wait-forked-but-failed-child

Author: Kivooeo

tests/ui/process/process-spawn-failure.rs

@@ -1,3 +1,9 @@
+//! Tests that repeatedly spawning a failing command does not create zombie processes.
+//! Spawns a deliberately invalid command multiple times, verifies each spawn fails,
+//! then uses `ps` (on Unix) to detect any leftover zombie (defunct) child processes.
+//! Checks Rust's process spawning cleans up resources properly.
+//! Skipped on platforms without `ps` utility.
+
 //@ run-pass
 //@ needs-subprocess
 //@ ignore-vxworks no 'ps'
@@ -36,35 +42,42 @@ fn find_zombies() {
     // the PPID column contains a "-" for the respective process.
     // Filter out any lines that have a "-" as the PPID as the PPID is
     // expected to be an integer.
-    let filtered_ps: Vec<_> = ps_output
-        .lines()
-        .filter(|line| line.split_whitespace().nth(1) != Some("-"))
-        .collect();
+    let filtered_ps: Vec<_> =
+        ps_output.lines().filter(|line| line.split_whitespace().nth(1) != Some("-")).collect();
 
     for (line_no, line) in filtered_ps.into_iter().enumerate() {
-        if 0 < line_no && 0 < line.len() &&
-           my_pid == line.split(' ').filter(|w| 0 < w.len()).nth(1)
-                         .expect("1st column should be PPID")
-                         .parse().ok()
-                         .expect("PPID string into integer") &&
-           line.contains("defunct") {
+        if 0 < line_no
+            && 0 < line.len()
+            && my_pid
+                == line
+                    .split(' ')
+                    .filter(|w| 0 < w.len())
+                    .nth(1)
+                    .expect("1st column should be PPID")
+                    .parse()
+                    .ok()
+                    .expect("PPID string into integer")
+            && line.contains("defunct")
+        {
             panic!("Zombie child {}", line);
         }
     }
 }
 
 #[cfg(windows)]
-fn find_zombies() { }
+fn find_zombies() {}
 
 fn main() {
     let too_long = format!("/NoSuchCommand{:0300}", 0u8);
 
-    let _failures = (0..100).map(|_| {
-        let mut cmd = Command::new(&too_long);
-        let failed = cmd.spawn();
-        assert!(failed.is_err(), "Make sure the command fails to spawn(): {:?}", cmd);
-        failed
-    }).collect::<Vec<_>>();
+    let _failures = (0..100)
+        .map(|_| {
+            let mut cmd = Command::new(&too_long);
+            let failed = cmd.spawn();
+            assert!(failed.is_err(), "Make sure the command fails to spawn(): {:?}", cmd);
+            failed
+        })
+        .collect::<Vec<_>>();
 
     find_zombies();
     // then _failures goes out of scope