What does this function return? EthernetClass::localIP()

Using Arduino Programming Questions
1

Here is the function:

IPAddress EthernetClass::localIP()
{
  IPAddress ret;
  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
  W5100.getIPAddress(ret.raw_address());
  SPI.endTransaction();
  return ret;
}

It looks to me like it's returning a local object which will no longer be valid after it returns, or am I missing something?

2

I'd understand why you'd think that. But whats actually happening is it's creating that local object, changing it, then when it goes to return it, it makes a copy and returns that.

Although thats the process, the compiler should optimise this so the copy never takes place.

3

Good point and now it makes sense. Thank you for explaining this :slight_smile: