[PATCH] perf tools: Enable warnings through HOSTCFLAGS

[John Garry]

The tools build system uses KBUILD_HOSTCFLAGS symbol for obvious purposes.

However this is not set for anything under tools/

As such, host tools apps built have no compiler warnings enabled.

Declare HOSTCFLAGS for perf tools build, and also use that symbol in
declaration of host_c_flags. HOSTCFLAGS comes from EXTRA_WARNINGS, which
is independent of target platform/arch warning flags.

Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
--
Using HOSTCFLAGS, as opposed to KBUILD_HOSTCFLAGS, is going opposite
direction to commit 96f14fe738b6 ("kbuild: Rename HOSTCFLAGS to
KBUILD_HOSTCFLAGS"), so would like further opinion from Laura and
Masahiro.

diff --git a/tools/build/Build.include b/tools/build/Build.include
index 2cf3b1bde86e..c2a95ab47379 100644
--- a/tools/build/Build.include
+++ b/tools/build/Build.include
@@ -99,7 +99,7 @@ cxx_flags = -Wp,-MD,$(depfile) -Wp,-MT,$@ $(CXXFLAGS) -D"BUILD_STR(s)=\#s" $(CXX
 ###
 ## HOSTCC C flags
 
-host_c_flags = -Wp,-MD,$(depfile) -Wp,-MT,$@ $(KBUILD_HOSTCFLAGS) -D"BUILD_STR(s)=\#s" $(HOSTCFLAGS_$(basetarget).o) $(HOSTCFLAGS_$(obj))
+host_c_flags = -Wp,-MD,$(depfile) -Wp,-MT,$@ $(HOSTCFLAGS) -D"BUILD_STR(s)=\#s" $(HOSTCFLAGS_$(basetarget).o) $(HOSTCFLAGS_$(obj))
 
 # output directory for tests below
 TMPOUT = .tmp_$$$$
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 4a9baed28f2e..9b95ba09657f 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -17,6 +17,7 @@ detected     = $(shell echo "$(1)=y"       >> $(OUTPUT).config-detected)
 detected_var = $(shell echo "$(1)=$($(1))" >> $(OUTPUT).config-detected)
 
 CFLAGS := $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
+HOSTCFLAGS := $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
 
 include $(srctree)/tools/scripts/Makefile.arch
 
@@ -211,6 +212,7 @@ endif
 ifneq ($(WERROR),0)
   CORE_CFLAGS += -Werror
   CXXFLAGS += -Werror
+  HOSTCFLAGS += -Werror
 endif
 
 ifndef DEBUG
@@ -292,6 +294,9 @@ CXXFLAGS += -ggdb3
 CXXFLAGS += -funwind-tables
 CXXFLAGS += -Wno-strict-aliasing
 
+HOSTCFLAGS += -Wall
+HOSTCFLAGS += -Wextra
+
 # Enforce a non-executable stack, as we may regress (again) in the future by
 # adding assembler files missing the .GNU-stack linker note.
 LDFLAGS += -Wl,-z,noexecstack
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index a3966f290297..8ca656aa8b06 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -226,7 +226,7 @@ else
 endif
 
 export srctree OUTPUT RM CC CXX LD AR CFLAGS CXXFLAGS V BISON FLEX AWK
-export HOSTCC HOSTLD HOSTAR
+export HOSTCC HOSTLD HOSTAR HOSTCFLAGS
 
 include $(srctree)/tools/build/Makefile.include
 
-- 
2.17.1