Support OSX

[nibanks]

Along with Windows and Linux, we need OSX support as well.

[mxms0]

Seems reasonable to rename any of the linux code to posix, as it should almost line-for-line work; Will need CMake modifications to not enable LTTng on Macos though. I'm currently testing feature-functionality in MacOS.

EDIT: epoll doesn't exist on MacOS; Needs some love. Unsure if it's worth implementing support for kqueue.

[nibanks]

Renaming linux to posix seems reasonable. The LTTng dependency is configurable at build time, so we can use some other tracing strategy on MacOS. As far as epoll or kqueue, I don't care either way. If kqueue is universally supported (and just as performance) then I'm fine with moving it all over.

[larseggert]

I have some very rough changes to make this compile under Darwin in https://github.com/larseggert/msquic/tree/darwin.

There are a lot of FIXMEs, so this clearly won't run.

But it compiles with cmake -DQUIC_ENABLE_LOGGING=OFF -DQUIC_BUILD_TEST=OFF ...

I also had to suppress some additional warnings due to -Werror being used. Some of those looked like they might actually be worth fixing...

[nibanks]

Thanks @larseggert! That seems like a great start! I know @maximus- was looking more into this. It might be worth starting a feature/mac branch for this work.

[mxms0]

I googled around a bit and couldn't get a firm answer on whether or not LTTng works on macOS. I'm also wondering if kqueue is the best for high performance IO on macOS.. I think it is?

[larseggert]

I have no idea if LTTNG works on MacOS, but -DQUIC_ENABLE_LOGGING=OFF removes the dependency.

I think kqueue is the logical choice, esp. since it also provides some functionality that eventfd on Linux is used for. I think it might be possible to replace epoll and eventfd with kqueue.

[mxms0]

I've made a branch users/mxms/macos to track this work. This looks a lot like @larseggert's work so far, except everything is just empty. Currently building with -DQUIC_ENABLE_LOGGING=OFF -DQUIC_BUILD_TEST=OFF -DQUIC_TLS=stub. Also lots of CMake hackery.