From patchwork Sun Oct 21 14:00:20 2012
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Subject: A steadier steady_clock
Date: Sun, 21 Oct 2012 04:00:20 -0000
From: Sam Varshavchik <mrsam@courier-mta.com>
X-Patchwork-Id: 192996
Message-Id: <cone.1350828020.51066.30326.1000@monster.email-scan.com>
To: gcc-patches@gcc.gnu.org

Based on a casual browsing of clock_gettime(3), CLOCK_MONOTONIC_RAW seems to  
be a better fit for std::chrono::steady_clock's requirements as given in  
20.11.7.2, with recent Linux kernels,

Something like this:


Index: libstdc++-v3/src/c++11/chrono.cc
===================================================================
--- libstdc++-v3/src/c++11/chrono.cc	(revision 192652)
+++ libstdc++-v3/src/c++11/chrono.cc	(working copy)
@@ -70,7 +70,11 @@
     {
       timespec tp;
       // -EINVAL, -EFAULT
+#ifdef CLOCK_MONOTONIC_RAW
+      clock_gettime(CLOCK_MONOTONIC_RAW, &tp);
+#else
       clock_gettime(CLOCK_MONOTONIC, &tp);
+#endif
       return time_point(duration(chrono::seconds(tp.tv_sec)
 				 + chrono::nanoseconds(tp.tv_nsec)));
     }