Auto merge of #81825 - voidc:pidfd, r=joshtriplett

Add Linux-specific pidfd process extensions (take 2)

Continuation of #77168.
I addressed the following concerns from the original PR:

- make `CommandExt` and `ChildExt` sealed traits
- wrap file descriptors in `PidFd` struct representing ownership over the fd
- add `take_pidfd` to take the fd out of `Child`
- close fd when dropped

Tracking Issue: #82971

1 files changed, 45 insertions, 0 deletions

diff --git a/src/test/ui/command/command-create-pidfd.rs b/src/test/ui/command/command-create-pidfd.rs
new file mode 100644
index 00000000000..93321ac536a
--- /dev/null
+++ b/src/test/ui/command/command-create-pidfd.rs
@@ -0,0 +1,45 @@
+// run-pass
+// only-linux - pidfds are a linux-specific concept
+
+#![feature(linux_pidfd)]
+#![feature(rustc_private)]
+
+extern crate libc;
+
+use std::io::Error;
+use std::os::linux::process::{ChildExt, CommandExt};
+use std::process::Command;
+
+fn has_clone3() -> bool {
+    let res = unsafe { libc::syscall(libc::SYS_clone3, 0, 0) };
+    let err = (res == -1)
+        .then(|| Error::last_os_error())
+        .expect("probe syscall should not succeed");
+    err.raw_os_error() != Some(libc::ENOSYS)
+}
+
+fn main() {
+    // pidfds require the clone3 syscall
+    if !has_clone3() {
+        return;
+    }
+
+    // We don't assert the precise value, since the standard library
+    // might have opened other file descriptors before our code runs.
+    let _ = Command::new("echo")
+        .create_pidfd(true)
+        .spawn()
+        .unwrap()
+        .pidfd().expect("failed to obtain pidfd");
+
+    let _ = Command::new("echo")
+        .create_pidfd(false)
+        .spawn()
+        .unwrap()
+        .pidfd().expect_err("pidfd should not have been created when create_pid(false) is set");
+
+    let _ = Command::new("echo")
+        .spawn()
+        .unwrap()
+        .pidfd().expect_err("pidfd should not have been created");
+}