Re: [Xen-devel] [PATCH] x86/tss: Fix clang build following c/s 7888440625

[Wei Liu <wl@xxxxxxx>]

On Tue, Aug 13, 2019 at 01:01:17PM +0100, Andrew Cooper wrote:
> Clang-3.5 from Debian Jessie fails with:
> 
>   smpboot.c:829:29: error: statement expression not allowed at file scope
>           BUILD_BUG_ON(sizeof(this_cpu(tss_page)) != PAGE_SIZE);
>                               ^
>   /local/xen.git/xen/include/asm/percpu.h:14:7: note: expanded from macro
>           'this_cpu'
>       (*RELOC_HIDE(&per_cpu__##var, get_cpu_info()->per_cpu_offset))
>         ^
>   /local/xen.git/xen/include/xen/compiler.h:98:3: note: expanded from macro
>           'RELOC_HIDE'
>     ({ unsigned long __ptr;                       \
>     ^
>   /local/xen.git/xen/include/xen/lib.h:26:53: note: expanded from macro
>           'BUILD_BUG_ON'
>   #define BUILD_BUG_ON(cond) ((void)BUILD_BUG_ON_ZERO(cond))
>                                                       ^
>   /local/xen.git/xen/include/xen/lib.h:25:57: note: expanded from macro
>           'BUILD_BUG_ON_ZERO'
>   #define BUILD_BUG_ON_ZERO(cond) sizeof(struct { int:-!!(cond); })
>                                                           ^
>   1 error generated.
>   /local/xen.git/xen/Rules.mk:202: recipe for target 'smpboot.o' failed
> 
> This is obviously a compiler bug because the BUILD_BUG_ON() is not at file
> scope.  However, it can be worked around by using a local variable.
> 
> Spotted by Gitlab CI.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Wei Liu <wl@xxxxxxx>

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