What does a C# for loop do when all the expressions are missing. eg for(;;) {}

Question

I can only assume it's an infinite loop.

Can I leave out any of the three expressions in a for loop? Is there a default for each when omitted?

Answer 1

Yes, it's an infinite loop.

Examples:

for (; ;) { } (aka: The Crab)

while (true) { }

do { } while (true)

Answer 2

It is indeed an infinite loop.

Under the hood the compiler/jitter will optimize this to (effectively) a simple JMP operation.

It's also effectively the same as:

while (true)
{
}

(except that this is also optimized away, since the (true) part of a while expression usually requires some sort of comparison, however in this case, there's nothing to compare. Just keep on looping!)

Answer 3

Yes, that's an infinite loop. You can leave out any of the three expressions, though in my experience it's typically either the first or all 3.