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Title

Use of Deprecated Solidity Functions

Relationships

CWE-477: Use of Obsolete Function

Description

Several functions and operators in Solidity are deprecated. Using them leads to reduced code quality. With new major versions of the Solidity compiler, deprecated functions and operators may result in side effects and compile errors.

Remediation

Solidity provides alternatives to the deprecated constructions. Most of them are aliases, thus replacing old constructions will not break current behavior. For example, sha3 can be replaced with keccak256.

Deprecated	Alternative
`suicide(address)`	`selfdestruct(address)`
`block.blockhash(uint)`	`blockhash(uint)`
`sha3(...)`	`keccak256(...)`
`callcode(...)`	`delegatecall(...)`
`throw`	`revert()`
`msg.gas`	`gasleft`
`constant`	`view`
`var`	corresponding type name

References

Samples

deprecated_simple.sol

pragma solidity ^0.4.24;

contract DeprecatedSimple {

    // Do everything that's deprecated, then commit suicide.

    function useDeprecated() public constant {

        bytes32 blockhash = block.blockhash(0);
        bytes32 hashofhash = sha3(blockhash);

        uint gas = msg.gas;

        if (gas == 0) {
            throw;
        }

        address(this).callcode();

        var a = [1,2,3];

        var (x, y, z) = (false, "test", 0);

        suicide(address(0));
    }

    function () public {}

}

deprecated_simple_fixed.sol

pragma solidity ^0.4.24;

contract DeprecatedSimpleFixed {

    function useDeprecatedFixed() public view {

        bytes32 bhash = blockhash(0);
        bytes32 hashofhash = keccak256(bhash);

        uint gas = gasleft();

        if (gas == 0) {
            revert();
        }

        address(this).delegatecall();

        uint8[3] memory a = [1,2,3];

        (bool x, string memory y, uint8 z) = (false, "test", 0);

        selfdestruct(address(0));
    }

    function () external {}

}