Replace libc with rustix in some modules

Unfortunately this isn't a total removal, for two reasons:

- We still need "libc" for the Xlib XIM implementation, for locales.
- BSD requires libc to check for main-threadedness.

First one we can likely resolve in the near future, not so sure about
the second one without using some weird pthreads trick.

Cargo.toml

@@ -36,7 +36,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 
 [features]
 default = ["x11", "wayland", "wayland-dlopen", "wayland-csd-adwaita"]
-x11 = ["x11-dl", "bytemuck", "rustix", "percent-encoding", "xkbcommon-dl/x11", "x11rb"]
+x11 = ["x11-dl", "bytemuck", "percent-encoding", "xkbcommon-dl/x11", "x11rb"]
 wayland = ["wayland-client", "wayland-backend", "wayland-protocols", "sctk", "fnv", "memmap2"]
 wayland-dlopen = ["wayland-backend/dlopen"]
 wayland-csd-adwaita = ["sctk-adwaita", "sctk-adwaita/ab_glyph"]
@@ -123,7 +123,7 @@ wayland-client = { version = "0.30.0", optional = true }
 wayland-backend = { version = "0.1.0", default_features = false, features = ["client_system"], optional = true }
 wayland-protocols = { version = "0.30.0", features = [ "staging"], optional = true }
 calloop = "0.10.5"
-rustix = { version = "0.38.4", default-features = false, features = ["std", "system", "process"], optional = true }
+rustix = { version = "0.38.4", default-features = false, features = ["std", "system", "thread", "process"] }
 x11-dl = { version = "2.18.5", optional = true }
 x11rb = { version = "0.12.0", default-features = false, features = ["allow-unsafe-code", "dl-libxcb", "xinput", "xkb"], optional = true }
 xkbcommon-dl = "0.4.0"

src/platform_impl/linux/mod.rs

@@ -935,9 +935,7 @@ fn sticky_exit_callback<T, F>(
 
 #[cfg(target_os = "linux")]
 fn is_main_thread() -> bool {
-    use libc::{c_long, getpid, syscall, SYS_gettid};
-
-    unsafe { syscall(SYS_gettid) == getpid() as c_long }
+    rustix::thread::gettid() == rustix::process::getpid()
 }
 
 #[cfg(any(target_os = "dragonfly", target_os = "freebsd", target_os = "openbsd"))]

src/platform_impl/linux/x11/event_processor.rs

@@ -1,6 +1,11 @@
-use std::{cell::RefCell, collections::HashMap, rc::Rc, slice, sync::Arc};
-
-use libc::{c_char, c_int, c_long, c_ulong};
+use std::{
+    cell::RefCell,
+    collections::HashMap,
+    os::raw::{c_char, c_int, c_long, c_ulong},
+    rc::Rc,
+    slice,
+    sync::Arc,
+};
 
 use x11rb::protocol::xproto::{self, ConnectionExt as _};
 use x11rb::x11_utils::Serialize;

src/platform_impl/linux/x11/mod.rs

@@ -230,7 +230,7 @@ impl<T: 'static> EventLoop<T> {
                 xconn.display,
                 &mut xinput_major_ver,
                 &mut xinput_minor_ver,
-            ) != ffi::Success as libc::c_int
+            ) != ffi::Success as std::os::raw::c_int
             {
                 panic!(
                     "X server has XInput extension {xinput_major_ver}.{xinput_minor_ver} but does not support XInput2",

src/platform_impl/linux/x11/window.rs

@@ -1,14 +1,12 @@
 use std::{
     cmp, env,
     ffi::CString,
-    mem::{replace, MaybeUninit},
+    mem::replace,
     os::raw::*,
     path::Path,
-    ptr, slice,
     sync::{Arc, Mutex, MutexGuard},
 };
 
-use libc;
 use raw_window_handle::{RawDisplayHandle, RawWindowHandle, XlibDisplayHandle, XlibWindowHandle};
 use x11rb::{
     connection::Connection,
@@ -542,22 +540,10 @@ impl UnownedWindow {
         let atoms = self.xconn.atoms();
         let pid_atom = atoms[_NET_WM_PID];
         let client_machine_atom = atoms[WM_CLIENT_MACHINE];
-        unsafe {
-            // 64 would suffice for Linux, but 256 will be enough everywhere (as per SUSv2). For instance, this is
-            // the limit defined by OpenBSD.
-            const MAXHOSTNAMELEN: usize = 256;
-            // `assume_init` is safe here because the array consists of `MaybeUninit` values,
-            // which do not require initialization.
-            let mut buffer: [MaybeUninit<c_char>; MAXHOSTNAMELEN] =
-                MaybeUninit::uninit().assume_init();
-            let status = libc::gethostname(buffer.as_mut_ptr() as *mut c_char, buffer.len());
-            if status != 0 {
-                return Ok(None);
-            }
-            ptr::write(buffer[MAXHOSTNAMELEN - 1].as_mut_ptr() as *mut u8, b'\0'); // a little extra safety
-            let hostname_length = libc::strlen(buffer.as_ptr() as *const c_char);
 
-            let hostname = slice::from_raw_parts(buffer.as_ptr() as *const c_char, hostname_length);
+        // Get the hostname and the PID.
+        let uname = rustix::system::uname();
+        let pid = rustix::process::getpid();
 
         self.xconn
             .change_property(
@@ -565,7 +551,7 @@ impl UnownedWindow {
                 pid_atom,
                 xproto::Atom::from(xproto::AtomEnum::CARDINAL),
                 xproto::PropMode::REPLACE,
-                    &[libc::getpid() as util::Cardinal],
+                &[pid.as_raw_nonzero().get() as util::Cardinal],
             )?
             .ignore_error();
         let flusher = self.xconn.change_property(
@@ -573,11 +559,10 @@ impl UnownedWindow {
             client_machine_atom,
             xproto::Atom::from(xproto::AtomEnum::STRING),
             xproto::PropMode::REPLACE,
-                &hostname[0..hostname_length],
+            uname.nodename().to_bytes(),
         );
         flusher.map(Some)
     }
-    }
 
     fn set_window_types(
         &self,

src/platform_impl/linux/x11/xdisplay.rs

@@ -46,7 +46,7 @@ unsafe impl Send for XConnection {}
 unsafe impl Sync for XConnection {}
 
 pub type XErrorHandler =
-    Option<unsafe extern "C" fn(*mut ffi::Display, *mut ffi::XErrorEvent) -> libc::c_int>;
+    Option<unsafe extern "C" fn(*mut ffi::Display, *mut ffi::XErrorEvent) -> std::os::raw::c_int>;
 
 impl XConnection {
     pub fn new(error_handler: XErrorHandler) -> Result<XConnection, XNotSupported> {