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, 19 insertions, 6 deletions

diff --git a/src/test/ui/command/command-pre-exec.rs b/src/test/ui/command/command-pre-exec.rs
index 61914e22930..10a8b19159e 100644
--- a/src/test/ui/command/command-pre-exec.rs
+++ b/src/test/ui/command/command-pre-exec.rs
@@ -8,8 +8,6 @@
 // ignore-sgx no processes
 #![feature(process_exec, rustc_private)]
 
-extern crate libc;
-
 use std::env;
 use std::io::Error;
 use std::os::unix::process::CommandExt;
@@ -17,6 +15,23 @@ use std::process::Command;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 
+#[cfg(not(target_os = "linux"))]
+fn getpid() -> u32 {
+    use std::process;
+    process::id()
+}
+
+/// We need to directly use the getpid syscall instead of using `process::id()`
+/// because the libc wrapper might return incorrect values after a process was
+/// forked.
+#[cfg(target_os = "linux")]
+fn getpid() -> u32 {
+    extern crate libc;
+    unsafe {
+        libc::syscall(libc::SYS_getpid) as _
+    }
+}
+
 fn main() {
     if let Some(arg) = env::args().nth(1) {
         match &arg[..] {
@@ -68,14 +83,12 @@ fn main() {
     };
     assert_eq!(output.raw_os_error(), Some(102));
 
-    let pid = unsafe { libc::getpid() };
-    assert!(pid >= 0);
+    let pid = getpid();
     let output = unsafe {
         Command::new(&me)
             .arg("empty")
             .pre_exec(move || {
-                let child = libc::getpid();
-                assert!(child >= 0);
+                let child = getpid();
                 assert!(pid != child);
                 Ok(())
             })