Though our implementation of cpu sets doesn't need it, software from
Linux environments expects this definition to be present. It's
documented on the Linux CPU_SET(3) man page but was left out due to
oversight.
Addresses https://cygwin.com/ml/cygwin/2019-12/msg00248.html
The CPU_SET macros defined in Cygwin's include/sys/cpuset.h must not
be visible in an application's namespace unless _GNU_SOURCE has been
#defined. Internally this means wrapping them in #if __GNU_VISIBLE.
This patch supplies an implementation of the CPU_SET(3) processor
affinity macros as documented on the relevant Linux man page.
There is a mostly superset implementation of cpusets under newlib's
libc/sys/RTEMS/include/sys that has Linux and FreeBSD compatibility
and is built on top of FreeBSD bitsets. This Cygwin implementation
and the RTEMS one could be combined if desired at some future point.
Have sched_getaffinity() interface like glibc's, and provide an
undocumented internal interface __sched_getaffinity_sys() like the Linux
kernel's sched_getaffinity() for benefit of taskset(1).
Mark Geisert
Corinna Vinschen