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Diffstat (limited to 'src/doc/reference.md')
| -rw-r--r-- | src/doc/reference.md | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/src/doc/reference.md b/src/doc/reference.md index c34a136a68e..cf9504736eb 100644 --- a/src/doc/reference.md +++ b/src/doc/reference.md @@ -2066,26 +2066,28 @@ fn macos_only() { } // This function is only included when either foo or bar is defined -#[cfg(foo)] -#[cfg(bar)] +#[cfg(any(foo, bar))] fn needs_foo_or_bar() { // ... } // This function is only included when compiling for a unixish OS with a 32-bit // architecture -#[cfg(unix, target_word_size = "32")] +#[cfg(all(unix, target_word_size = "32"))] fn on_32bit_unix() { // ... } + +// This function is only included when foo is not defined +#[cfg(not(foo))] +fn needs_not_foo() { + // ... +} ``` This illustrates some conditional compilation can be achieved using the -`#[cfg(...)]` attribute. Note that `#[cfg(foo, bar)]` is a condition that needs -both `foo` and `bar` to be defined while `#[cfg(foo)] #[cfg(bar)]` only needs -one of `foo` and `bar` to be defined (this resembles in the disjunctive normal -form). Additionally, one can reverse a condition by enclosing it in a -`not(...)`, like e. g. `#[cfg(not(target_os = "win32"))]`. +`#[cfg(...)]` attribute. `any`, `all` and `not` can be used to assemble +arbitrarily complex configurations through nesting. The following configurations must be defined by the implementation: |