Function rsconf::declare_cfg

pub fn declare_cfg(name: &str, enabled: bool)

Informs the compiler of a cfg with the name name, enabled if enabled is set to true.

Enables conditional compilation of code behind #[cfg(name)] or with if cfg!(name) (without quotes around name).

As of rust 1.80, using #[attr(cfg = "foo")] when said feature is not enabled results in a compile-time warning as rust tries to protect against inadvertent use of invalid/unknown features. Unlike enable_cfg(), this function informs rustc about the presence of a feature called name even when it’s not enabled, so that #[attr(not(cfg = "foo"))] does not cause cause warnings when the foo cfg is not enabled.

See also: declare_cfg_values().