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SubjectRe: [PATCH v5 00/31] kconfig: move compiler capability tests to Kconfig
2018-05-28 21:23 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
> 2018-05-28 18:21 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
>>
>> [Introduction]
>>
>> The motivation of this work is to move the compiler option tests to
>> Kconfig from Makefile. A number of kernel features require the
>> compiler support. Enabling such features blindly in Kconfig ends up
>> with a lot of nasty build-time testing in Makefiles. If a chosen
>> feature turns out unsupported by the compiler, what the build system
>> can do is either to disable it (silently!) or to forcibly break the
>> build, despite Kconfig has let the user to enable it. By moving the
>> compiler capability tests to Kconfig, Kconfig entries will be visible
>> only when they are available.
>>
>> [Major Changes in V5]
>>
>> V5 removed the complexity unnecessary for Kconfig.
>>
>> - In order to make the implementation simpler, I drop the lazy
>> argument expansion.
>> In V5, parameters are expanded before passed to a function.
>> (the same behavior as v3)
>>
>> - Replace 'warning', 'error' functions with 'warning-if',
>> 'error-if' functions. The new functions are effective
>> only when the condition part is 'y'.
>>
>> - In V4, '$' must be followed by '$' or '('.
>> '$$' meant an escaped '$'.
>>
>> V4 caused a build error for ARC architecture due to the
>> following line:
>> https://github.com/torvalds/linux/blob/v4.17-rc4/arch/arc/Kconfig#L252
>>
>> Of course, we could rephrase "D$" to "D cache", but
>> I treaked the grammar a little bit.
>>
>> Kconfig decided to not support single-letter variable as in "$X".
>> Nor curly braces as in "${CC}" are not supported.
>> This means variable/function references in Kconfig always start
>> with "$(".
>> We can use '$' not followed by '(' as-is.
>> We do not need the "$$" escape sequence.
>> If necessary, we can use a trick to print '$(' verbatim. See below.
>>
>> - Fix a wrong behavior of simply expanded variables.
>> V4 expanded simply expanded variables when used, but it should not.
>>
>> For example,
>>
>> dollar := $
>> X := 1
>> Y := $(dollar)(X)
>> $(info,$(Y))
>>
>> V5 prints '$(X)', not '1'.
>>
>> - Remove a space after a comma is $( ) context.
>> Actually, spaces do not matter in most cases.
>>
>> You can write either
>>
>> $(cc-option,-fstack-protector)
>>
>> or
>>
>> $(cc-option, -fstack-protector)
>>
>> In fact, both style co-exist in our Makefiles too.
>> However, there are some cases where they do matter.
>>
>> I remove spaces after commas for consistency.
>> If you are unsure, no-space-after-comma is always safe.
>>
>> [Major Changes in V4]
>>
>> - In V4, I slightly change the syntax of a function call.
>> I chose grammatical consistency and simplicity.
>> Anyway, Kconfig is deviating from Make behavior already.
>>
>> In v3, a function call looked like this:
>>
>> $(func-name arg1,arg2,arg3)
>>
>> In v4, a function is invoked like follows:
>>
>> $(func-name,arg1,arg2,arg3)
>>
>> The difference is that the function name and the first argument
>> are separated by a comma.
>>
>> - V3 supported single-letter variable like $X.
>> V4 dropped it because we do not need multiple ways to do the
>> same thing.
>> You must always enclose a variable name like $(X).
>>
>> - Support lazy argument expansion. This is necessary for implementing
>> 'if', 'and', 'or' functions as in Make.
>>
>> - Add more built-in functions:
