Re: [hurd, commited 2/2] x86 tls: Use _Static_assert for TLS access size assertion

[Florian Weimer]

* Samuel Thibault:

> Florian Weimer, le lun. 17 févr. 2020 10:41:49 +0100, a ecrit:
>> > ---
>> >  sysdeps/i386/nptl/tls.h      | 46 ++++++++++++++++--------------------
>> >  sysdeps/mach/hurd/i386/tls.h | 46 ++++++++++++++++--------------------
>> >  sysdeps/x86_64/nptl/tls.h    | 46 ++++++++++++++++--------------------
>> >  3 files changed, 60 insertions(+), 78 deletions(-)
>> >
>> > diff --git a/sysdeps/i386/nptl/tls.h b/sysdeps/i386/nptl/tls.h
>> > index ffead90857..28053a77f3 100644
>> > --- a/sysdeps/i386/nptl/tls.h
>> > +++ b/sysdeps/i386/nptl/tls.h
>> > @@ -255,6 +255,9 @@ tls_fill_user_desc (union user_desc_init *desc,
>> >  /* Read member of the thread descriptor directly.  */
>> >  # define THREAD_GETMEM(descr, member) \
>> >    ({ __typeof (descr->member) __value;                                    
>> >       \
>> > +     _Static_assert (sizeof (__value) == 1                                
>> >       \
>> > +            || sizeof (__value) == 4                                    \
>> > +            || sizeof (__value) == 8);                                  \
>> >       if (sizeof (__value) == 1)                                           
>> >       \
>> 
>> This (and the other changes) broke the x86_64-linux-gnu build.
>
> Uh?
>
> It built successfully on my box, I wonder what difference we have.

I think single-argument _Static_assert is only available with GCC 9
and later.