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Using extcodehash instead of extcodesize for less gas #1802

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Jul 8, 2019
Merged

Using extcodehash instead of extcodesize for less gas #1802

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6252cc4
Using extcodehash instead of extcodesize for less gas
PhABC Jun 18, 2019
9846990
Fix
PhABC Jun 18, 2019
72364d8
Add explainer
PhABC Jun 19, 2019
c6f7fbe
Update Address.sol
PhABC Jun 19, 2019
f63644a
add changelog entry
frangio Jul 8, 2019
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5 changes: 5 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -5,6 +5,11 @@
### New features:
* `Address.toPayable`: added a helper to convert between address types without having to resort to low-level casting. ([#1773](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1773))

### Improvements:
* `Address.isContract`: switched from `extcodesize` to `extcodehash` for less gas usage. ([#1802](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1802))

### Bugfixes

## 2.3.0 (2019-05-27)

### New features:
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12 changes: 8 additions & 4 deletions contracts/utils/Address.sol
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Expand Up @@ -18,11 +18,15 @@ library Address {
// This method relies in extcodesize, which returns 0 for contracts in
// construction, since the code is only stored at the end of the
// constructor execution.

uint256 size;

// According to EIP-1052, 0x0 is the value returned for not-yet created accounts
// and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
// for accounts without code, i.e. `keccak256('')`
bytes32 codehash;
bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
// solhint-disable-next-line no-inline-assembly
assembly { size := extcodesize(account) }
return size > 0;
assembly { codehash := extcodehash(account) }
return (codehash != 0x0 && codehash != accountHash);
}

/**
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