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

[Peter Rosin]

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.
Not that I'm complaining if those tests are always performed though,
just trying to keep the arguments honest...

(but again, I haven't actually checked if AC_PROG_CC triggers
AC_PROG_CC_C_O)

Cheers,
Peter