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std::comm: use Unsafe to avoid U.B. & -> &mut transmutes.

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This commit is contained in:
Huon Wilson 2014-05-04 23:35:48 +10:00
parent 781ac3e777
commit edd9bad4ee
1 changed files with 49 additions and 34 deletions
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83
src/libstd/comm/mod.rs
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@ -271,7 +271,6 @@
// And now that you've seen all the races that I found and attempted to fix,
// here's the code for you to find some more!
use cast;
use cell::Cell;
use clone::Clone;
use iter::Iterator;
@ -284,6 +283,7 @@ use result::{Ok, Err, Result};
use rt::local::Local;
use rt::task::{Task, BlockedTask};
use sync::arc::UnsafeArc;
use ty::Unsafe;
pub use comm::select::{Select, Handle};
@ -318,11 +318,6 @@ mod stream;
mod shared;
mod sync;
// FIXME #13933: Remove/justify all `&T` to `&mut T` transmutes
unsafe fn transmute_mut<'a,T>(x: &'a T) -> &'a mut T {
cast::transmute::<&_, &mut _>(x)
}
// Use a power of 2 to allow LLVM to optimize to something that's not a
// division, this is hit pretty regularly.
static RESCHED_FREQ: int = 256;
@ -330,7 +325,7 @@ static RESCHED_FREQ: int = 256;
/// The receiving-half of Rust's channel type. This half can only be owned by
/// one task
pub struct Receiver<T> {
inner: Flavor<T>,
inner: Unsafe<Flavor<T>>,
receives: Cell<uint>,
// can't share in an arc
marker: marker::NoShare,
@ -346,7 +341,7 @@ pub struct Messages<'a, T> {
/// The sending-half of Rust's asynchronous channel type. This half can only be
/// owned by one task, but it can be cloned to send to other tasks.
pub struct Sender<T> {
inner: Flavor<T>,
inner: Unsafe<Flavor<T>>,
sends: Cell<uint>,
// can't share in an arc
marker: marker::NoShare,
@ -395,6 +390,27 @@ enum Flavor<T> {
Sync(UnsafeArc<sync::Packet<T>>),
}
#[doc(hidden)]
trait UnsafeFlavor<T> {
fn inner_unsafe<'a>(&'a self) -> &'a Unsafe<Flavor<T>>;
unsafe fn mut_inner<'a>(&'a self) -> &'a mut Flavor<T> {
&mut *self.inner_unsafe().get()
}
unsafe fn inner<'a>(&'a self) -> &'a Flavor<T> {
&*self.inner_unsafe().get()
}
}
impl<T> UnsafeFlavor<T> for Sender<T> {
fn inner_unsafe<'a>(&'a self) -> &'a Unsafe<Flavor<T>> {
&self.inner
}
}
impl<T> UnsafeFlavor<T> for Receiver<T> {
fn inner_unsafe<'a>(&'a self) -> &'a Unsafe<Flavor<T>> {
&self.inner
}
}
/// Creates a new asynchronous channel, returning the sender/receiver halves.
///
/// All data sent on the sender will become available on the receiver, and no
@ -463,7 +479,7 @@ pub fn sync_channel<T: Send>(bound: uint) -> (SyncSender<T>, Receiver<T>) {
impl<T: Send> Sender<T> {
fn new(inner: Flavor<T>) -> Sender<T> {
Sender { inner: inner, sends: Cell::new(0), marker: marker::NoShare }
Sender { inner: Unsafe::new(inner), sends: Cell::new(0), marker: marker::NoShare }
}
/// Sends a value along this channel to be received by the corresponding
@ -537,7 +553,7 @@ impl<T: Send> Sender<T> {
task.map(|t| t.maybe_yield());
}
let (new_inner, ret) = match self.inner {
let (new_inner, ret) = match *unsafe { self.inner() } {
Oneshot(ref p) => {
let p = p.get();
unsafe {
@ -569,8 +585,8 @@ impl<T: Send> Sender<T> {
};
unsafe {
let mut tmp = Sender::new(Stream(new_inner));
mem::swap(&mut transmute_mut(self).inner, &mut tmp.inner);
let tmp = Sender::new(Stream(new_inner));
mem::swap(self.mut_inner(), tmp.mut_inner());
}
return ret;
}
@ -578,7 +594,7 @@ impl<T: Send> Sender<T> {
impl<T: Send> Clone for Sender<T> {
fn clone(&self) -> Sender<T> {
let (packet, sleeper) = match self.inner {
let (packet, sleeper) = match *unsafe { self.inner() } {
Oneshot(ref p) => {
let (a, b) = UnsafeArc::new2(shared::Packet::new());
match unsafe { (*p.get()).upgrade(Receiver::new(Shared(a))) } {
@ -603,8 +619,8 @@ impl<T: Send> Clone for Sender<T> {
unsafe {
(*packet.get()).inherit_blocker(sleeper);
let mut tmp = Sender::new(Shared(packet.clone()));
