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Replace std::mem::uninitialized with MaybeUninit (#1027)

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* Replace `std::mem::uninitialized` with `MaybeUninit`

* Avoid undefined behavior when using `MaybeUninit`

* Restore unused `PointerState` fields as internally public

* Zero-initialize some struct values in Xlib FFI calls

* Reform usage of `MaybeUninit` in Xlib FFI

* Prefer safe zero-initialization using `Default`, when possible
* Zero-initialize integers and floats using `0` or `0.0`
* Use `MaybeUninit::uninit` for large byte buffers and union types
* Use `MaybeUninit::uninit` when the resulting value is ignored
This commit is contained in:
Murarth 2019-07-11 09:34:32 -07:00 • committed by Hal Gentz
parent 17b8310517
commit 7daf146801
9 changed files with 186 additions and 126 deletions
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51
src/platform_impl/linux/x11/window.rs
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@ -1,4 +1,14 @@
use std::{cmp, collections::HashSet, env, ffi::CString, mem, os::raw::*, path::Path, sync::Arc};
use std::{
cmp,
collections::HashSet,
env,
ffi::CString,
mem::{self, MaybeUninit},
os::raw::*,
path::Path,
ptr, slice,
sync::Arc,
};
use libc;
use parking_lot::Mutex;
@ -410,11 +420,11 @@ impl UnownedWindow {
unsafe {
// XSetInputFocus generates an error if the window is not visible, so we wait
// until we receive VisibilityNotify.
let mut event = mem::uninitialized();
let mut event = MaybeUninit::uninit();
(xconn.xlib.XIfEvent)(
// This will flush the request buffer IF it blocks.
xconn.display,
&mut event as *mut ffi::XEvent,
event.as_mut_ptr(),
Some(visibility_predicate),
window.xwindow as _,
);
@ -449,19 +459,22 @@ impl UnownedWindow {
let pid_atom = unsafe { self.xconn.get_atom_unchecked(b"_NET_WM_PID\0") };
let client_machine_atom = unsafe { self.xconn.get_atom_unchecked(b"WM_CLIENT_MACHINE\0") };
unsafe {
let (hostname, hostname_length) = {
// 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;
let mut hostname: [c_char; MAXHOSTNAMELEN] = mem::uninitialized();
let status = libc::gethostname(hostname.as_mut_ptr(), hostname.len());
if status != 0 {
return None;
}
hostname[MAXHOSTNAMELEN - 1] = '\0' as c_char; // a little extra safety
let hostname_length = libc::strlen(hostname.as_ptr());
(hostname, hostname_length as usize)
};
// 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 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);
self.xconn
.change_property(
self.xwindow,
@ -1134,13 +1147,13 @@ impl UnownedWindow {
let cursor = unsafe {
// We don't care about this color, since it only fills bytes
// in the pixmap which are not 0 in the mask.
let dummy_color: ffi::XColor = mem::uninitialized();
let mut dummy_color = MaybeUninit::uninit();
let cursor = (self.xconn.xlib.XCreatePixmapCursor)(
self.xconn.display,
pixmap,
pixmap,
&dummy_color as *const _ as *mut _,
&dummy_color as *const _ as *mut _,
dummy_color.as_mut_ptr(),
dummy_color.as_mut_ptr(),
0,
0,
);