Upgrade EVM for better compatibility with ETH ecosystem

[hayeah]

The popular OpenZeppelin contracts can't run on QTUM's EVM. Two instructions are missing:

• returndatasize
• returndatacopy

There are also upcoming "revert with reason" instruction (EIP 140) that would help a lot with debugging. Toolchains and Solidity will soon have support for this.

[mahuaibo]

I have the same problem.
1）returndatasize
2）returndatacopy
The contract does not work properly.

[hayeah]

Just to add more detail to this problem. returndatasize and returndatacopy are used when a contract calls another contract's method, and uses the return value.

contract A {
  B b;
  function callBar() returns(uint256) {
    return b.bar();
  }
}

contract B {
  function bar() returns(uint256) {
    return 2;
  }
}

[hayeah]

To follow up further on this issue, we can work around this problem by asking solc to emit code for homestead instead of byzantium:

solc --bin --asm --evm-version homestead Foo.sol

The generated code would avoid using returndatacopy and returndatasize.

Also, beware of the return value truncation issue:

bytes, int256, small structs should be ok.

[dwalintukan]

👍 for upgrading the EVM.

Just tried deploying my compiled contracts which was compiled with the newest solc 0.4.24, but it results in throwing a BadInstruction error.

It compiles and deploys fine on Remix though.

[Earlz]

An upgraded EVM is planned to be included in the x86 hard fork

[ethgamble]

use my fork of solar, added --evm-version homestead by default

go get -u github.com/ethgamble/solar/cli/solar

[paulofelipe84]

Hi, I just wanted to confirm if I got it right:

As of now, isn't there any way of calling a contract function from another contract in qtum?

[qtum-neil]

Hi, I just wanted to confirm if I got it right:

As of now, isn't there any way of calling a contract function from another contract in qtum?

You can call other contract's functions in Qtum, make sure to compile both contracts with --evm-version homestead

[paulofelipe84]

Thanks! Is there a way of compiling for that version using Remix?

[paulofelipe84]

Thanks! Is there a way of compiling for that version using Remix?

Just replying that question, using Remix's compiler version 0.4.21 will do it.

[qtum-neil]

Fixed here: #736