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Delve into clock rabbit hole
The worst issue I had with consts.sh for clock_gettime is how it defined too many clocks. So I looked into these clocks all day to figure out how how they overlap in functionality. I discovered counter-intuitive things such as how CLOCK_MONOTONIC should be CLOCK_UPTIME on MacOS and BSD, and that CLOCK_BOOTTIME should be CLOCK_MONOTONIC on MacOS / BSD. Windows 10 also has some incredible new APIs, that let us simplify clock_gettime(). - Linux CLOCK_REALTIME -> GetSystemTimePreciseAsFileTime() - Linux CLOCK_MONOTONIC -> QueryUnbiasedInterruptTimePrecise() - Linux CLOCK_MONOTONIC_RAW -> QueryUnbiasedInterruptTimePrecise() - Linux CLOCK_REALTIME_COARSE -> GetSystemTimeAsFileTime() - Linux CLOCK_MONOTONIC_COARSE -> QueryUnbiasedInterruptTime() - Linux CLOCK_BOOTTIME -> QueryInterruptTimePrecise() Documentation on the clock crew has been added to clock_gettime() in the docstring and in redbean's documentation too. You can read that to learn interesting facts about eight essential clocks that survived this purge. This is original research you will not find on Google, OpenAI, or Claude I've tested this change by porting *NSYNC to become fully clock agnostic since it has extensive tests for spotting irregularities in time. I have also included these tests in the default build so they no longer need to be run manually. Both CLOCK_REALTIME and CLOCK_MONOTONIC are good across the entire amd64 and arm64 test fleets.
This commit is contained in:
Justine Tunney
parent
8f8145105c
commit
dd8544c3bd
87 changed files with 939 additions and 900 deletions
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@ -571,28 +571,60 @@ syscon close CLOSE_RANGE_CLOEXEC 4 4 -1 -1 -1 -1 -1 -1 #
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# clock_{gettime,settime} timers
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#
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# Executive Summary
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# - CLOCK_MONOTONIC shouldn't count suspended time
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# - CLOCK_BOOTTIME is monotonic and should count suspended time
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# - Only CLOCK_REALTIME and CLOCK_MONOTONIC can be used with futexes
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# - CLOCK_MONOTONIC_RAW should fail with EINVAL if host lacks support
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# - CLOCK_MONOTONIC and CLOCK_BOOTTIME should be relative to system boot time
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# - COARSE can be CLK_TCK behind (~20ms) and will EINVAL on RHEL5 which isn't worth polyfilling
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#
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# FreeBSD defines the following rosetta stone
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# Taken from freebsd/sys/compat/linux/linux_time.c
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# - Linux CLOCK_MONOTONIC -> FreeBSD CLOCK_UPTIME [5]
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# - Linux CLOCK_MONOTONIC_RAW -> FreeBSD CLOCK_UPTIME_FAST [8]
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# - Linux CLOCK_REALTIME_COARSE -> FreeBSD CLOCK_REALTIME_FAST [10]
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# - Linux CLOCK_MONOTONIC_COARSE -> FreeBSD CLOCK_UPTIME_FAST [8]
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# - Linux CLOCK_BOOTTIME -> FreeBSD CLOCK_MONOTONIC [4]
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#
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# For MacOS we define the following mappings
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# - Linux CLOCK_MONOTONIC -> MacOS CLOCK_UPTIME_RAW [8]
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# - Linux CLOCK_MONOTONIC_RAW -> MacOS CLOCK_UPTIME_RAW [8]
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# - Linux CLOCK_REALTIME_COARSE -> MacOS CLOCK_REALTIME [0]
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# - Linux CLOCK_MONOTONIC_COARSE -> MacOS CLOCK_UPTIME_RAW_APPROX [9]
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# - Linux CLOCK_BOOTTIME -> MacOS CLOCK_MONOTONIC [6]
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#
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# For OpenBSD we define the following mappings
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# - Linux CLOCK_MONOTONIC -> OpenBSD CLOCK_UPTIME [5]
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# - Linux CLOCK_MONOTONIC_RAW -> EINVAL because OpenBSD ntpd can adjfreq(2)
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# - Linux CLOCK_REALTIME_COARSE -> OpenBSD CLOCK_REALTIME [0]
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# - Linux CLOCK_MONOTONIC_COARSE -> OpenBSD CLOCK_UPTIME [5]
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# - Linux CLOCK_BOOTTIME -> OpenBSD CLOCK_MONOTONIC [3]
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#
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# For NetBSD we define the following mappings
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# - Linux CLOCK_MONOTONIC -> NetBSD CLOCK_MONOTONIC [3] TODO: suspend?
