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< p > The macro provided by this crate, < code > cfg_if< / code > , is similar to the < code > if/elif< / code > C
preprocessor macro by allowing definition of a cascade of < code > #[cfg]< / code > cases,
emitting the implementation which matches first.< / p >
< p > This allows you to conveniently provide a long list < code > #[cfg]< / code > ’
without having to rewrite each clause multiple times.< / p >
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< h2 id = "example" > < a class = "doc-anchor" href = "#example" > §< / a > Example< / h2 >
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< div class = "example-wrap" > < pre class = "rust rust-example-rendered" > < code > < span class = "macro" > cfg_if::cfg_if!< / span > {
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< span class = "kw" > if < / span > < span class = "attr" > #[cfg(unix)] < / span > {
< span class = "kw" > fn < / span > foo() { < span class = "comment" > /* unix specific functionality */ < / span > }
} < span class = "kw" > else if < / span > < span class = "attr" > #[cfg(target_pointer_width = < span class = "string" > "32"< / span > )] < / span > {
< span class = "kw" > fn < / span > foo() { < span class = "comment" > /* non-unix, 32-bit functionality */ < / span > }
} < span class = "kw" > else < / span > {
< span class = "kw" > fn < / span > foo() { < span class = "comment" > /* fallback implementation */ < / span > }
}
}
< / code > < / pre > < / div >
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< / div > < / details > < h2 id = "macros" class = "section-header" > Macros< a href = "#macros" class = "anchor" > §< / a > < / h2 > < ul class = "item-table" > < li > < div class = "item-name" > < a class = "macro" href = "macro.cfg_if.html" title = "macro cfg_if::cfg_if" > cfg_if< / a > < / div > < div class = "desc docblock-short" > The main macro provided by this crate. See crate documentation for more
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information.< / div > < / li > < / ul > < / section > < / div > < / main > < / body > < / html >
