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Subject: Re: [PHP-DEV] offsetof and XtOffsetOf
From: rowan.collins@gmail.com (Rowan Collins)

Levi Morrison wrote on 05/06/2015 14:58:
> On Thu, Jun 4, 2015 at 11:58 PM, Joe Watkins <pthreads@pthreads.org> wrote:
>> Explained here: http://lxr.php.net/xref/PHP_TRUNK/main/php.h#415
>>
>>
>> On Fri, Jun 5, 2015 at 5:06 AM, Levi Morrison <levim@php.net> wrote:
>>> The macro offsetof is required by the C89 standard to be defined in
>>> stddef.h and remains in newer standards. The macro XtOffsetOf is
>>> non-standard that is as far as I can tell a part of the X Toolkit
>>> Intrinsics or Xlib.
>>>
>>> Does anyone know the reasons why we are using the non-standard macro
>>> instead of the standard one?
> Thanks, Joe. However, that code just explains why are macros are that
> way. It doesn't justify the use of XtOffsetOf over offsetof, just how
> the ifdefs were obtained.
>

If I read it right, it's just a polyfill - if offsetof is defined, 
XtOffsetOf is just made an alias of it on line 444.

Presumably, contra the standard, there are some implementations that 
don't (or didn't) define it.

Regards,
-- 
Rowan Collins
[IMSoP]