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fix failed() cheatcode error #359

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merged 6 commits into from
Aug 28, 2024
Merged

fix failed() cheatcode error #359

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e46f43a
fix failed() cheatcode error
daejunpark Aug 27, 2024
10f85d9
add test
daejunpark Aug 27, 2024
03850b3
updated test expected
daejunpark Aug 27, 2024
6a06382
Merge remote-tracking branch 'origin/main' into fix/failed-cheatcode
daejunpark Aug 27, 2024
d1a4380
fix: handle the case where resolve_address_alias returns None
daejunpark Aug 28, 2024
714d39c
add svm.enableSymbolicStorage tests
daejunpark Aug 28, 2024
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18 changes: 18 additions & 0 deletions src/halmos/cheatcodes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -354,6 +354,18 @@ class hevm_cheat_code:
)
)

# abi.encodePacked(
# bytes4(keccak256("load(address,bytes32)")),
# abi.encode(HEVM_ADDRESS, bytes32("failed"))
# )
failed_payload = ByteVec(
bytes.fromhex(
"667f9d70"
+ "0000000000000000000000007109709ecfa91a80626ff3989d68f67f5b1dd12d"
+ "6661696c65640000000000000000000000000000000000000000000000000000"
)
)

# bytes4(keccak256("assume(bool)"))
assume_sig: int = 0x4C63E562

Expand Down Expand Up @@ -533,6 +545,12 @@ def handle(sevm, ex, arg: ByteVec, stack, step_id) -> ByteVec | None:

# vm.load(address,bytes32)
elif funsig == hevm_cheat_code.load_sig:
# vm.load(HEVM_ADDRESS, "failed") is handled separately
if arg == hevm_cheat_code.failed_payload:
# since fail(), which triggers vm.store(HEVM_ADDRESS, "failed", 1), halts immediately, (see vm.store() above)
# the "failed" slot is never assigned, thus vm.load(HEVM_ADDRESS, "failed") always return zero at this point
return ByteVec(con(0))
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would it be bad to return 0 if load_account_alias is None?

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ideally we wouldn't handle hevm as an edge case

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good idea! how should we do for vm.store() with nonexistent account?

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done for vm.load().

for vm.store(), currently an exception is raised if the given account doesn't exist.

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for vm.store(), currently an exception is raised if the given account doesn't exist

ok, so the idea is that we need to first deploy code at an address and then we can vm.store to it? is that because deploying resets the storage?

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so far, we have the invariant that for any address x, x in ex.code iff x in ex.storage. now, if we allow vm.store() for nonexistent addresses, the invariant would no longer hold, which leads to some logic changes in the codebase.

another invariant we have is that all addresses in ex.code/ex.storage are concrete. if the given address is symbolic, this invariant would be broken. note that calls to symbolic addresses don't break this, because of branching over concrete aliases, and calls to nonexistent address are essentially no-op.

while these invariants are convenient for various reasons, they aren't absolutely necessary. so we can break them and adjust our logic, if needed, although this would increase code complexity.

i'd suggest we wait until we see concrete use cases where vm.store() is used with nonexistent or symbolic addresses, before deciding how to redesign this logic.


load_account = uint160(arg.get_word(4))
load_slot = uint256(arg.get_word(36))
load_account_alias = sevm.resolve_address_alias(
Expand Down
9 changes: 9 additions & 0 deletions tests/expected/all.json
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Expand Up @@ -1024,6 +1024,15 @@
"num_paths": null,
"time": null,
"num_bounded_loops": null
},
{
"name": "check_failed_cheatcode()",
"exitcode": 0,
"num_models": 0,
"models": null,
"num_paths": null,
"time": null,
"num_bounded_loops": null
}
],
"test/Foundry.t.sol:FoundryTest": [
Expand Down
5 changes: 5 additions & 0 deletions tests/regression/test/Foundry.t.sol
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Expand Up @@ -37,6 +37,11 @@ contract EarlyFailTest is Test {
// - counterexample caused by assert(x > 0): x == 0
assert(x > 0);
}

function check_failed_cheatcode() public {
// since fail() halts immediately, failed() always return true here
assertFalse(failed());
}
}

contract FoundryTest is Test {
Expand Down
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