Attributes.md

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Attributes

Compiletime configuration for code

// sinle attributes
#attribute
statement

// multiple attribute, order doesnt matter
#[attribute1, attribute2, ...]
statement

// same as
#attribute1
#[attribute2, ...]
statement

Cfg attribute

if condition is false remove statement (after ast parsing, before linking)

#cfg(cond)
statement

Cfg_if macro

Allows to get condition in code

if #cfg_if(cond) { .. }
let is_cond = #cfg_if(cond);

Condition syntax

cond -> any(cond [, cond]*)
cond -> all(cond [, cond]*)
cond -> not(cond)

cond -> name
cond -> name = value

Available names

linux, macos, windows

target_os = "macos"
target_arch = "aarch64"
pointer_width = "64"

Expand attribute

#expand {
    statement
    ...
}

is equivalent to (don't create new local context, expanded before linking)

statement
...

Multiline attributes

Expand propagate attributes to every statement, so it can be used to apply attribute to multiple lines of code

#[attribute] #expand {
    statement
    ...
    statement
}

// same as

#[attribute]
statement
...
#[attribute]
statement