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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-09-02 23:25:55 -0500
committerGustavo A. R. Silva <gustavoars@kernel.org>2020-10-29 13:17:58 -0500
commit4169e889e5889405d54cec27d6e9f7f0ce3c7096 (patch)
treea6a81568fa8c7b48df1227e69815fdeb17c0a876 /include
parent3650b228f83adda7e5ee532e2b90429c03f7b9ec (diff)
include: jhash/signal: Fix fall-through warnings for Clang
In preparation to enable -Wimplicit-fallthrough for Clang, explicitly add break statements instead of letting the code fall through to the next case. This patch adds four break statements that, together, fix almost 40,000 warnings when building Linux 5.10-rc1 with Clang 12.0.0 and this[1] change reverted. Notice that in order to enable -Wimplicit-fallthrough for Clang, such change[1] is meant to be reverted at some point. So, this patch helps to move in that direction. Something important to mention is that there is currently a discrepancy between GCC and Clang when dealing with switch fall-through to empty case statements or to cases that only contain a break/continue/return statement[2][3][4]. Now that the -Wimplicit-fallthrough option has been globally enabled[5], any compiler should really warn on missing either a fallthrough annotation or any of the other case-terminating statements (break/continue/return/ goto) when falling through to the next case statement. Making exceptions to this introduces variation in case handling which may continue to lead to bugs, misunderstandings, and a general lack of robustness. The point of enabling options like -Wimplicit-fallthrough is to prevent human error and aid developers in spotting bugs before their code is even built/ submitted/committed, therefore eliminating classes of bugs. So, in order to really accomplish this, we should, and can, move in the direction of addressing any error-prone scenarios and get rid of the unintentional fallthrough bug-class in the kernel, entirely, even if there is some minor redundancy. Better to have explicit case-ending statements than continue to have exceptions where one must guess as to the right result. The compiler will eliminate any actual redundancy. [1] commit e2079e93f562c ("kbuild: Do not enable -Wimplicit-fallthrough for clang for now") [2] https://github.com/ClangBuiltLinux/linux/issues/636 [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91432 [4] https://godbolt.org/z/xgkvIh [5] commit a035d552a93b ("Makefile: Globally enable fall-through warning") Co-developed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/jhash.h2
-rw-r--r--include/linux/signal.h2
2 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/jhash.h b/include/linux/jhash.h
index cfb62e9f37be..ab7f8c152b89 100644
--- a/include/linux/jhash.h
+++ b/include/linux/jhash.h
@@ -99,6 +99,7 @@ static inline u32 jhash(const void *key, u32 length, u32 initval)
case 2: a += (u32)k[1]<<8; fallthrough;
case 1: a += k[0];
__jhash_final(a, b, c);
+ break;
case 0: /* Nothing left to add */
break;
}
@@ -136,6 +137,7 @@ static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
case 2: b += k[1]; fallthrough;
case 1: a += k[0];
__jhash_final(a, b, c);
+ break;
case 0: /* Nothing left to add */
break;
}
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 7bbc0e9cf084..b256f9c65661 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -238,6 +238,7 @@ static inline void siginitset(sigset_t *set, unsigned long mask)
memset(&set->sig[1], 0, sizeof(long)*(_NSIG_WORDS-1));
break;
case 2: set->sig[1] = 0;
+ break;
case 1: ;
}
}
@@ -250,6 +251,7 @@ static inline void siginitsetinv(sigset_t *set, unsigned long mask)
memset(&set->sig[1], -1, sizeof(long)*(_NSIG_WORDS-1));
break;
case 2: set->sig[1] = -1;
+ break;
case 1: ;
}
}

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