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Sasha Levin authored
This reverts commit 82017e26, which is upstream commit fe0640eb. 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 is 82017e26 ("compiler.h: > update definition of unreachable()") (upstream commit fe0640eb). > Reverting the commit fixes the problem. > > Kernel 4.17 dropped support for older versions of gcc in upstream commit > cafa0010 ("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 commit 815f0ddb ("include/linux/compiler*.h: make > compiler-*.h mutually exclusive") was a fix for cafa0010. This was > not backported to 4.14. > > Upstream commit fe0640eb ("compiler.h: update definition of > unreachable()") was a fix for 815f0ddb . 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>
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