dev: use consts for empty hash (#1431)

<!--- Please provide a general summary of your changes in the title
above -->

<!-- Give an estimate of the time you spent on this PR in terms of work
days.
Did you spend 0.5 days on this PR or rather 2 days?  -->

Time spent on this PR:

## Pull request type

<!-- Please try to limit your pull request to one type,
submit multiple pull requests if needed. -->

Please check the type of change your PR introduces:

- [ ] Bugfix
- [ ] Feature
- [ ] Code style update (formatting, renaming)
- [ ] Refactoring (no functional changes, no api changes)
- [ ] Build related changes
- [ ] Documentation content changes
- [ ] Other (please describe):

## What is the current behavior?

<!-- Please describe the current behavior that you are modifying,
or link to a relevant issue. -->

Resolves #1410

## What is the new behavior?

<!-- Please describe the behavior or changes that are being added by
this PR. -->

-
-
-

<!-- Reviewable:start -->
- - -
This change is [<img src="https://reviewable.io/review_button.svg"
height="34" align="absmiddle"
alt="Reviewable"/>](https://reviewable.io/reviews/kkrt-labs/kakarot/1431)
<!-- Reviewable:end -->

src/kakarot/account.cairo

@@ -125,7 +125,7 @@ namespace Account {
             assert balance_ptr = new Uint256(balance.low, balance.high);
             // empty code hash see https://eips.ethereum.org/EIPS/eip-1052
             tempvar code_hash_ptr = new Uint256(
-                304396909071904405792975023732328604784, 262949717399590921288928019264691438528
+                low=Constants.EMPTY_CODE_HASH_LOW, high=Constants.EMPTY_CODE_HASH_HIGH
             );
             let account = Account.init(
                 address=address,
@@ -699,7 +699,7 @@ namespace Account {
         if (code_len == 0) {
             // see https://eips.ethereum.org/EIPS/eip-1052
             let empty_code_hash = Uint256(
-                304396909071904405792975023732328604784, 262949717399590921288928019264691438528
+                low=Constants.EMPTY_CODE_HASH_LOW, high=Constants.EMPTY_CODE_HASH_HIGH
             );
             return empty_code_hash;
         }

src/kakarot/constants.cairo

@@ -16,7 +16,8 @@ namespace Constants {
     // ACCOUNTS
     const MAX_NONCE = 2 ** 64 - 1;
     const MAX_CODE_SIZE = 0x6000;
-
+    const EMPTY_CODE_HASH_LOW = 0xe500b653ca82273b7bfad8045d85a470;
+    const EMPTY_CODE_HASH_HIGH = 0xc5d2460186f7233c927e7db2dcc703c0;
     const BURN_ADDRESS = 0xdead;
 }
 

src/kakarot/state.cairo

@@ -18,6 +18,7 @@ from kakarot.gas import Gas
 from utils.dict import default_dict_copy
 from utils.utils import Helpers
 from utils.uint256 import uint256_add, uint256_sub, uint256_eq
+from kakarot.constants import Constants
 
 namespace State {
     // @dev Create a new empty State
@@ -466,7 +467,7 @@ namespace Internals {
         let (bytecode) = alloc();
         // empty code hash see https://eips.ethereum.org/EIPS/eip-1052
         tempvar code_hash_ptr = new Uint256(
-            304396909071904405792975023732328604784, 262949717399590921288928019264691438528
+            Constants.EMPTY_CODE_HASH_LOW, Constants.EMPTY_CODE_HASH_HIGH
         );
         let account = Account.init(
             address=address,

tests/src/kakarot/test_account.cairo

@@ -10,6 +10,7 @@ from starkware.cairo.common.memcpy import memcpy
 from kakarot.model import model
 from kakarot.account import Account
 from tests.utils.helpers import TestHelpers
+from kakarot.constants import Constants
 
 func test__init__should_return_account_with_default_dict_as_storage{
     syscall_ptr: felt*, pedersen_ptr: HashBuiltin*, range_check_ptr, bitwise_ptr: BitwiseBuiltin*
@@ -173,9 +174,7 @@ func test__fetch_original_storage__state_modified{
     let starknet_address = Account.compute_starknet_address(evm_address);
     tempvar address = new model.Address(starknet_address, evm_address);
     let (local code: felt*) = alloc();
-    tempvar code_hash = new Uint256(
-        304396909071904405792975023732328604784, 262949717399590921288928019264691438528
-    );
+    tempvar code_hash = new Uint256(Constants.EMPTY_CODE_HASH_LOW, Constants.EMPTY_CODE_HASH_HIGH);
     tempvar balance = new Uint256(0, 0);
     let account = Account.init(address, 0, code, code_hash, 0, balance);
 

tests/src/kakarot/test_state.cairo

@@ -16,6 +16,7 @@ from backend.starknet import Starknet
 from kakarot.state import State, Internals
 from kakarot.account import Account
 from kakarot.storages import Kakarot_native_token_address
+from kakarot.constants import Constants
 from utils.dict import dict_keys
 
 func test__init__should_return_state_with_default_dicts() {
@@ -172,9 +173,7 @@ func test___copy_accounts__should_handle_null_pointers{range_check_ptr}() {
     tempvar address = new model.Address(1, 2);
     tempvar balance = new Uint256(1, 0);
     let (code) = alloc();
-    tempvar code_hash = new Uint256(
-        304396909071904405792975023732328604784, 262949717399590921288928019264691438528
-    );
+    tempvar code_hash = new Uint256(Constants.EMPTY_CODE_HASH_LOW, Constants.EMPTY_CODE_HASH_HIGH);
     let account = Account.init(address, 0, code, code_hash, 1, balance);
     dict_write{dict_ptr=accounts}(address.evm, cast(account, felt));
     let empty_address = 'empty address';
@@ -202,9 +201,7 @@ func test__is_account_warm__account_in_state{
     tempvar address = new model.Address(starknet_address, evm_address);
     tempvar balance = new Uint256(1, 0);
     let (code) = alloc();
-    tempvar code_hash = new Uint256(
-        304396909071904405792975023732328604784, 262949717399590921288928019264691438528
-    );
+    tempvar code_hash = new Uint256(Constants.EMPTY_CODE_HASH_LOW, Constants.EMPTY_CODE_HASH_HIGH);
     let account = Account.init(address, 0, code, code_hash, 1, balance);
     tempvar state = State.init();