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[PATCH 34/35] tools build: Use the same CC for feature detection and actual build

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From: Arnaldo Carvalho de Melo <acme@redhat.com>

	When build with: 'make CC=clang' we were not using that CC to do
feature detection, which resulted in features being detected with gcc
and then the actual tools being built with clang.

	Most of the time these compilers are compatible enough, so no
problem was being noticed.

	As soon as a system with an old enough clang, one that hasn't
the cpuid.h header is used, and a gcc with it, the "get_cpuid" feature
will be found available but then code that will use can't be compiled.

	Noticed with this combination:

  / $ gcc --version | head -1
  gcc (Alpine 6.3.0) 6.3.0
  / $ clang --version | head -1
  clang version 3.8.1 (tags/RELEASE_381/final)
  / $ cat /etc/alpine-release
  3.5.0
  / $

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-60q18nvlvgpyfv7e2qqgx4ou@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/build/feature/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index ab1e2bbc2e96..09c9626ea666 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -53,8 +53,8 @@ FILES=                                          \
 
 FILES := $(addprefix $(OUTPUT),$(FILES))
 
-CC := $(CROSS_COMPILE)gcc -MD
-CXX := $(CROSS_COMPILE)g++ -MD
+CC ?= $(CROSS_COMPILE)gcc -MD
+CXX ?= $(CROSS_COMPILE)g++ -MD
 PKG_CONFIG := $(CROSS_COMPILE)pkg-config
 LLVM_CONFIG ?= llvm-config
 
-- 
2.9.3

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[GIT PULL 00/35] perf/core improvements and fixes Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 22/35] perf cpumap: Introduce cpu_map__snprint_mask() Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 12/35] perf comm: Convert comm_str.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 30/35] perf tools: Force uncore events to system wide monitoring Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 27/35] perf probe: Generalize probe event file open routine Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 17/35] perf thread: convert thread.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 25/35] kretprobes: Ensure probe location is at function entry Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 13/35] perf dso: Convert dso.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 21/35] perf ftrace: Add support for --pid option Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 19/35] perf evlist: Clarify a bit the use of perf_mmap->refcnt Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 23/35] perf ftrace: Add support for -a and -C option Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 10/35] perf cgroup: Convert cgroup_sel.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 07/35] tools include: Provide gcc based cmpxchg fallback for !x86 Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 20/35] perf tools: Allow sorting by symbol size Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 28/35] perf intel-PT/BTS: Add missing initialization Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 33/35] perf bench futex: Fix build on musl + clang Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 05/35] tools arch x86: Introduce atomic_cmpxchg() Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 14/35] perf map: Convert map.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 16/35] perf evlist: Convert perf_map.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 06/35] tools include: Introduce atomic_cmpxchg_{relaxed,release}() Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 24/35] perf ftrace: Use pager for displaying result Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 35/35] perf bench numa: Add more comment for -c option Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 11/35] perf cpumap: Convert cpu_map.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 02/35] perf stat: Issue a HW watchdog disable hint Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 26/35] trace/kprobes: Allow return probes with offsets and absolute addresses Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 15/35] perf map: Convert map_groups.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 01/35] perf vendor events: Add mapping for KnightsMill PMU events Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 32/35] perf bench futex: Use __maybe_unused Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 29/35] trace/kprobes: Add back warning about offset in return probes Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 31/35] tools build: Add test for sched_getcpu() Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 09/35] tools include: Adopt kernel's refcount.h Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 18/35] perf thread_map: Convert thread_map.refcnt from atomic_t to refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  [PATCH 34/35] tools build: Use the same CC for feature detection and actual build Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-03-06 20:50 +0100
  Re: [GIT PULL 00/35] perf/core improvements and fixes Ingo Molnar <mingo@kernel.org> - 2017-03-07 08:20 +0100

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