add clear error message to give more information at out of gas (#50)

* add clear error message to give more information at out of gas

* unit round down

crates/gas/src/meter.rs

@@ -224,14 +224,25 @@ impl InitiaGasMeter {
 
     #[inline]
     fn charge(&mut self, amount: InternalGas) -> PartialVMResult<()> {
+        // copy the value for error message
+        let balance = self.balance;
+
         match self.balance.checked_sub(amount) {
             Some(new_balance) => {
                 self.balance = new_balance;
                 Ok(())
             }
             None => {
                 self.balance = 0.into();
-                Err(PartialVMError::new(StatusCode::OUT_OF_GAS))
+                let gas_used: Gas = (self.gas_limit.checked_sub(balance).unwrap() + amount)
+                    .to_unit_round_down_with_params(&self.gas_params.txn);
+
+                Err(
+                    PartialVMError::new(StatusCode::OUT_OF_GAS).with_message(format!(
+                        "gas_limit: {}, gas_used: {}",
+                        self.gas_limit, gas_used
+                    )),
+                )
             }
         }
     }

crates/natives/src/crypto/ed25519.rs

@@ -178,7 +178,9 @@ pub fn native_batch_verify(
     } else if public_keys_len == 1 && messages_len == signatures_len {
         public_keys = repeats_vec_of_vec_u8(public_keys[0].to_vec(), signatures_len);
     } else {
-        return Err(SafeNativeError::Abort { abort_code: NUMBER_OF_ARGUMENTS_MISMATCH });
+        return Err(SafeNativeError::Abort {
+            abort_code: NUMBER_OF_ARGUMENTS_MISMATCH,
+        });
     }
 
     debug_assert_eq!(messages.len(), signatures_len);