3 ms·

I think register is closer to const, as in: it's a hint to the programmer not the compiler. So if you want to make absolutely sure that a variable can always b

• moonchild 4y ago
  Taking the address of a variable does not prevent the compiler from putting it in a register. Indeed, it can be convenient to have small utility functions which are always inlined, which take pointers to their results; this should not and does not prevent those results from staying in registers.
  • saagarjha 4y ago
    Correct, but preventing people from taking the address of things actually makes a difference for certain constructs in the standard (fore example, when it comes to trap representations).
• int_19h 4y ago
  Yes, you can treat "register" as a hint "no pointer to this ever exists anywhere in this program" for the reader. But you can only use it for locals, and that kind of metadata would be most useful (to other devs) on globals and fields - they can already see if a local ever has & applied to it or not. OTOH I didn't recall this bit, but apparently you can also apply it to arrays. Which keeps them indexable, but you can't take addresses of elements nor of the whole array anymore. Now I'm not sure if the compiler can do anything useful with this, but it would allow it to play with alignment and padding - e.g. storing "register bool x[10]" as 10 words rather than 10 bytes. Is there any architecture on which that would be beneficial, though?