Add C2X timespec_getres

ISO C2X adds a timespec_getres function alongside the C11 timespec_get, with functionality similar to that of POSIX clock_getres (including allowing a NULL pointer to be passed to the function). Implement this function for glibc, similarly to the implementation of timespec_get. This includes a basic test like that of timespec_get, but no documentation in the manual, given that TIME_UTC and timespec_get aren't documented in the manual at all. The handling of 64-bit time follows that in timespec_get; people maintaining patch series for 64-bit time will need to update them accordingly (to export __timespec_getres64, redirect calls in time.h and run the test for _TIME_BITS=64). Tested for x86_64 and x86, and (previous version; only testcase differs) with build-many-glibcs.py.
2021-05-17 20:55:21 +00:00 · 2021-05-17 20:55:21 +00:00 · e5ac7bd679
parent c6b6b4f2c7
commit e5ac7bd679
44 changed files with 189 additions and 2 deletions
--- a/2
+++ b/2
@ -23,6 +23,8 @@ Major new features:
  /proc to be mounted.  However, different than fexecve, if the syscall is not
  supported by the kernel an error is returned instead of trying a fallback.

+* The ISO C2X function timespec_getres has been added.
+
 Deprecated and removed features, and other changes affecting compatibility:

 * The function pthread_mutex_consistent_np has been deprecated; programs
--- a/include/time.h
+++ b/include/time.h
@ -28,6 +28,9 @@ libc_hidden_proto (__clock_gettime)
 extern __typeof (clock_settime) __clock_settime;
 libc_hidden_proto (__clock_settime)

+extern __typeof (clock_getres) __clock_getres;
+libc_hidden_proto (__clock_getres)
+
 extern __typeof (clock_nanosleep) __clock_nanosleep;
 libc_hidden_proto (__clock_nanosleep);

@ -306,6 +309,7 @@ extern double __difftime (time_t time1, time_t time0);
 # define __clock_nanosleep_time64 __clock_nanosleep
 # define __clock_gettime64 __clock_gettime
 # define __timespec_get64 __timespec_get
+# define __timespec_getres64 __timespec_getres
 #else
 extern int __clock_nanosleep_time64 (clockid_t clock_id,
                                     int flags, const struct __timespec64 *req,
@ -315,6 +319,8 @@ extern int __clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp);
 libc_hidden_proto (__clock_gettime64)
 extern int __timespec_get64 (struct __timespec64 *ts, int base);
 libc_hidden_proto (__timespec_get64)
+extern int __timespec_getres64 (struct __timespec64 *ts, int base);
+libc_hidden_proto (__timespec_getres64)
 #endif

 #if __TIMESIZE == 64
--- a/sysdeps/mach/hurd/i386/libc.abilist
+++ b/sysdeps/mach/hurd/i386/libc.abilist
@ -2208,6 +2208,7 @@ GLIBC_2.34 __isnanf128 F
 GLIBC_2.34 __libc_start_main F
 GLIBC_2.34 _hurd_libc_proc_init F
 GLIBC_2.34 execveat F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
--- a/sysdeps/posix/clock_getres.c
+++ b/sysdeps/posix/clock_getres.c
@ -62,6 +62,7 @@ __clock_getres (clockid_t clock_id, struct timespec *res)

  return retval;
 }
+libc_hidden_def (__clock_getres)

 versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
 /* clock_getres moved to libc in version 2.17;
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@ -2445,6 +2445,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@ -2536,6 +2536,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/arc/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
@ -2204,6 +2204,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@ -311,6 +311,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@ -308,6 +308,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/clock_getres.c
+++ b/sysdeps/unix/sysv/linux/clock_getres.c
@ -79,6 +79,7 @@ __clock_getres (clockid_t clock_id, struct timespec *res)
  return retval;
 }
 #endif
+libc_hidden_def (__clock_getres)

 versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
 /* clock_getres moved to libc in version 2.17;
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@ -2388,6 +2388,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@ -2341,6 +2341,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@ -2524,6 +2524,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@ -2377,6 +2377,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@ -312,6 +312,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@ -2467,6 +2467,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@ -2439,6 +2439,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@ -2436,6 +2436,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@ -2432,6 +2432,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@ -2430,6 +2430,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@ -2438,6 +2438,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@ -2432,6 +2432,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@ -2478,6 +2478,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@ -2494,6 +2494,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@ -2527,6 +2527,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@ -2342,6 +2342,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@ -2641,6 +2641,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
@ -2206,6 +2206,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@ -2406,6 +2406,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@ -2492,6 +2492,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@ -2379,6 +2379,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@ -2348,6 +2348,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@ -2345,6 +2345,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@ -2485,6 +2485,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@ -2398,6 +2398,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/timespec_getres.c
+++ b/sysdeps/unix/sysv/linux/timespec_getres.c
@ -0,0 +1,50 @@
+/* Get resolution of a time base.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <time.h>
+
+/* Set TS to resolution of time base BASE.  */
+int
+__timespec_getres64 (struct __timespec64 *ts, int base)
+{
+  if (base == TIME_UTC)
+    {
+      __clock_getres64 (CLOCK_REALTIME, ts);
+      return base;
+    }
+  return 0;
+}
+
+#if __TIMESIZE != 64
+libc_hidden_def (__timespec_getres64)
+
+int
+__timespec_getres (struct timespec *ts, int base)
+{
+  int ret;
+  struct __timespec64 tp64;
+
+  ret = __timespec_getres64 (&tp64, base);
+
+  if (ret == TIME_UTC && ts != NULL)
+    *ts = valid_timespec64_to_timespec (tp64);
+
+  return ret;
+}
+#endif
+strong_alias (__timespec_getres, timespec_getres);
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@ -2357,6 +2357,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@ -2460,6 +2460,7 @@ GLIBC_2.34 sem_wait F
 GLIBC_2.34 thrd_detach F
 GLIBC_2.34 thrd_exit F
 GLIBC_2.34 thrd_join F
+GLIBC_2.34 timespec_getres F
 GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
--- a/time/Makefile
+++ b/time/Makefile
@ -36,7 +36,7 @@ routines := offtime asctime clock ctime ctime_r difftime \
 	    stime dysize timegm ftime			 \
 	    getdate strptime strptime_l			 \
 	    strftime wcsftime strftime_l wcsftime_l	 \
-	    timespec_get				 \
+	    timespec_get timespec_getres		 \
 	    clock_getcpuclockid clock_getres		 \
 	    clock_gettime clock_settime clock_nanosleep

@ -50,7 +50,7 @@ tests	:= test_time clocktest tst-posixtz tst-strptime tst_wcsftime \
 	   tst-clock tst-clock2 tst-clock_nanosleep tst-cpuclock1 \
 	   tst-adjtime tst-ctime tst-difftime tst-mktime4 tst-clock_settime \
 	   tst-settimeofday tst-itimer tst-gmtime tst-timegm \
-	   tst-timespec_get
+	   tst-timespec_get tst-timespec_getres

 include ../Rules

--- a/time/Versions
+++ b/time/Versions
@ -74,6 +74,9 @@ libc {
    clock_getres; clock_gettime; clock_settime; clock_getcpuclockid;
    clock_nanosleep;
  }
+  GLIBC_2.34 {
+    timespec_getres;
+  }
  GLIBC_PRIVATE {
    # same as clock_gettime; used in other libraries
    __clock_gettime;
--- a/time/clock_getres.c
+++ b/time/clock_getres.c
@ -27,6 +27,7 @@ __clock_getres (clockid_t clock_id, struct timespec *res)
  __set_errno (ENOSYS);
  return -1;
 }
+libc_hidden_def (__clock_getres)

 versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
 /* clock_getres moved to libc in version 2.17;
--- a/time/time.h
+++ b/time/time.h
@ -259,6 +259,13 @@ extern int timespec_get (struct timespec *__ts, int __base)
 #endif


+#if __GLIBC_USE (ISOC2X)
+/* Set TS to resolution of time base BASE.  */
+extern int timespec_getres (struct timespec *__ts, int __base)
+     __THROW;
+#endif
+
+
 #ifdef __USE_XOPEN_EXTENDED
 /* Set to one of the following values to indicate an error.
     1  the DATEMSK environment variable is null or undefined,
--- a/time/timespec_getres.c
+++ b/time/timespec_getres.c
@ -0,0 +1,32 @@
+/* Get resolution of a time base.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <time.h>
+
+
+/* Set TS to resolution of time base BASE.  */
+int
+timespec_getres (struct timespec *ts, int base)
+{
+  if (base == TIME_UTC)
+    {
+      __clock_getres (CLOCK_REALTIME, ts);
+      return base;
+    }
+  return 0;
+}
--- a/time/tst-timespec_getres.c
+++ b/time/tst-timespec_getres.c
@ -0,0 +1,51 @@
+/* Basic tests for timespec_getres.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <time.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  {
+    struct timespec ts;
+    TEST_COMPARE (timespec_getres (&ts, 0), 0);
+    TEST_COMPARE (timespec_getres (NULL, 0), 0);
+  }
+
+  {
+    struct timespec ts;
+    TEST_COMPARE (timespec_getres (&ts, TIME_UTC), TIME_UTC);
+    /* Expect all supported systems to support TIME_UTC with
+       resolution better than one second.  */
+    TEST_VERIFY (ts.tv_sec == 0);
+    TEST_VERIFY (ts.tv_nsec > 0);
+    TEST_VERIFY (ts.tv_nsec < 1000000000);
+    TEST_COMPARE (timespec_getres (NULL, TIME_UTC), TIME_UTC);
+    /* Expect the resolution to be the same as that reported for
+       CLOCK_REALTIME with clock_getres.  */
+    struct timespec cts;
+    TEST_COMPARE (clock_getres (CLOCK_REALTIME, &cts), 0);
+    TEST_COMPARE (ts.tv_sec, cts.tv_sec);
+    TEST_COMPARE (ts.tv_nsec, cts.tv_nsec);
+  }
+
+  return 0;
+}
+
+#include <support/test-driver.c>