Preventing the Derivation of Default

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

Library

• bindgen::Builder::no_default

Command Line

• --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],
        }
    }
}