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Date: Wed, 5 Aug 2020 19:51:19 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: kernel test robot <lkp@...el.com>
Cc: kbuild-all@...ts.01.org, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [vhost:vhost 32/52] include/linux/typecheck.h:12:18: warning:
comparison of distinct pointer types lacks a cast
On Thu, Aug 06, 2020 at 04:17:13AM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git vhost
> head: 4c05433bc6fb4ae172270f0279be8ba89a3da64f
> commit: b025584098e621d88894d28e80af686958e273af [32/52] virtio_input: convert to LE accessors
> config: parisc-randconfig-r003-20200805 (attached as .config)
> compiler: hppa-linux-gcc (GCC) 9.3.0
> 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
> git checkout b025584098e621d88894d28e80af686958e273af
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=parisc
Weird. So the following fixes it:
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index ecb166c824bb..8fe857e27ef3 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -357,10 +357,10 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
*/
#define virtio_le_to_cpu(x) \
_Generic((x), \
- __u8: (x), \
- __le16: le16_to_cpu(x), \
- __le32: le32_to_cpu(x), \
- __le64: le64_to_cpu(x) \
+ __u8: (u8)(x), \
+ __le16: (u16)le16_to_cpu(x), \
+ __le32: (u32)le32_to_cpu(x), \
+ __le64: (u64)le64_to_cpu(x) \
)
#define virtio_cpu_to_le(x, m) \
@@ -400,7 +400,6 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
*(ptr) = virtio_le_to_cpu(virtio_cread_v); \
} while(0)
-/* Config space accessors. */
#define virtio_cwrite_le(vdev, structname, member, ptr) \
do { \
typeof(((structname*)0)->member) virtio_cwrite_v = \
How could this be? le16_to_cpu doesn't return a u16?
I suspect this compiler gets confused by _Generic.
Let's hope it does not also miscompile the code :)
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/irqflags.h:15,
> from include/asm-generic/cmpxchg-local.h:6,
> from arch/parisc/include/asm/cmpxchg.h:89,
> from arch/parisc/include/asm/atomic.h:10,
> from include/linux/atomic.h:7,
> from arch/parisc/include/asm/bitops.h:13,
> from include/linux/bitops.h:29,
> from include/linux/kernel.h:12,
> from include/linux/list.h:9,
> from include/linux/module.h:12,
> from drivers/virtio/virtio_input.c:2:
> drivers/virtio/virtio_input.c: In function 'virtinput_probe':
> >> include/linux/typecheck.h:12:18: warning: comparison of distinct pointer types lacks a cast
> 12 | (void)(&__dummy == &__dummy2); \
> | ^~
> include/linux/virtio_config.h:405:3: note: in expansion of macro 'typecheck'
> 405 | typecheck(typeof(virtio_le_to_cpu(virtio_cread_v)), *(ptr)); \
> | ^~~~~~~~~
> drivers/virtio/virtio_input.c:247:3: note: in expansion of macro 'virtio_cread_le'
> 247 | virtio_cread_le(vi->vdev, struct virtio_input_config,
> | ^~~~~~~~~~~~~~~
> >> include/linux/typecheck.h:12:18: warning: comparison of distinct pointer types lacks a cast
> 12 | (void)(&__dummy == &__dummy2); \
> | ^~
> include/linux/virtio_config.h:405:3: note: in expansion of macro 'typecheck'
> 405 | typecheck(typeof(virtio_le_to_cpu(virtio_cread_v)), *(ptr)); \
> | ^~~~~~~~~
> drivers/virtio/virtio_input.c:249:3: note: in expansion of macro 'virtio_cread_le'
> 249 | virtio_cread_le(vi->vdev, struct virtio_input_config,
> | ^~~~~~~~~~~~~~~
> >> include/linux/typecheck.h:12:18: warning: comparison of distinct pointer types lacks a cast
> 12 | (void)(&__dummy == &__dummy2); \
> | ^~
> include/linux/virtio_config.h:405:3: note: in expansion of macro 'typecheck'
> 405 | typecheck(typeof(virtio_le_to_cpu(virtio_cread_v)), *(ptr)); \
> | ^~~~~~~~~
> drivers/virtio/virtio_input.c:251:3: note: in expansion of macro 'virtio_cread_le'
> 251 | virtio_cread_le(vi->vdev, struct virtio_input_config,
> | ^~~~~~~~~~~~~~~
> >> include/linux/typecheck.h:12:18: warning: comparison of distinct pointer types lacks a cast
> 12 | (void)(&__dummy == &__dummy2); \
> | ^~
> include/linux/virtio_config.h:405:3: note: in expansion of macro 'typecheck'
> 405 | typecheck(typeof(virtio_le_to_cpu(virtio_cread_v)), *(ptr)); \
> | ^~~~~~~~~
> drivers/virtio/virtio_input.c:253:3: note: in expansion of macro 'virtio_cread_le'
> 253 | virtio_cread_le(vi->vdev, struct virtio_input_config,
> | ^~~~~~~~~~~~~~~
>
> vim +12 include/linux/typecheck.h
>
> e0deaff470900a4 Andrew Morton 2008-07-25 4
> e0deaff470900a4 Andrew Morton 2008-07-25 5 /*
> e0deaff470900a4 Andrew Morton 2008-07-25 6 * Check at compile time that something is of a particular type.
> e0deaff470900a4 Andrew Morton 2008-07-25 7 * Always evaluates to 1 so you may use it easily in comparisons.
> e0deaff470900a4 Andrew Morton 2008-07-25 8 */
> e0deaff470900a4 Andrew Morton 2008-07-25 9 #define typecheck(type,x) \
> e0deaff470900a4 Andrew Morton 2008-07-25 10 ({ type __dummy; \
> e0deaff470900a4 Andrew Morton 2008-07-25 11 typeof(x) __dummy2; \
> e0deaff470900a4 Andrew Morton 2008-07-25 @12 (void)(&__dummy == &__dummy2); \
> e0deaff470900a4 Andrew Morton 2008-07-25 13 1; \
> e0deaff470900a4 Andrew Morton 2008-07-25 14 })
> e0deaff470900a4 Andrew Morton 2008-07-25 15
>
> :::::: The code at line 12 was first introduced by commit
> :::::: e0deaff470900a4c3222ca7139f6c9639e26a2f5 split the typecheck macros out of include/linux/kernel.h
>
> :::::: TO: Andrew Morton <akpm@...ux-foundation.org>
> :::::: CC: Linus Torvalds <torvalds@...ux-foundation.org>
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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