On Sat, 2014-03-22 at 09:37 -0700, Behan Webster wrote: > On 03/22/14 09:29, James Bottomley wrote: > > On Sat, 2014-03-22 at 08:48 -0700, behanw@xxxxxxxxxxxxxxxxxx wrote: > >> From: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx> > >> > >> Fix uninitialized return code in default case in cmpxchg-local.h > >> > >> This patch fixes the code to prevent an uninitialized return value that is detected > >> when compiling with clang. The bug produces numerous warnings when compiling the > >> Linux kernel with clang. > >> > >> Signed-off-by: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx> > >> Signed-off-by: Mark Charlebois <charlebm@xxxxxxxxx> > >> --- > >> include/asm-generic/cmpxchg-local.h | 1 + > >> 1 file changed, 1 insertion(+) > >> > >> diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h > >> index d8d4c89..9112111 100644 > >> --- a/include/asm-generic/cmpxchg-local.h > >> +++ b/include/asm-generic/cmpxchg-local.h > >> @@ -41,6 +41,7 @@ static inline unsigned long __cmpxchg_local_generic(volatile void *ptr, > >> break; > >> default: > >> wrong_size_cmpxchg(ptr); > >> + __builtin_unreachable(); > > No, that's got to be unreachable() so that it works in all compilers, > > (__builtin_unreachable is a gcc-4 ism). > It is also supported by clang. OK, but it's not supported by gcc-3. So gcc-3 would crap out seeing the statement, which is why we have to wrapper it. > > Got to say this still looks wrong. If wrong_size_cmpxchg() cannot > > return, the function should be annotated as such with __noreturn (like > > panic()) so the unreachable() should be superfluous. > Okay. I can try that instead. Great; This seems to work for me (but then my compiler doesn't see the unreachable problem). James --- diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h index d8d4c89..70bef78 100644 --- a/include/asm-generic/cmpxchg-local.h +++ b/include/asm-generic/cmpxchg-local.h @@ -4,7 +4,8 @@ #include <linux/types.h> #include <linux/irqflags.h> -extern unsigned long wrong_size_cmpxchg(volatile void *ptr); +extern unsigned long wrong_size_cmpxchg(volatile void *ptr) + __noreturn; /* * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
