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improve: Reduce gas and minimize overflow risk in for loops #148

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Merged
merged 1 commit into from
Apr 26, 2022
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improve: Reduce gas and minimize overflow risk in for loops #148

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6 changes: 3 additions & 3 deletions contracts/HubPool.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -864,8 +864,8 @@ contract HubPool is HubPoolInterface, Testable, Lockable, MultiCaller, Ownable {
int256[] memory netSendAmounts,
uint256[] memory bundleLpFees
) internal {
uint32 length = uint32(l1Tokens.length);
for (uint32 i = 0; i < length; ) {
uint256 length = l1Tokens.length;
for (uint256 i = 0; i < length; ) {
address l1Token = l1Tokens[i];
// Validate the L1 -> L2 token route is stored. If it is not then the output of the bridging action
// could send tokens to the 0x0 address on the L2.
Expand Down Expand Up @@ -900,7 +900,7 @@ contract HubPool is HubPoolInterface, Testable, Lockable, MultiCaller, Ownable {
// Allocate LP fees and protocol fees from the bundle to the associated pooled token trackers.
_allocateLpAndProtocolFees(l1Token, bundleLpFees[i]);

// L1 tokens length won't be > types(uint32).length, so use unchecked block to save gas. Based on the
// L1 tokens length won't be > types(uint256).length, so use unchecked block to save gas. Based on the
// stress test results in /test/gas-analytics/HubPool.RootExecution.ts, the UMIP should limit the L1 token
// count in valid proposals to be ~100 so any PoolRebalanceLeaves with > 100 l1Tokens should not make it
// to this stage.
Expand Down
6 changes: 3 additions & 3 deletions contracts/SpokePool.sol
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Expand Up @@ -550,13 +550,13 @@ abstract contract SpokePool is SpokePoolInterface, Testable, Lockable, MultiCall

// Send each relayer refund address the associated refundAmount for the L2 token address.
// Note: Even if the L2 token is not enabled on this spoke pool, we should still refund relayers.
uint32 length = uint32(relayerRefundLeaf.refundAmounts.length);
for (uint32 i = 0; i < length; ) {
uint256 length = relayerRefundLeaf.refundAmounts.length;
for (uint256 i = 0; i < length; ) {
uint256 amount = relayerRefundLeaf.refundAmounts[i];
if (amount > 0)
IERC20(relayerRefundLeaf.l2TokenAddress).safeTransfer(relayerRefundLeaf.refundAddresses[i], amount);

// OK because we assume refund array length won't be > types(uint32).max.
// OK because we assume refund array length won't be > types(uint256).max.
// Based on the stress test results in /test/gas-analytics/SpokePool.RelayerRefundLeaf.ts, the UMIP should
// limit the refund count in valid proposals to be ~800 so any RelayerRefundLeaves with > 800 refunds should
// not make it to this stage.
Expand Down