semi colon after if statement

Projects Programming
1

what is the effect of putting a semi colon on an if statement? I'm sure this used to flag as an error (before version 1.0) but it doesn't any more and code seems to function differently with it/without it. so I was wondering what is meant to happen when you do this? (I hope that makes sense)

void loop()
{
 if(a >= b);
  {
    digitalWrite(13, LOW);
  }
}

the code is not relevant just an example

2

I'm sure this used to flag as an error (before version 1.0) but it doesn't any more and code seems to function differently with it/without it.

No, it didn't, and yes, it does.

The ; after the if() statement becomes the empty body of the if statement. Only the empty body will be executed, meaning that nothing happens.

3

And this is executed unconditionally:

  {
    digitalWrite(13, LOW);
  }
4

Ahh i see now, thanks that explains nicely XD