emitted enum type changes type depending on usage

[metaspace]

Hi!

We have observed the following behavior when generating bindings for the Linux kernel:

test_a.h:

enum foo {
  BAR,
  BAZ,
};

bindgen test_a.h:

/* automatically generated by rust-bindgen 0.71.1 */
pub const foo_BAR: foo = 0;
pub const foo_BAZ: foo = 1;
pub type foo = ::std::os::raw::c_uint;

test_b.h

extern enum foo do_something(void);

enum foo {
  BAR,
  BAZ,
};

bindgen test_b.h:

/* automatically generated by rust-bindgen 0.71.1 */

unsafe extern "C" {
    pub fn do_something() -> foo;
}
pub const foo_BAR: foo = 0;
pub const foo_BAZ: foo = 1;
pub type foo = i32;

The type of foo has changed.

This leads to some confusion, because depending on kernel configuration, include files might change ordering. We currently fix this by using as casts when we use constants that are affected:

/// Restart policy for timers.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
#[repr(u32)]
pub enum HrTimerRestart {
    /// Timer should not be restarted.
    #[allow(clippy::unnecessary_cast)]
    NoRestart = bindings::hrtimer_restart_HRTIMER_NORESTART as u32,
    /// Timer should be restarted.
    #[allow(clippy::unnecessary_cast)]
    Restart = bindings::hrtimer_restart_HRTIMER_RESTART as u32,
}

Is there anything we can do to prevent this behavior?

[ojeda]

I opened #3179 for this.

[metaspace]

Duplicate of #3179