From a849a33a0453c75cf0e90d504177e60e8d7da7b7 Mon Sep 17 00:00:00 2001
From: Chris Pick <chris@chrispick.com>
Date: Mon, 13 Nov 2023 20:43:23 -0500
Subject: [PATCH] Add `signal_ignore()` and `signal_default()`

Provide safe mechanisms to ignore or reset a signal's action to the
default.

Fixes #587.
---
 src/sys/signal.rs       | 16 ++++++++++++++++
 test/sys/test_signal.rs | 16 ++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/sys/signal.rs b/src/sys/signal.rs
index 408471143f..9167452bbd 100644
--- a/src/sys/signal.rs
+++ b/src/sys/signal.rs
@@ -964,6 +964,22 @@ pub unsafe fn signal(signal: Signal, handler: SigHandler) -> Result<SigHandler>
     })
 }
 
+/// Reset the specified signal to its default action.
+///
+/// `signal` can be any signal except `SIGKILL` or `SIGSTOP`.
+pub fn signal_default(signal: Signal) -> Result<()> {
+    // SAFETY: restoring a default handler is safe if the old handler isn't called
+    unsafe { self::signal(signal, SigHandler::SigDfl) }.map(drop)
+}
+
+/// Ignore the specified signal.
+///
+/// `signal` can be any signal except `SIGKILL` or `SIGSTOP`.
+pub fn signal_ignore(signal: Signal) -> Result<()> {
+    // SAFETY: ignoring a signal is safe if the old handler isn't called
+    unsafe { self::signal(signal, SigHandler::SigIgn) }.map(drop)
+}
+
 fn do_pthread_sigmask(how: SigmaskHow,
                        set: Option<&SigSet>,
                        oldset: Option<*mut libc::sigset_t>) -> Result<()> {
diff --git a/test/sys/test_signal.rs b/test/sys/test_signal.rs
index ca25ff9ab0..7aa6cf8492 100644
--- a/test/sys/test_signal.rs
+++ b/test/sys/test_signal.rs
@@ -141,3 +141,19 @@ fn test_signal() {
     // Restore default signal handler
     unsafe { signal(Signal::SIGINT, SigHandler::SigDfl) }.unwrap();
 }
+
+#[test]
+fn test_safe_signal() {
+    let _m = crate::SIGNAL_MTX.lock();
+
+    signal_ignore(SIGINT).unwrap();
+    raise(Signal::SIGINT).unwrap();
+
+    signal_default(SIGINT).unwrap();
+
+    // Ensure default was restored
+    assert_eq!(
+        unsafe { signal(Signal::SIGINT, SigHandler::SigDfl) }.unwrap(),
+        SigHandler::SigDfl
+    );
+}