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From: Simon Wright <simon.j.wright@mac.com>
Newsgroups: comp.lang.ada
Subject: Re: real_time.clock is not monotonic
Date: Wed, 21 Feb 2007 20:17:15 +0000
Organization: Pushface
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frederic.ormancey@atosorigin.com writes:

> I'll alert Gnat community with this bad implementation, as
> gettimeofday() is affected by NTP and others date adjustements. in
> LRM, Ada.Real_Time.Clock shall be monotonic => Gnat runtime is not
> compliant

I reported this with GNAT 3.16, not sure if there's a solution yet.

> Did someone have a solution for this problem ? another implementation
> using a Linux monotonic clock ?

The Booch Components have a clock that might be a possibility: OK on
Windows and Linux (not sure about Solaris x86, no idea for 64-bit
OSs):

   with System.Machine_Code;

   separate (BC.Support.High_Resolution_Time)
   function Clock return Time is
      type Half is (Low, High);
      Lower, Upper : Interfaces.Unsigned_32;
      Results : array (Half) of Interfaces.Unsigned_32;
      Result : Time;
      for Result'Address use Results (Low)'Address;
   begin
      System.Machine_Code.Asm
        ("rdtsc" & ASCII.LF & ASCII.HT &
           "movl %%eax, %0"& ASCII.LF & ASCII.HT &
           "movl %%edx, %1",
         Outputs => (Interfaces.Unsigned_32'Asm_Output ("=g", Lower),
                     Interfaces.Unsigned_32'Asm_Output ("=g", Upper)),
         Clobber => "eax, edx",
         Volatile => True);
      Results := (Low => Lower, High => Upper);
      return Result;
   end Clock;