[linux-next:master 9529/10007] mm/hugetlb.c:1591:9: warning: no previous prototype for function 'hugetlb_basepage_index'
1:58 a.m.
tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head: 19ae1f2bd9c091059f80646604ccef8a1e614f57
commit: 1878ae46bd82ef0403393aee4935f29c07d5848b [9529/10007] mm, futex: fix shared futex
pgoff on shmem huge page
config: arm64-randconfig-r014-20210615 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project
64720f57bea6a6bf033feef4a5751ab9c0c3b401)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
~/bin/make.cross
chmod +x ~/bin/make.cross
# install arm64 cross compiling tool for clang build
# apt-get install binutils-aarch64-linux-gnu
#
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commi...
git remote add linux-next
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
git fetch --no-tags linux-next master
git checkout 1878ae46bd82ef0403393aee4935f29c07d5848b
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp(a)intel.com>
All warnings (new ones prefixed by >>):
> mm/hugetlb.c:1591:9: warning: no previous prototype for function
'hugetlb_basepage_index' [-Wmissing-prototypes]
pgoff_t
hugetlb_basepage_index(struct page *page)
^
mm/hugetlb.c:1591:1: note: declare 'static' if the function is not intended to
be used outside of this translation unit
pgoff_t hugetlb_basepage_index(struct page *page)
^
static
include/linux/types.h:131:17: note: expanded from macro 'pgoff_t'
#define pgoff_t unsigned long
^
1 warning generated.
vim +/hugetlb_basepage_index +1591 mm/hugetlb.c
1590
1591 pgoff_t hugetlb_basepage_index(struct page *page)
1592 {
1593 struct page *page_head = compound_head(page);
1594 pgoff_t index = page_index(page_head);
1595 unsigned long compound_idx;
1596
1597 if (compound_order(page_head) >= MAX_ORDER)
1598 compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
1599 else
1600 compound_idx = page - page_head;
1601
1602 return (index << compound_order(page_head)) + compound_idx;
1603 }
1604
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
2:03 a.m.
On Tue, Jun 15, 2021 at 11:58:36PM +0800, kernel test robot wrote:
COMPILER_INSTALL_PATH=$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?
4:32 a.m.
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"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- W=1 olddefconfig
mm/hugetlb.c
mm/hugetlb.c:1591:9: warning: no previous prototype for 'hugetlb_basepage_index'
[-Wmissing-prototypes]
1591 | pgoff_t hugetlb_basepage_index(struct page *page)
| ^~~~~~~~~~~~~~~~~~~~~~
Cheers,
Nathan
4:50 a.m.
On Tue, Jun 15, 2021 at 11:32 AM Nathan Chancellor <nathan(a)kernel.org> wrote:
On Tue, Jun 15, 2021 at 05:03:40PM +0100, Matthew Wilcox wrote:
> On Tue, Jun 15, 2021 at 11:58:36PM +0800, kernel test robot wrote:
> > COMPILER_INSTALL_PATH=$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"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- W=1 olddefconfig
mm/hugetlb.c
mm/hugetlb.c:1591:9: warning: no previous prototype for 'hugetlb_basepage_index'
[-Wmissing-prototypes]
1591 | pgoff_t hugetlb_basepage_index(struct page *page)
| ^~~~~~~~~~~~~~~~~~~~~~
Since this is a commonly recurring warning for W=1 builds, then this
function either should be declared as having static linkage if its
uses are local to the same file, or a prototype should be declared in
a header so that callers and callee agree on function signature.
--
Thanks,
~Nick Desaulniers
5:01 a.m.
On Tue, Jun 15, 2021 at 11:50:40AM -0700, Nick Desaulniers wrote:
On Tue, Jun 15, 2021 at 11:32 AM Nathan Chancellor
<nathan(a)kernel.org> wrote:
>
> On Tue, Jun 15, 2021 at 05:03:40PM +0100, Matthew Wilcox wrote:
> > On Tue, Jun 15, 2021 at 11:58:36PM +0800, kernel test robot wrote:
> > > COMPILER_INSTALL_PATH=$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"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- W=1
olddefconfig mm/hugetlb.c
> mm/hugetlb.c:1591:9: warning: no previous prototype for
'hugetlb_basepage_index' [-Wmissing-prototypes]
> 1591 | pgoff_t hugetlb_basepage_index(struct page *page)
> | ^~~~~~~~~~~~~~~~~~~~~~
Since this is a commonly recurring warning for W=1 builds, then this
function either should be declared as having static linkage if its
uses are local to the same file, or a prototype should be declared in
a header so that callers and callee agree on function signature.
Oh, you haven't understood the problem.
static inline int bar(void)
{
int foo(void);
return foo();
}
int foo(void) { return 1; }
The prototype isn't _missing_. It's just no longer in scope.
Since gcc and clang behave the same way here, we should adjust the source
to make foo visible outside bar. But this is a case where both compilers
are wrong.
9:37 a.m.
On Tue, 15 Jun 2021, Matthew Wilcox wrote:
On Tue, Jun 15, 2021 at 11:50:40AM -0700, Nick Desaulniers wrote:
> On Tue, Jun 15, 2021 at 11:32 AM Nathan Chancellor <nathan(a)kernel.org> wrote:
> > On Tue, Jun 15, 2021 at 05:03:40PM +0100, Matthew Wilcox wrote:
> > > On Tue, Jun 15, 2021 at 11:58:36PM +0800, kernel test robot wrote:
> > > > COMPILER_INSTALL_PATH=$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.
I guess I'd better start W=1-ing - not my habit before, sorry.
I can't tell what's right or wrong for the compiler, but it sure is
odd that if I add a bogus ", int flags" to hugetlb_basepage_index()
in mm/hugetlb.c, then building with gcc (10) and W=1 says
CC mm/hugetlb.o
mm/hugetlb.c:1591:9: warning: no previous prototype for ‘hugetlb_basepage_index’
[-Wmissing-prototypes]
1591 | pgoff_t hugetlb_basepage_index(struct page *page, int flags)
| ^~~~~~~~~~~~~~~~~~~~~~
mm/hugetlb.c:1591:9: error: conflicting types for ‘hugetlb_basepage_index’
In file included from mm/hugetlb.c:14:
./include/linux/pagemap.h:543:18: note: previous declaration of ‘hugetlb_basepage_index’
was here
543 | extern pgoff_t hugetlb_basepage_index(struct page *page);
| ^~~~~~~~~~~~~~~~~~~~~~
So, it manages to conflict with no previous prototype!
(I didn't try clang with W=1, presumably similar.)
Both gcc and clang with W=0 do issue the conflicting types error,
as I hoped and assumed that they would when I put in the prototype.
Oh well, thanks for moving it Matthew: whatever the rights and wrongs,
neither of us want to be generating unnecessary noise.
Hugh
462
days inactive
462
days old
5 comments
5 participants
participants (5)
-
Hugh Dickins -
kernel test robot -
Matthew Wilcox -
Nathan Chancellor -
Nick Desaulniers