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Make default stdio lock() return 'static handles
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This also deletes the unstable API surface area previously added to expose this
functionality on new methods rather than built into the current set.
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@Mark-Simulacrum
Mark-Simulacrum committed Feb 13, 2022
1 parent 9c3a3e3 commit 398cccd
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Showing 3 changed files with 18 additions and 228 deletions.
2 changes: 0 additions & 2 deletions library/std/src/io/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -268,8 +268,6 @@ pub use self::buffered::WriterPanicked;
pub use self::stdio::set_output_capture;
#[unstable(feature = "print_internals", issue = "none")]
pub use self::stdio::{_eprint, _print};
#[unstable(feature = "stdio_locked", issue = "86845")]
pub use self::stdio::{stderr_locked, stdin_locked, stdout_locked};
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::{
buffered::{BufReader, BufWriter, IntoInnerError, LineWriter},
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238 changes: 15 additions & 223 deletions library/std/src/io/stdio.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -307,48 +307,6 @@ pub fn stdin() -> Stdin {
}
}

/// Constructs a new locked handle to the standard input of the current
/// process.
///
/// Each handle returned is a guard granting locked access to a shared
/// global buffer whose access is synchronized via a mutex. If you need
/// more explicit control over locking, for example, in a multi-threaded
/// program, use the [`io::stdin`] function to obtain an unlocked handle,
/// along with the [`Stdin::lock`] method.
///
/// The lock is released when the returned guard goes out of scope. The
/// returned guard also implements the [`Read`] and [`BufRead`] traits for
/// accessing the underlying data.
///
/// **Note**: The mutex locked by this handle is not reentrant. Even in a
/// single-threaded program, calling other code that accesses [`Stdin`]
/// could cause a deadlock or panic, if this locked handle is held across
/// that call.
///
/// ### Note: Windows Portability Consideration
/// When operating in a console, the Windows implementation of this stream does not support
/// non-UTF-8 byte sequences. Attempting to read bytes that are not valid UTF-8 will return
/// an error.
///
/// # Examples
///
/// ```no_run
/// #![feature(stdio_locked)]
/// use std::io::{self, BufRead};
///
/// fn main() -> io::Result<()> {
/// let mut buffer = String::new();
/// let mut handle = io::stdin_locked();
///
/// handle.read_line(&mut buffer)?;
/// Ok(())
/// }
/// ```
#[unstable(feature = "stdio_locked", issue = "86845")]
pub fn stdin_locked() -> StdinLock<'static> {
stdin().into_locked()
}

impl Stdin {
/// Locks this handle to the standard input stream, returning a readable
/// guard.
Expand All @@ -372,8 +330,10 @@ impl Stdin {
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn lock(&self) -> StdinLock<'_> {
self.lock_any()
pub fn lock(&self) -> StdinLock<'static> {
// Locks this handle with 'static lifetime. This depends on the
// implementation detail that the underlying `Mutex` is static.
StdinLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
}

/// Locks this handle and reads a line of input, appending it to the specified buffer.
Expand Down Expand Up @@ -407,43 +367,6 @@ impl Stdin {
self.lock().read_line(buf)
}

// Locks this handle with any lifetime. This depends on the
// implementation detail that the underlying `Mutex` is static.
fn lock_any<'a>(&self) -> StdinLock<'a> {
StdinLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
}

/// Consumes this handle to the standard input stream, locking the
/// shared global buffer associated with the stream and returning a
/// readable guard.
///
/// The lock is released when the returned guard goes out of scope. The
/// returned guard also implements the [`Read`] and [`BufRead`] traits
/// for accessing the underlying data.
///
/// It is often simpler to directly get a locked handle using the
/// [`stdin_locked`] function instead, unless nearby code also needs to
/// use an unlocked handle.
///
/// # Examples
///
/// ```no_run
/// #![feature(stdio_locked)]
/// use std::io::{self, BufRead};
///
/// fn main() -> io::Result<()> {
/// let mut buffer = String::new();
/// let mut handle = io::stdin().into_locked();
///
/// handle.read_line(&mut buffer)?;
/// Ok(())
/// }
/// ```
#[unstable(feature = "stdio_locked", issue = "86845")]
pub fn into_locked(self) -> StdinLock<'static> {
self.lock_any()
}

/// Consumes this handle and returns an iterator over input lines.
///
/// For detailed semantics of this method, see the documentation on
Expand All @@ -463,7 +386,7 @@ impl Stdin {
#[must_use = "`self` will be dropped if the result is not used"]
#[unstable(feature = "stdin_forwarders", issue = "87096")]
pub fn lines(self) -> Lines<StdinLock<'static>> {
self.into_locked().lines()
self.lock().lines()
}
}

