[cmake-developers] Filesystem timestamp checks

[Ben Boeckel]

On Thu, Oct 15, 2015 at 22:58:29 +0300, Ruslan Baratov via cmake-developers wrote:
> Test: https://github.com/forexample/date-resolution-test
> Log: https://travis-ci.org/forexample/date-resolution-test/builds/85021483
<snip>
> Any other ideas?

I patched make locally to output the mtimes used when it fails this[1].
The times are the same down to the nanosecond. I had originally thought
that may be make isn't using nanosecond precision, but it does.

I think the kernel and/or filesystem may be taking shortcuts here. There
is no way (I can think of) that a file can have the exact same filestamp
when there's a fork/exec in between modifications; those operations just
take too long.

--Ben

[1]Make's internal debugging is too slow and never triggers the bug;
same with using gdb with a script.