some unknown generating when default value is set in c

here is my input structure.

  typedef struct {
      const char *base_path;            /**< Mounting point. */
      const char *partition_label;      /**< Label of partition to use. */
      uint8_t format_if_mount_failed:1; /**< Format the file system if it fails to mount. */
      uint8_t dont_mount:1;             /**< Don't attempt to mount or format. Overrides format_if_mount_failed */
  } esp_vfs_littlefs_conf_t;

Bindgen Invocation

    let builder = bindgen::Builder::default()
            .use_core()
            .layout_tests(false)
            .rustfmt_bindings(false)
            .derive_default(true)
            .clang_arg("-D__bindgen")
            // Include directories provided by the build system
            // should be first on the search path (before sysroot includes),
            // or else libc's <dirent.h> does not correctly override sysroot's <dirent.h>
            .clang_args(&self.clang_args)
            .clang_args(sysroot_args)
            .clang_args(&["-x", if cpp { "c++" } else { "c" }])
            .clang_args(cpp_args);

Actual Results

#[doc = "Configuration structure for esp_vfs_littlefs_register."]
#[repr(C)]
#[derive(Debug, Copy, Clone)]
pub struct esp_vfs_littlefs_conf_t {
    #[doc = "< Mounting point."]
    pub base_path: *const c_types::c_char,
    #[doc = "< Label of partition to use."]
    pub partition_label: *const c_types::c_char,
    pub _bitfield_align_1: [u8; 0],
    pub _bitfield_1: __BindgenBitfieldUnit<[u8; 1usize]>,
    pub __bindgen_padding_0: [u8; 3usize],
}

Expected Results

  #[doc = "Configuration structure for esp_vfs_littlefs_register."]
  #[repr(C)]
  #[derive(Debug, Copy, Clone)]
  pub struct esp_vfs_littlefs_conf_t {
    #[doc = "< Mounting point."]
    pub base_path: *const c_types::c_char,
    #[doc = "< Label of partition to use."]
    pub partition_label: *const c_types::c_char,
    #[doc = "< Format the file system if it fails to mount."]
    pub format_if_mount_failed: u8,
    #[doc = "< Don't attempt to mount or format. Overrides format_if_mount_failed"]
    pub dont_mount: u8,
}

Reproduce the generated bindings from the esp_vfs_littlefs_conf_t input and the shown bindgen::Builder invocation, then trace how the two C bitfields become _bitfield_1 and padding. Done means the generated Rust struct exposes format_if_mount_failed and dont_mount as separate u8 fields with their documentation preserved.