Poll on macOS 10.12 is broken

Re:Poll on macOS 10.12 is broken by blinkingled on Tuesday October 11, 2016 @07:00PM (#12689216)

That is NOT undefined behavior. That is at the most not-clearly-defined behavior that is bounded, with TWO possible outcomes - Apple switches between those (not at runtime - but across OS releases!!) and that's not correct in any sense of the word! Dereferencing NULL/Wild/free()ed pointer (again not applicable to this case - we are not dereferencing the NULL FD set - NULL here specifies empty) is undefined behavior - not specified if that will fail silently or cause you to call a function or trap or a hundred other things - not bounded or in other words without specific choices. Vastly different from either return after timeout or immediately. Do one thing consistently, preferably same as what other UNIXes are doing, or if you do otherwise stick to it. This isn't undefined behavior where code does something and result can be unknown - this is deliberate behavior!

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Re:Poll on macOS 10.12 is broken by eridius on Tuesday October 11, 2016 @07:36PM (#12689379)

There are more than 2 possible choices if you read the spec as leaving the empty set case undefined. There's 2 choices that are likely to result, but that doesn't mean the implementation can't do something else instead.

> Apple switches between those (not at runtime - but across OS releases!!) and that's not correct in any sense of the word!

Assuming it's undefined, then sure it is. Linus treats accidental implementation-defined behavior as guaranteed in Linux. But Apple only guarantees documented behavior. If something is undocumented, Apple is free to change it. In practice, they try to keep backwards compatibility (even going to such lengths as preserving old bugs for certain apps based on bundle ID), but that doesn't mean they guarantee backwards compatibility for undocumented behavior, or that they're wrong when they change something that affects undocumented behavior.

> This isn't undefined behavior where code does something and result can be unknown - this is deliberate behavior!

Given that the behavior changed, I'm willing to bet it's not deliberate behavior but is an artifact of implementation.

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[dead]

Re:Poll on macOS 10.12 is broken by dang on Wednesday October 12, 2016 @02:37PM (#12695422)

This comment violates the HN guidelines. Please don't post uncivilly again.

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Re:Poll on macOS 10.12 is broken by eridius on Tuesday October 11, 2016 @08:27PM (#12689583)

Now you're just being deliberately offensive. I do not appreciate you implying that I'm a troll. I've been nothing but honest throughout this whole discussion and have explained my reasoning many times. The fact that you interpret your disagreement with me as proof that I'm a troll is incredibly arrogant.

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