Messages in this thread |  | | From | Nick Desaulniers <> | Date | Tue, 21 Aug 2018 09:57:11 -0700 | Subject | Re: [PATCH] compiler-gcc: get back Clang build |
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On Tue, Aug 21, 2018 at 9:33 AM Joe Perches <joe@perches.com> wrote: > > On Tue, 2018-08-21 at 15:48 +0900, Masahiro Yamada wrote: > > Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6") > > missed the fact that <linux/compiler-gcc.h> is included by Clang > > as well as by GCC. > > > > Clang actually defines __GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__ > > and it looks like GCC 4.2.1. > > > > $ scripts/gcc-version.sh -p clang > > 040201 > > > > If you try to build the kernel with Clang, you will get the > > "Sorry, your compiler is too old - please upgrade it." > > followed by a bunch of "unknown attribute" warnings. > > > > Add !defined(__clang__) to the minimum version check. > > > > Also, revive the version test blocks for versions >= 4.2.1 > > in order to disable features not supported by Clang. > > What is the minimum clang version required to compile the kernel?
Depends on the architecture and which kernel version/LTS branch you're using. I'm trying to backport fixes to LTS branches, but sometimes a compiler upgrade is required. I know that's not great, but I'm actively trying to fix it.
> What features are not supported by the minimum clang version? > > On my system, using clang > > $ clang -v > clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final) > > and > > $ git checkout v4.16 ; make clean ; make CC=clang defconfig ; make CC=clang > HEAD is now at 0adb32858b0b... Linux 4.16 > > is successful > > but > > $ git checkout v4.17 ; make clean ; make CC=clang defconfig ; make CC=clang > HEAD is now at 29dcea88779c... Linux 4.17 > arch/x86/Makefile:184: *** Compiler lacks asm-goto support.. Stop. > arch/x86/Makefile:184: *** Compiler lacks asm-goto support.. Stop. >
See commit e501ce9 ("x86: Force asm-goto").
$ git describe --contains e501ce9 | sed 's/~.*//' v4.17-rc1
-- Thanks, ~Nick Desaulniers
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