Re: [PATCH v2 2/2] perf jevents: Enable warnings through HOSTCFLAGS

[Jiri Olsa]

On Fri, Oct 22, 2021 at 10:42:11AM +0100, John Garry wrote:
> On 21/10/2021 13:48, Jiri Olsa wrote:
> > > +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 7df13e74450c..118bcdc70bb4 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 $(srctree)/tools/build/Makefile.include
> > > diff --git a/tools/perf/pmu-events/Build b/tools/perf/pmu-events/Build
> > > index a055dee6a46a..d5c287f069a2 100644
> > > --- a/tools/perf/pmu-events/Build
> > > +++ b/tools/perf/pmu-events/Build
> > > @@ -1,7 +1,7 @@
> > >   hostprogs := jevents
> > >   jevents-y	+= json.o jsmn.o jevents.o
> > > -HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include
> > > +HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include $(HOSTCFLAGS)
> > so the the host cflags are made of:
> > 
> > host_c_flags = -Wp,-MD,$(depfile) -Wp,-MT,$@ $(KBUILD_HOSTCFLAGS) -D"BUILD_STR(s)=\#s" $(HOSTCFLAGS_$(basetarget).o) $(HOSTCFLAGS_$(obj))
> > 
> 
> ok, so IIRC, then the rule for building .o from .c in
> tools/build/Makefile.build will pick up HOSTCFLAGS through this variable, so
> we then don't need to explicitly mention it in the per-target rule, so can
> have this as before in pmu-events/Build
> 
> HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include
> 
> right?
> 
> (Indeed I guess that we can get rid of -I$(srctree)/tools/include as well)

hm, the -I.. should stay no? I don't see that
it's being added soem other way

jirka


---
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 0ae2e3d8b832..374f65b52157 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 7df13e74450c..118bcdc70bb4 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