Fix i586 compilation and add more checks

src/header/time/mod.rs

@@ -48,7 +48,7 @@ pub use strptime::strptime;
 const YEARS_PER_ERA: time_t = 400;
 const DAYS_PER_ERA: time_t = 146097;
 const SECS_PER_DAY: time_t = 24 * 60 * 60;
-const NANOSECONDS: i64 = 1_000_000_000;
+const NANOSECONDS: c_long = 1_000_000_000;
 const UTC_STR: &core::ffi::CStr = c"UTC";
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/time.h.html>.
@@ -64,32 +64,40 @@ impl timespec {
 
     /// similar logic with timeradd
     pub fn add(base: timespec, interval: timespec) -> Option<timespec> {
-        let delta_sec = base.tv_sec + interval.tv_sec;
-        let delta_nsec = base.tv_nsec + interval.tv_nsec;
+        let Some(delta_sec) = base.tv_sec.checked_add(interval.tv_sec) else {
+            return None;
+        };
+        let Some(delta_nsec) = base.tv_nsec.checked_add(interval.tv_nsec) else {
+            return None;
+        };
 
         if delta_sec < 0 || delta_nsec < 0 {
             return None;
         }
 
         Some(Self {
-            tv_sec: delta_sec + (delta_nsec / NANOSECONDS),
+            tv_sec: delta_sec + (delta_nsec / NANOSECONDS) as time_t,
             tv_nsec: delta_nsec % NANOSECONDS,
         })
     }
     /// similar logic with timersub
     pub fn subtract(later: timespec, earlier: timespec) -> Option<timespec> {
-        let delta_sec = later.tv_sec - earlier.tv_sec;
-        let delta_nsec = later.tv_nsec - earlier.tv_nsec;
+        let Some(delta_sec) = later.tv_sec.checked_sub(earlier.tv_sec) else {
+            return None;
+        };
+        let Some(delta_nsec) = later.tv_nsec.checked_sub(earlier.tv_nsec) else {
+            return None;
+        };
 
         let time = if delta_nsec < 0 {
             let roundup_sec = -delta_nsec / NANOSECONDS + 1;
             timespec {
-                tv_sec: delta_sec - roundup_sec,
+                tv_sec: delta_sec - (roundup_sec as time_t),
                 tv_nsec: roundup_sec * NANOSECONDS - delta_nsec,
             }
         } else {
             timespec {
-                tv_sec: delta_sec + (delta_nsec / NANOSECONDS),
+                tv_sec: delta_sec + (delta_nsec / NANOSECONDS) as time_t,
                 tv_nsec: delta_nsec % NANOSECONDS,
             }
         };