os: add a convenient way to ignore certain system signals (#19632)

vlib/os/signal.v

@@ -41,3 +41,7 @@ pub enum Signal {
 }
 
 pub type SignalHandler = fn (Signal)
+
+// An empty system signal handler (callback function) used to mask the specified system signal.
+fn ignore_signal_handler(signal Signal) {
+}

vlib/os/signal_darwin.c.v

@@ -0,0 +1,39 @@
+[has_globals]
+module os
+
+#include <signal.h>
+
+// A convenient way to ignore certain system signals when there is no need to process certain system signals,
+// Masking of system signals under posix systems requires a distinction between main and background threads.
+// Since there is no good way to easily tell whether the current thread is the main or background thread,
+// So a global variable is introduced to make the distinction.
+
+fn C.pthread_self() usize
+
+__global main_thread_id = u64(C.pthread_self())
+
+fn is_main_thread() bool {
+	return main_thread_id == u64(C.pthread_self())
+}
+
+fn C.sigaddset(set &u32, signum int) int
+fn C.sigemptyset(set &u32)
+fn C.sigprocmask(how int, set &u32, oldset &u32) int
+
+// signal_ignore to mask system signals, e.g.: signal_ignore(.pipe, .urg, ...)
+pub fn signal_ignore(args ...Signal) {
+	if is_main_thread() {
+		// for main thread.
+		for arg in args {
+			C.signal(int(arg), ignore_signal_handler)
+		}
+	} else {
+		// for background threads.
+		mask1 := u32(0)
+		C.sigemptyset(&mask1)
+		for arg in args {
+			C.sigaddset(&mask1, int(arg))
+		}
+		C.sigprocmask(C.SIG_BLOCK, &mask1, unsafe { nil })
+	}
+}

vlib/os/signal_default.c.v

@@ -0,0 +1,5 @@
+module os
+
+// unsupported platforms
+pub fn signal_ignore(args ...Signal) {
+}

vlib/os/signal_linux.c.v

@@ -0,0 +1,42 @@
+[has_globals]
+module os
+
+#include <signal.h>
+
+// A convenient way to ignore certain system signals when there is no need to process certain system signals,
+// Masking of system signals under posix systems requires a distinction between main and background threads.
+// Since there is no good way to easily tell whether the current thread is the main or background thread,
+// So a global variable is introduced to make the distinction.
+
+fn C.pthread_self() usize
+
+__global main_thread_id = u64(C.pthread_self())
+
+fn is_main_thread() bool {
+	return main_thread_id == u64(C.pthread_self())
+}
+
+[typedef]
+struct C.sigset_t {}
+
+fn C.sigaddset(set &C.sigset_t, signum int) int
+fn C.sigemptyset(set &C.sigset_t)
+fn C.sigprocmask(how int, set &C.sigset_t, oldset &C.sigset_t) int
+
+// signal_ignore to mask system signals, e.g.: signal_ignore(.pipe, .urg, ...)
+pub fn signal_ignore(args ...Signal) {
+	if is_main_thread() {
+		// for main thread.
+		for arg in args {
+			C.signal(int(arg), ignore_signal_handler)
+		}
+	} else {
+		// for background threads.
+		mask1 := C.sigset_t{}
+		C.sigemptyset(&mask1)
+		for arg in args {
+			C.sigaddset(&mask1, int(arg))
+		}
+		C.sigprocmask(C.SIG_BLOCK, &mask1, unsafe { nil })
+	}
+}

vlib/os/signal_test.v

@@ -33,3 +33,15 @@ fn test_signal_opt_return_former_handler() {
 	// this should work, but makes the CI fail because of a bug in clang -fsanitize=memory
 	// assert func2 == former_handler
 }
+
+fn signal_ignore_in_background_thread() {
+	os.signal_ignore(.pipe, .urg)
+	assert true
+}
+
+fn test_signal_ignore() {
+	os.signal_ignore(.pipe, .urg)
+	assert true
+	t := spawn signal_ignore_in_background_thread()
+	t.wait()
+}