tree: https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git treewide/gnu99 head: df0f3c59f076be0ab4a6d8de53fdeef871394594 commit: df0f3c59f076be0ab4a6d8de53fdeef871394594 [1/1] treewide: use -std=gnu99 config: um-i386_defconfig (https://download.01.org/0day-ci/archive/20220113/202201130624.MemBkw6f-lk...) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/commit/?id... git remote add mark https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git git fetch --no-tags mark treewide/gnu99 git checkout df0f3c59f076be0ab4a6d8de53fdeef871394594 # save the config file to linux build tree mkdir build_dir make W=1 O=build_dir ARCH=um SUBARCH=i386 SHELL=/bin/bash arch/um/kernel/ fs/isofs/ If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): In file included from arch/um/include/asm/fixmap.h:54, from arch/um/include/asm/pgtable.h:11, from include/linux/pgtable.h:6, from include/linux/mm.h:33, from include/linux/memblock.h:13, from arch/um/kernel/mem.c:8: arch/um/kernel/mem.c: In function 'paging_init': 21 | #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT)) | ^~ arch/um/kernel/mem.c:167:10: note: in expansion of macro '__fix_to_virt' 167 | vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK; | ^~~~~~~~~~~~~ arch/um/kernel/mem.c: At top level: arch/um/kernel/mem.c:184:8: warning: no previous prototype for 'pgd_alloc' [-Wmissing-prototypes] 184 | pgd_t *pgd_alloc(struct mm_struct *mm) | ^~~~~~~~~ arch/um/kernel/mem.c:197:7: warning: no previous prototype for 'uml_kmalloc' [-Wmissing-prototypes] 197 | void *uml_kmalloc(int size, int flags) | ^~~~~~~~~~~ -- fs/isofs/util.c: In function 'iso_date': 40 | tz |= (-1 << 8); | ^~ vim +21 include/asm-generic/fixmap.h d57c33c5daa4ef Mark Salter 2014-01-23 20 d57c33c5daa4ef Mark Salter 2014-01-23 @21 #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT)) d57c33c5daa4ef Mark Salter 2014-01-23 22 #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT) d57c33c5daa4ef Mark Salter 2014-01-23 23 :::::: The code at line 21 was first introduced by commit :::::: d57c33c5daa4efa9e4d303bd0faf868080b532be add generic fixmap.h :::::: TO: Mark Salter <msalter(a)redhat.com&gt; :::::: CC: Linus Torvalds <torvalds(a)linux-foundation.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org