Why smart contract function fails with "Error 3090004: Missing required authority"?

Question

WHAT I WANT

From the contract mycontract I want to call a function function1. The function function1 calls another function of mycontract called function2. The function function2 calls an action of another contract othercontr. Both function1 and function2 use _selfinside.

user --> function1(...) --> function2(_self, ...)-->action[of othercontract]

WHAT IS WORKING

If I call directly function2(_self, ...), the function receives correctly _self and works fine.

WHAT IS NOT WORKING

I tried the following options as function2 arguments:

1. _self is not recognized ad does not compile;
2. N(_self) gives the error: "Error 3050000: Action validate exception; inline action's authorizing actor .self does not exist";
3. N(mycontract) gives the error in the section ERROR.

CRIME SCENE

checksum256 result = function1(paramA, paramB);

checksum256 function1(uint8_t paramA, uint8_t paramB) {
    ...
    // Option 1. function2(_self, paramC, paramD);        
    // Option 2. function2(N(_self), paramC, paramD);
    // Option 3.
    function2(N(mycontract), paramC, paramD);
    ...
}

checksum256 function2(account_name user, uint8_t paramC, uint8_t paramD) {
    ... 
    // Calling the action "actionname" of the contract "mycontract".
    // The action "actionname" saves in a table the param "user", which is the action caller.   
    action(
      permission_level{user, N(active)},
      N(othercontr), N(actionname),
      std::make_tuple(user, paramC, paramD)
    ).send();
    ...
}

ERROR

Error 3090004: Missing required authority Ensure that you have the related authority inside your transaction!; If you are currently using 'cleos push action' command, try to add the relevant authority using -p option.

Answer 1

The issue was inside an emplace().

Basically, I was not setting the payer. After, hard coding the payer as N(mycontract), I don't get the error anymore and the functions work correctly.