obstack.h __PTR_ALIGN vs. ubsan

[Jeff Law]

On 9/1/2021 10:03 PM, Alan Modra via Binutils wrote:
> Current ubsan complains on every use of __PTR_ALIGN (when ptrdiff_t is
> as large as a pointer), due to making calculations relative to a NULL
> pointer.  This patch avoids the problem by extracting out and
> simplifying __BPTR_ALIGN for the usual case.  I've continued to use
> ptrdiff_t here, where it might be better to throw away __BPTR_ALIGN
> entirely and just assume uintptr_t exists.
>
> OK to apply for gcc?
>
> 	* obstack.h (__PTR_ALIGN): Expand and simplify __BPTR_ALIGN
> 	rather than calculating relative to a NULL pointer.
OK
jeff