# git rev-parse -q --verify 21466c8b8fbaaec5c54d1f8565657dc2f6b25583^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/mirror/linux-kbuild.git for-next
# git rev-parse -q --verify 21466c8b8fbaaec5c54d1f8565657dc2f6b25583^{commit}
21466c8b8fbaaec5c54d1f8565657dc2f6b25583
# git checkout -q -f -B kisskb 21466c8b8fbaaec5c54d1f8565657dc2f6b25583
# git clean -qxdf
# < git log -1
# commit 21466c8b8fbaaec5c54d1f8565657dc2f6b25583
# Author: Masahiro Yamada <masahiroy@kernel.org>
# Date:   Wed Apr 8 00:53:52 2020 +0900
# 
#     kbuild: add dummy toolchains to enable all cc-option etc. in Kconfig
#     
#     Staring v4.18, Kconfig evaluates compiler capabilities, and hides CONFIG
#     options your compiler does not support. This works well if you configure
#     and build the kernel on the same host machine.
#     
#     It is inconvenient if you prepare the .config that is carried to a
#     different build environment (typically this happens when you package
#     the kernel for distros) because using a different compiler potentially
#     produces different CONFIG options than the real build environment.
#     So, you probably want to make as many options visible as possible.
#     In other words, you need to create a super-set of CONFIG options that
#     cover any build environment. If some of the CONFIG options turned out
#     to be unsupported on the build machine, they are automatically disabled
#     by the nature of Kconfig.
#     
#     However, it is not feasible to get a full-featured compiler for every
#     arch.
#     
#     This issue was discussed here:
#     
#       https://lkml.org/lkml/2019/12/9/620
#     
#     Other than distros, savedefconfig is also a problem. Some arch sub-systems
#     periodically resync defconfig files. If you use a less-capable compiler
#     for savedefconfig, options that do not meet 'depends on $(cc-option,...)'
#     will be forcibly disabled. So, 'make defconfig && make savedefconfig'
#     may silently change the behavior.
#     
#     This commit adds a set of dummy toolchains that pretend to support any
#     feature.
#     
#     Most of compiler features are tested by cc-option, which simply checks
#     the exit code of $(CC). The dummy tools are shell scripts that always
#     exit with 0. So, $(cc-option, ...) is evaluated as 'y'.
#     
#     There are more complicated checks such as:
#     
#       scripts/gcc-x86_{32,64}-has-stack-protector.sh
#       scripts/gcc-plugin.sh
#       scripts/tools-support-relr.sh
#     
#     scripts/dummy-tools/gcc passes all checks.
#     
#     From the top directory of the source tree, you can do:
#     
#        $ make CROSS_COMPILE=scripts/dummy-tools/ oldconfig
#     
#     Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
#     Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-ld --version
# < git log --format=%s --max-count=1 21466c8b8fbaaec5c54d1f8565657dc2f6b25583
# < make -s -j 80 ARCH=ia64 O=/kisskb/build/kbuild_ia64-defconfig_ia64-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-  defconfig
# < make -s -j 80 ARCH=ia64 O=/kisskb/build/kbuild_ia64-defconfig_ia64-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-  help
# make -s -j 80 ARCH=ia64 O=/kisskb/build/kbuild_ia64-defconfig_ia64-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-  olddefconfig
# make -s -j 80 ARCH=ia64 O=/kisskb/build/kbuild_ia64-defconfig_ia64-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-  
<stdin>:1511:2: warning: #warning syscall clone3 not implemented [-Wcpp]
/kisskb/src/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:72:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:401:21: note: 'pdeo' was declared here
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:204:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/mm/vmstat.c: In function 'sysctl_vm_numa_stat_handler':
/kisskb/src/mm/vmstat.c:90:5: warning: 'oldval' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/ext4/extents.c: In function 'ext4_convert_unwritten_io_end_vec':
/kisskb/src/fs/ext4/extents.c:5009:23: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/futex.c: In function 'do_futex':
/kisskb/src/kernel/futex.c:1676:3: warning: 'oldval' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/futex.c:1652:6: note: 'oldval' was declared here
/kisskb/src/fs/namei.c: In function 'handle_dots':
/kisskb/src/fs/namei.c:1805:10: warning: 'inode' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/namei.c:1805:10: warning: 'seq' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/nfs/read.c: In function 'nfs_read_completion':
/kisskb/src/fs/nfs/read.c:196:5: warning: value computed is not used [-Wunused-value]
/kisskb/src/fs/nfs/read.c: In function 'nfs_readpage':
/kisskb/src/fs/nfs/read.c:353:2: warning: value computed is not used [-Wunused-value]
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c: In function 'drm_dp_mst_dsc_aux_for_port':
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5497:9: warning: missing braces around initializer [-Wmissing-braces]
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5497:9: warning: (near initialization for 'desc.ident') [-Wmissing-braces]
/kisskb/src/fs/nfsd/nfs4xdr.c: In function 'nfsd4_encode_components_esc':
/kisskb/src/fs/nfsd/nfs4xdr.c:2151:9: warning: 'str' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/mm/hugetlb.c: In function 'alloc_pool_huge_page':
/kisskb/src/mm/hugetlb.c:1741:5: warning: 'page' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/udf/unicode.c: In function 'udf_name_conv_char':
/kisskb/src/fs/udf/unicode.c:132:8: warning: 'c' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/usb/core/devio.c: In function 'async_completed':
/kisskb/src/drivers/usb/core/devio.c:625:23: warning: 'errno' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/io_uring.c: In function '__io_sqe_files_update':
/kisskb/src/fs/io_uring.c:6617:13: warning: 'err' may be used uninitialized in this function [-Wuninitialized]
No errors detected in 22336 functions.
Completed OK
# rm -rf /kisskb/build/kbuild_ia64-defconfig_ia64-gcc4.6
# Build took: 0:02:05.183393