seccomp: install output atomically

Signed-off-by: Ophestra <cat@gensokyo.uk>

seccomp/output.go

@@ -0,0 +1,30 @@
+package seccomp
+
+import "C"
+import "sync/atomic"
+
+var printlnP atomic.Pointer[func(v ...any)]
+
+func SetOutput(f func(v ...any)) {
+	if f == nil {
+		// avoid storing nil function
+		printlnP.Store(nil)
+	} else {
+		printlnP.Store(&f)
+	}
+}
+
+func GetOutput() func(v ...any) {
+	if fp := printlnP.Load(); fp == nil {
+		return nil
+	} else {
+		return *fp
+	}
+}
+
+//export F_println
+func F_println(v *C.char) {
+	if fp := printlnP.Load(); fp != nil {
+		(*fp)(C.GoString(v))
+	}
+}