POSIX isn't the C stdlib though, that's mostly a confusion caused by UNIXes where the libc is the defacto operating system API (and fully implements the POSIX standard).
TBF though, I guess one can implement non-blocking IO in C11 with just the stdlib by moving blocking IO calls into threads.
Isn't threading generally handled by POSIX as well? The p in pthreads?
If you're writing C code in 2024 and your target is a system that has an OS, then it's safe to use select and poll. They're going to be there. This hand wringing over "oh no, they aren't supported on every platform" is silly because the only platforms where they don't exist are the ones where they don't make sense anyway.
AFAIK select() and poll() are still not supported in MSVC though. IIRC at least select() is provided by 'WinSock' (the Berkeley socket API emulation on Windows), but it only works for socket handles, not for C stdlib file descriptors.
In general, if you're used to POSIX, Windows and MSVC is a world of pain. Sometimes a function under the same name exists but works differently, and sometimes a function exists with an underscore, and still works differently. It's usually better to write your own higher level wrapper functions which call into POSIX functions on UNIX-like operating systems, and into Win32 functions on Windows (e.g. ignoring the C stdlib for those feature areas).
Mostly because before Satya took over, C on Windows was considered a done deal, and everything was to be done in C++, with C related updated only to the extent required by ISO C++ compliance.
Eventually the change of direction in Microsoft's management, made them backtrack on that decision.
Additionally, in what concerns C++ compliance, they are leading up to C++23 in compliance, while everyone else is still missing on full modules, some concepts stuff, parallel STL,...
Although something has happened, as the VC++ team has switched away to something else, maybe due to the Rust adoption, .NET finally being AOT proper with lowlevel stuff in C#, or something else.
I guess the difference is that you need maybe 5 peeps to keep the C compiler frontend and stdlib uptodate (in their spare time), but 500 fulltime to do the same thing for C++, and half of those are needed just to decipher the C++ standard text ;)
I mean, no. The most basic of uses on windows require #ifdef'ing as the prototypes, types, error codes and macros in wsock2 aren't exactly the POSIX ones (WSAPoll instead of poll, etc.).
Also some software still target windows xp and this one doesn't even have poll, only select
poll() and select() are POSIX-isms that are not necessarily going to be present in every system's C standard library.
The only reason they happen to be available on Windows is that Microsoft, in an uncharacteristicly freak stroke of respect for existing standards, decided to make WinSock (mostly) function-for-function compatible with BSD sockets.
In practice poll and select exist everywhere it makes sense. There aren't a ton of independent Unix vendors each with their own expensive and broken C implementation running around anymore.
Both are available if you use --std=c89 on gcc and clang. At this point it is safe to assume they are available unless you're doing something weird like writing C for some tiny microcontroller. Practically speaking this has been true for at least 20 years.
> Both are available if you use --std=c89 on gcc and clang.
This is irrelevant - that switch doesn’t have anything to do with controlling functionality not provided by the C standard library. Since poll and select aren’t part of it to begin with it doesn’t affect their availability.
epoll and signalfd will be available (on a gcc target where they are available obviously) as well with that switch I don’t think that makes them C standard library functionality.
select/poll differs enough across common platforms. In MSVC, poll isn’t there, sure you can emulate but now the goal post moving is getting ridiculous. The arguments to select are only superficially compatible (A practical example is that POSIX select supports pipes, but this will not work on Windows outside of specific environments or 3rd party implementations)
"WSAPoll" because it's not a POSIX poll even though the signature is the same at it works similarly for sockets and I guess Microsoft thought through it better 15 years later.
But the original claim is just that select/poll are "everywhere it makes sense", but this depends on what you define select/poll to be. I think something close to POSIX is what makes sense. If you can't use it on pipes and FIFOs (and even regular files without getting an error) that seems like a pretty contrived definition.
The whole moving around of definition of what is the C standard library just because of popularity seems unproductive. ("You can do nonblocking IO using the C std library." -- no, you can't) Most popular 3rd party libraries support or can easily support the most popular targets due in large part to them being popular, that means "in practice, they exist everywhere it makes sense." Does this mean all popular 3rd party libraries are part of the C standard library?
Colloquially redefining terms like what is the C standard library just sows confusion with no benefit (as was illustrated earlier in regards to threads; C11 threads are not pthreads), just say what you mean in this case.
Yes, it is remarkable what little you actually get when you strictly stick to the actual C89/C99/C11 definitions of what's in "The C Standard Library". I still get tripped up on it, and often have to double check: Surely sigaction() is part of the C Standard! NOPE it's POSIX, but signal() is! Surely strptime() is part of the standard! NOPE, but strftime() is. termios stuff? NOPE. It's a minefield out there.
Yeah, and on those platforms the functions exist if they make sense. If you're talking about some tiny embedded thing with no MMU or OS then it might not, but programming on those is a specialized task anyway so it doesn't really matter.
