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tools build: Use the same CC for feature detection and actual build
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	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>
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Arnaldo Carvalho de Melo committed Mar 3, 2017
1 parent a0f213e commit c8c1886
Showing 1 changed file with 2 additions and 2 deletions.
4 changes: 2 additions & 2 deletions tools/build/feature/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -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

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