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Date: Tue, 8 Oct 2013 10:46:10 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>, David Ahern <dsahern@gmail.com>
Subject: Re: [PATCH 37/50] tools/perf/build: Improve printout-of
 auto-detected features
Message-ID: <20131008084610.GB3295@gmail.com>
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* Jiri Olsa <jolsa@redhat.com> wrote:

> On Mon, Oct 07, 2013 at 01:56:30PM +0200, Ingo Molnar wrote:
> 
> SNIP
> 
> > +#
> > +# Only print out our features if we rebuilt the testcases or if a test failed:
> > +#
> > +ifeq ($(test-all-failed), 1)
> > +  $(foreach feat,$(CORE_FEATURE_TESTS) DUMMY,$(call feature_print,$(feat)))
> > +  $(info )
> > +endif
> 
> found the DUMMY! what do I win? ;-)

:-)

So, this is a bit of a GNU Make mystery to me. If I have a failure for at 
least one of the features, and if I leave out that DUMMY then I get this 
printout:

...                       libperl: [ OFF ]
...                     libpython: [ on  ]
...             libpython-version: [ on  ]
...                      libslang: [ on  ]
...                     libunwind: [ on  ]
...                       on-exit: [ on  ]
...                stackprotector: [ on  ]
...            stackprotector-all: [ on  ]

    GEN python/perf.so

Note how the last entry is missing: volatile-register-var.

If I add the DUMMY I get the full printout:

...                       libperl: [ OFF ]
...                     libpython: [ on  ]
...             libpython-version: [ on  ]
...                      libslang: [ on  ]
...                     libunwind: [ on  ]
...                       on-exit: [ on  ]
...                stackprotector: [ on  ]
...            stackprotector-all: [ on  ]
...         volatile-register-var: [ on  ]

    GEN python/perf.so

Somehow GNU Make appears to be eating terminal ouput - or I might have 
misunderstood something.

I hope it's the latter - but if it's the former then the DUMMY entry is 
needed :-/

Thanks,

	Ingo