Why are empty expressions legal in C/C++?

Question

int main()
{
  int var = 0;; // Typo which compiles just fine
}

Answer 1

while (1) {
    ;  /* do nothing */
}

There are times when you want to sit and do nothing. An event/interrupt driven embedded application or when you don't want a function to exit such as when setting up threads and waiting for the first context switch.

example: http://lxr.linux.no/linux+v2.6.29/arch/m68k/mac/misc.c#L523