This reverts commit 82017e26e51596ee577171a33f357377ec6513b5, which is upstream commit fe0640eb30b7da261ae84d252ed9ed3c7e68dfd8.
On Fri, Jun 28, 2019 at 8:53 AM Tony Battersby <[email protected]> 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 82017e26e515 ("compiler.h: > update definition of unreachable()") (upstream commit fe0640eb30b7). > Reverting the commit fixes the problem. > > Kernel 4.17 dropped support for older versions of gcc in upstream commit > cafa0010cd51 ("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 815f0ddb346c ("include/linux/compiler*.h: make > compiler-*.h mutually exclusive") was a fix for cafa0010cd51. This was > not backported to 4.14. > > Upstream commit fe0640eb30b7 ("compiler.h: update definition of > unreachable()") was a fix for 815f0ddb346c. 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 <[email protected]> CC: Tony Battersby <[email protected]>, Signed-off-by: Sasha Levin <[email protected]> --- include/linux/compiler.h | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 67c3934fb9ed..a704d032713b 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -119,10 +119,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, # define ASM_UNREACHABLE #endif #ifndef unreachable -# define unreachable() do { \ - annotate_unreachable(); \ - __builtin_unreachable(); \ -} while (0) +# define unreachable() do { annotate_reachable(); do { } while (1); } while (0) #endif /* -- 2.20.1
