Re: [PATCH v4 05/30] bpftool: Avoid adding EXTRA_CFLAGS to HOST_CFLAGS

[Quentin Monnet <qmo@kernel.org>]

2026-03-13 15:56 UTC+0000 ~ Leo Yan <leo.yan@arm.com>
> On Thu, Mar 12, 2026 at 10:19:01AM -0700, Ian Rogers wrote:
>> On Wed, Mar 11, 2026 at 1:30 AM Leo Yan <leo.yan@arm.com> wrote:
>>>
>>> Prepare for future changes where EXTRA_CFLAGS may include flags not
>>> applicable to the host compiler.
>>>
>>> Move the HOST_CFLAGS assignment before appending EXTRA_CFLAGS to
>>> CFLAGS so that HOST_CFLAGS does not inherit flags from EXTRA_CFLAGS.
>>>
>>> Acked-by: Quentin Monnet <qmo@kernel.org>
>>> Signed-off-by: Leo Yan <leo.yan@arm.com>
>>> ---
>>>  tools/bpf/bpftool/Makefile | 8 ++++++--
>>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
>>> index 519ea5cb8ab1c0ee31acc67fc5f96b40e21005c2..3e7d8359e1b2a81a29a47544be8539e3b191a0e8 100644
>>> --- a/tools/bpf/bpftool/Makefile
>>> +++ b/tools/bpf/bpftool/Makefile
>>> @@ -81,6 +81,12 @@ CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ \
>>>  ifneq ($(BPFTOOL_VERSION),)
>>>  CFLAGS += -DBPFTOOL_VERSION='"$(BPFTOOL_VERSION)"'
>>>  endif
>>> +
>>> +# This must be done before appending EXTRA_CFLAGS to CFLAGS to avoid
>>> +# including flags that are not applicable to the host compiler.
>>> +HOST_CFLAGS := $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),\
>>> +               $(subst $(CLANG_CROSS_FLAGS),,$(CFLAGS)))
>>> +
>>>  ifneq ($(EXTRA_CFLAGS),)
>>>  CFLAGS += $(EXTRA_CFLAGS)
>>>  endif
>>> @@ -88,8 +94,6 @@ ifneq ($(EXTRA_LDFLAGS),)
>>>  LDFLAGS += $(EXTRA_LDFLAGS)
>>>  endif
>>>
>>> -HOST_CFLAGS := $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),\
>>> -               $(subst $(CLANG_CROSS_FLAGS),,$(CFLAGS)))
>>>  HOST_LDFLAGS := $(LDFLAGS)
>>
>> Should HOST_LDFLAGS be similarly moved? Otherwise, it seems target
>> flags in EXTRA_LDFLAGS will be added for the host.
> 
> Though this series is irrelevant to LDFLAGS, I am fine to move
> HOST_LDFLAGS together.


If we move the HOST_LDFLAGS earlier so that they no longer receive the
EXTRA_LDFLAGS, then we lose the possibility to use any EXTRA variable to
pass additional flags to HOST_LDFLAGS. So OK to move, but maybe add a
"HOST_LDFLAGS += $(HOST_EXTRALDFLAGS)" to it for consistency with the
processing of HOST_CFLAGS?

Quentin