FiraERC20

FiraERC20 is the custom ERC-20 base used by every token in the protocol, providing a built-in reentrancy guard and transfer hooks.

Source: src/fira_bonding/erc20/FiraERC20.sol, FiraERC20Permit.sol, FiraERC20Upg.sol, FiraERC20PermitUpg.sol

Variants

Contract	Permit	Upgradeable	Used by
FiraERC20	No	No	BT, FiraMarket (LP)
FiraERC20Permit	EIP-2612	No	—
FiraERC20Upg	No	Yes (Initializable)	—
FiraERC20PermitUpg	EIP-2612	Yes (Initializable)	FW tokens

Reentrancy guard

A _reentrancyStatus slot flips between _NOT_ENTERED (1) and _ENTERED (2). The nonReentrant modifier is available to all contracts that inherit FiraERC20. This means FiraMarket (which extends FiraERC20 as its LP token) gets reentrancy protection without extra inheritance.

Transfer hooks

• _beforeTokenTransfer — Virtual, overridden by CT (distributes interest) and FW (enforces pause)
• _afterTokenTransfer — Virtual, available for derived contracts

Permit (EIP-2612)

FiraERC20Permit adds gasless approvals via permit(owner, spender, value, deadline, v, r, s). Uses EIP-712 typed data for domain separation. The DOMAIN_SEPARATOR is computed at construction time and cached.

Design decisions

• No receive or fallback — only contracts that need ETH (FWBase, Router) add receive()
• Storage layout matches between upgradeable and non-upgradeable variants