4

Having a simple contract structure like this:

pragma solidity ^0.4.8;

contract A {
  uint public a1;
}

contract B is A {
  uint8 public b1;
}

I can compile it with:

> solc --combined-json "abi,bin" inheritance.sol > ./out/test_output.json

To get the following:

{
  "contracts": {
    "A": {
      "abi": "[{\"constant\":true,\"inputs\":[],\"name\":\"a1\",\"outputs\":[{\"name\":\"\",\"type\":\"uint256\"}],\"payable\":false,\"type\":\"function\"}]",
      "bin": "6060604052346000575b608e806100176000396000f30060606040526000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063119552a114603c575b6000565b346000576046605c565b6040518082815260200191505060405180910390f35b600054815600a165627a7a723058205a60899c35d4ed35d09808494352b2a1170b28969925c2aa7e86a45128a569c60029"
    },
    "B": {
      "abi": "[{\"constant\":true,\"inputs\":[],\"name\":\"a1\",\"outputs\":[{\"name\":\"\",\"type\":\"uint256\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[],\"name\":\"b1\",\"outputs\":[{\"name\":\"\",\"type\":\"uint8\"}],\"payable\":false,\"type\":\"function\"}]",
      "bin": "606060405234610000575b60d1806100186000396000f30060606040526000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063119552a1146046578063ee495002146066575b6000565b346000576050608c565b6040518082815260200191505060405180910390f35b3460005760706092565b604051808260ff1660ff16815260200191505060405180910390f35b60005481565b600160009054906101000a900460ff16815600a165627a7a72305820c2b3dacd4eb8217e675d9a1ab699d05e0e267d2f98d09a8a81a0b1251e8adfbe0029"
    }
  },
  "version": "0.4.8+commit.60cc1668.Darwin.appleclang"
}

Adding a constructor to the A contract, I am receiving empty bin section for B. Source code:

pragma solidity ^0.4.8;

contract A {
  uint public a1;

  function A (address _a) {
  }
}

contract B is A {

  uint8 public b1;
}

Resulting json:

{
  "contracts": {
    "A": {
      "abi": "[{\"constant\":true,\"inputs\":[],\"name\":\"a1\",\"outputs\":[{\"name\":\"\",\"type\":\"uint256\"}],\"payable\":false,\"type\":\"function\"},{\"inputs\":[{\"name\":\"_a\",\"type\":\"address\"}],\"payable\":false,\"type\":\"constructor\"}]",
      "bin": "6060604052346000576040516020806100c4833981016040528080519060200190919050505b5b505b608e806100366000396000f30060606040526000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063119552a114603c575b6000565b346000576046605c565b6040518082815260200191505060405180910390f35b600054815600a165627a7a72305820b498791e10bedac88be35dd16a0733002f88d24b34bb81fd03d029cda7db4fa00029"
    },
    "B": {
      "abi": "[{\"constant\":true,\"inputs\":[],\"name\":\"a1\",\"outputs\":[{\"name\":\"\",\"type\":\"uint256\"}],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[],\"name\":\"b1\",\"outputs\":[{\"name\":\"\",\"type\":\"uint8\"}],\"payable\":false,\"type\":\"function\"}]",
      "bin": ""
    }
  },
  "version": "0.4.8+commit.60cc1668.Darwin.appleclang"
}

Parameterless constructor in A doesn't interfere with bin section of B.

  • 2
    A point of note - you also see this behaviour if you have defined an interface in Solidity, but one of your method implementations doesn't match the original interface definitions - e.g. if it's missing a parameter in its definition. – Conor Svensson Oct 6 '17 at 8:47
2

You cannot construct A if you do not give it a parameter. This will give you a binary for B:

contract A {
  uint public a1;

  function A (address _a) {
  }
}

contract B is A {
  uint8 public b1;

  function B(address _a) A(_a) {
  }
}

This too:

contract A {
  uint public a1;

  function A (address _a) {
  }
}

contract B is A {
  uint8 public b1;

  function B() A(0x0011223344556677889900112233445566778899) {
  }
}

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