Enable CLOCK_BOOTTIME on more platforms. (#757)

Enable `CLOCK_BOOTTIME` and `CLOCK_BOOTTIME_ALARM` on more platforms,
and add a testcase for it.

Author: sunfishcode

src/backend/libc/time/syscalls.rs

@@ -166,10 +166,15 @@ pub(crate) fn clock_gettime_dynamic(id: DynamicClockId<'_>) -> io::Result<Timesp
         #[cfg(linux_kernel)]
         DynamicClockId::Tai => c::CLOCK_TAI,
 
-        #[cfg(any(linux_kernel, target_os = "openbsd"))]
+        #[cfg(any(
+            freebsdlike,
+            linux_kernel,
+            target_os = "fuchsia",
+            target_os = "openbsd"
+        ))]
         DynamicClockId::Boottime => c::CLOCK_BOOTTIME,
 
-        #[cfg(linux_kernel)]
+        #[cfg(any(linux_kernel, target_os = "fuchsia"))]
         DynamicClockId::BoottimeAlarm => c::CLOCK_BOOTTIME_ALARM,
     };
 

src/clockid.rs

@@ -96,10 +96,15 @@ pub enum DynamicClockId<'a> {
     Tai,
 
     /// `CLOCK_BOOTTIME`, available on Linux >= 2.6.39
-    #[cfg(any(linux_kernel, target_os = "openbsd"))]
+    #[cfg(any(
+        freebsdlike,
+        linux_kernel,
+        target_os = "fuchsia",
+        target_os = "openbsd"
+    ))]
     Boottime,
 
     /// `CLOCK_BOOTTIME_ALARM`, available on Linux >= 2.6.39
-    #[cfg(linux_kernel)]
+    #[cfg(any(linux_kernel, target_os = "fuchsia"))]
     BoottimeAlarm,
 }

tests/time/clocks.rs

@@ -5,6 +5,29 @@
 #[cfg(not(any(solarish, target_os = "netbsd", target_os = "redox")))]
 use rustix::time::{clock_gettime, ClockId};
 
+/// Attempt to test that the boot clock is monotonic. Time may or may not
+/// advance, but it shouldn't regress.
+#[cfg(any(
+    freebsdlike,
+    linux_kernel,
+    target_os = "fuchsia",
+    target_os = "openbsd"
+))]
+#[test]
+fn test_boottime_clock() {
+    use rustix::time::{clock_gettime_dynamic, DynamicClockId};
+
+    if let Ok(a) = clock_gettime_dynamic(DynamicClockId::Boottime) {
+        if let Ok(b) = clock_gettime_dynamic(DynamicClockId::Boottime) {
+            if b.tv_sec == a.tv_sec {
+                assert!(b.tv_nsec >= a.tv_nsec);
+            } else {
+                assert!(b.tv_sec > a.tv_sec);
+            }
+        }
+    }
+}
+
 /// Attempt to test that the uptime clock is monotonic. Time may or may not
 /// advance, but it shouldn't regress.
 #[cfg(any(freebsdlike, target_os = "openbsd"))]