Unrolled build for rust-lang#125970

Rollup merge of rust-lang#125970 - RalfJung:before_exec, r=m-ou-se

CommandExt::before_exec: deprecate safety in edition 2024

Similar to `set_var`, we had to find out after 1.0 was released that `before_exec` should have been unsafe. We partially rectified this by deprecating that function a long time ago, but since rust-lang#124636 we have the ability to also deprecate the safety of the old function and make it a *hard error* to call the old function outside `unsafe` in the next edition. So just in case anyone still uses the old function, let's ensure this can't be ignored when moving code to the new edition.

Cc `@rust-lang/libs-api`

Tracking:

- rust-lang#124866

library/std/src/os/unix/process.rs

@@ -109,13 +109,21 @@ pub trait CommandExt: Sealed {
  /// Schedules a closure to be run just before the `exec` function is
  /// invoked.
  ///
- /// This method is stable and usable, but it should be unsafe. To fix
- /// that, it got deprecated in favor of the unsafe [`pre_exec`].
+ /// `before_exec` used to be a safe method, but it needs to be unsafe since the closure may only
+ /// perform operations that are *async-signal-safe*. Hence it got deprecated in favor of the
+ /// unsafe [`pre_exec`]. Meanwhile, Rust gained the ability to make an existing safe method
+ /// fully unsafe in a new edition, which is how `before_exec` became `unsafe`. It still also
+ /// remains deprecated; `pre_exec` should be used instead.
  ///
  /// [`pre_exec`]: CommandExt::pre_exec
  #[stable(feature = "process_exec", since = "1.15.0")]
  #[deprecated(since = "1.37.0", note = "should be unsafe, use `pre_exec` instead")]
- fn before_exec<F>(&mut self, f: F) -> &mut process::Command
+ #[cfg_attr(bootstrap, rustc_deprecated_safe_2024)]
+ #[cfg_attr(
+ not(bootstrap),
+ rustc_deprecated_safe_2024(audit_that = "the closure is async-signal-safe")
+ )]
+ unsafe fn before_exec<F>(&mut self, f: F) -> &mut process::Command
  where
  F: FnMut() -> io::Result<()> + Send + Sync + 'static,
  {

tests/ui/rust-2024/unsafe-before_exec.e2024.stderr

@@ -0,0 +1,11 @@
+error[E0133]: call to unsafe function `before_exec` is unsafe and requires unsafe block
+ --> $DIR/unsafe-before_exec.rs:14:5
+ |
+LL | cmd.before_exec(|| Ok(()));
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
+ |
+ = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0133`.

tests/ui/rust-2024/unsafe-before_exec.rs

@@ -0,0 +1,17 @@
+//@ revisions: e2021 e2024
+//@ only-unix
+//@[e2021] edition: 2021
+//@[e2021] check-pass
+//@[e2024] edition: 2024
+//@[e2024] compile-flags: -Zunstable-options
+
+use std::process::Command;
+use std::os::unix::process::CommandExt;
+
+#[allow(deprecated)]
+fn main() {
+ let mut cmd = Command::new("sleep");
+ cmd.before_exec(|| Ok(()));
+ //[e2024]~^ ERROR call to unsafe function `before_exec` is unsafe
+ drop(cmd); // we don't actually run the command.
+}