>> 'if', 'error', 'filename', 'lineno'
>>
>> - Error out if a recursive variable references itself eventually.
>> For example, X = $(X)
>> ends up with a circular expansion. It must be terminated
>> since the expansion would continue eternally.
>>
>> - Update Documentation and unit-tests, accordingly.
>>
>> [Major Changes in V3]
>>
>> This version looks more like Make.
>>
>> - Use = operator instead of 'macro' keyword
>> to define a user-defined function.
>>
>> - 'Recursively expanded variable' is implemented as a side-effect.
>> A variable is a function with zero argument.
>>
>> - Support simply expanded variable which is defined by := operator
>>
>> - Support += operator.
>> Probably, this feature will be useful to accumulate compiler flags.
>> At least, Clang needs some prerequisite flags such as triplet
>> to test other compiler flags.
>>
>> - Support $(info ...) and $(warning ...) built-in functions,
>> which were useful while I was debugging this.
>>
>> - Add documentation
>>
>> - Add unit tests
>>
>> - Collect helpers to scripts/Kconfig.include
>>
>> [Old Versions]
>>
>> V4: https://lkml.org/lkml/2018/5/17/97
>> V3: https://lkml.org/lkml/2018/4/13/37
>> V2: https://lkml.org/lkml/2018/2/16/610
>> V1: https://lkml.org/lkml/2018/2/16/610
>> RFC: https://lkml.org/lkml/2018/2/8/429
>>
>>
>> Masahiro Yamada (31):
>> kbuild: remove kbuild cache
>> kbuild: remove CONFIG_CROSS_COMPILE support
>> kconfig: reference environment variables directly and remove 'option
>> env='
>> kconfig: remove string expansion in file_lookup()
>> kconfig: remove string expansion for mainmenu after yyparse()
>> kconfig: remove sym_expand_string_value()
>> kconfig: make default prompt of mainmenu less specific
>> kconfig: add built-in function support
>> kconfig: add 'shell' built-in function
>> kconfig: replace $(UNAME_RELEASE) with function call
>> kconfig: begin PARAM state only when seeing a command keyword
>> kconfig: support user-defined function and recursively expanded
>> variable
>> kconfig: support simply expanded variable
>> kconfig: support append assignment operator
>> kconfig: expand lefthand side of assignment statement
>> kconfig: add 'info', 'warning-if', and 'error-if' built-in functions
>> kconfig: add 'filename' and 'lineno' built-in variables
>> kconfig: error out if a recursive variable references itself
>> Documentation: kconfig: document a new Kconfig macro language
>> kconfig: test: add Kconfig macro language tests
>> kconfig: show compiler version text in the top comment
>> kconfig: add basic helper macros to scripts/Kconfig.include
>> stack-protector: test compiler capability in Kconfig and drop AUTO
>> mode
>> kconfig: add CC_IS_GCC and GCC_VERSION
>> kconfig: add CC_IS_CLANG and CLANG_VERSION
>> gcov: remove CONFIG_GCOV_FORMAT_AUTODETECT
>> kcov: test compiler capability in Kconfig and correct dependency
>> gcc-plugins: move GCC version check for PowerPC to Kconfig
>> gcc-plugins: test plugin support in Kconfig and clean up Makefile
>> gcc-plugins: allow to enable GCC_PLUGINS for COMPILE_TEST
>> Documentation: kconfig: add recommended way to describe compiler
>> support
>>
>> Documentation/kbuild/kconfig-language.txt | 26 +-
>> Documentation/kbuild/kconfig-macro-language.txt | 242 +++++++++
>> Kconfig | 10 +-
>> MAINTAINERS | 3 +-
>> Makefile | 105 +---
>> arch/Kconfig | 49 +-
>> arch/powerpc/Kconfig | 2 +-
>> arch/sh/Kconfig | 4 +-
>> arch/sparc/Kconfig | 4 +-
>> arch/um/Kconfig.common | 4 -
>> arch/x86/Kconfig | 15 +-
>> arch/x86/um/Kconfig | 10 +-
>> init/Kconfig | 40 +-
