bruno created this revision.
bruno added reviewers: mclow.lists, dexonsmith, EricWF.
bruno added a subscriber: cfe-commits.
CLOCK_MONOTONIC is only defined on Darwin on libc versions >= 1133 and its
behaviour differs from Linux. CLOCK_UPTIME on Darwin actually matches
CLOCK_MONOTONIC on Linux, due to historical coincidence (Linux doesn't match
POSIX here but Darwin does). Use CLOCK_UPTIME_RAW on Darwin since the _RAW
version gives nanosecond precision and is lower overhead.
https://reviews.llvm.org/D27429
Files:
src/chrono.cpp
Index: src/chrono.cpp
===================================================================
--- src/chrono.cpp
+++ src/chrono.cpp
@@ -75,8 +75,19 @@
steady_clock::now() _NOEXCEPT
{
struct timespec tp;
+#if defined(__APPLE__) && defined(CLOCK_UPTIME_RAW)
+ // CLOCK_MONOTONIC is only defined on Darwin on libc versions >= 1133 and
+ // its behaviour differs from Linux.
+ // CLOCK_UPTIME on Darwin actually matches CLOCK_MONOTONIC on Linux, due to
+ // historical coincidence (Linux doesn't match POSIX here but Darwin does).
+ // Use CLOCK_UPTIME_RAW on Darwin since the _RAW version gives nanosecond
+ // precision and is lower overhead.
+ if (0 != clock_gettime(CLOCK_UPTIME_RAW, &tp))
+ __throw_system_error(errno, "clock_gettime(CLOCK_UPTIME_RAW) failed");
+#else
if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
__throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
+#endif
return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
}
Index: src/chrono.cpp
===================================================================
--- src/chrono.cpp
+++ src/chrono.cpp
@@ -75,8 +75,19 @@
steady_clock::now() _NOEXCEPT
{
struct timespec tp;
+#if defined(__APPLE__) && defined(CLOCK_UPTIME_RAW)
+ // CLOCK_MONOTONIC is only defined on Darwin on libc versions >= 1133 and
+ // its behaviour differs from Linux.
+ // CLOCK_UPTIME on Darwin actually matches CLOCK_MONOTONIC on Linux, due to
+ // historical coincidence (Linux doesn't match POSIX here but Darwin does).
+ // Use CLOCK_UPTIME_RAW on Darwin since the _RAW version gives nanosecond
+ // precision and is lower overhead.
+ if (0 != clock_gettime(CLOCK_UPTIME_RAW, &tp))
+ __throw_system_error(errno, "clock_gettime(CLOCK_UPTIME_RAW) failed");
+#else
if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
__throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
+#endif
return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
}
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