mem::swap(&mut transmute_mut(self).inner, &mut tmp.inner);
let tmp = Sender::new(Shared(packet.clone()));
mem::swap(self.mut_inner(), tmp.mut_inner());
}
Sender::new(Shared(packet))
}
@ -613,7 +629,7 @@ impl<T: Send> Clone for Sender<T> {
#[unsafe_destructor]
impl<T: Send> Drop for Sender<T> {
fn drop(&mut self) {
match self.inner {
match *unsafe { self.mut_inner() } {
Oneshot(ref mut p) => unsafe { (*p.get()).drop_chan(); },
Stream(ref mut p) => unsafe { (*p.get()).drop_chan(); },
Shared(ref mut p) => unsafe { (*p.get()).drop_chan(); },
@ -710,7 +726,7 @@ impl<T: Send> Drop for SyncSender<T> {
impl<T: Send> Receiver<T> {
fn new(inner: Flavor<T>) -> Receiver<T> {
Receiver { inner: inner, receives: Cell::new(0), marker: marker::NoShare }
Receiver { inner: Unsafe::new(inner), receives: Cell::new(0), marker: marker::NoShare }
}
/// Blocks waiting for a value on this receiver
@ -762,7 +778,7 @@ impl<T: Send> Receiver<T> {
}
loop {
let mut new_port = match self.inner {
let new_port = match *unsafe { self.inner() } {
Oneshot(ref p) => {
match unsafe { (*p.get()).try_recv() } {
Ok(t) => return Ok(t),
@ -795,8 +811,8 @@ impl<T: Send> Receiver<T> {
}
};
unsafe {
mem::swap(&mut transmute_mut(self).inner,
&mut new_port.inner);
mem::swap(self.mut_inner(),
new_port.mut_inner());
}
}
}
@ -815,7 +831,7 @@ impl<T: Send> Receiver<T> {
/// the value found on the receiver is returned.
pub fn recv_opt(&self) -> Result<T, ()> {
loop {
let mut new_port = match self.inner {
let new_port = match *unsafe { self.inner() } {
Oneshot(ref p) => {
match unsafe { (*p.get()).recv() } {
Ok(t) => return Ok(t),
@ -842,8 +858,7 @@ impl<T: Send> Receiver<T> {
Sync(ref p) => return unsafe { (*p.get()).recv() }
};
unsafe {
mem::swap(&mut transmute_mut(self).inner,
&mut new_port.inner);
mem::swap(self.mut_inner(), new_port.mut_inner());
}
}
}
@ -858,7 +873,7 @@ impl<T: Send> Receiver<T> {
impl<T: Send> select::Packet for Receiver<T> {
fn can_recv(&self) -> bool {
loop {
let mut new_port = match self.inner {
let new_port = match *unsafe { self.inner() } {
Oneshot(ref p) => {
match unsafe { (*p.get()).can_recv() } {
Ok(ret) => return ret,
@ -879,15 +894,15 @@ impl<T: Send> select::Packet for Receiver<T> {
}
};
unsafe {
mem::swap(&mut transmute_mut(self).inner,
&mut new_port.inner);
mem::swap(self.mut_inner(),
new_port.mut_inner());
}
}
}
fn start_selection(&self, mut task: BlockedTask) -> Result<(), BlockedTask>{
loop {
let (t, mut new_port) = match self.inner {
let (t, new_port) = match *unsafe { self.inner() } {
Oneshot(ref p) => {
match unsafe { (*p.get()).start_selection(task) } {
oneshot::SelSuccess => return Ok(()),
@ -911,8 +926,8 @@ impl<T: Send> select::Packet for Receiver<T> {
};
task = t;
unsafe {
mem::swap(&mut transmute_mut(self).inner,
&mut new_port.inner);
mem::swap(self.mut_inner(),
new_port.mut_inner());
}
}
}
@ -920,7 +935,7 @@ impl<T: Send> select::Packet for Receiver<T> {
fn abort_selection(&self) -> bool {
let mut was_upgrade = false;
loop {
let result = match self.inner {
let result = match *unsafe { self.inner() } {
Oneshot(ref p) => unsafe { (*p.get()).abort_selection() },
Stream(ref p) => unsafe {
(*p.get()).abort_selection(was_upgrade)
@ -932,11 +947,11 @@ impl<T: Send> select::Packet for Receiver<T> {
(*p.get()).abort_selection()
},
};
let mut new_port = match result { Ok(b) => return b, Err(p) => p };
let new_port = match result { Ok(b) => return b, Err(p) => p };
was_upgrade = true;
unsafe {
mem::swap(&mut transmute_mut(self).inner,
&mut new_port.inner);
mem::swap(self.mut_inner(),
new_port.mut_inner());
}
}
}
@ -949,7 +964,7 @@ impl<'a, T: Send> Iterator<T> for Messages<'a, T> {
#[unsafe_destructor]
impl<T: Send> Drop for Receiver<T> {
fn drop(&mut self) {
match self.inner {
match *unsafe { self.mut_inner() } {
Oneshot(ref mut p) => unsafe { (*p.get()).drop_port(); },
Stream(ref mut p) => unsafe { (*p.get()).drop_port(); },
Shared(ref mut p) => unsafe { (*p.get()).drop_port(); },