>> kernel/gcov/Kconfig | 17 +-
>> kernel/gcov/Makefile | 2 -
>> lib/Kconfig.debug | 11 +-
>> scripts/Kbuild.include | 101 +---
>> scripts/Kconfig.include | 30 ++
>> scripts/Makefile.gcc-plugins | 91 +---
>> scripts/Makefile.kcov | 10 +-
>> scripts/clang-version.sh | 18 +-
>> scripts/gcc-plugins/Makefile | 1 +
>> scripts/gcc-x86_32-has-stack-protector.sh | 7 +-
>> scripts/gcc-x86_64-has-stack-protector.sh | 5 -
>> scripts/kconfig/confdata.c | 33 +-
>> scripts/kconfig/kconf_id.c | 1 -
>> scripts/kconfig/lkc.h | 5 +-
>> scripts/kconfig/lkc_proto.h | 15 +-
>> scripts/kconfig/menu.c | 3 -
>> scripts/kconfig/preprocess.c | 572 +++++++++++++++++++++
>> scripts/kconfig/symbol.c | 109 ----
>> .../tests/no_write_if_dep_unmet/expected_config | 2 +-
>> .../kconfig/tests/preprocess/builtin_func/Kconfig | 27 +
>> .../tests/preprocess/builtin_func/__init__.py | 9 +
>> .../tests/preprocess/builtin_func/expected_stderr | 5 +
>> .../tests/preprocess/builtin_func/expected_stdout | 1 +
>> .../tests/preprocess/circular_expansion/Kconfig | 5 +
>> .../preprocess/circular_expansion/__init__.py | 11 +
>> .../preprocess/circular_expansion/expected_stderr | 1 +
>> scripts/kconfig/tests/preprocess/escape/Kconfig | 44 ++
>> .../kconfig/tests/preprocess/escape/__init__.py | 8 +
>> .../tests/preprocess/escape/expected_stderr | 10 +
>> scripts/kconfig/tests/preprocess/variable/Kconfig | 53 ++
>> .../kconfig/tests/preprocess/variable/__init__.py | 8 +
>> .../tests/preprocess/variable/expected_stderr | 9 +
>> scripts/kconfig/util.c | 33 +-
>> scripts/kconfig/zconf.l | 95 +++-
>> scripts/kconfig/zconf.y | 46 +-
>> 48 files changed, 1345 insertions(+), 567 deletions(-)
>> create mode 100644 Documentation/kbuild/kconfig-macro-language.txt
>> create mode 100644 scripts/Kconfig.include
>> create mode 100644 scripts/kconfig/preprocess.c
>> create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/Kconfig
>> create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/__init__.py
>> create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/expected_stderr
>> create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/expected_stdout
>> create mode 100644 scripts/kconfig/tests/preprocess/circular_expansion/Kconfig
>> create mode 100644 scripts/kconfig/tests/preprocess/circular_expansion/__init__.py
>> create mode 100644 scripts/kconfig/tests/preprocess/circular_expansion/expected_stderr
>> create mode 100644 scripts/kconfig/tests/preprocess/escape/Kconfig
>> create mode 100644 scripts/kconfig/tests/preprocess/escape/__init__.py
>> create mode 100644 scripts/kconfig/tests/preprocess/escape/expected_stderr
>> create mode 100644 scripts/kconfig/tests/preprocess/variable/Kconfig
>> create mode 100644 scripts/kconfig/tests/preprocess/variable/__init__.py
>> create mode 100644 scripts/kconfig/tests/preprocess/variable/expected_stderr
>>
>> --
>> 2.7.4
>>
>
>
>
> I pushed this series to
>
> git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git
> kconfig-shell-v5
>


I pushed this series to the for-next branch.
Unless a significant problem is reported,
I'd like to merge this series in the upcoming MW.
At least, I need to keep it in linux-next for a while.

Your comments and tags are still appreciated.
I will add tags (or replace patches if necessary) later,
but I want this series tested in linux-next
to expose to more developers' eyes.

It passed my local test. O-day bot did not report anything so far.


--
Best Regards
Masahiro Yamada

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