Re: [PATCH 1/2] kbuild: Add macros cc-option-3 and __cc-option-3
From: Masahiro Yamada
Date: Sun Aug 06 2017 - 21:01:59 EST
Sorry for my late reply.
2017-08-03 1:46 GMT+09:00 Matthias Kaehlcke <mka@xxxxxxxxxxxx>:
> El Fri, Jul 21, 2017 at 02:56:56PM -0700 Matthias Kaehlcke ha dit:
>> The macro cc-option receives two parameters (the second may be empty). It
>> returns the first parameter if it is a valid compiler option, otherwise
>> the second one. It is not evaluated if the second parameter is a valid
>> compiler option. This seems to be fine in virtually all cases, however
>> there are scenarios where the second paramater needs to be evaluated too,
>> and an empty value (or a third option) should be returned if it is not
>> The macro cc-option-3 receives three parameters and returns parameter 1
>> or 2 (in this order) if one of them is found to be a valid compiler
>> option, and otherwise paramater 3. The macro __cc-option-3 works
> Any comment on this?
>> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
>> scripts/Kbuild.include | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
>> index dd8e2dde0b34..dc83635f2317 100644
>> --- a/scripts/Kbuild.include
>> +++ b/scripts/Kbuild.include
>> @@ -113,6 +113,11 @@ as-instr = $(call try-run,\
>> __cc-option = $(call try-run,\
>> $(1) -Werror $(2) $(3) -c -x c /dev/null -o "$$TMP",$(3),$(4))
>> +# __cc-option-3
>> +# Usage: MY_CFLAGS += $(call __cc-option-3,$(CC),$(MY_CFLAGS),\
>> +# -mpreferred-stack-boundary=2,-mstack-alignment=4,)
>> +__cc-option-3 = $(call __cc-option,$(1),$(2),$(3),$(call __cc-option,$(1),$(2),$(4),$(5)))
>> # Do not attempt to build with gcc plugins during cc-option tests.
>> # (And this uses delayed resolution so the flags will be up to date.)
>> CC_OPTION_CFLAGS = $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS))
>> @@ -123,6 +128,10 @@ CC_OPTION_CFLAGS = $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS))
>> cc-option = $(call __cc-option, $(CC),\
>> $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS),$(1),$(2))
>> +# cc-option-3
>> +# Usage: cflags-y += $(call cc-option-3,-mpreferred-stack-boundary=3,-mstack-alignment=8,)
>> +cc-option-3 = $(call cc-option,$(1),$(call cc-option,$(2),$(3)))
I do not like this macro much for the following reasons:
I guess your motivation is to evaluate the second option,
not receive the third option.
If this is the demand, I thought it might be nicer to
change cc-option to always evaluate the second option.
(I do no have a good idea for the implementation.)
cc-option-3 = $(call cc-option,$(1),$(call cc-option,$(2),$(3)))
evaluates the inner $(call cc-option,) first.
This works a bit differently from our expectation.
For example, let's consider the following case.
I think we generally expect -Oz, -Os are tested in this order.
(If -Oz is supported by the compiler, the test for -Os will be skipped.)
In fact, cc-option-3 tests -Os, -Oz in this order
because inner cc-option is evaluated before the outer one.
The test for -Os may or may not be necessary.
I do not have a good idea to improve this...