dedicated safe integer truncation integration test (#435)

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/integration/contracts/MLoad.sol

@@ -20,7 +20,7 @@ pragma solidity ^0.8.28;
                 "dest": {
                     "Instantiated": 0
                 },
-                "data": "e2179b8e"
+                "data": "0be0e4a60000000000000000000000000000000000000000000000000000000000000000"
             }
         }
     ]
@@ -29,12 +29,12 @@ pragma solidity ^0.8.28;
 
 contract MLoad {
     constructor() payable {
-        assert(g() == 0);
+        assert(loadAt(0) == 0);
     }
 
-    function g() public payable returns (uint m) {
+    function loadAt(uint _offset) public payable returns (uint m) {
         assembly {
-            m := mload(0)
+            m := mload(_offset)
         }
     }
 }

crates/integration/src/cases.rs

@@ -234,6 +234,15 @@ sol!(
 );
 case!("MCopy.sol", MCopy, memcpyCall, memcpy, payload: Bytes);
 
+sol!(
+    contract MLoad {
+        constructor() payable;
+
+        function loadAt(uint _offset) public payable returns (uint m);
+    }
+);
+case!("MLoad.sol", MLoad, loadAtCall, load_at, _offset: U256);
+
 sol!(
     contract Call {
         function value_transfer(address payable destination) public payable;

crates/integration/src/tests.rs

@@ -714,3 +714,41 @@ fn invalid_opcode_works() {
 
     assert_eq!(result.weight_consumed, GAS_LIMIT);
 }
+
+/// Load from heap memory using an out of bounds offset and expect the
+/// contract to hit the `invalid` syscall to use all gas (like on EVM).
+///
+/// The offset is picked such that a regular truncate would be in bounds.
+#[test]
+fn safe_truncate_int_to_xlen_works() {
+    let offset = 0x10000000_00000000u64;
+    let data = Contract::load_at(Uint::from(offset)).calldata;
+    let mut actions = instantiate("contracts/MLoad.sol", "MLoad");
+    actions.append(&mut vec![
+        Call {
+            origin: TestAddress::Alice,
+            dest: TestAddress::Instantiated(0),
+            value: 0,
+            gas_limit: None,
+            storage_deposit_limit: None,
+            data,
+        },
+        VerifyCall(VerifyCallExpectation {
+            success: false,
+            ..Default::default()
+        }),
+    ]);
+
+    let results = Specs {
+        actions,
+        differential: true,
+        ..Default::default()
+    }
+    .run();
+
+    let CallResult::Exec { result, .. } = results.last().unwrap() else {
+        unreachable!()
+    };
+
+    assert_eq!(result.weight_consumed, GAS_LIMIT);
+}