #![deny(missing_docs)] |
| #![cfg_attr(test, deny(warnings))] |
| |
| </span><span class="doccomment">/// The main macro provided by this crate. See crate documentation for more |
| /// information. |
| </span><span class="attribute">#[macro_export] |
| </span><span class="macro">macro_rules! </span>cfg_if { |
| <span class="comment">// match if/else chains with a final `else` |
| </span>($( |
| <span class="kw">if </span><span class="attribute">#[cfg(<span class="macro-nonterminal">$meta</span>:meta)] </span>{ $(<span class="macro-nonterminal">$tokens</span>:tt)* } |
| ) <span class="kw">else </span>* <span class="kw">else </span>{ |
| $(<span class="macro-nonterminal">$tokens2</span>:tt)* |
| }) => { |
| <span class="macro-nonterminal">$</span><span class="macro">crate::cfg_if! </span>{ |
| @<span class="macro-nonterminal">__items |
| </span>() ; |
| $( ( (<span class="macro-nonterminal">$meta</span>) ($(<span class="macro-nonterminal">$tokens</span>)<span class="kw-2">*</span>) ), )* |
| ( () ($(<span class="macro-nonterminal">$tokens2</span>)<span class="kw-2">*</span>) ), |
| } |
| }; |
| |
| <span class="comment">// match if/else chains lacking a final `else` |
| </span>( |
| <span class="kw">if </span><span class="attribute">#[cfg(<span class="macro-nonterminal">$i_met</span>:meta)] </span>{ $(<span class="macro-nonterminal">$i_tokens</span>:tt)* } |
| $( |
| <span class="kw">else if </span><span class="attribute">#[cfg(<span class="macro-nonterminal">$e_met</span>:meta)] </span>{ $(<span class="macro-nonterminal">$e_tokens</span>:tt)* } |
| )* |
| ) => { |
| <span class="macro-nonterminal">$</span><span class="macro">crate::cfg_if! </span>{ |
| @<span class="macro-nonterminal">__items |
| </span>() ; |
| ( (<span class="macro-nonterminal">$i_met</span>) ($(<span class="macro-nonterminal">$i_tokens</span>)<span class="kw-2">*</span>) ), |
| $( ( (<span class="macro-nonterminal">$e_met</span>) ($(<span class="macro-nonterminal">$e_tokens</span>)<span class="kw-2">*</span>) ), )* |
| ( () () ), |
| } |
| }; |
| |
| <span class="comment">// Internal and recursive macro to emit all the items |
| // |
| // Collects all the negated cfgs in a list at the beginning and after the |
| // semicolon is all the remaining items |
| </span>(@__items ($(<span class="macro-nonterminal">$not</span>:meta,)<span class="kw-2">*</span>) ; ) => {}; |
| (@__items ($(<span class="macro-nonterminal">$not</span>:meta,)<span class="kw-2">*</span>) ; ( ($(<span class="macro-nonterminal">$m</span>:meta),<span class="kw-2">*</span>) ($(<span class="macro-nonterminal">$tokens</span>:tt)<span class="kw-2">*</span>) ), $(<span class="macro-nonterminal">$rest</span>:tt)<span class="kw-2">*</span>) => { |
| <span class="comment">// Emit all items within one block, applying an appropriate #[cfg]. The |
| // #[cfg] will require all `$m` matchers specified and must also negate |
| // all previous matchers. |
| </span><span class="attribute">#[cfg(all($(<span class="macro-nonterminal">$m</span>,)* not(any($(<span class="macro-nonterminal">$not</span>),<span class="kw-2">*</span>))))] </span><span class="macro-nonterminal">$</span><span class="macro">crate::cfg_if! </span>{ @<span class="macro-nonterminal">__identity </span>$(<span class="macro-nonterminal">$tokens</span>)* } |
| |
| <span class="comment">// Recurse to emit all other items in `$rest`, and when we do so add all |
| // our `$m` matchers to the list of `$not` matchers as future emissions |
| // will have to negate everything we just matched as well. |
| </span><span class="macro-nonterminal">$</span><span class="macro">crate::cfg_if! </span>{ @<span class="macro-nonterminal">__items </span>($(<span class="macro-nonterminal">$not</span>,)* $(<span class="macro-nonterminal">$m</span>,)<span class="kw-2">*</span>) ; $(<span class="macro-nonterminal">$rest</span>)* } |
| }; |
| |
| <span class="comment">// Internal macro to make __apply work out right for different match types, |
| // because of how macros matching/expand stuff. |
| </span>(@__identity $(<span class="macro-nonterminal">$tokens</span>:tt)<span class="kw-2">*</span>) => { |
| $(<span class="macro-nonterminal">$tokens</span>)* |
| }; |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="macro">cfg_if! </span>{ |
