code: def _concrete_call(
      call: Call, state: GlobalState, address: int, meminstart: Variable
  ) -> List[Issue]:
      
      if not re.search(r"calldata.*\[0", str(state.mstate.memory[meminstart.val])):
          return []
  
      issue = Issue(
          contract=state.environment.active_account.contract_name,
          function_name=state.environment.active_function_name,
          address=address,
          swc_id=DELEGATECALL_TO_UNTRUSTED_CONTRACT,
          bytecode=state.environment.code.bytecode,
          title="Delegatecall Proxy",
          severity="Low",
          description_head="The contract implements a delegatecall proxy.",
          description_tail="The smart contract forwards the received calldata via delegatecall. Note that callers "
          "can execute arbitrary functions in the callee contract and that the callee contract "
          "can access the storage of the calling contract. "
          "Make sure that the callee contract is audited properly.",
          gas_used=(state.mstate.min_gas_used, state.mstate.max_gas_used),
      )
  
      target = hex(call.to.val) if call.to.type == VarType.CONCRETE else str(call.to)
      issue.description += "DELEGATECALL target: {}".format(target)
  
      return [issue]
docs: :param call: The current call's information
      :param state: The current state
      :param address: The PC address
      :param meminstart: memory starting position
      :return: issues