GNU bug report logs - #7671
Presetting various *CLEANFILES variables

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Behdad Esfahbod <behdad <at> behdad.org>
To: bug-automake <at> gnu.org
Subject: Presetting various *CLEANFILES variables
Date: Fri, 17 Dec 2010 19:55:22 -0500

Hi,

Currently, automake doesn't set any of the various *CLEANFILES variables.
Since the "+=" syntax is not portable when the variables are not initialized
(and causes an automake warning), this leaves no option for Makefile.am
snippets from various tools other than using the *clean-local targets to do
their cleanups.  The problem with this is that it's imperative as opposed to
declarative.

I've been maintaining a pieces of Makefile.am snippet called git.mk:

  http://git.gnome.org/browse/pango/tree/git.mk

What it does is to generate .gitignore files based on what "make
maintainer-clean" removes.  However, because of the problem stated above, I
cannot simply aggregate the various *CLEANFILES variables and also have to add
support for individual tools (autoconf, automake, libtool, gtk-doc,
gnome-doc-utils, mallard, intltool, and gsettings so far).

If instead automake was changed to always pre-initialize *CLEANFILES
variables, all snippets could just append to do variables and my git.mk
snippet would be more generic and much more simpler at the same time.

So I want to suggest that automake be changed to initialized *CLEANFILES if
the Makefile.am doesn't initialize them explicitly.

In another note, if that change is made and my git.mk simplified to not have
tool-specific logic in it, it would be a great addition to automake itself.

Cheers,
behdad

Message #8 received at 7671 <at> debbugs.gnu.org (full text, mbox):

From: Stefano Lattarini <stefano.lattarini <at> gmail.com>
To: Behdad Esfahbod <behdad <at> behdad.org>
Cc: 7671 <at> debbugs.gnu.org
Subject: Re: bug#7671: Presetting various *CLEANFILES variables
Date: Sat, 18 Dec 2010 11:02:45 +0100

On Saturday 18 December 2010, Behdad Esfahbod wrote:
> Hi,
>
Hello Behdad.

> Currently, automake doesn't set any of the various *CLEANFILES variables.
> Since the "+=" syntax is not portable when the variables are not initialized
> (and causes an automake warning), this leaves no option for Makefile.am
> snippets from various tools other than using the *clean-local targets to do
> their cleanups.  The problem with this is that it's imperative as opposed to
> declarative.
>
I agree this might be quite annoying sometimes.

> I've been maintaining a pieces of Makefile.am snippet called git.mk:
> 
>   http://git.gnome.org/browse/pango/tree/git.mk
> 
> What it does is to generate .gitignore files based on what "make
> maintainer-clean" removes.  However, because of the problem stated above,
> I cannot simply aggregate the various *CLEANFILES variables and also have
> to add support for individual tools (autoconf, automake, libtool, gtk-doc,
> gnome-doc-utils, mallard, intltool, and gsettings so far).
>
Note that the *CLEANFILES variables cannot be used to remove directories,
so, for your approach to be really useful in all cases (i.e. also be able
to git-ignore generated directories easily), a similar set of *CLEANDIRS
variables would be needed.

And IMHO adding them would be a good idea regardless of your particular
use case.

> If instead automake was changed to always pre-initialize *CLEANFILES
> variables, all snippets could just append to do variables and my git.mk
> snippet would be more generic and much more simpler at the same time.
> So I want to suggest that automake be changed to initialized *CLEANFILES
> if the Makefile.am doesn't initialize them explicitly.
>
If the change you propose can be implemented without breaking backward
compatibility (and I think it probably can), then I'm all in favor of it.

I'd like to hear Ralf's opinion on this before taking any further
action, though.

> In another note, if that change is made and my git.mk simplified to not have
> tool-specific logic in it, it would be a great addition to automake itself.
> 
> Cheers,
> behdad
> 

Thanks,
   Stefano

Message #11 received at 7671 <at> debbugs.gnu.org (full text, mbox):

From: Behdad Esfahbod <behdad <at> behdad.org>
To: Stefano Lattarini <stefano.lattarini <at> gmail.com>
Cc: 7671 <at> debbugs.gnu.org
Subject: Re: bug#7671: Presetting various *CLEANFILES variables
Date: Sun, 19 Dec 2010 04:51:29 -0500

Hi Stefano,

Thanks for the prompt reply.

