library: sub_timespec use arithmetic to avoid overflow

Signed-off-by: Eval EXEC <[email protected]>

Author: eval-exec

library/std/src/sys/pal/unix/time.rs

@@ -139,9 +139,10 @@ impl Timespec {
     #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
     pub const fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
         // FIXME: const PartialOrd
-        let mut cmp = self.tv_sec - other.tv_sec;
+        // Use saturating arithmetic to avoid overflow when comparing extreme values
+        let mut cmp = self.tv_sec.saturating_sub(other.tv_sec);
         if cmp == 0 {
-            cmp = self.tv_nsec.as_inner() as i64 - other.tv_nsec.as_inner() as i64;
+            cmp = self.tv_nsec.as_inner() as i64 - other.tv_nsec.as_inner() as i64
         }
 
         if cmp >= 0 {