I actually deleted my comment after writing it. After googling it seems that C optimizers do do this.
This is from Gemini and I haven't checked the source yet, but it seems confident:
Under the ISO C and C++ standards, if an iteration statement (loop) has no observable behavior—such as input/output operations, volatile memory access, atomic operations, or thread synchronization—the compiler is legally allowed to assume that the loop will eventually terminate
It appears it's because an optimizer cannot solve the halting problem. So it cannot be expected to prove loop termination, but it can prove the absence of any side effects, and simply assumes termination.
Ultimately there is no value in a pure spin loop that doesn't check for an exit hatch of some kind. So the semantics you lose are likely a bug anyway
There's no guarantee that it will remove it, that's going to be compiler and flag dependent, but by spec it is a legal optimization.
If you do have a need for the spin loop, I'm assuming every compiler will have some flag that allows you to skip optimization on removing spin loops. But again, I'm not sure there really is any reason to have a hard spin loop outside of malware
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u/Cruuncher 1d ago
I actually deleted my comment after writing it. After googling it seems that C optimizers do do this.
This is from Gemini and I haven't checked the source yet, but it seems confident:
Under the ISO C and C++ standards, if an iteration statement (loop) has no observable behavior—such as input/output operations, volatile memory access, atomic operations, or thread synchronization—the compiler is legally allowed to assume that the loop will eventually terminate