Messages in this thread Patch in this message | | | From | trix@redhat ... | Subject | [PATCH 1/1] bug: mark generic BUG() as unreachable | Date | Thu, 17 Jun 2021 14:43:28 -0700 |
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From: Tom Rix <trix@redhat.com>
This spurious error is reported for powerpc64, CONFIG_BUG=n
fs/afs/dir.c: In function 'afs_dir_set_page_dirty': fs/afs/dir.c:51:1: error: no return statement in function returning non-void [-Werror=return-type] 51 | } | ^
When CONFIG_BUG=y is BUG is expanded from #define BUG() do { BUG_ENTRY("twi 31, 0, 0", 0); unreachable(); } while (0)
to
static int afs_dir_set_page_dirty(struct page *page) { do { __asm__ __volatile__( "1: " "twi 31, 0, 0" ... do { ; asm volatile(""); __builtin_unreachable(); } while (0); } while (0); }
When CONFIG_BUG=n, the generic BUG() is used which expands out to
static int afs_dir_set_page_dirty(struct page *page) { do {} while (1); }
Without the __builtin_unreachable(), gcc reports the warning
ref: gcc docs https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html " ... without the __builtin_unreachable, GCC issues a warning that control reaches the end of a non-void function."
So add an unreachable() to the generic BUG(), the resulting expansiion will be
static int afs_dir_set_page_dirty(struct page *page) { do { do {} while (1); do { ; asm volatile(""); __builtin_unreachable(); } while (0); } while (0); }
Signed-off-by: Tom Rix <trix@redhat.com> --- include/asm-generic/bug.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h index f152b9bb916fc..b250e06d7de26 100644 --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -177,7 +177,10 @@ void __warn(const char *file, int line, void *caller, unsigned taint, #else /* !CONFIG_BUG */ #ifndef HAVE_ARCH_BUG -#define BUG() do {} while (1) +#define BUG() do { \ + do {} while (1); \ + unreachable(); \ + } while (0) #endif #ifndef HAVE_ARCH_BUG_ON -- 2.26.3
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