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Use Cell instead of RefCell for LOCAL_{STDOUT,STDERR}.

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This commit is contained in:
Mara Bos 2020-11-03 22:59:04 +01:00
parent f534b75f05
commit 08b7cb79e0
1 changed files with 16 additions and 15 deletions
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31
library/std/src/io/stdio.rs
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@ -5,7 +5,7 @@ mod tests;
use crate::io::prelude::*; use crate::io::prelude::*;
use crate::cell::RefCell; use crate::cell::{Cell, RefCell};
use crate::fmt; use crate::fmt;
use crate::io::{self, BufReader, Initializer, IoSlice, IoSliceMut, LineWriter}; use crate::io::{self, BufReader, Initializer, IoSlice, IoSliceMut, LineWriter};
use crate::lazy::SyncOnceCell; use crate::lazy::SyncOnceCell;
@ -20,15 +20,15 @@ type LocalStream = Arc<Mutex<Vec<u8>>>;
thread_local! { thread_local! {
/// Used by the test crate to capture the output of the print! and println! macros. /// Used by the test crate to capture the output of the print! and println! macros.
static LOCAL_STDOUT: RefCell<Option<LocalStream>> = { static LOCAL_STDOUT: Cell<Option<LocalStream>> = {
RefCell::new(None) Cell::new(None)
} }
} }
thread_local! { thread_local! {
/// Used by the test crate to capture the output of the eprint! and eprintln! macros, and panics. /// Used by the test crate to capture the output of the eprint! and eprintln! macros, and panics.
static LOCAL_STDERR: RefCell<Option<LocalStream>> = { static LOCAL_STDERR: Cell<Option<LocalStream>> = {
RefCell::new(None) Cell::new(None)
} }
} }
@ -906,13 +906,12 @@ impl fmt::Debug for StderrLock<'_> {
)] )]
#[doc(hidden)] #[doc(hidden)]
pub fn set_panic(sink: Option<LocalStream>) -> Option<LocalStream> { pub fn set_panic(sink: Option<LocalStream>) -> Option<LocalStream> {
use crate::mem;
if sink.is_none() && !LOCAL_STREAMS.load(Ordering::Relaxed) { if sink.is_none() && !LOCAL_STREAMS.load(Ordering::Relaxed) {
// LOCAL_STDERR is definitely None since LOCAL_STREAMS is false. // LOCAL_STDERR is definitely None since LOCAL_STREAMS is false.
return None; return None;
} }
LOCAL_STREAMS.store(true, Ordering::Relaxed); LOCAL_STREAMS.store(true, Ordering::Relaxed);
LOCAL_STDERR.with(move |slot| mem::replace(&mut *slot.borrow_mut(), sink)) LOCAL_STDERR.with(move |slot| slot.replace(sink))
} }
/// Resets the thread-local stdout handle to the specified writer /// Resets the thread-local stdout handle to the specified writer
@ -931,13 +930,12 @@ pub fn set_panic(sink: Option<LocalStream>) -> Option<LocalStream> {
)] )]
#[doc(hidden)] #[doc(hidden)]
pub fn set_print(sink: Option<LocalStream>) -> Option<LocalStream> { pub fn set_print(sink: Option<LocalStream>) -> Option<LocalStream> {
use crate::mem;
if sink.is_none() && !LOCAL_STREAMS.load(Ordering::Relaxed) { if sink.is_none() && !LOCAL_STREAMS.load(Ordering::Relaxed) {
// LOCAL_STDOUT is definitely None since LOCAL_STREAMS is false. // LOCAL_STDOUT is definitely None since LOCAL_STREAMS is false.
return None; return None;
} }
LOCAL_STREAMS.store(true, Ordering::Relaxed); LOCAL_STREAMS.store(true, Ordering::Relaxed);
LOCAL_STDOUT.with(move |slot| mem::replace(&mut *slot.borrow_mut(), sink)) LOCAL_STDOUT.with(move |slot| slot.replace(sink))
} }
pub(crate) fn clone_io() -> (Option<LocalStream>, Option<LocalStream>) { pub(crate) fn clone_io() -> (Option<LocalStream>, Option<LocalStream>) {
@ -946,10 +944,13 @@ pub(crate) fn clone_io() -> (Option<LocalStream>, Option<LocalStream>) {
return (None, None); return (None, None);
} }
( let clone = |cell: &Cell<Option<LocalStream>>| {
LOCAL_STDOUT.with(|s| s.borrow().clone()), let s = cell.take();
LOCAL_STDERR.with(|s| s.borrow().clone()), cell.set(s.clone());
) s
};
(LOCAL_STDOUT.with(clone), LOCAL_STDERR.with(clone))
} }
/// Write `args` to output stream `local_s` if possible, `global_s` /// Write `args` to output stream `local_s` if possible, `global_s`
@ -964,7 +965,7 @@ pub(crate) fn clone_io() -> (Option<LocalStream>, Option<LocalStream>) {
/// However, if the actual I/O causes an error, this function does panic. /// However, if the actual I/O causes an error, this function does panic.
fn print_to<T>( fn print_to<T>(
args: fmt::Arguments<'_>, args: fmt::Arguments<'_>,
local_s: &'static LocalKey<RefCell<Option<LocalStream>>>, local_s: &'static LocalKey<Cell<Option<LocalStream>>>,
global_s: fn() -> T, global_s: fn() -> T,
label: &str, label: &str,
) where ) where
@ -977,7 +978,7 @@ fn print_to<T>(
// panic/print goes to the global sink instead of our local sink. // panic/print goes to the global sink instead of our local sink.
s.take().map(|w| { s.take().map(|w| {
let _ = w.lock().unwrap_or_else(|e| e.into_inner()).write_fmt(args); let _ = w.lock().unwrap_or_else(|e| e.into_inner()).write_fmt(args);
*s.borrow_mut() = Some(w); s.set(Some(w));
}) })
}) == Ok(Some(())) }) == Ok(Some(()))
{ {