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fix(levm): handle sdiv with zero dividend and negative divisor #1241

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merged 4 commits into from
Nov 25, 2024
Merged

fix(levm): handle sdiv with zero dividend and negative divisor #1241

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a0f4638
Add edge case test
maximopalopoli Nov 22, 2024
02428fb
Fix edge case
maximopalopoli Nov 22, 2024
4382581
Refactor to clarify the situation with checked_add
maximopalopoli Nov 22, 2024
7301780
cargo fmt
maximopalopoli Nov 22, 2024
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21 changes: 11 additions & 10 deletions crates/vm/levm/src/opcode_handlers/arithmetic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ impl VM {

let dividend = current_call_frame.stack.pop()?;
let divisor = current_call_frame.stack.pop()?;
if divisor.is_zero() {
if divisor.is_zero() || dividend.is_zero() {
current_call_frame.stack.push(U256::zero())?;
return Ok(OpcodeSuccess::Continue);
}
Expand All @@ -92,15 +92,16 @@ impl VM {
} else {
divisor
};
let Some(quotient) = dividend.checked_div(divisor) else {
current_call_frame.stack.push(U256::zero())?;
return Ok(OpcodeSuccess::Continue);
};
let quotient_is_negative = dividend_is_negative ^ divisor_is_negative;
let quotient = if quotient_is_negative {
negate(quotient)
} else {
quotient
let quotient = match dividend.checked_div(divisor) {
Some(quot) => {
let quotient_is_negative = dividend_is_negative ^ divisor_is_negative;
if quotient_is_negative {
negate(quot)
} else {
quot
}
}
None => U256::zero(),
};

current_call_frame.stack.push(quotient)?;
Expand Down
13 changes: 13 additions & 0 deletions crates/vm/levm/tests/edge_case_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -101,3 +101,16 @@ fn test_is_negative() {
let mut current_call_frame = vm.call_frames.pop().unwrap();
vm.execute(&mut current_call_frame);
}

#[test]
fn test_sdiv_zero_dividend_and_negative_divisor() {
let mut vm = new_vm_with_bytecode(Bytes::copy_from_slice(&[
0x7F, 0xC5, 0xD2, 0x46, 0x01, 0x86, 0xF7, 0x23, 0x3C, 0x92, 0x7E, 0x7D, 0xB2, 0xDC, 0xC7,
0x03, 0xC0, 0xE5, 0x00, 0xB6, 0x53, 0xCA, 0x82, 0x27, 0x3B, 0x7B, 0xFA, 0xD8, 0x04, 0x5D,
0x85, 0xA4, 0x70, 0x5F, 0x05,
]))
.unwrap();
let mut current_call_frame = vm.call_frames.pop().unwrap();
vm.execute(&mut current_call_frame);
assert_eq!(current_call_frame.stack.pop().unwrap(), U256::zero());
}
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