Thread

C++26: Trivial infinite loops are no longer undefined behaviour

173 points · 290 comments · ibobev

JoshTriplett · 1789746575 · focus · HN ↗
> When both conditions are met, the loop body is replaced with a call to std::this_thread::yield().
Insert screaming here.
An infinite loop, with no library calls whatsoever, gets a system call inserted. That's a horrible surprise waiting to happen.
The entire concept of the "forward progress guarantee" is broken. An infinite loop should compile to an infinite loop. Nothing more, nothing less.
1. saghm · 1789750371 · focus · HN ↗
  I guess given that it was UB before, the compiler was already allowed to put a system call here if it wanted for some reason
  1. cryptonector · 1789793593 · focus · HN ↗
    Yes, but now it has to. I guess that's better? than UB, maybe.
    saghm · 1789862493 · focus · HN ↗
    Oh, definitely agreed. It's still not great, but it's a lot better than before.

Unofficial Hacker News client; not affiliated with Y Combinator.