Which will probably be never.
C does exactly what you tell it, no more. Why waste cycles setting a variable to a zero state when a correct program will set it to whatever initial state it expects? It is not user friendly, but it is performant.
Except that this is wrong. C is free to do all kinds of things you didn’t ask it to, and will often initialize your variables without you writing it.
Machine code would be a better example of what he’s talking about imo. Not an expert or anything of course.
Odds are that your computer doesn’t export any language where it will do exactly as you say (amd64 machine code certainly won’t execute exactly as written). And how much difference it makes varies from one language to another.
But the specific example from the OP, of uninitialized variables, is one of those cases where the C spec famously goes completely out of line and says your code can do whatever, run with a random value, fail, initialize it, format your hard drive, make a transaction on your bank account… whatever.
