Add initial #![feature(on_broken_pipe)] code

Author: Enselic

compiler/rustc_feature/src/unstable.rs

@@ -610,6 +610,8 @@ declare_features! (
     (unstable, offset_of_enum, "1.75.0", Some(120141)),
     /// Allows using fields with slice type in offset_of!
     (unstable, offset_of_slice, "1.81.0", Some(126151)),
+    /// Allows changing pre-main() `SIGPIPE` behavior
+    (unstable, on_broken_pipe, "CURRENT_RUSTC_VERSION", Some(150588)),
     /// Allows using `#[optimize(X)]`.
     (unstable, optimize_attribute, "1.34.0", Some(54882)),
     /// Allows specifying nop padding on functions for dynamic patching.

compiler/rustc_span/src/symbol.rs

@@ -1603,6 +1603,7 @@ symbols! {
         old_name,
         omit_gdb_pretty_printer_section,
         on,
+        on_broken_pipe,
         on_const,
         on_unimplemented,
         opaque,

library/std/src/io/mod.rs

@@ -2216,6 +2216,46 @@ pub(crate) fn stream_len_default<T: Seek + ?Sized>(self_: &mut T) -> Result<u64>
     Ok(len)
 }
 
+/// Specifies what [`ErrorKind::BrokenPipe`] behavior a program should have. In
+/// practice this affects the `SIGPIPE` setup code that runs before `fn main()`.
+/// Currently only relevant to the `unix` family of operating systems.
+#[unstable(feature = "on_broken_pipe", issue = "150588")]
+#[non_exhaustive] // We want to be able to add more variants later.
+#[derive(Debug)]
+pub enum OnBrokenPipe {
+    /// Set `SIGPIPE` to `SIG_IGN` so that pipe I/O problems are reported as
+    /// [`ErrorKind::BrokenPipe`] errors. Reset `SIGPIPE` to `SIG_DFL` before
+    /// child `exec()`.
+    ///
+    /// Both of these behaviors have been the default since Rust 1.0.
+    #[unstable(feature = "on_broken_pipe", issue = "150588")]
+    BackwardsCompatible,
+    /// Set `SIGPIPE` to `SIG_IGN` so that pipe I/O problems kills the process.
+    /// Don't touch `SIGPIPE` before child `exec()`.
+    ///
+    /// This is mainly useful when you want programs to terminate when their
+    /// output is piped to short-lived programs like `head`.
+    #[unstable(feature = "on_broken_pipe", issue = "150588")]
+    Kill,
+    /// Set `SIGPIPE` to `SIG_DFL` so that pipe I/O problems are reported as
+    /// [`ErrorKind::BrokenPipe`] errors. Don't touch `SIGPIPE` before child
+    /// `exec()`.
+    #[unstable(feature = "on_broken_pipe", issue = "150588")]
+    Error,
+    /// Never touch `SIGPIPE`, including before child `exec()`.
+    /// `SIGPIPE` disposition is always inherited from the parent process.
+    /// This typically means that programs behave as with [`Self::Kill`].
+    #[unstable(feature = "on_broken_pipe", issue = "150588")]
+    Inherit,
+}
+
+/// How to change SIGPIPE disposition before `fn main()` is invoked.
+#[eii(on_broken_pipe)]
+#[unstable(feature = "on_broken_pipe", issue = "150588")]
+pub fn on_broken_pipe() -> OnBrokenPipe {
+    OnBrokenPipe::BackwardsCompatible
+}
+
 /// Enumeration of possible methods to seek within an I/O object.
 ///
 /// It is used by the [`Seek`] trait.

library/std/src/lib.rs

@@ -333,6 +333,7 @@
 #![feature(exact_size_is_empty)]
 #![feature(exclusive_wrapper)]
 #![feature(extend_one)]
+#![feature(extern_item_impls)]
 #![feature(float_algebraic)]
 #![feature(float_gamma)]
 #![feature(float_minimum_maximum)]

tests/ui/feature-gates/feature-gate-on-broken-pipe.rs

@@ -0,0 +1,8 @@
+fn main() {
+    // None of these shall be allowed without the feature gate.
+    let _ = std::io::OnBrokenPipe::BackwardsCompatible; //~ ERROR: use of unstable library feature `on_broken_pipe`
+    let _ = std::io::OnBrokenPipe::Kill; //~ ERROR: use of unstable library feature `on_broken_pipe`
+    let _ = std::io::OnBrokenPipe::Error; //~ ERROR: use of unstable library feature `on_broken_pipe`
+    let _ = std::io::OnBrokenPipe::Inherit; //~ ERROR: use of unstable library feature `on_broken_pipe`
+    let _ = std::io::on_broken_pipe(); //~ ERROR: use of unstable library feature `on_broken_pipe`
+}

tests/ui/feature-gates/feature-gate-on-broken-pipe.stderr

@@ -0,0 +1,53 @@
+error[E0658]: use of unstable library feature `on_broken_pipe`
+  --> $DIR/feature-gate-on-broken-pipe.rs:3:13
+   |
+LL |     let _ = std::io::OnBrokenPipe::BackwardsCompatible;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #150588 <https://github.com/rust-lang/rust/issues/150588> for more information
+   = help: add `#![feature(on_broken_pipe)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: use of unstable library feature `on_broken_pipe`
+  --> $DIR/feature-gate-on-broken-pipe.rs:4:13
+   |
+LL |     let _ = std::io::OnBrokenPipe::Kill;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #150588 <https://github.com/rust-lang/rust/issues/150588> for more information
+   = help: add `#![feature(on_broken_pipe)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: use of unstable library feature `on_broken_pipe`
+  --> $DIR/feature-gate-on-broken-pipe.rs:5:13
+   |
+LL |     let _ = std::io::OnBrokenPipe::Error;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #150588 <https://github.com/rust-lang/rust/issues/150588> for more information
+   = help: add `#![feature(on_broken_pipe)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: use of unstable library feature `on_broken_pipe`
+  --> $DIR/feature-gate-on-broken-pipe.rs:6:13
+   |
+LL |     let _ = std::io::OnBrokenPipe::Inherit;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #150588 <https://github.com/rust-lang/rust/issues/150588> for more information
+   = help: add `#![feature(on_broken_pipe)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: use of unstable library feature `on_broken_pipe`
+  --> $DIR/feature-gate-on-broken-pipe.rs:7:13
+   |
+LL |     let _ = std::io::on_broken_pipe();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #150588 <https://github.com/rust-lang/rust/issues/150588> for more information
+   = help: add `#![feature(on_broken_pipe)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0658`.