TRC-44: Address.isContract instruction

[llwslc]

tip: 44
title: TRC-44 Address.isContract instructions
author: llwslc<llwslc@gmail.com> 
discussions to: https://github.com/tronprotocol/TIPs/issues/43
category: TRC
status: accept
created: 2019-07-10

Simple Summary

To provide a new opcode, which returns the type of the address.

Abstract

This TIP specifies a new opcode, which determines whether the address type is a contract address.

Motivation

Some contracts need to limit its callers, such as some functions can only be called by the user, not by the contract.

Specification

A new opcode, ISCONTRACT, is introduced, with number 0xD4. The ISCONTRACT takes one argument from the stack, pushes to the stack the boolean value whether the address type is a contract address.

In case the address does not exist false is pushed to the stack.

example:

contract Test {
    function checkAddr(address addr) view public returns (bool) {
        return addr.isContract;
    }
}

The energy cost of the ISCONTRACT is 400.

Backwards Compatibility

There are no backwards compatibility concerns.

Test Cases

1. The ISCONTRACT of a contract address is true.
2. The ISCONTRACT of an account address is false.
3. The ISCONTRACT of a non-existent address is false.
4. The ISCONTRACT of a precompiled contract is false.
5. The ISCONTRACT of self address in constructor function is true.
6. The ISCONTRACT of a selfdestructed contract address is false.

[Sh11thead]

I think it is a good suggestion. Ability to extend TVM's access to blockchain while enriching the capabilities of smart contracts