| <span class="kw">if </span><span class="attribute">#[cfg(test)] </span>{ |
| <span class="kw">use </span>core::option::Option <span class="kw">as </span>Option2; |
| <span class="kw">fn </span>works1() -> Option2<u32> { <span class="prelude-val">Some</span>(<span class="number">1</span>) } |
| } <span class="kw">else </span>{ |
| <span class="kw">fn </span>works1() -> <span class="prelude-ty">Option</span><u32> { <span class="prelude-val">None </span>} |
| } |
| } |
| |
| <span class="macro">cfg_if! </span>{ |
| <span class="kw">if </span><span class="attribute">#[cfg(foo)] </span>{ |
| <span class="kw">fn </span>works2() -> bool { <span class="bool-val">false </span>} |
| } <span class="kw">else if </span><span class="attribute">#[cfg(test)] </span>{ |
| <span class="kw">fn </span>works2() -> bool { <span class="bool-val">true </span>} |
| } <span class="kw">else </span>{ |
| <span class="kw">fn </span>works2() -> bool { <span class="bool-val">false </span>} |
| } |
| } |
| |
| <span class="macro">cfg_if! </span>{ |
| <span class="kw">if </span><span class="attribute">#[cfg(foo)] </span>{ |
| <span class="kw">fn </span>works3() -> bool { <span class="bool-val">false </span>} |
| } <span class="kw">else </span>{ |
| <span class="kw">fn </span>works3() -> bool { <span class="bool-val">true </span>} |
| } |
| } |
| |
| <span class="macro">cfg_if! </span>{ |
| <span class="kw">if </span><span class="attribute">#[cfg(test)] </span>{ |
| <span class="kw">use </span>core::option::Option <span class="kw">as </span>Option3; |
| <span class="kw">fn </span>works4() -> Option3<u32> { <span class="prelude-val">Some</span>(<span class="number">1</span>) } |
| } |
| } |
| |
| <span class="macro">cfg_if! </span>{ |
| <span class="kw">if </span><span class="attribute">#[cfg(foo)] </span>{ |
| <span class="kw">fn </span>works5() -> bool { <span class="bool-val">false </span>} |
| } <span class="kw">else if </span><span class="attribute">#[cfg(test)] </span>{ |
| <span class="kw">fn </span>works5() -> bool { <span class="bool-val">true </span>} |
| } |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>it_works() { |
| <span class="macro">assert!</span>(works1().is_some()); |
| <span class="macro">assert!</span>(works2()); |
| <span class="macro">assert!</span>(works3()); |
| <span class="macro">assert!</span>(works4().is_some()); |
| <span class="macro">assert!</span>(works5()); |
| } |
| |
| <span class="attribute">#[test] |
| #[allow(clippy::assertions_on_constants)] |
| </span><span class="kw">fn </span>test_usage_within_a_function() { |
| <span class="macro">cfg_if! </span>{<span class="kw">if </span><span class="attribute">#[cfg(debug_assertions)] </span>{ |
| <span class="comment">// we want to put more than one thing here to make sure that they |
| // all get configured properly. |
| </span><span class="macro">assert!</span>(<span class="macro">cfg!</span>(debug_assertions)); |
| <span class="macro">assert_eq!</span>(<span class="number">4</span>, <span class="number">2</span>+<span class="number">2</span>); |
| } <span class="kw">else </span>{ |
| <span class="macro">assert!</span>(works1().is_some()); |
| <span class="macro">assert_eq!</span>(<span class="number">10</span>, <span class="number">5</span>+<span class="number">5</span>); |
| }} |
| } |
| |
| <span class="kw">trait </span>Trait { |
| <span class="kw">fn </span>blah(<span class="kw-2">&</span><span class="self">self</span>); |
| } |
| |
| <span class="attribute">#[allow(dead_code)] |
| </span><span class="kw">struct </span>Struct; |
| |
| <span class="kw">impl </span>Trait <span class="kw">for </span>Struct { |
| <span class="macro">cfg_if! </span>{ |
| <span class="kw">if </span><span class="attribute">#[cfg(feature = <span class="string">"blah"</span>)] </span>{ |
| <span class="kw">fn </span>blah(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="macro">unimplemented!</span>(); |
| } |
| } <span class="kw">else </span>{ |
| <span class="kw">fn </span>blah(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="macro">unimplemented!</span>(); |
| } |
| } |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="cfg_if" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