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# - Linux CLOCK_MONOTONIC_RAW -> NetBSD CLOCK_MONOTONIC [3] NetBSD clock_gettime(2) says it isn't impacted by adjfreq(2)
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# - Linux CLOCK_REALTIME_COARSE -> NetBSD CLOCK_REALTIME [0]
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# - Linux CLOCK_MONOTONIC_COARSE -> NetBSD CLOCK_MONOTONIC [3]
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# - Linux CLOCK_BOOTTIME -> NetBSD CLOCK_MONOTONIC [3] TODO: suspend?
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#
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# For Windows we define the following mappings
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# - Linux CLOCK_REALTIME -> GetSystemTimePreciseAsFileTime()
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# - Linux CLOCK_MONOTONIC -> QueryUnbiasedInterruptTimePrecise()
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# - Linux CLOCK_MONOTONIC_RAW -> QueryUnbiasedInterruptTimePrecise()
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# - Linux CLOCK_REALTIME_COARSE -> GetSystemTimeAsFileTime()
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# - Linux CLOCK_MONOTONIC_COARSE -> QueryUnbiasedInterruptTime()
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# - Linux CLOCK_BOOTTIME -> QueryInterruptTimePrecise()
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#
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# group name GNU/Systemd GNU/Systemd (Aarch64) XNU's Not UNIX! MacOS (Arm64) FreeBSD OpenBSD NetBSD The New Technology Commentary
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syscon clock CLOCK_REALTIME 0 0 0 0 0 0 0 0 # consensus
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syscon clock CLOCK_REALTIME_PRECISE 0 0 0 0 9 0 0 0 #
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syscon clock CLOCK_REALTIME_FAST 0 0 0 0 10 0 0 0 #
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syscon clock CLOCK_REALTIME_COARSE 5 5 0 0 10 0 0 2 # Linux 2.6.32+; bsd consensus; not available on RHEL5
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syscon clock CLOCK_MONOTONIC 1 1 6 6 4 3 3 1 # XNU/NT faked; could move backwards if NTP introduces negative leap second
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syscon clock CLOCK_MONOTONIC_RAW 4 4 4 4 4 3 3 1 # actually monotonic; not subject to NTP adjustments; Linux 2.6.28+; XNU/NT/FreeBSD/OpenBSD faked; not available on RHEL5 (will fallback to CLOCK_MONOTONIC)
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syscon clock CLOCK_MONOTONIC_RAW_APPROX 4 4 5 5 4 3 3 1 # goes faster on xnu, otherwise faked
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syscon clock CLOCK_MONOTONIC_PRECISE 1 1 6 6 11 3 3 1 #
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syscon clock CLOCK_MONOTONIC_FAST 1 1 6 6 12 3 3 1 #
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syscon clock CLOCK_MONOTONIC_COARSE 6 6 5 5 12 3 3 1 # Linux 2.6.32+; bsd consensus; not available on RHEL5
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syscon clock CLOCK_PROCESS_CPUTIME_ID 2 2 12 12 15 2 0x40000000 4 # NetBSD lets you bitwise a PID into clockid_t
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syscon clock CLOCK_REALTIME 0 0 0 0 0 0 0 0 #
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syscon clock CLOCK_MONOTONIC 1 1 8 8 5 5 3 1 #
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syscon clock CLOCK_PROCESS_CPUTIME_ID 2 2 12 12 15 2 0x40000000 4 #
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syscon clock CLOCK_THREAD_CPUTIME_ID 3 3 16 16 14 4 0x20000000 5 #
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syscon clock CLOCK_PROF 127 127 127 127 2 127 2 127 #
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syscon clock CLOCK_BOOTTIME 7 7 7 127 127 6 127 3 #
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syscon clock CLOCK_REALTIME_ALARM 8 8 127 127 127 127 127 127 #
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syscon clock CLOCK_BOOTTIME_ALARM 9 9 127 127 127 127 127 127 #
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syscon clock CLOCK_TAI 11 11 127 127 127 127 127 127 #
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syscon clock CLOCK_UPTIME 127 127 8 8 5 5 127 127 #
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syscon clock CLOCK_UPTIME_PRECISE 127 127 127 127 7 127 127 127 #
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syscon clock CLOCK_UPTIME_FAST 127 127 127 127 8 127 127 127 #
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syscon clock CLOCK_SECOND 127 127 127 127 13 127 127 127 #
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syscon clock CLOCK_MONOTONIC_RAW 4 4 127 8 8 127 3 1 # Linux 2.6.28+
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syscon clock CLOCK_REALTIME_COARSE 5 5 0 0 10 0 0 2 # Linux 2.6.32+
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syscon clock CLOCK_MONOTONIC_COARSE 6 6 9 9 8 5 3 6 # Linux 2.6.32+
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syscon clock CLOCK_BOOTTIME 7 7 6 6 4 3 3 3 # Linux 2.6.39+
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# poll()
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#
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@ -1,2 +1,2 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_BOOTTIME,7,7,7,127,127,6,127,3
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.syscon clock,CLOCK_BOOTTIME,7,7,6,6,4,3,3,3
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_BOOTTIME_ALARM,9,9,127,127,127,127,127,127
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@ -1,2 +1,2 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_MONOTONIC,1,1,6,6,4,3,3,1
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.syscon clock,CLOCK_MONOTONIC,1,1,8,8,5,5,3,1
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@ -1,2 +1,2 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_MONOTONIC_COARSE,6,6,5,5,12,3,3,1
