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Date:   Fri, 18 Dec 2020 15:12:23 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Masahiro Yamada <masahiroy@...nel.org>
CC:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Emese Revfy <re.emese@...il.com>,
        <linux-hardening@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] gcc-plugins: simplify GCC plugin-dev capability test


On 18/12/2020 15:09, Marek Szyprowski wrote:
> 
> On 18.12.2020 16:03, Jon Hunter wrote:
>> On 18/12/2020 10:05, Marek Szyprowski wrote:
>>> On 18.12.2020 10:43, Masahiro Yamada wrote:
>>>> On Fri, Dec 18, 2020 at 4:58 PM Marek Szyprowski
>>>> <m.szyprowski@...sung.com> wrote:
>>>>> On 03.12.2020 13:57, Masahiro Yamada wrote:
>>>>>> Linus pointed out a third of the time in the Kconfig parse stage comes
>>>>>> from the single invocation of cc1plus in scripts/gcc-plugin.sh [1],
>>>>>> and directly testing plugin-version.h for existence cuts down the
>>>>>> overhead a lot. [2]
>>>>>>
>>>>>> This commit takes one step further to kill the build test entirely.
>>>>>>
>>>>>> The small piece of code was probably intended to test the C++ designated
>>>>>> initializer, which was not supported until C++20.
>>>>>>
>>>>>> In fact, with -pedantic option given, both GCC and Clang emit a warning.
>>>>>>
>>>>>> $ echo 'class test { public: int test; } test = { .test = 1 };' | g++ -x c++ -pedantic - -fsyntax-only
>>>>>> <stdin>:1:43: warning: C++ designated initializers only available with '-std=c++2a' or '-std=gnu++2a' [-Wpedantic]
>>>>>> $ echo 'class test { public: int test; } test = { .test = 1 };' | clang++ -x c++ -pedantic - -fsyntax-only
>>>>>> <stdin>:1:43: warning: designated initializers are a C++20 extension [-Wc++20-designator]
>>>>>> class test { public: int test; } test = { .test = 1 };
>>>>>>                                              ^
>>>>>> 1 warning generated.
>>>>>>
>>>>>> Otherwise, modern C++ compilers should be able to build the code, and
>>>>>> hopefully skipping this test should not make any practical problem.
>>>>>>
>>>>>> Checking the existence of plugin-version.h is still needed to ensure
>>>>>> the plugin-dev package is installed. The test code is now small enough
>>>>>> to be embedded in scripts/gcc-plugins/Kconfig.
>>>>>>
>>>>>> [1] https://protect2.fireeye.com/v1/url?k=03db90e1-5c40a828-03da1bae-0cc47a336fae-4cc36f5830aeb78d&q=1&e=dfdc1cf9-82d6-4ca5-b35d-1782e918bde3&u=https%3A%2F%2Flore.kernel.org%2Flkml%2FCAHk-%3DwjU4DCuwQ4pXshRbwDCUQB31ScaeuDo1tjoZ0_PjhLHzQ%40mail.gmail.com%2F
>>>>>> [2] https://protect2.fireeye.com/v1/url?k=965b670a-c9c05fc3-965aec45-0cc47a336fae-e34339513ff747c0&q=1&e=dfdc1cf9-82d6-4ca5-b35d-1782e918bde3&u=https%3A%2F%2Flore.kernel.org%2Flkml%2FCAHk-%3DwhK0aQxs6Q5ijJmYF1n2ch8cVFSUzU5yUM_HOjig%3D%2Bvnw%40mail.gmail.com%2F
>>>>>>
>>>>>> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
>>>>>> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>>>>> This patch landed in linux next-20201217 as commit 1e860048c53e
>>>>> ("gcc-plugins: simplify GCC plugin-dev capability test").
>>>>>
>>>>> It causes a build break with my tests setup, but I'm not sure weather it
>>>>> is really an issue of this commit or a toolchain I use. However I've
>>>>> checked various versions of the gcc cross-compilers released by Linaro
>>>>> at https://protect2.fireeye.com/v1/url?k=053727b6-5aac1f7f-0536acf9-0cc47a336fae-5bd799e7ce6b1b9b&q=1&e=dfdc1cf9-82d6-4ca5-b35d-1782e918bde3&u=https%3A%2F%2Freleases.linaro.org%2Fcomponents%2Ftoolchain%2Fbinaries%2F and all
>>>>> fails with the same error:
>>>>>
>>>>> $ make ARCH=arm
>>>>> CROSS_COMPILE=../../cross/gcc-arm-10.2-2020.11-x86_64-arm-none-eabi/bin/arm-none-eabi-
>>>>> zImage
>>>>>      HOSTCXX scripts/gcc-plugins/arm_ssp_per_task_plugin.so
>>>>> In file included from
>>>>> /home/mszyprow/dev/cross/gcc-arm-10.2-2020.11-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/10.2.1/plugin/include/gcc-plugin.h:28:0,
>>>>>                     from scripts/gcc-plugins/gcc-common.h:7,
>>>>>                     from scripts/gcc-plugins/arm_ssp_per_task_plugin.c:3:
>>>>> /home/mszyprow/dev/cross/gcc-arm-10.2-2020.11-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/10.2.1/plugin/include/system.h:687:10:
>>>>> fatal error: gmp.h: No such file or directory
>>>>>     #include <gmp.h>
>>>>>              ^~~~~~~
>>>>> compilation terminated.
>>>>> scripts/gcc-plugins/Makefile:47: recipe for target
>>>>> 'scripts/gcc-plugins/arm_ssp_per_task_plugin.so' failed
>>>>> make[2]: *** [scripts/gcc-plugins/arm_ssp_per_task_plugin.so] Error 1
>>>>> scripts/Makefile.build:496: recipe for target 'scripts/gcc-plugins' failed
>>>>> make[1]: *** [scripts/gcc-plugins] Error 2
>>>>> Makefile:1190: recipe for target 'scripts' failed
>>>>> make: *** [scripts] Error 2
>>>>>
>>>>> Compilation works if I use the cross-gcc provided by
>>>>> gcc-7-arm-linux-gnueabi/gcc-arm-linux-gnueabi Ubuntu packages, which is:
>>>>>
>>>>> $ arm-linux-gnueabi-gcc --version
>>>>> arm-linux-gnueabi-gcc (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0
>>>>>
>>>> I can compile gcc-plugins with Linaro toolchians.
>>>>
>>>> The version of mine is this:
>>>>
>>>> masahiro@...ar:~/ref/linux-next$
>>>> ~/tools/arm-linaro-7.5/bin/arm-linux-gnueabihf-gcc --version
>>>> arm-linux-gnueabihf-gcc (Linaro GCC 7.5-2019.12) 7.5.0
>>>> Copyright (C) 2017 Free Software Foundation, Inc.
>>>> This is free software; see the source for copying conditions.  There is NO
>>>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>>>>
>>>>
>>>>
>>>>
>>>> Maybe, it depends on the host environment?
>>>>
>>>>
>>>> Please try this:
>>>>
>>>> $ sudo apt install libgmp-dev
>>> Indeed, it was missing on my setup. Sorry for the noise.
>>
>> So this change also breaks the build on our farm build machines and
>> while we can request that packages are installed on these machines, it
>> takes time. Is there anyway to avoid this?
> 
> You can temporarily revert 1e860048c53e (this patch).


Again that works locally, but these automated builders just pull the
latest -next branch and build.

Jon

-- 
nvpublic

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