bug#13378: [IMPORTANT] Make the 'subdir-objects' setup the default, and only available one

[Stefano Lattarini]

On 01/08/2013 10:11 PM, Peter Rosin wrote:
> On 2013-01-08 20:27, Stefano Lattarini wrote:
>> On 01/08/2013 04:29 PM, Eric Blake wrote:
>>> On 01/08/2013 08:15 AM, Stefano Lattarini wrote:
>>>>  In addition, AM_PROG_CC_C_O is not required by
>>>> projects that don't care about catering to inferior compilers.
>>>
>>> How much speed penalty and configure bloat are we talking about by
>>> allowing projects to omit the use of this macro if they don't care about
>>> inferior compilers?
>>>
>> Almost zero bloat.  The code simply re-uses a cache variable set by
>> AC_PROG_CC, and, *for losing compilers only*, plays some dirty but
>> inexpensive tricks with $CC redefinition.
> 
> Not quite, the cache variable is from AC_PROG_CC_C_O which is is not
> invoked by AC_PROG_CC, at least I don't think so? AM_PROG_CC_C_O
> requires AC_PROG_CC_C_O so it costs a couple of extra compile tests.
>
Ouch.  Thanks for correcting me on this.

> Not that I'm complaining if those tests are always performed though,
> just trying to keep the arguments honest...
>
Alas, I wasn't being dishonest here, just dumb/distracted ;-)

> (but again, I haven't actually checked if AC_PROG_CC triggers
> AC_PROG_CC_C_O)
> 
Nope.  Maybe it could do so in future Autoconf version though?
This would be a good occasion to fix some weird AC_PROG_CC_C_O
behaviours (e.g., the fact that it's checking both "cc" and
"$CC").  Eric, WDYT?

Regards,
  Stefano