On Mon, Oct 26, 2020 at 10:52:56PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <[email protected]> > > Clang points out that adding something to NULL is notallowed > in standard C: > > fs/kernfs/file.c:127:15: warning: performing pointer arithmetic on a > null pointer has undefined behavior [-Wnull-pointer-arithmetic] > return NULL + !*ppos; > ~~~~ ^ > fs/seq_file.c:529:14: warning: performing pointer arithmetic on a > null pointer has undefined behavior [-Wnull-pointer-arithmetic] > return NULL + (*pos == 0); > > Rephrase the function to do the same thing without triggering that > warning. Linux already relies on a specific binary representation > of NULL, so it makes no real difference here. The instance in > kernfs was copied from single_start, so fix both at once. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Fixes: c2b19daf6760 ("sysfs, kernfs: prepare read path for kernfs") > Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]> > --- > fs/kernfs/file.c | 2 +- > fs/seq_file.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c > index f277d023ebcd..b55e6ef4d677 100644 > --- a/fs/kernfs/file.c > +++ b/fs/kernfs/file.c > @@ -124,7 +124,7 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t > *ppos) > * The same behavior and code as single_open(). Returns > * !NULL if pos is at the beginning; otherwise, NULL. > */ > - return NULL + !*ppos; > + return (void *)(uintptr_t)!*ppos; > } > } > > diff --git a/fs/seq_file.c b/fs/seq_file.c > index 31219c1db17d..d456468eb934 100644 > --- a/fs/seq_file.c > +++ b/fs/seq_file.c > @@ -526,7 +526,7 @@ EXPORT_SYMBOL(seq_dentry); > > static void *single_start(struct seq_file *p, loff_t *pos) > { > - return NULL + (*pos == 0); > + return (void *)(uintptr_t)(*pos == 0); > } > > static void *single_next(struct seq_file *p, void *v, loff_t *pos) > -- > 2.27.0 >
