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@xxxxxxxxxx> 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@xxxxxxxxx> > > > > > > > > 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@xxxxxxxxx/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.
