Re: drivers/infiniband/hw/qib/qib_sysfs.c:413:1: error: static_assert expression is not an integral constant expression

[Jason Gunthorpe <jgg@nvidia.com>]

On Sat, Sep 11, 2021 at 08:17:08PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   926de8c4326c14fcf35f1de142019043597a4fac
> commit: 84f969e1c48ed3825986e91a0786e363d57f69d1 IB/qib: Fix null pointer subtraction compiler warning
> date:   3 days ago
> config: x86_64-randconfig-a014-20210911 (attached as .config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 261cbe98c38f8c1ee1a482fe76511110e790f58a)
> 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
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=84f969e1c48ed3825986e91a0786e363d57f69d1
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout 84f969e1c48ed3825986e91a0786e363d57f69d1
>         # save the attached .config to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross O=build_dir ARCH=x86_64 SHELL=/bin/bash
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
> >> drivers/infiniband/hw/qib/qib_sysfs.c:413:1: error: static_assert expression is not an integral constant expression
>    QIB_DIAGC_ATTR(rc_resends);
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~
>    drivers/infiniband/hw/qib/qib_sysfs.c:406:16: note: expanded from macro 'QIB_DIAGC_ATTR'
>            static_assert(&((struct qib_ibport *)0)->rvp.n_##N != (u64 *)NULL);    \
>            ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    include/linux/build_bug.h:77:50: note: expanded from macro 'static_assert'
>    #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
>                                     ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
>    include/linux/build_bug.h:78:56: note: expanded from macro '__static_assert'
>    #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
>                                                           ^~~~
>    drivers/infiniband/hw/qib/qib_sysfs.c:413:1: note: cannot access field of null pointer
>    drivers/infiniband/hw/qib/qib_sysfs.c:406:43: note: expanded from macro 'QIB_DIAGC_ATTR'
>            static_assert(&((struct qib_ibport *)0)->rvp.n_##N != (u64 *)NULL);    \
>                                                     ^
>    drivers/infiniband/hw/qib/qib_sysfs.c:414:1: error: static_assert expression is not an integral constant expression
>    QIB_DIAGC_ATTR(seq_naks);
>    ^~~~~~~~~~~~~~~~~~~~~~~~

Nick/Nathan

Clang is being a real PITA here - do you know of a solution?

This macro would like to know that the passed in member name has a u64
type, all the things I've come up with fail on clang - but many work
fine on gcc. Frankly I think this case is a clang bug myself..

Thanks,
Jason