13 ms·

Just curious, can you give me some examples of GNU-isms/macOS-isms? I have a suspicion what they might be, but I'm not sure.

bluejekyll 10y ago
Asynchronous IO, hardly anyone uses the POSIX standard of select and poll anymore, and instead use kqueue (bsd/macOS) and epoll (Linux). I should add that this is for performance critical software.
- JdeBP 10y ago
  I'll agree that a lot of people prefer and recommend things like kqueue+kevent over select/poll. But my experience is that the statement that "hardly anyone uses" select/poll is still erroneous. On an out-of-the-box installation of FreeBSD/TrueOS, most processes listed by "ps" show a wchan of things like ttyin, select, poll, pause, uwait, wait, or nanslp. On the FreeBSD machine that I am typing at right now exactly one program is waiting in kqread, one of the inner processes of Chrome. Install my nosh toolset, and a fair amount of that changes, because my programs use kqueue+kevent and suddenly the "ps" output is full of kqreads. But what's left is still not "hardly anyone", by a long chalk. Would that it were! There's a nasty kernel panic somewhere in the innards of the kevent system on FreeBSD, where a sleeping thread holds a non-sleepable lock, that only manifests itself (at least for me) when there are a lot of programs using kqueue+kevent on a system that is doing a lot of stuff. If more people used kqueue+kevent in more programs, there would be more people wanting it fixed. (-:
  - bluejekyll 10y ago
    Yeah. I considered this critique, which is why I added the performance caveat. The thing is, libraries of other languages are being written abstractly over the native eventing systems on the OSes. For example, the MIO library in Rust, is an abstraction over epoll, kqueue, and the MS primative. Not one over the POSIX standard. This means that if you use that in a Rust library, you get that platform independence for free.
- cperciva 10y ago
  The standard select and poll syscalls perform just fine if you only have a handful of sockets. Heck, they perform just fine as long as a nontrivial proportion of your sockets are ready at any given time. The place you need kqueue and epoll is when most of your connections are idle -- IRC servers and web servers with large keepalive times. But the vast majority of processes are not IRC or web servers.
astrange 10y ago
dispatch and XPC are very popular macOS APIs that are "POSIX level". At least one of those is open source.
jmgao 10y ago
One hilarious one is basename(3), which is two functions with different behavior, but the same name. The one you get depends on which headers you include, and what _GNU_SOURCE is set to. See http://man7.org/linux/man-pages/man3/basename.3.html http://man7.org/linux/man-pages/man3/basename.3.html for the manpage.

bluejekyll 10y ago

Asynchronous IO, hardly anyone uses the POSIX standard of select and poll anymore, and instead use kqueue (bsd/macOS) and epoll (Linux). I should add that this is for performance critical software.

JdeBP 10y ago
I'll agree that a lot of people prefer and recommend things like kqueue+kevent over select/poll. But my experience is that the statement that "hardly anyone uses" select/poll is still erroneous. On an out-of-the-box installation of FreeBSD/TrueOS, most processes listed by "ps" show a wchan of things like ttyin, select, poll, pause, uwait, wait, or nanslp. On the FreeBSD machine that I am typing at right now exactly one program is waiting in kqread, one of the inner processes of Chrome. Install my nosh toolset, and a fair amount of that changes, because my programs use kqueue+kevent and suddenly the "ps" output is full of kqreads. But what's left is still not "hardly anyone", by a long chalk. Would that it were! There's a nasty kernel panic somewhere in the innards of the kevent system on FreeBSD, where a sleeping thread holds a non-sleepable lock, that only manifests itself (at least for me) when there are a lot of programs using kqueue+kevent on a system that is doing a lot of stuff. If more people used kqueue+kevent in more programs, there would be more people wanting it fixed. (-:
- bluejekyll 10y ago
  Yeah. I considered this critique, which is why I added the performance caveat. The thing is, libraries of other languages are being written abstractly over the native eventing systems on the OSes. For example, the MIO library in Rust, is an abstraction over epoll, kqueue, and the MS primative. Not one over the POSIX standard. This means that if you use that in a Rust library, you get that platform independence for free.
cperciva 10y ago
The standard select and poll syscalls perform just fine if you only have a handful of sockets. Heck, they perform just fine as long as a nontrivial proportion of your sockets are ready at any given time. The place you need kqueue and epoll is when most of your connections are idle -- IRC servers and web servers with large keepalive times. But the vast majority of processes are not IRC or web servers.

astrange 10y ago

dispatch and XPC are very popular macOS APIs that are "POSIX level". At least one of those is open source.

jmgao 10y ago

One hilarious one is basename(3), which is two functions with different behavior, but the same name. The one you get depends on which headers you include, and what _GNU_SOURCE is set to. See http://man7.org/linux/man-pages/man3/basename.3.html http://man7.org/linux/man-pages/man3/basename.3.html for the manpage.