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Re: Linux 2.6 nanosecond time stamp weirdness breaks GCC build

From: Joe Buck <Joe dot Buck at synopsys dot COM>
To: Andi Kleen <ak at suse dot de>,Ulrich Weigand <weigand at i1 dot informatik dot uni-erlangen dot de>,gcc at gcc dot gnu dot org, linux-kernel at vger dot kernel dot org, schwidefsky at de dot ibm dot com
Date: Thu, 1 Apr 2004 14:39:08 -0800
Subject: Re: Linux 2.6 nanosecond time stamp weirdness breaks GCC build
References: <200404011928.VAA23657@faui1d.informatik.uni-erlangen.de> <20040401220957.5f4f9ad2.ak@suse.de> <20040401203923.GA32177@nevyn.them.org>

[ Linux 2.6 losing the nanoseconds from a file timestamp ]

There are two different failure modes, but in most cases only one
results in a real problem.

Case 1: make falsely thinks that the .o is younger than the .c.  It
decides not to rebuild the .o, resulting in a bad build.

Case 2: make falsely thinks that the .c is younger than the .o.  It
recompiles the .c file, even though it didn't have to.  Harmless.

So if we can make the bad situation look like a tie, and always rebuild
in the case of a tie, we will obtain valid builds, sometimes with
an extra compilation or two.

Follow-Ups:
- Re: Linux 2.6 nanosecond time stamp weirdness breaks GCC build
  - From: Paul Jarc
- Re: Linux 2.6 nanosecond time stamp weirdness breaks GCC build
  - From: Ulrich Weigand

References:
- Linux 2.6 nanosecond time stamp weirdness breaks GCC build
  - From: Ulrich Weigand
- Re: Linux 2.6 nanosecond time stamp weirdness breaks GCC build
  - From: Andi Kleen
- Re: Linux 2.6 nanosecond time stamp weirdness breaks GCC build
  - From: Daniel Jacobowitz

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