[PATCH 0/2] tools/perf: tools: Fix perf build issues

[PATCH 0/2] tools/perf: tools: Fix perf build issues

[Masami Hiramatsu]

Hi,

These are the patches to fix the perf build issues which I reported in
the previous email.

https://lore.kernel.org/lkml/162037766527.94840.4323848545957010011.stgit@devnote2/

There are 2 issues I found and are fixed with these patches.

 - Since the EXTRA_CLFAGS/WARNINGS are listed before -Wall/-Wextra in
   CFLAGS, all -Wno-* flags in the EXTRA_CFLAGS/WARNINGS are ignored.
   This makes EXTRA_WARNINGS ignored and developers can not use EXTRA_CLFAGS
   for debugging compiler warnings.

 - Clang's missing-field-initializers warning is too sensitive compared
   with GCC. I think "{ NULL }" kind of syntax is allowed for simplify code.


Thank you,

---

Masami Hiramatsu (2):
      perf build: Move EXTRA_CFLAGS and EXTRA_WARNINGS at the end of CFLAGS
      tools: Add -Wno-missing-field-initializers to for clang


 tools/perf/Makefile.config     |    3 ++-
 tools/scripts/Makefile.include |    4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>

[PATCH 1/2] perf build: Move EXTRA_CFLAGS and EXTRA_WARNINGS at the end of CFLAGS

[Masami Hiramatsu]

Move EXTRA_CFLAGS and EXTRA_WARNINGS at the end of CFLAGS so that
additional flags will be passed to the compiler correctly.

CFLAGS is composed by CORE_CFLAGS, INC_FLAGS, EXTRA_CFLAGS, and
EXTRA_WARNINGS in the following order;

CFLAGS = $EXTRA_CFLAGS $EXTRA_WARNINGS $CORE_CFLAGS $INC_FLAGS

But since CORE_CFLAGS includes "-Wall" and "-Wextra", the other -Wno-*
flags in EXTRA_CFLAGS and EXTRA_WARNINGS are overridden and ignored.

To fix this issue, move those EXTRA_* at the end of CFLAGS definition
as below.

CFLAGS = $CORE_CFLAGS $INC_FLAGS $EXTRA_CFLAGS $EXTRA_WARNINGS

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 tools/perf/Makefile.config |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 406a9519145e..2ad46c66bc7b 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -16,7 +16,7 @@ $(shell printf "" > $(OUTPUT).config-detected)
 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))
+CFLAGS :=
 
 include $(srctree)/tools/scripts/Makefile.arch
 
@@ -340,6 +340,7 @@ INC_FLAGS += -I$(srctree)/tools/lib/
 CORE_CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE
 
 CFLAGS   += $(CORE_CFLAGS) $(INC_FLAGS)
+CFLAGS   += $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
 CXXFLAGS += $(INC_FLAGS)
 
 LIBPERF_CFLAGS := $(CORE_CFLAGS) $(EXTRA_CFLAGS)

[PATCH 2/2] tools: Add -Wno-missing-field-initializers to for clang

[Masami Hiramatsu]

Since clang's -Wmissing-field-initializers warns valid syntax of
initializing data structure (e.g. initializing static data
structure with single NULL, the rest of fields are initialized
with zero), it is better to disable this warning option
for clang for now.
This can stop building perf because -Werror is also specified.

Note that same issue on gcc has been fixed in 4.7.0, so we don't need
this for gcc.

 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36750

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 tools/scripts/Makefile.include |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index f9271f3ea912..4fd5d33ded03 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -89,6 +89,10 @@ ifeq ($(CC_NO_CLANG), 1)
 EXTRA_WARNINGS += -Wstrict-aliasing=3
 endif
 
+ifneq ($(CC_NO_CLANG), 1)
+EXTRA_WARNINGS += -Wno-missing-field-initializers
+endif
+
 # Hack to avoid type-punned warnings on old systems such as RHEL5:
 # We should be changing CFLAGS and checking gcc version, but this
 # will do for now and keep the above -Wstrict-aliasing=3 in place

Re: [PATCH 2/2] tools: Add -Wno-missing-field-initializers to for clang

[Nick Desaulniers]

On Tue, May 11, 2021 at 8:02 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> Since clang's -Wmissing-field-initializers warns valid syntax of
> initializing data structure (e.g. initializing static data
> structure with single NULL, the rest of fields are initialized
> with zero), it is better to disable this warning option
> for clang for now.
> This can stop building perf because -Werror is also specified.
>
> Note that same issue on gcc has been fixed in 4.7.0, so we don't need
> this for gcc.
>
>  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36750
>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>

Seems fine, it's only enabled for the kernel at W=2 anyways.
Acked-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  tools/scripts/Makefile.include |    4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index f9271f3ea912..4fd5d33ded03 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -89,6 +89,10 @@ ifeq ($(CC_NO_CLANG), 1)
>  EXTRA_WARNINGS += -Wstrict-aliasing=3
>  endif
>
> +ifneq ($(CC_NO_CLANG), 1)
> +EXTRA_WARNINGS += -Wno-missing-field-initializers
> +endif
> +
>  # Hack to avoid type-punned warnings on old systems such as RHEL5:
>  # We should be changing CFLAGS and checking gcc version, but this
>  # will do for now and keep the above -Wstrict-aliasing=3 in place
>


-- 
Thanks,
~Nick Desaulniers