From: trix@redhat.com
To: arnd@arndb.de
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Tom Rix <trix@redhat.com>
Subject: [PATCH 1/1] bug: mark generic BUG() as unreachable
Date: Thu, 17 Jun 2021 14:43:28 -0700 [thread overview]
Message-ID: <20210617214328.3501174-3-trix@redhat.com> (raw)
In-Reply-To: <20210617214328.3501174-1-trix@redhat.com>
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
next prev parent reply other threads:[~2021-06-17 21:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 21:43 [PATCH 0/1] bug: mark generic BUG() as unreachable trix
2021-06-17 21:43 ` trix [this message]
2021-06-18 8:20 ` [PATCH 1/1] " Arnd Bergmann
2021-06-18 13:43 ` Tom Rix
2021-06-18 14:35 ` Arnd Bergmann
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