On 12/18/10 05:02, Stefano Lattarini wrote:

> Note that the *CLEANFILES variables cannot be used to remove directories,
> so, for your approach to be really useful in all cases (i.e. also be able
> to git-ignore generated directories easily), a similar set of *CLEANDIRS
> variables would be needed.

Good point.  I didn't think about that.


> And IMHO adding them would be a good idea regardless of your particular
> use case.

Agreed.


>> If instead automake was changed to always pre-initialize *CLEANFILES
>> variables, all snippets could just append to do variables and my git.mk
>> snippet would be more generic and much more simpler at the same time.
>> So I want to suggest that automake be changed to initialized *CLEANFILES
>> if the Makefile.am doesn't initialize them explicitly.
>>
> If the change you propose can be implemented without breaking backward
> compatibility (and I think it probably can), then I'm all in favor of it.
> 
> I'd like to hear Ralf's opinion on this before taking any further
> action, though.

Indeed.

Cheers,
behdad


>> In another note, if that change is made and my git.mk simplified to not have
>> tool-specific logic in it, it would be a great addition to automake itself.
>>
>> Cheers,
>> behdad
>>
> 
> Thanks,
>    Stefano
> 

Message #14 received at 7671 <at> debbugs.gnu.org (full text, mbox):

From: Ralf Wildenhues <Ralf.Wildenhues <at> gmx.de>
To: Behdad Esfahbod <behdad <at> behdad.org>
Cc: 7671 <at> debbugs.gnu.org
Subject: Re: bug#7671: Presetting various *CLEANFILES variables
Date: Sun, 19 Dec 2010 12:43:54 +0100

Hello Behdad, and thanks for the bug report,

* Behdad Esfahbod wrote on Sat, Dec 18, 2010 at 01:55:22AM CET:
> If instead automake was changed to always pre-initialize *CLEANFILES
> variables, all snippets could just append to do variables and my git.mk
> snippet would be more generic and much more simpler at the same time.

What you can do now is either
- require your users to pre-initialize variables, or
- ship a header fragment to be included first, that sets the needed
  variables.

Your proposed change would break typo detection, if we allowed += for
all unset variables.  The question is whether typo detection is worth
it.  If we only do it for *CLEANFILES variables, that would be very
inconsistent.  Users have the same problems with lots of other variables
(EXTRA_DIST, SUFFIXES, SUBDIRS, etc, the list is not stable; see for
example gnulib/gnulib-tool for others).  They would not be helped, while
at the same time Automake semantics becomes harder to grasp.

There are more subtle issues with conditionals and with variables that
are already set by automake or that are AC_SUBSTed from configure.ac; in
fact, most of all the uniqe/once-only/override warning machinery is to
disallow ambiguities in these cases.

For example, automake sets DIST_COMMON, an internal variable.  Assume
the user writes
  DIST_COMMON += foo

Should that add to the automake-given list?  I would guess so.  But what
about the following (assuming AC_SUBST([substed])):
  foo = foo

  if COND1
    foo = bar
    substed = bar
    DIST_COMMON = bar
  else
    foo += baz
    substed += baz
    DIST_COMMON += baz
  endif

The expectation again is clear, and for 'foo' things work out, but it is
not possible to realize for substed with the current implementation where
AC_SUBST([substed]) generates a single
  substed = @substed@

line in Makefile.in.  It might be fixable, but I haven't looked into it
and assume that at least the disjoint-condition handling may turn out
ugly.

Cheers,
Ralf

Message #17 received at 7671 <at> debbugs.gnu.org (full text, mbox):

From: Behdad Esfahbod <behdad <at> behdad.org>
To: Ralf Wildenhues <Ralf.Wildenhues <at> gmx.de>
Cc: 7671 <at> debbugs.gnu.org
Subject: Re: bug#7671: Presetting various *CLEANFILES variables
Date: Mon, 20 Dec 2010 15:53:23 -0500

On 12/19/10 06:43, Ralf Wildenhues wrote:
> What you can do now is either
> - require your users to pre-initialize variables, or
> - ship a header fragment to be included first, that sets the needed
>   variables.

Yeah, that's what we currently do in a few occasions, but I can't sell that to
others when they can remove files in *clean-local targets without such
conditions imposed on their users.

That said, your concerns are real.  I let you guys decide if you want to close
this WONTFIX or address it some other way.

Cheers,
behdad

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