[mosquitto-dev] why is librt needed?

[Greg Troxel <gdt@xxxxxxxxxx>]

In lib's CMakeLists.txt, it includes librt if it exists, in general,
except for a list where it doesn't.   I've been carrying a patch to add
NetBSD to the "don't add librt" list.

Looking at this harder, I don't understand at all.

Looking at POSIX, I don't see a requirement to include librt.

NetBSD has /usr/lib/librt.a (and .so).   Extracting defined symbols, and
grepping for them in mosquitto sources, I find no matches.


So:

  Does mosquitto use POSIX realtime calls at all?  If so, which ones?

  Is librt needed on any system?

  Is it a good idea to add it to the link  in general, if it exists?

  Why is it excluded on APPLE and ANDROID?  What breaks?