Private padding and alignment fields + missing Defaut/Clone/Copy implementations

Input C/C++ Header

// libfuse fetched using pkg_config
// Generating bindings for 'fuse.h'

Bindgen Invocation

bindgen::builder()
        // Add clang flags
        .clang_args(compile_flags)
        // Derive Debug, Copy and Default
        .derive_default(true)
        .derive_copy(true)
        .derive_debug(true)
        // Add CargoCallbacks so build.rs is rerun on header changes
        .parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))
        // Whitelist "fuse_*" symbols and blocklist everything else
        .allowlist_recursively(false)
        .allowlist_type("[fF][uU][sS][eE].*")
        .allowlist_function("[fF][uU][sS][eE].*")
        .allowlist_var("[fF][uU][sS][eE].*")
        .blocklist_type("fuse_log_func_t")
        .blocklist_function("fuse_set_log_func");
        // Let's generate!
        .header(header_path)
        .generate()
        .unwrap_or_else(|_| panic!("Failed to generate {} bindings", header))

Actual Results

// Extract of the generated bindings file

pub struct stat {
    pub st_dev: ::dev_t,
    pub st_ino: ::ino_t,
    pub st_nlink: ::nlink_t,
    pub st_mode: ::mode_t,
    pub st_uid: ::uid_t,
    pub st_gid: ::gid_t,
    __pad0: ::c_int,
    pub st_rdev: ::dev_t,
    pub st_size: ::off_t,
    pub st_blksize: ::blksize_t,
    pub st_blocks: ::blkcnt_t,
    pub st_atime: ::time_t,
    pub st_atime_nsec: i64,
    pub st_mtime: ::time_t,
    pub st_mtime_nsec: i64,
    pub st_ctime: ::time_t,
    pub st_ctime_nsec: i64,
    __unused: [i64; 3],
}

Expected Results

• Both __pad0 and __unused should be marked as pub
• Derives for Default, Clone and Copy are missing

The same problems occur on many other structs.

Reproduce the issue against libfuse's fuse.h using the shown bindgen builder options, then trace how allowlisted C/C++ structs receive field visibility and derives. Done means padding fields such as __pad0 and __unused are public and affected structs receive Default, Clone, and Copy derives.