Expand Down Expand Up @@ -649,42 +572,6 @@ pub fn stdout() -> Stdout {
}
}

/// Constructs a new locked handle to the standard output of the current
/// process.
///
/// Each handle returned is a guard granting locked access to a shared
/// global buffer whose access is synchronized via a mutex. If you need
/// more explicit control over locking, for example, in a multi-threaded
/// program, use the [`io::stdout`] function to obtain an unlocked handle,
/// along with the [`Stdout::lock`] method.
///
/// The lock is released when the returned guard goes out of scope. The
/// returned guard also implements the [`Write`] trait for writing data.
///
/// ### Note: Windows Portability Consideration
/// When operating in a console, the Windows implementation of this stream does not support
/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
/// an error.
///
/// # Examples
///
/// ```no_run
/// #![feature(stdio_locked)]
/// use std::io::{self, Write};
///
/// fn main() -> io::Result<()> {
/// let mut handle = io::stdout_locked();
///
/// handle.write_all(b"hello world")?;
///
/// Ok(())
/// }
/// ```
#[unstable(feature = "stdio_locked", issue = "86845")]
pub fn stdout_locked() -> StdoutLock<'static> {
stdout().into_locked()
}

pub fn cleanup() {
if let Some(instance) = STDOUT.get() {
// Flush the data and disable buffering during shutdown
Expand Down Expand Up @@ -712,55 +599,20 @@ impl Stdout {
/// use std::io::{self, Write};
///
/// fn main() -> io::Result<()> {
/// let stdout = io::stdout();
/// let mut handle = stdout.lock();
/// let mut stdout = io::stdout().lock();
///
/// handle.write_all(b"hello world")?;
/// stdout.write_all(b"hello world")?;
///
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn lock(&self) -> StdoutLock<'_> {
self.lock_any()
}

// Locks this handle with any lifetime. This depends on the
// implementation detail that the underlying `ReentrantMutex` is
// static.
fn lock_any<'a>(&self) -> StdoutLock<'a> {
pub fn lock(&self) -> StdoutLock<'static> {
// Locks this handle with 'static lifetime. This depends on the
// implementation detail that the underlying `ReentrantMutex` is
// static.
StdoutLock { inner: self.inner.lock() }
}

/// Consumes this handle to the standard output stream, locking the
/// shared global buffer associated with the stream and returning a
/// writable guard.
///
/// The lock is released when the returned lock goes out of scope. The
/// returned guard also implements the [`Write`] trait for writing data.
///
/// It is often simpler to directly get a locked handle using the
/// [`io::stdout_locked`] function instead, unless nearby code also
/// needs to use an unlocked handle.
///
/// # Examples
///
/// ```no_run
/// #![feature(stdio_locked)]
/// use std::io::{self, Write};
///
/// fn main() -> io::Result<()> {
/// let mut handle = io::stdout().into_locked();
///
/// handle.write_all(b"hello world")?;
///
/// Ok(())
/// }
/// ```
#[unstable(feature = "stdio_locked", issue = "86845")]
pub fn into_locked(self) -> StdoutLock<'static> {
self.lock_any()
}
}

#[stable(feature = "std_debug", since = "1.16.0")]
Expand Down Expand Up @@ -935,35 +787,6 @@ pub fn stderr() -> Stderr {
}
}

/// Constructs a new locked handle to the standard error of the current
/// process.
///
/// This handle is not buffered.
///
/// ### Note: Windows Portability Consideration
/// When operating in a console, the Windows implementation of this stream does not support
/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
/// an error.
///
/// # Example
///
/// ```no_run
/// #![feature(stdio_locked)]
/// use std::io::{self, Write};
///
/// fn main() -> io::Result<()> {
/// let mut handle = io::stderr_locked();
///
/// handle.write_all(b"hello world")?;
///
/// Ok(())
/// }
/// ```
#[unstable(feature = "stdio_locked", issue = "86845")]
pub fn stderr_locked() -> StderrLock<'static> {
stderr().into_locked()
}

impl Stderr {
/// Locks this handle to the standard error stream, returning a writable
/// guard.
Expand All @@ -986,43 +809,12 @@ impl Stderr {
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn lock(&self) -> StderrLock<'_> {
self.lock_any()
}

// Locks this handle with any lifetime. This depends on the
// implementation detail that the underlying `ReentrantMutex` is
// static.
fn lock_any<'a>(&self) -> StderrLock<'a> {
pub fn lock(&self) -> StderrLock<'static> {
// Locks this handle with 'static lifetime. This depends on the
// implementation detail that the underlying `ReentrantMutex` is
// static.
StderrLock { inner: self.inner.lock() }
}

/// Locks and consumes this handle to the standard error stream,
/// returning a writable guard.
///
/// The lock is released when the returned guard goes out of scope. The
/// returned guard also implements the [`Write`] trait for writing
/// data.
///
/// # Examples
///
/// ```
/// #![feature(stdio_locked)]
/// use std::io::{self, Write};
///
/// fn foo() -> io::Result<()> {
/// let stderr = io::stderr();
/// let mut handle = stderr.into_locked();
///
/// handle.write_all(b"hello world")?;
///
/// Ok(())
/// }
/// ```
#[unstable(feature = "stdio_locked", issue = "86845")]
pub fn into_locked(self) -> StderrLock<'static> {
self.lock_any()
}
}

#[stable(feature = "std_debug", since = "1.16.0")]
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6 changes: 3 additions & 3 deletions library/std/src/io/stdio/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,17 +50,17 @@ fn panic_doesnt_poison() {
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn test_lock_stderr() {
test_lock(stderr, stderr_locked);
test_lock(stderr, || stderr().lock());
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn test_lock_stdin() {
test_lock(stdin, stdin_locked);
test_lock(stdin, || stdin().lock());
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn test_lock_stdout() {
test_lock(stdout, stdout_locked);
test_lock(stdout, || stdout().lock());
}

// Helper trait to make lock testing function generic.
Expand Down

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