Assigning values to bytes causes an ABICoder v1 decoding exception.

[Subway2023]

Description

Assigning a value to a bytes variable using assembly results in an abnormal return value.

Environment

• Compiler version: 0.8.28
• Target EVM version (as per compiler settings): None
• Framework/IDE (e.g. Truffle or Remix): Remix
• EVM execution environment / backend / blockchain client: None
• Operating system: None

Steps to Reproduce

By commenting out pragma abicoder v1;, you manually enable or disable ABICoder v1.

// pragma abicoder v1;
contract Combined {
    function complexFunction() public pure returns (bytes memory, uint, bytes20[] memory, uint) {
        (bytes memory a, uint b, bytes20[] memory c, uint d) = simplifiedFunction();
        // manipulate memory outputs
        assembly {
            let ptr := mload(0x40)
            a := ptr
        }
        // optional loop and manipulation
        for (uint i = 0; i < c.length; i++) {
            if (i == 2) {
                continue;
            }
            c[i] = bytes20(uint160(c[i]) ^ 0xFFFF);
        }
        return (a, b, c, d);
    }
    function simplifiedFunction() internal pure returns (bytes memory a, uint b, bytes20[] memory c, uint d) {
        a = "ESCAPE\\SEQUENCE\\TEST";
        b = type(uint).max;
        c = new bytes20[](4);
        c[0] = bytes20(uint160(1234));
        c[3] = bytes20(uint160(6789));
        d = 0x1234;
    }
}

Not use ABICoder v1

{
	"0": "bytes: 0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080",
	"1": "uint256: 115792089237316195423570985008687907853269984665640564039457584007913129639935",
	"2": "bytes20[]: 0x000000000000000000000000000000000000fb2d,0x000000000000000000000000000000000000ffff,0x0000000000000000000000000000000000000000,0x000000000000000000000000000000000000e57a",
	"3": "uint256: 4660"
}

use ABICoder v1

{
	"0": "bytes: 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000012340000000000000000000000000000000000000000000000000000000000000080",
	"1": "uint256: 115792089237316195423570985008687907853269984665640564039457584007913129639935",
	"2": "bytes20[]: 0x000000000000000000000000000000000000fb2d,0x000000000000000000000000000000000000ffff,0x0000000000000000000000000000000000000000,0x000000000000000000000000000000000000e57a",
	"3": "uint256: 4660"
}

The result of the first return value is abnormal. Why do fff and 1234 appear?