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> empty file descriptor set is undefined behavior Umm the behavior of poll changed across os x versions. That's the bug. You don't break user space. Also I'm

> empty file descriptor set is undefined behavior Umm the behavior of poll changed across os x versions. That's the bug. You don't break user space. Also I'm not sure how you're claiming it's POSIX compliant given - * poll() is defined by POSIX and The Single Unix Specification it specifically says: If none of the defined events have occurred on any selected file descriptor, poll() waits at least timeout milliseconds for an event to occur on any of the selected file descriptors 10.12 and lesser than 10.9 versions poll implementation returns immediately.

eridius 10y ago
The fact that behavior changed doesn't mean it's a bug. If the behavior in question is undefined behavior, then it can be subject to change without warning. And the argument here is that the cited wording assumes a non-empty set of file descriptors, because the way it's worded doesn't make sense if there are no file descriptors. If there are no file descriptors, it's impossible for an event to happen, so there's nothing to wait on.
- blinkingled 10y ago
  Every other UNIX like platform behaves one way (returns after timeout for empty/NULL fd set) and always has, but if you want to pick the interpretation that makes it a non bug in OS X - then you have to agree that it was buggy under OS X between 10.9 and 10.12! Can't have it both ways :) Also whatever you say - no sane OS vendor keeps alternating between different undefined behaviors causing pain for developers. MS, Linux, FreeBSD - AFAIK they all do everything to not break user space. Linus has famously said - if you break a working userspace binary - it's a bug!
  - eridius 10y ago
    > you have to agree that it was buggy under OS X between 10.9 and 10.12 No you don't. Neither behavior has to be buggy. That's what undefined behavior means, that any and all possible behaviors are valid because no specific behavior is defined as correct. > Linus has famously said - if you break a working userspace binary - it's a bug! That's a very hard-line stance, and it means accidents of implementation become guaranteed behavior which can be extremely restrictive down the line. Linus obviously believes that this philosophy is correct for Linux, but that doesn't mean it's correct for OS X.
    - blinkingled 10y ago
      I think this is going beyond reason - not correct for OS X?! What does that mean? It's not just Linux either - MS does the same thing. You don't cause developers and users pain by randomly changing stuff - correct or incorrect to you doesn't factor. If something was working it is a reasonable expectation for any mainstream OS that it will continue to work. If you don't agree with that then your choice - the world hasn't worked that way in a while. It would be one thing if they always consistently returned immediately in poll if you passed NULL but alternating between returning immediately and returning after timeout with no guarantee which OS version will change it again in future - that's madness. Hey but ok - for you I will say it - Apple can do no wrong!
      - eridius 10y ago
        > You don't cause developers and users pain by randomly changing stuff That's different than the hard-line stance that Linus takes. Either you're deliberately mischaracterizing what's going on, or you don't actually understand what you were referencing. In any case, just because some API behaved in a particular way in a degenerate possibly-undefined case doesn't mean the OS needs to preserve that behavior in the future. It was probably an artifact of implementation, so if the implementation changes, the undefined behavior may change too. And that's perfectly alright, if it's undefined behavior. Sure, if you are aware of the particular behavior and aware that apps are relying on it, and it's not an undue burden, then it's a good idea to preserve the existing behavior. But that's a lot of "ifs" there.
        blinkingled 10y ago
        So you are saying you will feel better if you made the assumption that it is a burden for Apple to stick to one behaviour _and_ you will ignore that a very popular library curl was depending on it and so far had to twice adjust their code. But yeah we will assume undue burden for Apple to keep it working one way. And No, I am not misunderstanding anything I am sure - as are the libcurl authors! You so far seem to be the only person arguing otherwise with no proof that there is undue burden for Apple while ignoring causing impact s twice for not an obscure library! Ok, I'm done here.

eridius 10y ago

The fact that behavior changed doesn't mean it's a bug. If the behavior in question is undefined behavior, then it can be subject to change without warning. And the argument here is that the cited wording assumes a non-empty set of file descriptors, because the way it's worded doesn't make sense if there are no file descriptors. If there are no file descriptors, it's impossible for an event to happen, so there's nothing to wait on.

blinkingled 10y ago
Every other UNIX like platform behaves one way (returns after timeout for empty/NULL fd set) and always has, but if you want to pick the interpretation that makes it a non bug in OS X - then you have to agree that it was buggy under OS X between 10.9 and 10.12! Can't have it both ways :) Also whatever you say - no sane OS vendor keeps alternating between different undefined behaviors causing pain for developers. MS, Linux, FreeBSD - AFAIK they all do everything to not break user space. Linus has famously said - if you break a working userspace binary - it's a bug!
- eridius 10y ago
  > you have to agree that it was buggy under OS X between 10.9 and 10.12 No you don't. Neither behavior has to be buggy. That's what undefined behavior means, that any and all possible behaviors are valid because no specific behavior is defined as correct. > Linus has famously said - if you break a working userspace binary - it's a bug! That's a very hard-line stance, and it means accidents of implementation become guaranteed behavior which can be extremely restrictive down the line. Linus obviously believes that this philosophy is correct for Linux, but that doesn't mean it's correct for OS X.
  - blinkingled 10y ago
    I think this is going beyond reason - not correct for OS X?! What does that mean? It's not just Linux either - MS does the same thing. You don't cause developers and users pain by randomly changing stuff - correct or incorrect to you doesn't factor. If something was working it is a reasonable expectation for any mainstream OS that it will continue to work. If you don't agree with that then your choice - the world hasn't worked that way in a while. It would be one thing if they always consistently returned immediately in poll if you passed NULL but alternating between returning immediately and returning after timeout with no guarantee which OS version will change it again in future - that's madness. Hey but ok - for you I will say it - Apple can do no wrong!
    - eridius 10y ago
      > You don't cause developers and users pain by randomly changing stuff That's different than the hard-line stance that Linus takes. Either you're deliberately mischaracterizing what's going on, or you don't actually understand what you were referencing. In any case, just because some API behaved in a particular way in a degenerate possibly-undefined case doesn't mean the OS needs to preserve that behavior in the future. It was probably an artifact of implementation, so if the implementation changes, the undefined behavior may change too. And that's perfectly alright, if it's undefined behavior. Sure, if you are aware of the particular behavior and aware that apps are relying on it, and it's not an undue burden, then it's a good idea to preserve the existing behavior. But that's a lot of "ifs" there.
      - blinkingled 10y ago
        So you are saying you will feel better if you made the assumption that it is a burden for Apple to stick to one behaviour _and_ you will ignore that a very popular library curl was depending on it and so far had to twice adjust their code. But yeah we will assume undue burden for Apple to keep it working one way. And No, I am not misunderstanding anything I am sure - as are the libcurl authors! You so far seem to be the only person arguing otherwise with no proof that there is undue burden for Apple while ignoring causing impact s twice for not an obscure library! Ok, I'm done here.