u256.fromBytes fails with out of memory error on bytes array

[liquitious]

• works: let latestRandomSeed: u256 = u256.fromU32(sha256(latestRandomSeed.toUint8Array())[0]);
• works: u256.fromBytes(latestRandomSeed.toUint8Array()) (where latestRandomSeed is u256)
• crashes: u256.fromBytes(sha256(latestRandomSeed.toUint8Array())). both LE and BE fail with error: [OPNetUnit HELP PANIC]: Error: out of memory

Note that sha256(latestRandomSeed.toUint8Array()) works and logging it I get something like: 109,8,85,163,53,128,47,11,194,9,70,243,196,140,5,182,185,140,20,181,120,2,13,95,66,161,102,185,127,230,245,159

Easiest way to reproduce that shows issue is not related to sha256:

// this crashes with out of memory error!!
latestRandomSeed = u256.fromBytes([
                109, 8, 85, 163, 53, 128, 47, 11, 194, 9, 70, 243, 196, 140, 5, 182, 185, 140, 20,
                181, 120, 2, 13, 95, 66, 161, 102, 185, 127, 230, 245, 159,
            ] as u8[]);

even on an array of len 2 bytes or 4 bytes we get this same crash

[BlobMaster41]

Thanks for reporting. ill investigate

[BlobMaster41]

crashes: u256.fromBytes(sha256(latestRandomSeed.toUint8Array())). both LE and BE fail with error: [OPNetUnit HELP PANIC]: Error: out of memory

This means that your contract is using more memory that what you have specified. Are you using the asconfig file included in the project? This file set the memory at a maximum of 512 memory pages which equals to 32.768mb. This is the maximum a contract can consume.

If your memory is that high, your gas will be very high.

[liquitious]

I drew incorrect conclusion that error was due to the u256.fromBytes. It is actually the following Safemath.mod we do. It seems this method if implemented inefficiently so if we pass a large number in we get a crash. Looks like solidity has optimized the % operation: https://github.com/polynetwork/eth-contracts/blob/master/contracts/libs/math/SafeMath.sol#L154

[liquitious]

Opened new issue here: #42