Cyril Brulebois kibi at debian.org
Wed Mar 9 09:52:27 PST 2011


Soeren Sandmann <sandmann at cs.au.dk> (09/03/2011):
> I'm not sure I understand the issue. Where would those timestamp
> skews come from? The automake manual says something about CVS. Does
> it apply to git as well?

with another package (I think graphviz), that happened to me on some
Debian buildd daemons (I think sparc or hppa). Unpacking the source
package means basically unpacking a tarball and applying a diff
against it; I'm quoting the README.Debian file from the autotools-dev
Debian package:
| The problem with time-stamp skews and Debian source packages:
| -------------------------------------------------------------
| Time-stamp skew is not a problem for the packages that employ the current
| best practice, which is to remove all auto-generated files and regenerate
| them all on every build.  However, for the packages that are not prepared to
| regenerate their build system, it can be a big problem.
| As of the time this document is being written, dpkg-source cannot
| automatically fix the severe time-stamp skew problems that applying a diff
| file over a tarball-extracted tree generate.  The result of these
| time-stamp skew problems is that most programs that use autoconf and
| automake will often try to regenerate their configure and Makefiles.
| This IS guaranteed to cause severe headaches if your package did not expect
| it and did not enforce a controlled environment for the build system to be
| rebuilt properly.
| Users of automake should use AM_MAINTAINER_MODE in configure.{ac,in}, as
| that will tell automake to generate Makefiles that do not try to rebuild
| the configure files by default.  Ask upstream to use it too, it is better
| for the normal users.
| One can fix the time-stamp skews using a proper chain of "touch foo &&
| touch bar..." in the debian/rules file, to make sure files will not be
| regenerated without need.  The time-stamps have to be updated before
| configure runs.
| Proper ordering of the touch commands is extremely important, so you must
| enforce it using the '&&'.  Get it wrong, and you will break the build.
| Miss one file you need to touch, and you will have a lurking problem
| waiting to spring on you.
| When in doubt, you can clean the build tree and touch every file TO THE
| SAME TIME-STAMP (hint: use touch -r).

So, as you can see, if such issues happen, we have workarounds; which
is why I'm not going to insist on your applying my patch.

I hope it clarifies.

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