epoll event constants should be declared as u32

[tremon015]

The current implementation declares all EPOLL* event constants as c_int, but this isn't very useful given that the accompanying field in struct epoll_event is declared as u32.

pub const EPOLLIN: c_int = 0x1;

pub struct epoll_event {
    pub events: u32,
    pub u64: u64,
}

This makes using these constants very unergonomic:

error[E0308]: mismatched types
   --> src/bin/hld.rs:256:46
    |
256 |          if event.events & EPOLLIN == EPOLLIN {
    |                            ^^^^^^^ expected `u32`, found `i32`

error[E0277]: no implementation for `u32 & i32`
   --> src/bin/hld.rs:256:44
    |
256 |          if event.events & EPOLLIN == EPOLLIN {
    |                          ^ no implementation for `u32 & i32`
    |

The first thing every user of these constants will do is redefine them as u32. Can this be done in the libc crate itself? This applies to all EPOLL* event descriptors and input flags, but not the EPOLL_CTL_* operation constants.

[tremon015]

Taking a look at the kernel source itself, all values are of type __poll_t: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/eventpoll.h

And the __poll_t type is

typedef unsigned __bitwise __poll_t;

from https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/types.h#n59

[devnexen]

Feel free to open a PR :)

[tremon015]

Well, I can create a pull request with the straightforward s/// easily. However, I'm completely unsure of the further ramifications of this change. So I would really appreciate it if other people approach this request with due care :p