title: printf and (signed) int of unknown size
body: <p>I have a platform dependent type defined in my code:
  <code>typedef uint64_t myType;</code></p>
  
  <p>However on some more limited platform, it might be 32 bits.</p>
  
  <p>How do I <code>printf</code> it?
  As in, in the current situation, I can use <code>%llu</code>, but if on another platform it's 32 bits, this is not the best idea.</p>
  
  <p>I thought about using some macros, but would anyone know of a better way? I'd love to hear about some format specifier that could take the length from the next argument, for example.</p>