linux-kernel - Re: [PATCH] kbuild: terminate Kconfig when $(CC) or $(LD) is missing

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Date:   Tue, 14 May 2019 11:54:03 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Joel Stanley <joel@....id.au>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] kbuild: terminate Kconfig when $(CC) or $(LD) is missing

On Mon, May 13, 2019 at 1:47 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> On Thu, May 09, 2019 at 04:35:55PM +0900, Masahiro Yamada wrote:
> > If the compiler specified by $(CC) is not present, the Kconfig stage
> > sprinkles 'not found' messages, then succeeds.
> >
> >   $ make CROSS_COMPILE=foo defconfig
> >   /bin/sh: 1: foogcc: not found
> >   /bin/sh: 1: foogcc: not found
> >   *** Default configuration is based on 'x86_64_defconfig'
> >   ./scripts/gcc-version.sh: 17: ./scripts/gcc-version.sh: foogcc: not found
> >   ./scripts/gcc-version.sh: 18: ./scripts/gcc-version.sh: foogcc: not found
> >   ./scripts/gcc-version.sh: 19: ./scripts/gcc-version.sh: foogcc: not found
> >   ./scripts/gcc-version.sh: 17: ./scripts/gcc-version.sh: foogcc: not found
> >   ./scripts/gcc-version.sh: 18: ./scripts/gcc-version.sh: foogcc: not found
> >   ./scripts/gcc-version.sh: 19: ./scripts/gcc-version.sh: foogcc: not found
> >   ./scripts/clang-version.sh: 11: ./scripts/clang-version.sh: foogcc: not found
> >   ./scripts/gcc-plugin.sh: 11: ./scripts/gcc-plugin.sh: foogcc: not found
> >   init/Kconfig:16:warning: 'GCC_VERSION': number is invalid
> >   #
> >   # configuration written to .config
> >   #
> >
> > Terminate parsing files immediately if $(CC) or $(LD) is not found.
> > "make *config" will fail more nicely.
> >
> >   $ make CROSS_COMPILE=foo defconfig
> >   *** Default configuration is based on 'x86_64_defconfig'
> >   scripts/Kconfig.include:34: compiler 'foogcc' not found
> >   make[1]: *** [scripts/kconfig/Makefile;82: defconfig] Error 1
> >   make: *** [Makefile;557: defconfig] Error 2
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > ---
> >
> >  Makefile                | 2 +-
> >  scripts/Kconfig.include | 8 ++++++++
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 28965187c528..bd7ae11947cb 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -537,7 +537,7 @@ endif
> >  # Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
> >  # CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
> >  # and from include/config/auto.conf.cmd to detect the compiler upgrade.
> > -CC_VERSION_TEXT = $(shell $(CC) --version | head -n 1)
> > +CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1)
> >
> >  ifeq ($(config-targets),1)
> >  # ===========================================================================
> > diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> > index 87ff1dcc6bd5..0b267fb27f07 100644
> > --- a/scripts/Kconfig.include
> > +++ b/scripts/Kconfig.include
> > @@ -18,6 +18,10 @@ if-success = $(shell,{ $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)")
> >  # Return y if <command> exits with 0, n otherwise
> >  success = $(if-success,$(1),y,n)
> >
> > +# $(failure,<command>)
> > +# Return n if <command> exits with 0, y otherwise
> > +failure = $(if-success,$(1),n,y)
> > +
> >  # $(cc-option,<flag>)
> >  # Return y if the compiler supports <flag>, n otherwise
> >  cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null)
> > @@ -26,5 +30,9 @@ cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null)
> >  # Return y if the linker supports <flag>, n otherwise
> >  ld-option = $(success,$(LD) -v $(1))
> >
> > +# check if $(CC) and $(LD) exist
> > +$(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
> > +$(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
>
> As mentioned in the other thread, $(AS) should be checked as well since
> it's possible that neither $(CC) nor $(LD) will involve $(CROSS_COMPILE),
> like the combination of clang + ld.lld, whereas $(AS) will (currently)
> always involve $(CROSS_COMPILE).

Indeed.
This patch cannot check the presence of the intended gnu toolchains
if CC=clang LD=ld.lld

The reason for $(CC) / $(LD) checks in Kconfig
is because it evaluates some $(cc-option, ...) and $(ld-option, ...) calls.

Currently, Kconfig does not have as-option, but I will add it
sooner or later, so I am fine with adding
$(error-if,$(failure,command -v $(AS)),assembler '$(AS)' not found)




> > +
> >  # gcc version including patch level
> >  gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh $(CC))
> > --
> > 2.17.1
> >


--
Best Regards
Masahiro Yamada