5:01 a.m.
On Tue, Jun 15, 2021 at 11:50:40AM -0700, Nick Desaulniers wrote:
On Tue, Jun 15, 2021 at 11:32 AM Nathan Chancellor
<nathan(a)kernel.org> wrote:
>
> On Tue, Jun 15, 2021 at 05:03:40PM +0100, Matthew Wilcox wrote:
> > On Tue, Jun 15, 2021 at 11:58:36PM +0800, kernel test robot wrote:
> > > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross
ARCH=arm64
> > >
> > > If you fix the issue, kindly add following tag as appropriate
> > > Reported-by: kernel test robot <lkp(a)intel.com>
> > >
> > > All warnings (new ones prefixed by >>):
> > >
> > > >> mm/hugetlb.c:1591:9: warning: no previous prototype for function
'hugetlb_basepage_index' [-Wmissing-prototypes]
> > > pgoff_t hugetlb_basepage_index(struct page *page)
> >
> > So clang requires the prototype to still be in scope, while gcc doesn't.
> > Does one of our clangers want to file a bug about that?
>
> I see the exact same warning with GCC 11.1.0:
>
> $ curl -LSs
https://lore.kernel.org/linux-mm/202106152328.Mh5S48hE-lkp@intel.com/2-a.bin | gzip -d
> .config
>
> $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- W=1
olddefconfig mm/hugetlb.c
> mm/hugetlb.c:1591:9: warning: no previous prototype for
'hugetlb_basepage_index' [-Wmissing-prototypes]
> 1591 | pgoff_t hugetlb_basepage_index(struct page *page)
> | ^~~~~~~~~~~~~~~~~~~~~~
Since this is a commonly recurring warning for W=1 builds, then this
function either should be declared as having static linkage if its
uses are local to the same file, or a prototype should be declared in
a header so that callers and callee agree on function signature.
Oh, you haven't understood the problem.
static inline int bar(void)
{
int foo(void);
return foo();
}
int foo(void) { return 1; }
The prototype isn't _missing_. It's just no longer in scope.
Since gcc and clang behave the same way here, we should adjust the source
to make foo visible outside bar. But this is a case where both compilers
are wrong.