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    SubjectRe: [PATCH v2] kbuild: check the minimum compiler version in Kconfig
    On Thu, Jan 14, 2021 at 01:24:19PM +0900, Masahiro Yamada wrote:
    > Paul Gortmaker reported a regression in the GCC version check [1].
    > If you use GCC 4.8, the build breaks before showing the error message
    > "error Sorry, your version of GCC is too old - please use 4.9 or newer."
    >
    > I do not want to apply his fix-up since it implies we would not be able
    > to remove any cc-option test. Anyway, I admit checking the GCC version
    > in <linux/compiler-gcc.h> is too late.
    >
    > Almost at the same time, Linus also suggested to move the compiler
    > version error to Kconfig time. [2]
    >
    > I unified the similar two scripts, gcc-version.sh and clang-version.sh
    > into the new cc-version.sh. The old scripts invoked the compiler multiple
    > times (3 times for gcc-version.sh, 4 times for clang-version.sh). I
    > refactored the code so the new one invokes the compiler just once, and
    > also tried my best to use shell-builtin commands where possible.
    >
    > The new script runs faster.
    >
    > $ time ./scripts/clang-version.sh clang
    > 120000
    >
    > real 0m0.029s
    > user 0m0.012s
    > sys 0m0.021s
    >
    > $ time ./scripts/cc-version.sh clang
    > Clang 120000
    >
    > real 0m0.009s
    > user 0m0.006s
    > sys 0m0.004s
    >
    > The cc-version.sh also shows the error if the compiler is old:
    >
    > $ make defconfig CC=clang-9
    > *** Default configuration is based on 'x86_64_defconfig'
    > ***
    > *** Compiler is too old.
    > *** Your Clang version: 9.0.1
    > *** Minimum Clang version: 10.0.1
    > ***
    > scripts/Kconfig.include:46: Sorry, this compiler is unsupported.
    > make[1]: *** [scripts/kconfig/Makefile:81: defconfig] Error 1
    > make: *** [Makefile:602: defconfig] Error 2
    >
    > I removed the clang version check from <linux/compiler-clang.h>
    >
    > For now, I did not touch <linux/compiler-gcc.h> in order to avoid
    > merge conflict with [3], which has been queued up in the arm64 tree.
    > We will be able to clean it up later.
    >
    > I put the stub for ICC because I see <linux/compiler-intel.h> although
    > I am not sure if building the kernel with ICC is well-supported.
    >
    > [1] https://lkml.org/lkml/2021/1/10/250
    > [2] https://lkml.org/lkml/2021/1/12/1708
    > [3] https://lkml.org/lkml/2021/1/12/1533

    I would recommend the lore version of these links:

    [1]: https://lore.kernel.org/r/20210110190807.134996-1-paul.gortmaker@windriver.com
    [2]: https://lore.kernel.org/r/CAHk-=wh-+TMHPTFo1qs-MYyK7tZh-OQovA=pP3=e06aCVp6_kA@mail.gmail.com
    [3]: https://lore.kernel.org/r/20210112224832.10980-1-will@kernel.org

    > Fixes: 87de84c9140e ("kbuild: remove cc-option test of -Werror=date-time")
    > Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
    > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

    I like this a lot, I think that erroring as early as possible when
    something is misconfigured is a good user experience.

    Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
    Tested-by: Nathan Chancellor <natechancellor@gmail.com>

