Re: [PATCH 1/3] AC_CONFIG_MACRO_DIRS: new macro, mostly for aclocal

[Eric Blake]

On 11/09/2012 11:47 AM, Stefano Lattarini wrote:
>> I'm adding my own sign-off and squashing this in; basically, I'm
>> relaxing the documentation to plan for my subsequent patches where
>> AC_CONFIG_MACRO_DIR will not be treated as obsolescent, but leaving your
>> initial implementation separate from my improvements to make it clear
>> what my improvements accomplish.
>>
> How does this interact with the fact that aclocal 1.13 will handle
> *only* AC_CONFIG_MACRO_DIRS, while continuing (like it did before)
> to ignore AC_CONFIG_MACRO_DIR?  For a rationale about this, see:
> 
>   <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=12845>
> 
> I still believe we should make it clear that AC_CONFIG_MACRO_DIR is
> obsolescent and should no longer be used; albeit, to avoid gratuitous
> backward-incompatibility, we'll refrain to have it elicit any warning,
> at least for the time being ...

Automake should trace exactly one macro name: AC_CONFIG_MACRO_DIR_TRACE.
 This trace macro will hit once per directory, no matter whether the
user called AC_CONFIG_MACRO_DIR or AC_CONFIG_MACRO_DIRS.  Furthermore,
since the trace will hit once per directory, automake doesn't have to go
to any great lengths to do whitespace normalization - that will have
already been done by AC_CONFIG_MACRO_DIRS.

AC_CONFIG_MACRO_DIR can be traced (such as by older libtool), but will
hit exactly once (whether or not the user used AC_CONFIG_MACRO_DIR
directly or used AC_CONFIG_MACRO_DIRS).

Users should then decide what they are targetting:
- newer tools only (such as automake 1.13) - no need for
ACLOCAL_AMFLAGS, and use AC_CONFIG_MACRO_DIRS only
- hybrid support for older AND newer tools - use ACLOCAL_AMFLAGS, and
call AC_CONFIG_MACRO_DIR exactly once and first.  Newer automake will
warn about ACLOCAL_AMFLAGS, but will do the right thing by tracing
exactly AC_CONFIG_MACRO_DIR_TRACE (and nothing else).

I'm trying to document this in the patches that I'm writing (right now,
I'm working on the testsuite to make sure things are tested and
therefore will not regress).

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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