I have a solidity library that has a public function and it's returning a uint8[] array.

pragma solidity ^0.8.4;

library LibA {
    function getArray() public pure returns (uint8[] memory) {
        uint8[] memory arr;
        arr[0] = 100;

        return arr;

Then I have a Solidity smart contract that references the library and calls the function trying to access the array defined in the library. The code looks like this.

pragma solidity ^0.8.4;

import "./LibA.sol";

contract SampleContract {

    function doSomething(uint8 _index) public pure returns (uint8) {
        return LibA.getArray()[_index];

The code compiles just fine. I have a mocha unit test that is run using Hardhat to test the method and when I run the unit test I get the following exception.

Error: VM Exception while processing transaction: reverted with panic code 0x32 (Array accessed at an out-of-bounds or negative index)

I am quite new to Solidity and I'm having trouble understanding exactly what is the reason for the exception and how to resolve it. Some help would be greatly appreciated.

1 Answer 1


I've never worked with libraries before, however I believe the issue might be that you are trying to have a dynamically sized array in memory. This should be

uint8[] memory arr = new uint8[](arraySize);

in order to allocate the space in memory beforehand.

  • You are absolutely right. That was the issue. Thank you so much :) Nov 5, 2021 at 21:21

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