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This reverts commit82017e26e5, which is upstream commitfe0640eb30. On Fri, Jun 28, 2019 at 8:53 AM Tony Battersby <tonyb@cybernetics.com> wrote: > > Old versions of gcc cannot compile 4.14 since 4.14.113: > > ./include/asm-generic/fixmap.h:37: error: implicit declaration of function ‘__builtin_unreachable’ > > The stable commit that caused the problem is82017e26e5("compiler.h: > update definition of unreachable()") (upstream commitfe0640eb30). > Reverting the commit fixes the problem. > > Kernel 4.17 dropped support for older versions of gcc in upstream commit >cafa0010cd("Raise the minimum required gcc version to 4.6"). This > was not backported to 4.14 since that would go against the stable kernel > rules. > > Upstream commit815f0ddb34("include/linux/compiler*.h: make > compiler-*.h mutually exclusive") was a fix forcafa0010cd. This was > not backported to 4.14. > > Upstream commitfe0640eb30("compiler.h: update definition of > unreachable()") was a fix for815f0ddb34. This is the commit that was > backported to 4.14. But it only fixed a problem introduced in the other > commits, and without those commits, it ends up introducing a problem > instead of fixing one. So I recommend reverting that patch in 4.14, > which will enable old gcc to compile 4.14 again. If I understand > correctly, I believe that clang will still be able to compile 4.14 with > the patch reverted, although I haven't tried to compile with clang. > > The problematic commit is not present in 4.9.x, 4.4.x, 3.18.x, or 3.16.x. CC: Nick Desaulniers <ndesaulniers@google.com> CC: Tony Battersby <tonyb@cybernetics.com>, Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.