Check the precision of `getrusage` at runtime

1 files changed, 11 insertions, 1 deletions

diff --git a/spec/ruby/core/process/times_spec.rb b/spec/ruby/core/process/times_spec.rb
index 1cf8d5e8bb..d2610f6415 100644
--- a/spec/ruby/core/process/times_spec.rb
+++ b/spec/ruby/core/process/times_spec.rb
@@ -17,8 +17,18 @@ describe "Process.times" do
     end
   end
 
+  # TODO: The precision of `getrusage` depends on platforms (OpenBSD
+  # seems not supporting under-milliseconds in fact); this example is
+  # very questionable as an example of Ruby, and it just repeats the
+  # guard condition.
   guard -> do
-    Process.clock_gettime(:GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID)
+    1000.times.any? do
+      # If getrusage has precision beyond milliseconds, there will be
+      # very likely at least one non-zero microsecond results when
+      # repeating enough.
+      time = Process.clock_gettime(:GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID)
+      not ('%.6f' % time).end_with?('000')
+    end
   rescue Errno::EINVAL
     false
   end do