struct address field takes the value of the contract address when initialized

Question

I don't know if this is a quirk in the remix IDE or something solidity does itself, but I've found something interesting and would like to know why it occurs.

I have a struct x in a contract Y which has two fields:

Struct X {
   address owner;
   address renter;
}

Now, when I initialize the struct by calling the function createX() in the remix IDE:

function createX() public {
   X storage x;
   x.owner = msg.sender;
}

The renter address field gets the value of the contract address Y

Why does this happen? I expected the field to equal the zero address.

Answer 1

The Solidity compiler should emit a warning for this.

X storage x; declares an uninitialized storage reference. That means x points to slot 0 in storage. When you store msg.sender in x.owner, it overwrites whatever was in slot 0 (the first state variable you declared). x.renter, since you haven't modified it, should still hold whatever your second declared state variable was.