Re: [Automake-NG] [PATCH 01/14] [ng] deptrack: remove an obsolete comment

[Dave Hart]

On Thu, Jun 21, 2012 at 10:32 AM, Stefano Lattarini wrote:
> * lib/am/depend.am: Since in Automake-NG the generated Makefile calls
> '-include' (not 'include') on the dependency tracking '.Po' files, we
> can remove them at any time without causing any 'make' call to fail.

I assume you already understand the nuances, Stefano, but I don't like
the suggestion "we can remove them at any time without causing any
'make' call to fail."

I agree one can remove *.Po files using Automake-NG without causing
make to fail due to missing .Po include file.  However, there are many
other ways for any 'make' call to fail -- such as due to incorrect
dependency tracking caused by too-aggressive cleaning or stubbing of
*.Po files.

The natural intuition of the end user building with 'make' is to
assume deleting files created after the first 'make' is making the
source tree cleaner and thereby increase the odds of a subsequent
'make' succeeding and producing correct resulting outputs.  That
intuition misleads when it comes to .deps/*.Po files, which should not
be removed unless all of the dependent *.o files are removed first.

This understandable error caused recurring friction between myself and
another developer for years before I discovered why her incremental
builds of my commits failed to link due to incorrect dependency
tracking all too often.  She was using a script which updated source
from the VCS, then "cleaned" all the .deps dirs, then stubbed the *.Po
files using config.status (so they existed devoid of any
dependencies), and finally invoked configure and make.

Given the nonintuitive effect of "cleaning" .deps/*.Po files, I would
prefer if you try to avoid appearing to minimize the possibility of
"make" failing as a result.

Cheers,
Dave Hart