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.syscon clock,CLOCK_MONOTONIC_COARSE,6,6,9,9,8,5,3,6
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_MONOTONIC_FAST,1,1,6,6,12,3,3,1
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_MONOTONIC_PRECISE,1,1,6,6,11,3,3,1
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@ -1,2 +1,2 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_MONOTONIC_RAW,4,4,4,4,4,3,3,1
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.syscon clock,CLOCK_MONOTONIC_RAW,4,4,127,8,8,127,3,1
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_MONOTONIC_RAW_APPROX,4,4,5,5,4,3,3,1
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_PROF,127,127,127,127,2,127,2,127
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_REALTIME_ALARM,8,8,127,127,127,127,127,127
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_REALTIME_FAST,0,0,0,0,10,0,0,0
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_REALTIME_PRECISE,0,0,0,0,9,0,0,0
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_SECOND,127,127,127,127,13,127,127,127
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_TAI,11,11,127,127,127,127,127,127
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_UPTIME,127,127,8,8,5,5,127,127
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_UPTIME_FAST,127,127,127,127,8,127,127,127
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@ -1,2 +0,0 @@
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#include "libc/sysv/consts/syscon.internal.h"
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.syscon clock,CLOCK_UPTIME_PRECISE,127,127,127,127,7,127,127,127
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@ -2,42 +2,26 @@
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#define COSMOPOLITAN_LIBC_SYSV_CONSTS_CLOCK_H_
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COSMOPOLITAN_C_START_
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extern const int CLOCK_BOOTTIME;
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extern const int CLOCK_BOOTTIME_ALARM;
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extern int CLOCK_REALTIME_COARSE;
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extern const int CLOCK_MONOTONIC;
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extern const int CLOCK_MONOTONIC_COARSE;
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extern const int CLOCK_MONOTONIC_FAST;
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extern const int CLOCK_MONOTONIC_PRECISE;
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extern int CLOCK_MONOTONIC_RAW;
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extern int CLOCK_MONOTONIC_RAW_APPROX;
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extern const int CLOCK_PROCESS_CPUTIME_ID;
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extern const int CLOCK_PROF;
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extern const int CLOCK_REALTIME_ALARM;
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extern const int CLOCK_REALTIME_COARSE;
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extern const int CLOCK_REALTIME_FAST;
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extern const int CLOCK_REALTIME_PRECISE;
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extern const int CLOCK_SECOND;
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extern const int CLOCK_TAI;
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extern int CLOCK_MONOTONIC_COARSE;
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extern const int CLOCK_THREAD_CPUTIME_ID;
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extern const int CLOCK_UPTIME;
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extern const int CLOCK_UPTIME_FAST;
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extern const int CLOCK_UPTIME_PRECISE;
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extern const int CLOCK_PROCESS_CPUTIME_ID;
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extern const int CLOCK_BOOTTIME;
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COSMOPOLITAN_C_END_
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#define CLOCK_REALTIME 0
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#define CLOCK_REALTIME_FAST CLOCK_REALTIME_FAST
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#define CLOCK_REALTIME_PRECISE CLOCK_REALTIME_PRECISE
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#define CLOCK_REALTIME_COARSE CLOCK_REALTIME_COARSE
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#define CLOCK_REALTIME 0
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#define CLOCK_REALTIME_COARSE CLOCK_REALTIME_COARSE
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#define CLOCK_MONOTONIC CLOCK_MONOTONIC
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#define CLOCK_MONOTONIC_RAW CLOCK_MONOTONIC_RAW
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#define CLOCK_MONOTONIC_RAW_APPROX CLOCK_MONOTONIC_RAW_APPROX
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#define CLOCK_MONOTONIC_FAST CLOCK_MONOTONIC_FAST
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#define CLOCK_MONOTONIC_PRECISE CLOCK_MONOTONIC_PRECISE
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#define CLOCK_MONOTONIC_COARSE CLOCK_MONOTONIC_COARSE
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#define CLOCK_MONOTONIC CLOCK_MONOTONIC
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#define CLOCK_MONOTONIC_RAW CLOCK_MONOTONIC_RAW
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#define CLOCK_MONOTONIC_COARSE CLOCK_MONOTONIC_COARSE
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#define CLOCK_THREAD_CPUTIME_ID CLOCK_THREAD_CPUTIME_ID
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#define CLOCK_PROCESS_CPUTIME_ID CLOCK_PROCESS_CPUTIME_ID
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#define CLOCK_BOOTTIME CLOCK_BOOTTIME
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#endif /* COSMOPOLITAN_LIBC_SYSV_CONSTS_CLOCK_H_ */
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