    > ---
    >
    > Changes in v2:
    > - fix the function name
    >
    > include/linux/compiler-clang.h | 10 -----
    > init/Kconfig | 9 +++--
    > scripts/Kconfig.include | 6 +++
    > scripts/cc-version.sh | 69 ++++++++++++++++++++++++++++++++++
    > scripts/clang-version.sh | 19 ----------
    > scripts/gcc-version.sh | 20 ----------
    > 6 files changed, 80 insertions(+), 53 deletions(-)
    > create mode 100755 scripts/cc-version.sh
    > delete mode 100755 scripts/clang-version.sh
    > delete mode 100755 scripts/gcc-version.sh
    >
    > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
    > index 98cff1b4b088..04c0a5a717f7 100644
    > --- a/include/linux/compiler-clang.h
    > +++ b/include/linux/compiler-clang.h
    > @@ -3,16 +3,6 @@
    > #error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
    > #endif
    >
    > -#define CLANG_VERSION (__clang_major__ * 10000 \
    > - + __clang_minor__ * 100 \
    > - + __clang_patchlevel__)
    > -
    > -#if CLANG_VERSION < 100001
    > -#ifndef __BPF_TRACING__
    > -# error Sorry, your version of Clang is too old - please use 10.0.1 or newer.
    > -#endif
    > -#endif
    > -
    > /* Compiler specific definitions for Clang compiler */
    >
    > /* same as gcc, this was present in clang-2.6 so we can assume it works
    > diff --git a/init/Kconfig b/init/Kconfig
    > index b77c60f8b963..01108dd1318b 100644
    > --- a/init/Kconfig
    > +++ b/init/Kconfig
    > @@ -26,11 +26,11 @@ config CC_VERSION_TEXT
    > and then every file will be rebuilt.
    >
    > config CC_IS_GCC
    > - def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc)
    > + def_bool $(success,test $(cc-name) = GCC)
    >
    > config GCC_VERSION
    > int
    > - default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
    > + default $(cc-version) if CC_IS_GCC
    > default 0
    >
    > config LD_VERSION
    > @@ -38,14 +38,15 @@ config LD_VERSION
    > default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
    >
    > config CC_IS_CLANG
    > - def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang)
    > + def_bool $(success,test $(cc-name) = Clang)
    >
    > config LD_IS_LLD
    > def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
    >
    > config CLANG_VERSION
    > int
    > - default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
    > + default $(cc-version) if CC_IS_CLANG
    > + default 0
    >
    > config LLD_VERSION
    > int
    > diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
    > index a5fe72c504ff..cdc8726d2904 100644
    > --- a/scripts/Kconfig.include
    > +++ b/scripts/Kconfig.include
    > @@ -39,6 +39,12 @@ as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler
    > $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
    > $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
    >
    > +# Get the compiler name, version, and error out if it is unsupported.
    > +cc-info := $(shell,scripts/cc-version.sh $(CC))
    > +$(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this compiler is unsupported.)
    > +cc-name := $(shell,set -- $(cc-info); echo $1)
    > +cc-version := $(shell,set -- $(cc-info); echo $2)
    > +
    > # Fail if the linker is gold as it's not capable of linking the kernel proper
    > $(error-if,$(success, $(LD) -v | grep -q gold), gold linker '$(LD)' not supported)
    >
    > diff --git a/scripts/cc-version.sh b/scripts/cc-version.sh
    > new file mode 100755
    > index 000000000000..9c17c1de401c
    > --- /dev/null
    > +++ b/scripts/cc-version.sh
    > @@ -0,0 +1,69 @@
    > +#!/bin/sh
    > +# SPDX-License-Identifier: GPL-2.0
    > +#
    > +# Print the compiler name and its version in a 5 or 6-digit form.
    > +# Also, perform the minimum version check.
    > +
    > +set -e
    > +
