contract C { function test(bytes memory buf) public view returns (bool same, bool inplaceDecoded) { (uint256[] memory arr1, uint256[] memory arr2) = abi.decode(buf, (uint256[],uint256[])); assembly { // Check whether arr1 and arr2 end up at the same memory location. // This used to be the case, if both tail pointers in buf pointed to the // same memory region, i.e. this used to be false in the first two, but true // in the last three calls below. The desired behaviour is to always get distinct // memory regions, i.e. this should be false. same := eq(arr1, arr2) // Check whether (given the particular tail pointer of 0x40 for arr1 in the calls below) // arr1 points to the part of buf containing the encoding of arr1. // The position of the encoding of arr1 in buf is at offset 0x20 (length) + 0x40 (tail pointer) // of buf. // This used to be the case for all the test calls below, whereas now arr1 is always copied // from buf to a new memory area. Should always be false. inplaceDecoded := eq(arr1, add(buf, 0x60)) } } } // ==== // compileViaYul: also // ---- // test(bytes): 0x20, 0x80, 0x40, 0x60, 0, 0 -> false, false // test(bytes): 0x20, 0xC0, 0x40, 0x80, 1, 0x42, 1, 0x42 -> false, false // test(bytes): 0x20, 0x80, 0x40, 0x40, 1, 0x42 -> false, false // test(bytes): 0x20, 0x60, 0x40, 0x40, 0 -> false, false // test(bytes): 0x20, 0x80, 0x40, 0x40, 1, 0x42 -> false, false