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* [Xen-devel] [PATCH] x86/tss: Fix clang build following c/s 7888440625
@ 2019-08-13 12:01 Andrew Cooper
  2019-08-14 10:37 ` Wei Liu
  0 siblings, 1 reply; 2+ messages in thread
From: Andrew Cooper @ 2019-08-13 12:01 UTC (permalink / raw)
  To: Xen-devel; +Cc: Andrew Cooper, Wei Liu, Jan Beulich, Roger Pau Monné

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@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/smpboot.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 5057109a77..85c81c247e 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -826,9 +826,11 @@ static int setup_cpu_root_pgt(unsigned int cpu)
         rc = clone_mapping(idt_tables[cpu], rpt);
     if ( !rc )
     {
-        BUILD_BUG_ON(sizeof(this_cpu(tss_page)) != PAGE_SIZE);
+        struct tss_page *this_tss = &per_cpu(tss_page, cpu);
 
-        rc = clone_mapping(&per_cpu(tss_page, cpu).tss, rpt);
+        BUILD_BUG_ON(sizeof(*this_tss) != PAGE_SIZE);
+
+        rc = clone_mapping(&this_tss->tss, rpt);
     }
     if ( !rc )
         rc = clone_mapping((void *)per_cpu(stubs.addr, cpu), rpt);
-- 
2.11.0


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^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [Xen-devel] [PATCH] x86/tss: Fix clang build following c/s 7888440625
  2019-08-13 12:01 [Xen-devel] [PATCH] x86/tss: Fix clang build following c/s 7888440625 Andrew Cooper
@ 2019-08-14 10:37 ` Wei Liu
  0 siblings, 0 replies; 2+ messages in thread
From: Wei Liu @ 2019-08-14 10:37 UTC (permalink / raw)
  To: Andrew Cooper; +Cc: Xen-devel, Wei Liu, Jan Beulich, Roger Pau Monné

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@citrix.com>

Reviewed-by: Wei Liu <wl@xen.org>

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Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

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2019-08-14 10:37 ` Wei Liu

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