On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor <[email protected]> wrote: > > Clang warns that if the default case is taken, ret will be > uninitialized. > > ./arch/arm64/include/asm/percpu.h:196:2: warning: variable 'ret' is used > uninitialized whenever switch default is taken > [-Wsometimes-uninitialized] > default: > ^~~~~~~ > ./arch/arm64/include/asm/percpu.h:200:9: note: uninitialized use occurs > here > return ret; > ^~~ > ./arch/arm64/include/asm/percpu.h:157:19: note: initialize the variable > 'ret' to silence this warning > unsigned long ret, loop; > ^ > = 0 > > This warning appears several times while building the erofs filesystem. > While it's not strictly wrong, the BUILD_BUG will prevent this from > becoming a true problem. Initialize ret to 0 in the default case right > before the BUILD_BUG to silence all of these warnings.
Clang does semantic analysis BEFORE inlining/optimizations, so I can't determine that default is never reachable. Nathan, thanks for this patch. Reviewed-by: Nick Desaulniers <[email protected]> > > Reported-by: Prasad Sodagudi <[email protected]> > Signed-off-by: Nathan Chancellor <[email protected]> > --- > arch/arm64/include/asm/percpu.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h > index 9234013e759e..21a81b59a0cc 100644 > --- a/arch/arm64/include/asm/percpu.h > +++ b/arch/arm64/include/asm/percpu.h > @@ -96,6 +96,7 @@ static inline unsigned long __percpu_##op(void *ptr, > \ > : [val] "Ir" (val)); \ > break; \ > default: \ > + ret = 0; \ > BUILD_BUG(); \ > } \ > \ > @@ -125,6 +126,7 @@ static inline unsigned long __percpu_read(void *ptr, int > size) > ret = READ_ONCE(*(u64 *)ptr); > break; > default: > + ret = 0; > BUILD_BUG(); > } > > @@ -194,6 +196,7 @@ static inline unsigned long __percpu_xchg(void *ptr, > unsigned long val, > : [val] "r" (val)); > break; > default: > + ret = 0; > BUILD_BUG(); > } > > -- > 2.19.0 > -- Thanks, ~Nick Desaulniers
