Proposed change to make -j

[Yar Tikhiy]

On Thu, Nov 23, 2006 at 11:20:35PM +0000, John Birrell wrote:
> Currently 'make -j' reports an error if the number of jobs
> isn't specified.
> 
> I'd like to change make(1) to treat -j (without a number) as
> meaning "set the number of jobs to the number of processors".
> 
> On sun4v, each processor isn't too powerful and system performance
> is only decent when you use all the processors - 32 in my case.
> 
> I've been working on a parallel 'make release' process which
> would benefit from having -j set by default. At the moment I
> set MAKEFLAGS=j32 in my environment and this achieves the desired
> result, but -j would be more general.
> 
> Thoughts?

Besides the portability issues already pointed at, making option's
argument optional itself doesn't fit in the getopt(3) semantics and
is confusing.  As a rule, option's argument must be able to begin
with a dash.  If this extension to make(1) were good from the
technical POV, I'd suggest "-j -1", "-j max", "-j ncpu", or whatever,
but not a bare "-j".  Even if the make(1) code can handle such
optional arguments, other stock tools should not be spoiled by that.
IMHO :-)

-- 
Yar