Thread

1. 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. chowells · 1789784252 · focus · HN ↗

         Not only that, the code was wrong. The specification is quite clear that correct programs don't cause UB to be executed at run time. If your wrong code now produces wrong results, that's because it's wrong. That your compiler allowed you to get away with it for decades is a compiler bug, not a feature.

         Do I fully believe all of the above? Not exactly. But compiler authors do. Does it make a really good argument to never use C or C++? Yes. If only we had 50 years of optimization work in any language with better semantics.

         1. saghm · 1789792710 · focus · HN ↗

            Yeah, my slightly more verbose take is that a language that requires you to not ever make any mistakes in order to have a program behave in a predictable way is not a particularly good choice of language if you the ability to pick something else.

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