[PATCH v3 14/19] x86: Fix THREAD_GSCOPE_RESET_FLAG build on clang

[Uros Bizjak]

On 10/31/25 21:00, Adhemerval Zanella wrote:
> clang does not support __seg_fs in asm constraint.
> ---
>   sysdeps/x86_64/nptl/tls.h | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
> index abfeb880545..9d53f05e65c 100644
> --- a/sysdeps/x86_64/nptl/tls.h
> +++ b/sysdeps/x86_64/nptl/tls.h
> @@ -198,10 +198,18 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
>   # define THREAD_GSCOPE_FLAG_UNUSED 0
>   # define THREAD_GSCOPE_FLAG_USED   1
>   # define THREAD_GSCOPE_FLAG_WAIT   2
> +
> +/* clang does not support __seg_fs in asm constraint.  */
> +# ifdef __clang__
> +#  define FS_ASM "%%fs:"
> +# else
> +#  define FS_ASM
> +# endif
> +
>   # define THREAD_GSCOPE_RESET_FLAG() \
>     do									      \
>       { int __res;							      \
> -      asm volatile ("xchgl %1, %0"					      \
> +      asm volatile ("xchgl " FS_ASM "%1, %0"				      \
>   		    : "=r" (__res)					      \
>   		    : "m" (((struct pthread __seg_fs *)0)->header.gscope_flag), \
>   		      "0" (THREAD_GSCOPE_FLAG_UNUSED));			      \

LGTM.

Reviewed-by: Uros Bizjak <ubizjak@gmail.com>

Uros.