tree c6b837253f98cfad5abd4717801ab6405746a3e2
parent 03dbac7218007c7672fd5190785029ba8c32e0da
author Zbigniew Sarbinowski <zibi@ca.ibm.com> 1613154975 +0000
committer Copybara-Service <copybara-worker@google.com> 1613725598 -0800

[SystemZ][ZOS] Provide CLOCK_MONOTONIC alternative

We need CLOCK_MONOTONIC equivalent implementation for z/OS within libc++. The default implementation is asserting.

On z/OS the lack of  'clock_gettime()' and 'time_point()' force us to look for alternatives.
The current proposal is to use `gettimeofday()` for CLOCK_MONOTONIC  which is also used in CLOCK_REALTIME.  This will allow us to skip the assertion with compromised CLOCK_MONOTONIC implementation which will not guarantee to never go back in time because it will use `gettimeofday()` but only when it's set.

Is this a good compromise for platforms which does not support monotonic clock?
Hopefully this will spark the discussion and agreement how to proceed in this situation.

Reviewed By: #libc, ldionne, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D93542

GitOrigin-RevId: cb2d2ae56ae3f0554c40c2d7f231ca5058e4d50c