Messages in this thread |  | | From | Masahiro Yamada <> | Date | Mon, 7 Aug 2017 10:01:41 +0900 | Subject | Re: [PATCH 1/2] kbuild: Add macros cc-option-3 and __cc-option-3 |
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Hi Matthias,
Sorry for my late reply.
2017-08-03 1:46 GMT+09:00 Matthias Kaehlcke <mka@chromium.org>: > 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 >> valid. >> >> 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 >> analogously. > > Any comment on this? > > Thanks > > Matthias > >> Signed-off-by: Matthias Kaehlcke <mka@chromium.org> >> --- >> 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:
[1] 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.)
[2]
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.
$(call cc-option-3,-Oz,-Os,-O2)
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...
-- Best Regards Masahiro Yamada
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