It might be a little bit tricky to distinguish between the different kind of calls in solidity. Basically library call is realized on a low-level by delegate call and it is different from a standard call. In a standard call the context of the called contract is considered as active. In a library or delegate call the calling context, meaning variables, storage, visibility remain active. In other words in a library call only the function code of the called contract will be loaded, every other parameter remain the same. The situation can be best seen by the following contract examples:
contract CalledContract {
event showAddressEvent(address _from);
function test() payable public {
showAddressEvent(this);
}
}
contract CallingContract {
function callDifferentContracts(address _contractAddress) public {
require(_contractAddress.call(bytes4(keccak256("test()"))));
require(_contractAddress.delegatecall(bytes4(keccak256("test()"))));
testLib.calledSomeLibFun();
}
}
library testLib {
event showAddressEvent(address _from);
function calledSomeLibFun() public {
showAddressEvent(this);
}
}
By calling the callDifferentContracts function with the address of the CalledContract, the code first reveals the address of CalledContract as it is expected by a standard call. After that it shows the address of the CallingContract both at the delegatecall and at the library call examples.
