libdpf/thirdparty/portable-snippets/clock/README.md

Clock

This header provides a way to access time information. It's basically a more portable version of clock_gettime with fewer supported clocks. Currently supported clocks are:

• Wall clock
  • clock_gettime
  • gettimeofday
  • time
• CPU clock
  • clock_gettime
  • GetProcessTimes
  • getrusage
• Monotonic clock
  • clock_gettime
  • mach_absolute_time
  • QueryPerformanceCounter

If you are using a platform where a clock isn't provided, please let us know about it so we can try to figure out how to add support!

On some platforms, clock_gettime requires linking to librt. If you prefer, you can define PSNIP_CLOCK_NO_LIBRT prior to including clock.h and clock_gettime will only be used on platforms known to support using clock_gettime without linking against librt. The price will likely be lower-resolution CPU and wall clocks, and no monotonic clock.

Also, if you're compiling in a strict standard mode instead of a mode with GNU extensions (e.g., -std=c11 instead of -std=gnu11), POSIX extensions will not be enabled by default so you won't get to use the clock_gettime implementation; to avoid this, you can define _POSIX_C_SOURCE to 199309L or greater prior to including clock.h, or just define _GNU_SOURCE.

Dependencies

To maximize portability you should #include the exact-int module before including clock.h, but if you don't want to add the extra file to your project you can omit it and this module will simply rely on <stdint.h>. As an alternative you may define psnip_uint64_t, psnip_uint32_t, psnip_int64_t, psnip_int32_t to an appropriate value yourself before including clock.h.