test: test posix_spawn() and add negative test cases (nix-rust#2598)

* test: test posix_spawn()

* chore: downgrade which to 5.0.0 due to MSRV limit

* chore: use a homemade which

* refactor: clippy fix

* test: test posix_spawn()

* refactor: CStr literal syntax is not supported

* test: skip testing error cases under QEMU

test/test_spawn.rs

@@ -1,13 +1,115 @@
 use super::FORK_MTX;
+use nix::errno::Errno;
 use nix::spawn::{self, PosixSpawnAttr, PosixSpawnFileActions};
 use nix::sys::signal;
 use nix::sys::wait::{waitpid, WaitPidFlag, WaitStatus};
-use std::ffi::CString;
+use std::ffi::{CStr, CString};
+
+/// Helper function to find a binary in the $PATH
+fn which(exe_name: &str) -> Option<std::path::PathBuf> {
+    std::env::var_os("PATH").and_then(|paths| {
+        std::env::split_paths(&paths)
+            .filter_map(|dir| {
+                let full_path = dir.join(exe_name);
+                if full_path.is_file() {
+                    Some(full_path)
+                } else {
+                    None
+                }
+            })
+            .next()
+    })
+}
 
 #[test]
 fn spawn_true() {
     let _guard = FORK_MTX.lock();
 
+    let bin = which("true").unwrap();
+    let args = &[
+        CString::new("true").unwrap(),
+        CString::new("story").unwrap(),
+    ];
+    let vars: &[CString] = &[];
+    let actions = PosixSpawnFileActions::init().unwrap();
+    let attr = PosixSpawnAttr::init().unwrap();
+
+    let pid =
+        spawn::posix_spawn(bin.as_path(), &actions, &attr, args, vars).unwrap();
+
+    let status = waitpid(pid, Some(WaitPidFlag::empty())).unwrap();
+
+    match status {
+        WaitStatus::Exited(wpid, ret) => {
+            assert_eq!(pid, wpid);
+            assert_eq!(ret, 0);
+        }
+        _ => {
+            panic!("Invalid WaitStatus");
+        }
+    };
+}
+
+#[test]
+fn spawn_sleep() {
+    let _guard = FORK_MTX.lock();
+
+    let bin = which("sleep").unwrap();
+    let args = &[CString::new("sleep").unwrap(), CString::new("30").unwrap()];
+    let vars: &[CString] = &[];
+    let actions = PosixSpawnFileActions::init().unwrap();
+    let attr = PosixSpawnAttr::init().unwrap();
+
+    let pid =
+        spawn::posix_spawn(bin.as_path(), &actions, &attr, args, vars).unwrap();
+
+    let status =
+        waitpid(pid, WaitPidFlag::from_bits(WaitPidFlag::WNOHANG.bits()))
+            .unwrap();
+    match status {
+        WaitStatus::StillAlive => {}
+        _ => {
+            panic!("Invalid WaitStatus");
+        }
+    };
+
+    signal::kill(pid, signal::SIGTERM).unwrap();
+
+    let status = waitpid(pid, Some(WaitPidFlag::empty())).unwrap();
+    match status {
+        WaitStatus::Signaled(wpid, wsignal, _) => {
+            assert_eq!(pid, wpid);
+            assert_eq!(wsignal, signal::SIGTERM);
+        }
+        _ => {
+            panic!("Invalid WaitStatus");
+        }
+    };
+}
+
+#[test]
+// `posix_spawn(path_not_exist)` succeeds under QEMU, so ignore the test. No need
+// to investigate the root cause, this test still works in native environments, which
+// is sufficient to test the binding.
+#[cfg_attr(qemu, ignore)]
+fn spawn_cmd_does_not_exist() {
+    let _guard = FORK_MTX.lock();
+
+    let args = &[CString::new("buzz").unwrap()];
+    let envs: &[CString] = &[];
+    let actions = PosixSpawnFileActions::init().unwrap();
+    let attr = PosixSpawnAttr::init().unwrap();
+
+    let bin = "2b7433c4-523b-470c-abb5-d7ee9fd295d5-fdasf";
+    let errno =
+        spawn::posix_spawn(bin, &actions, &attr, args, envs).unwrap_err();
+    assert_eq!(errno, Errno::ENOENT);
+}
+
+#[test]
+fn spawnp_true() {
+    let _guard = FORK_MTX.lock();
+
     let bin = &CString::new("true").unwrap();
     let args = &[
         CString::new("true").unwrap(),
@@ -33,7 +135,7 @@ fn spawn_true() {
 }
 
 #[test]
-fn spawn_sleep() {
+fn spawnp_sleep() {
     let _guard = FORK_MTX.lock();
 
     let bin = &CString::new("sleep").unwrap();
@@ -67,3 +169,25 @@ fn spawn_sleep() {
         }
     };
 }
+
+#[test]
+// `posix_spawnp(bin_not_exist)` succeeds under QEMU, so ignore the test. No need
+// to investigate the root cause, this test still works in native environments, which
+// is sufficient to test the binding.
+#[cfg_attr(qemu, ignore)]
+fn spawnp_cmd_does_not_exist() {
+    let _guard = FORK_MTX.lock();
+
+    let args = &[CString::new("buzz").unwrap()];
+    let envs: &[CString] = &[];
+    let actions = PosixSpawnFileActions::init().unwrap();
+    let attr = PosixSpawnAttr::init().unwrap();
+
+    let bin = CStr::from_bytes_with_nul(
+        "2b7433c4-523b-470c-abb5-d7ee9fd295d5-fdasf\0".as_bytes(),
+    )
+    .unwrap();
+    let errno =
+        spawn::posix_spawnp(bin, &actions, &attr, args, envs).unwrap_err();
+    assert_eq!(errno, Errno::ENOENT);
+}