Re: [PATCH] AC_CONFIG_MACRO_DIRS: improve tracing and add sanity checks

[Stefano Lattarini]

Hello everybody, sorry for the delay.

On 11/13/2012 11:11 PM, Nick Bowler wrote:
> On 2012-11-13 14:59 -0700, Eric Blake wrote:
>> On 11/13/2012 02:37 PM, Nick Bowler wrote:
>>> [SNIP]
>>> No, it cannot use AC_CONFIG_MACRO_DIR_TRACE exclusively, since not all
>>> packages use AC_CONFIG_MACRO_DIR in the first place!
>>
>> You are correct that new libtool and automake cannot rely exclusively on
>> the new trace macro, but that's not a problem and doesn't change
>> anything we've done in autoconf.
>>
>> If AC_CONFIG_MACRO_DIR_TRACE has a trace hit, then autoconf 2.70 is in
>> effect.  Either the configure.ac used AC_CONFIG_MACRO_DIR (old-style)
>> (and you can assume ACLOCAL_AMFLAGS will exist and match), or it used
>> AC_CONFIG_MACRO_DIRS (new-style) (and ACLOACL_AMFLAGS is no longer
>> required),
> 
> No, these are not the only possibilities if AC_CONFIG_MACRO_DIR_TRACE
> appears in the m4 traces.  You have forgotten the case where ACLOCAL_AMFLAGS
> contains more than one -I option, and a user used AC_CONFIG_MACRO_DIR to
> shut up libtool.  This case was labeled (2) in both of the following:
> 
>   - https://lists.gnu.org/archive/html/autoconf-patches/2012-11/msg00057.html
>   - https://lists.gnu.org/archive/html/autoconf-patches/2012-11/msg00075.html
> 
>> but either way, this is the canonical location to be used.
> 
> No, because in the "shut up libtool" case there is an additional
> directory to consider that will not be found in the m4 traces.
> 
>> Automake 1.13 will error out if ACLOCAL_AMFLAGS exists but does not
>> match the trace (thus enforcing that _if_ you use the redundancy, you
>> use it correctly);
>
Actually, that is not the case ATM.  It might be a useful warning though,
so if anyone is willing to write a patch for it, I'll surely take it.
Such a patch will obviously have to cater for the situation outlined by
Nick above:

   We have AC_CONFIG_MACRO_DIR([dir-1]) to shut up libtool, but we have
   "-I dir-1 -I dir-2" in ACLOCAL_AMFLAGS.

and avoid to emit warnings in this case.

> but [Automake] will not care if you omit ACLOCAL_AMFLAGS.
>
Correct.  It will indeed be happy if you do :-)

> Then this will represent a regression in Automake in the case where a
> configure.ac does not include AC_CONFIG_MACRO_DIR all (for example,
> this would regress for at least GNU Gettext and my own packages).  But I
> believe you may be mistaken: I personally tested the patch series that
> Stefano posted and did not observe the behaviour you describe.
>
You are correct in this, since that behaviour is not (yet) implemented.

> So this will only be the case if Automake's behaviour has changed in the
> interim...
>
No, it hasn't; but patches are welcome.

Thanks,
  Stefano