bug#9037: distcheck should check for missing m4 files too (was: Re: bug#9026: Supporting $ACLOCAL_PATH?)

[Stefano Lattarini]

On Saturday 09 July 2011, Peter Johansson wrote:
> Hi Bruno,
> 
> On 7/8/11 5:24 PM, Bruno Haible wrote:
> > +If you are using GNU @code{automake} 1.10 or newer, it is even easier:
> > +Add the line
> > +
> > address@hidden
> > +ACLOCAL_AMFLAGS = --install -I m4
> > address@hidden example
> > +
> > address@hidden
> > +to your top level @file{Makefile.am}, and run @samp{aclocal --install -I 
> > m4}.
> > +This will copy the needed files to the @file{m4/} subdirectory 
> > automatically,
> > +before updating @file{aclocal.m4}.
> > +
> I used to do this as it is an easy way to stay up to date with 3rd party 
> m4 files. I stopped doing this, however, after Ralf Wildenhues made me 
> aware there is a risk doing so. The risk is that aclocal will copy 3rd 
> party m4 files into m4 not only for you but also for your users if they 
> happen to run aclocal. Say, e.g., that a user want to build a somewhat 
> old version of your package from git; he bootstraps and as he has newer 
> versions of the m4 files available on his system aclocal copies them 
> into m4, which may cause problems as they are not necessarily compatible 
> with your configure.ac. To avoid this from happen, I've removed the 
> --install flag from my packages and calls aclocal --install -I m4 
> frequently instead.
>
Oh, good point, I hadn't thought about the precise semantics of `--install'
when I wrote my answer.

> There is, obviously, a risk doing this way, as mentioned above in this 
> thread, because if I'm not careful I may release a tarball with missing 
> m4 files. Would distcheck detect a missing m4 file, or would it be 
> possible to modify distcheck so it could warn about this case?
>
I think improving distcheck to catch such an error would be worthwhile.
I'm not sure how easy or difficult that would be, though, and I can't
look into it right now; so I'm opening a new bug report to make sure we
won't forget about the issue.

Thanks,
  Stefano