Hi all, On Mon, 13 Nov 2017 12:43:08 +0100 Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Mon, Nov 13, 2017 at 9:09 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > On Mon 13-11-17 16:42:06, Stephen Rothwell wrote: > >> > >> After merging the akpm-current tree, today's linux-next build (powerpc > >> ppc64_defconfig) produced this warning: > >> > >> In file included from include/linux/mmzone.h:17:0, > >> from include/linux/mempolicy.h:10, > >> from mm/mempolicy.c:70: > >> mm/mempolicy.c: In function 'mpol_to_str': > >> include/linux/nodemask.h:107:41: warning: the address of 'nodes' will always evaluate as 'true' [-Waddress] > >> #define nodemask_pr_args(maskp) (maskp) ? MAX_NUMNODES : 0, (maskp) ? (maskp)->bits : NULL > >> ^ > >> mm/mempolicy.c:2817:11: note: in expansion of macro 'nodemask_pr_args' > >> nodemask_pr_args(&nodes)); > >> ^ > > > > Hmm, this warning is quite surprising to me. Sure in this particular > > case maskp will always be non-NULL so we always expand to > > MAX_NUMNODES, maskp->bits > > which is what we want. But we have other users which may be NULL. Does > > anybody understan why this warns at all? > > As I understand it, the warning tries to address a common typo of accidentally > testing the pointer to a stack object for being non-NULL, rather than the object > pointed to for being non-zero. > > Adding an extra '!= NULL' comparison gets rid of the warning for me: > > #define nodemask_pr_args(maskp) \ > ((maskp) != NULL) ? MAX_NUMNODES : 0, \ > ((maskp) != NULL) ?(maskp)->bits : NULL > > Arnd This warning now exists in Linus' tree :-( -- Cheers, Stephen Rothwell -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
