Replacing JOBS=x with -j for make parallelism did not work

[Magnus Ihse Bursie]

On 04/26/12 14:43, magnus.ihse.bursie at oracle.com wrote:
>> Changeset: 33eaa832ce5e
>> Author:    ihse
>> Date:      2012-04-26 14:43 +0200
>> URL:       http://hg.openjdk.java.net/build-infra/jdk8/rev/33eaa832ce5e
>>
>> Replace previous fix (JOBS=) with a solution that actually respects 
>> -j if
>> set on top-level Makefile.

Unfortunately, it turned out that this fix does not really work. :-(

If you run "make -j2", it works well. That was my test case, when doing 
the fix. However, when you run "make -j1", it does not -- this case is 
indistinguishable from just "make". Unfortunately, it is also one of the 
typical cases for wanting to override -j, to force non-parallel execution.

I can see a a bunch of possible solutions, none of them really optimal:

1) Restore the previous fix with JOBS=x

2) Really extract the actual make command line using ugly hacks (like 
some shell script magic and reading from /proc). Might be hard to get it 
properly working on all platforms.

3) Support a combination, so that both "make -j2" and "make JOBS=2" 
works, but if you want singlethreaded execution, you *must* specify 
"make JOBS=1".

Out of these, I'd prefer 1). Anyone else has an opinion?

/Magnus