int8, int128, int256

While uint[n] types can only contain positive integers, the int[n] types can contain both positive and negative numbers. As you know, int[n] variables store numbers ranging from -1 -> -(2 ^ (n-1)) on the negative side, and 0 -> ((2^n) - 1) on the positive side. This means that for the three int[n] types specified above, this would be their minimum and maximum values.

When it comes to storage of int[n] types, the positive values range from 0x00 in hex, (with the number of bytes after 0x corresponding to the number of bytes of the int[n] type) up till 0x7f. While the negative numbers range from 0xff to 0x80 backwards. It is reasonable as 0xff is greater than 0x80 on hexadecimal face value, so is -1 greater than -128 on the decimal scale.

int[n] types are packed in a similar way, just like their uint[n] counterparts.

You can try to store different int[n] types on Remix to see their storage layouts.

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.0;

contract Yul {
    // int<n> public variableName = value;
    int8 public int8Value = -1; // Slot 0.

    function getInt8() public view returns (bytes32) {
        assembly {
            mstore(0x80, sload(0x00))
            return(0x80, 0x20)
        }
    }
}

🚨 Due to the tricky nature of the storage of int[n] types, apply more care when storing and manipulating values from storage.

🚨 Do not store negative int[n] values directly from your Yul block of code, Yul treats it as a uint[n] type overflow, meaning that -1 will be converted to (2^256) - 1. This can lead to security breaches.