bug#13378: More work on subdir-objects, AC_PROG_CC and AM_PROG_CC_C_O

[Stefano Lattarini]

On 05/11/2013 11:57 AM, Stefano Lattarini wrote:
> Reference:
> <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13378#130>
> 
> Hello everybody, sorry for the delay.  This follow-up is looong
> overdue.
> 
> On 01/14/2013 11:23 AM, Stefano Lattarini wrote:
>> On 01/13/2013 10:06 PM, Nick Bowler wrote:
>>> On 2013-01-13, Stefano Lattarini <address@hidden> wrote:
>>>
>>>> Another useful follow-up would be to move the AM_PROG_CC_C_O in a private
>>>> macro (to be expanded in AC_CONFIG_COMMANDS_PRE like you did above), and
>>>> make AM_PROG_CC_C_O a no-op (without runtime deprecation).  That way, we
>>>> could rely on the improved semantic of having the potential '$CC' rewrite
>>>> placed near the end of configure, rather than near the beginning.  WDYT?
>>>
>>> With AC_CONFIG_COMMANDS_PRE, AM_PROG_CC_C_O would still be required if
>>> package authors want to make use of the "compile" wrapper in configure
>>> tests -- essentially, configure.ac can call AM_PROG_CC_C_O to force the
>>> test to happen where it is needed, rather than just before AC_OUTPUT.
>>>
>>> I think it'd be worthwhile to keep that working.
>>>
>> Ah, but the $CC rewrite has always been an undocumented hack, and relying
>> on it is a bad idea.  Still, your reasoning makes it clear that changing
>> that semantics abruptly might cause subtle backward-incompatibilities in
>> corner-case but perfectly valid situations.  Hmmm...  I think it's better
>> to follow your approach for now, and then, if and when we decide to fix
>> our macros not to rewrite $CC, do so with proper NEWS and documentation
>> warnings beforehand, and a viable deprecation plan.
>>
> The attached patches implement Nick's suggestion on the current code
> base (original patches from Nick has unfortunately gotten too much
> out-of-sync with the current codebase situation).  But note that the
> second (one-liner) is actually identical to the first patch originally
> posted by Nick <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13378#121>,
> so it's still in his name.
> 
> I plan to push these patches to maint in a couple of days if there is
> no objection.
> 
Patches pushed.

Regards,
  Stefano