iktok90-design/ai-smart-contract-auditor/pragma-and-addresses

Pragma & address-hygiene detection

When this applies

• Top of every Solidity file
• Constants and immutables typed address
• Constructor / initializer parameters typed address
• mapping(address => …) updates
• Any cross-chain deployment where addresses differ per chain

Detection patterns

Floating pragma (LOW-MEDIUM)

pragma solidity ^0.8.0;   // ← floats to any 0.8.x

Production deployments should pin: pragma solidity 0.8.24;. Floating pragma means audited bytecode ≠ deployed bytecode.

Outdated Solidity version (MEDIUM)

<0.8.0 lacks built-in overflow checks. <0.8.20 lacks PUSH0 opcode handling for some L2s. Audit pin date vs known compiler bugs.

Hardcoded address tied to a single chain (HIGH)

address constant WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;   // ← mainnet WETH, breaks on Base/Arbitrum

WETH/USDC/USDT all have different addresses per chain. Use a chain-configurable resolver.

Missing zero-address check (HIGH on key fields)

function setOwner(address newOwner) external onlyOwner {
    owner = newOwner;   // ← if 0x0, contract is bricked
}

Affects ownership, oracles, treasury, fee receiver, token addresses.

Address(0) as default sentinel (MEDIUM)

Using address(0) to mean "unset" works but is brittle — collides with default mapping values.

payable(0) as burn (LOW-MEDIUM)

Burning by sending to address(0)'s payable is legal but locks ether forever. Document intent.

address(this) in cross-chain context (HIGH for CREATE2 deployments)

address(this) differs unless deterministically deployed at same address across chains.

address public foo; instead of address public immutable foo; (LOW)

Mutable when it shouldn't be — gas cost + risk of accidental setter.

Chain-ID-dependent address resolution missing (HIGH)

if (block.chainid == 1) router = MAINNET_ROUTER;
else if (block.chainid == 42161) router = ARB_ROUTER;
else revert("unsupported chain");   // ← without this, unsupported chain silently uses mainnet address

Severity rubric

Remediation patterns

• Pin exact Solidity version: pragma solidity 0.8.24; (or whatever you tested with).
• Zero-address checks on every setter: require(newAddr != address(0), "zero address");.
• Chain-aware address resolver:

``solidity function _weth() internal view returns (address) { if (block.chainid == 1) return MAINNET_WETH; if (block.chainid == 8453) return BASE_WETH; if (block.chainid == 42161) return ARB_WETH; revert UnsupportedChain(); } ``

• Use OZ Ownable2Step so even a bad zero-address would require accept().
• For immutable-when-possible, mark with immutable keyword.

False-positive notes

• Test/mock files with hardcoded addresses are fine.
• address(0) checks may be redundant if subsequent OZ library calls already validate.
• Floating pragma in libraries (vs deployed contracts) is sometimes intentional.

Related

• [[access-control]]
• [[storage-layout]]
• [[upgrade-safety]]