| Message ID | 20180925194459.13088-1-natechancellor@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: percpu: Initialize ret in the default case | expand |
On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor <natechancellor@gmail.com> 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 <ndesaulniers@google.com> > > Reported-by: Prasad Sodagudi <psodagud@codeaurora.org> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > --- > 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 >
On Tue, Sep 25, 2018 at 1:24 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor > <natechancellor@gmail.com> 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 s/I/it/ > determine that default is never reachable. Nathan, thanks for this > patch. > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > > > > Reported-by: Prasad Sodagudi <psodagud@codeaurora.org> > > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > > --- > > 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
Hi Nathan, On Tue, Sep 25, 2018 at 12:44:59PM -0700, Nathan Chancellor 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. > > Reported-by: Prasad Sodagudi <psodagud@codeaurora.org> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> I've applied this to percpu/for-4.20. Thanks, Dennis
Hi Nick, On Tue, Sep 25, 2018 at 01:24:06PM -0700, Nick Desaulniers wrote: > On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor > <natechancellor@gmail.com> 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 <ndesaulniers@google.com> > Thanks for the explanation! Dennis
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(); }
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. Reported-by: Prasad Sodagudi <psodagud@codeaurora.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> --- arch/arm64/include/asm/percpu.h | 3 +++ 1 file changed, 3 insertions(+)