[PATCH] ucontext.h: Add __INDIRECT_RETURN

[Florian Weimer]

* H. J. Lu:

> +#ifndef __INDIRECT_RETURN
> +# if defined __CET__ && (__CET__ & 2) != 0
> +/* Note: Functions returned via indirect branch returns once.  Without

The grammar seems to be a bit off here.

> +   indirect_return attribute in GCC 9, use returns_twice attribute.  */
> +#  if __GNUC_PREREQ (9, 0)
> +#   define __INDIRECT_RETURN __attribute__ ((__indirect_return__))
> +#  else
> +#   define __INDIRECT_RETURN __attribute__ ((__returns_twice__))
> +#  endif
> +# endif
> +#endif

Do you expect distributions to backport support for the
indirect_return attribute into GCC 8?  Then this will not work.