    > +# When you raise the compiler version, please update
    > +# Documentation/process/changes.rst as well.
    > +gcc_min_version=4.9.0
    > +clang_min_version=10.0.1
    > +
    > +# print the compiler name, major version, minor version, patchlevel version
    > +get_compiler_info()
    > +{
    > + cat <<- EOF | "$@" -E -P -x c - 2>/dev/null
    > + #if defined(__clang__)
    > + Clang __clang_major__ __clang_minor__ __clang_patchlevel__
    > + #elif defined(__INTEL_COMPILER)
    > + /* How to get the version of intel compiler? */
    > + ICC 0 0 0
    > + #elif defined(__GNUC__)
    > + GCC __GNUC__ __GNUC_MINOR__ __GNUC_PATCHLEVEL__
    > + #else
    > + unsupported 0 0 0
    > + #endif
    > + EOF
    > +}
    > +
    > +# convert the version to a canonical 5 or 6-digit form for numerical comparison
    > +get_canonical_version()
    > +{
    > + IFS=.
    > + set -- $1
    > + echo $((10000 * $1 + 100 * $2 + $3))
    > +}
    > +
    > +# $@ instead of $1 because multiple words might be given e.g. CC="ccache gcc"
    > +orig_args="$@"
    > +set -- $(get_compiler_info "$@")
    > +
    > +name=$1
    > +version=$2.$3.$4
    > +
    > +case "$name" in
    > +GCC) min_version=$gcc_min_version;;
    > +Clang) min_version=$clang_min_version;;
    > +ICC) ;; # ICC min version undefined?
    > +*) echo "$orig_args: unknown compiler" >&2; exit 1;;
    > +esac
    > +
    > +cversion=$(get_canonical_version $version)
    > +
    > +if [ -n "$min_version" ]; then
    > +
    > + min_cversion=$(get_canonical_version $min_version)
    > +
    > + if [ "$cversion" -lt "$min_cversion" ]; then
    > + echo >&2 "***"
    > + echo >&2 "*** Compiler is too old."
    > + echo >&2 "*** Your $name version: $version"
    > + echo >&2 "*** Minimum $name version: $min_version"
    > + echo >&2 "***"
    > + exit 1
    > + fi
    > +fi
    > +
    > +echo $name $cversion
    > diff --git a/scripts/clang-version.sh b/scripts/clang-version.sh
    > deleted file mode 100755
    > index 6fabf0695761..000000000000
    > --- a/scripts/clang-version.sh
    > +++ /dev/null
    > @@ -1,19 +0,0 @@
    > -#!/bin/sh
    > -# SPDX-License-Identifier: GPL-2.0
    > -#
    > -# clang-version clang-command
    > -#
    > -# Print the compiler version of `clang-command' in a 5 or 6-digit form
    > -# such as `50001' for clang-5.0.1 etc.
    > -
    > -compiler="$*"
    > -
    > -if ! ( $compiler --version | grep -q clang) ; then
    > - echo 0
    > - exit 1
    > -fi
    > -
    > -MAJOR=$(echo __clang_major__ | $compiler -E -x c - | tail -n 1)
    > -MINOR=$(echo __clang_minor__ | $compiler -E -x c - | tail -n 1)
    > -PATCHLEVEL=$(echo __clang_patchlevel__ | $compiler -E -x c - | tail -n 1)
    > -printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL
    > diff --git a/scripts/gcc-version.sh b/scripts/gcc-version.sh
    > deleted file mode 100755
    > index ae353432539b..000000000000
    > --- a/scripts/gcc-version.sh
    > +++ /dev/null
    > @@ -1,20 +0,0 @@
    > -#!/bin/sh
    > -# SPDX-License-Identifier: GPL-2.0
    > -#
    > -# gcc-version gcc-command
    > -#
    > -# Print the gcc version of `gcc-command' in a 5 or 6-digit form
    > -# such as `29503' for gcc-2.95.3, `30301' for gcc-3.3.1, etc.
    > -
    > -compiler="$*"
    > -
    > -if [ ${#compiler} -eq 0 ]; then
    > - echo "Error: No compiler specified." >&2
    > - printf "Usage:\n\t$0 <gcc-command>\n" >&2
    > - exit 1
    > -fi
    > -
    > -MAJOR=$(echo __GNUC__ | $compiler -E -x c - | tail -n 1)
    > -MINOR=$(echo __GNUC_MINOR__ | $compiler -E -x c - | tail -n 1)
    > -PATCHLEVEL=$(echo __GNUC_PATCHLEVEL__ | $compiler -E -x c - | tail -n 1)
    > -printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL
    > --
    > 2.27.0
    >

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