Internal compiler error for call to unimplemented "super" function

[nweller]

The following contract produces an internal compiler error in various solc versions, including the most recent build in Remix:

contract a {
    function f() public;
}
contract b is a {
    function f() public { super.f(); }
}

It does compile (but cannot be deployed due to the missing implementation) if I rename a.f().

(This report is part of an ICE Center@ETH Zurich project on automated compiler validation funded by the Ethereum Foundation.)

[axic]

Internal compiler error during compilation:
/Users/alex/Projects/solidity/libsolidity/codegen/ContractCompiler.cpp(893): Throw in function void dev::solidity::ContractCompiler::appendModifierOrFunctionCode()
Dynamic exception type: boost::exception_detail::clone_impl<dev::solidity::InternalCompilerError>
std::exception::what: 
[dev::tag_comment*] = 

[chriseth]

What do you mean by "rename a.f()"? Can you post the full changed contract that does compile, please?

[nweller]

Sure - I meant that this compiles:

contract a {
    function f2() public;
}
contract b is a {
    function f() public { super.f2(); }  
}

This just shows that there's apparently some significance to having an implementation of the function in the sub class for the error to occur.

[chriseth]

Great, thanks!

[anurag-git]

@chriseth , would like to take up this issue. Let me know the strategy to proceed. I hope it is not too tricky.

[chriseth]

It might work to just ignore functions that do not have implementations in ContractType::nativeMembers.

[anurag-git]

@chriseth, Did some analysis, let me know your thoughts

contract a {
    function f() public;
}
contract b is a {
   // function f() public { super.f(); }
    function f() public {uint i=0; uint j; j=i;}
}

This code compiles after changing the contract as above. As per the issue we are trying to call base contract function (which is not implemented) in derived contract, hence the error. Error seems to be expected as per my understanding.

Below code also compiles,

contract a {
    //function f() public;
    function f() pure public {
       uint i=0; uint j; j=i;
    }
}
contract b is a {
    function f() pure public { super.f(); }
    //function f() public { super.f(); }
}

which basically says that if base contract function is implemented things work fine.

So do we consider this (calling unimplemented base contract function) as valid? If so, then I can proceed with my analysis to fix this issue.

[chriseth]

The initial code should result in an error stating something like super.f() is not available.

[anurag-git]

@chriseth, I have a solution ready, please help me to write test case so that I can push both changes at once.

[chriseth]

@anurag-git the initial code is a good test case. Put it in the syntaxTests directory and run isoltest. Use the update option if it prompts you for an action.

[dddejan]

If the super is changed to a in the original example, the compiler still fails with internal error.

contract a {
    function f() public;
}
contract b is a {
    function f() public { a.f(); }
}

[chriseth]

The issue in the latest comment is tracked in #7314