Unreliability of the build system

[Ian Lynagh]

On Mon, Jun 24, 2013 at 12:37:17PM +0100, Geoffrey Mainland wrote:
> 
> It looks like "/home/gmainlan/ghc/ghc-working-build/bindisttest/install
> dir/lib/ghc-7.7.20130624/package.conf.d" gets *younger*, leading to the
> recache error. Rather odd... Any ideas why this is happening?

That's expected: When we install xhtml, we add it to the DB, and the
cache gets updated.

It looks like the problem is this:

Timestamp 2013-06-24 11:02:14.669097 UTC for [...]/package.conf.d/package.cache
Timestamp 2013-06-24 11:02:14.669197 UTC for [...]/package.conf.d (NEWER

I would guess that we assume that when we write package.cache, the
directory gets updated with the same timestamp; but actually, both use
the timestamp at which they really happen. This is of course much more
likely to be a problem if your filesystem has sub-second precision.

If that's it, then it should be possible to fix it by explicitly setting
the modification time of the directory to match the cache when we write
the cache in ghc-pkg.


Thanks
Ian