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Date: Fri, 15 Jan 2016 16:23:52 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Wang Nan <wangnan0@huawei.com>
Cc: jolsa@redhat.com, linux-kernel@vger.kernel.org, pi3orama@163.com,
        lizefan@huawei.com, Jiri Olsa <jolsa@kernel.org>
Subject: Re: [PATCH v3 5/9] perf build: Add feature-dump target
Message-ID: <20160115192352.GF18367@kernel.org>
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Em Fri, Jan 15, 2016 at 04:11:39PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Jan 15, 2016 at 04:00:17AM +0000, Wang Nan escreveu:
> > From: Jiri Olsa <jolsa@kernel.org>
> > 
> > To provide FEATURE-DUMP into $(FEATURE_DUMP_COPY)
> > if defined, with no further action.
> > 
> > Get feature dump of the current build:
> >   $ make feature-dump
> >     BUILD:   Doing 'make -j4' parallel build
> > 
> >   Auto-detecting system features:
> >   ...                         dwarf: [ on  ]
> > 
> >   FEATURE-DUMP file available in FEATURE-DUMP
> 
> Trying to improve this, i.e. provide an absolute or relative path to where
> the file is really generated.
> 
> 
> FEATURE-DUMP file available in FEATURE-DUMP
> make: Leaving directory '/home/git/linux/tools/perf'
> [acme@zoo linux]$ cat FEATURE-DUMP
> cat: FEATURE-DUMP: No such file or directory
> [acme@zoo linux]$ find . -name FEATURE-DUMP
> ./tools/perf/FEATURE-DUMP
> [acme@zoo linux]$ 

Like what is done here already:

$(LIBBPF): fixdep FORCE
        $(Q)$(MAKE) -C $(BPF_DIR) O=$(OUTPUT) $(OUTPUT)libbpf.a FEATURES_DUMP=$(realpath $(OUTPUT)FEATURE-DUMP)

I.e. use realphat, like:


[acme@zoo linux]$ git diff
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index f758a72df1b3..ec701e61c9bd 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -618,7 +618,7 @@ ifdef FEATURE_DUMP_COPY
        @cp $(OUTPUT)FEATURE-DUMP $(FEATURE_DUMP_COPY)
        @echo "FEATURE-DUMP file copied into $(FEATURE_DUMP_COPY)"
 else
-       @echo "FEATURE-DUMP file available in $(OUTPUT)FEATURE-DUMP"
+       @echo "FEATURE-DUMP file available in $(realpath $(OUTPUT)FEATURE-DUMP)"
 endif
 
 #
[acme@zoo linux]$ make -C tools/perf feature-dump
make: Entering directory '/home/git/linux/tools/perf'
  BUILD:   Doing 'make -j4' parallel build

Auto-detecting system features:
...                         dwarf: [ on  ]
...                         glibc: [ on  ]
...                          gtk2: [ on  ]
...                      libaudit: [ on  ]
...                        libbfd: [ on  ]
...                        libelf: [ on  ]
...                       libnuma: [ on  ]
...        numa_num_possible_cpus: [ on  ]
...                       libperl: [ on  ]
...                     libpython: [ on  ]
...                      libslang: [ on  ]
...                     libunwind: [ on  ]
...            libdw-dwarf-unwind: [ on  ]
...                          zlib: [ on  ]
...                          lzma: [ on  ]
...                     get_cpuid: [ on  ]
...                           bpf: [ on  ]

FEATURE-DUMP file available in /home/git/linux/tools/perf/FEATURE-DUMP
make: Leaving directory '/home/git/linux/tools/perf'
[acme@zoo linux]$


Nitpicking a bit: libbpf uses FEATURES_DUMP, i.e. plural, which I think
is the proper naming, as there are multiple features being detected and
thus dumped, would you mind if I chainsaw it all into consistency using
FEATURES-DUMP, FEATURES_DUMP, etc?

- Arnaldo