fix typecast

runtime/src/read_only_accounts_cache.rs

@@ -38,9 +38,9 @@ impl ReadOnlyAccountCacheEntry {
             last_time: Self::timestamp(),
         }
     }
-    /// lower bits of current timestamp. We don't need higher bits and u32 fits with Index u32
+    /// lower bits of current timestamp. We don't need higher bits and u32 packs with Index u32 in `ReadOnlyAccountCacheEntry`
     fn timestamp() -> u32 {
-        (timestamp() % (u32::MAX as u64 + 1)) as u32
+        timestamp() as u32
     }
     /// ms since `last_time` timestamp
     fn ms_since_last_time(&self) -> u32 {
@@ -285,6 +285,18 @@ mod tests {
     /// tests like to deterministically update lru always
     const READ_ONLY_CACHE_MS_TO_SKIP_LRU_UPDATE_FOR_TESTS: u32 = 0;
 
+    #[test]
+    fn test_overflow() {
+        solana_logger::setup();
+        let l = u32::MAX as u64;
+        let l = l + 3;
+        log::error!("{}", (l % (u32::MAX as u64 + 1)) as u32);
+        log::error!("{}", l as u32);
+        let l = 3;
+        log::error!("{}", (l % (u32::MAX as u64 + 1)) as u32);
+        log::error!("{}", l as u32);
+    }
+
     #[test]
     fn test_read_only_accounts_cache_random() {
         const SEED: [u8; 32] = [0xdb; 32];