Preventing the Derivation of Default

By default, Default is not derived.

bindgen will attempt to derive/impl the Default traits on a best-effort basis. Sometimes, we need customize the implementation of Default for certain types. In these cases, the nodefault annotation can be used to prevent bindgen from automatically deriving the Default trait for a type.

Library

• bindgen::Builder::derive_default
• bindgen::Builder::no_default

Command Line

• --with-derive-default
• --no-default <regex>

Annotations

/**
 * We need to specify some preset values as the Default of Header.
 *
 * for example:
 *
 * <div rustbindgen nodefault></div>
 */
struct Header {
    unsigned int magic;
    unsigned char data[252];
};

...

Customize Implements

// Include the generated bindings.
include!(concat!(env!("OUT_DIR"), "/bindings.rs"));

impl Default for Header {
    fn default() -> Self {
        Self {
            magic: 0x10203040u32,
            data: [0; 252usize],
        }
    }
}