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From: Paul Eggert <eggert@cs.ucla.edu>
To: Daniel Colascione <dancol@dancol.org>
Cc: Emacs Development <Emacs-devel@gnu.org>
Subject: Re: Why named structs and unions? C11 supports anonymous structs and unions
Date: Sun, 11 Feb 2018 19:56:02 -0800	[thread overview]
Message-ID: <60430523-09f3-0873-de9f-c134967fdb50@cs.ucla.edu> (raw)
In-Reply-To: <53a9ab33-cdd5-99b3-aeef-f52776a5bf8d@dancol.org>

Daniel Colascione wrote:

> Now we get all the alignment benefits of alignas, but without the ugly "u.s." stuff.

That assumes C11, though. Currently Emacs assumes only C99. Although Emacs can 
use C11 features when 'configure' determines them to work, I don't offhand see 
how this could be done for this particular feature without contorting the C code 
even more than it's contorted now.

> Instead of XCONS(c)->car, we now write XCONS(c)->u.s.car.

Normally in C code we write XCAR (c) instead of writing either form. The u.s. 
business is intended to be used only within a small set of source-code locations 
that need to know the internal structure of Lisp objects, and most C code 
shouldn't care whether it's '->car' or '->u.s.car'. Admittedly there are more 
occurrences of '->u.s.' than we'd like.



  reply	other threads:[~2018-02-12  3:56 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-12  3:14 Why named structs and unions? C11 supports anonymous structs and unions Daniel Colascione
2018-02-12  3:56 ` Paul Eggert [this message]
2018-02-12  4:09   ` Daniel Colascione
2018-02-12  7:28     ` Paul Eggert
2018-02-12 20:22       ` Daniel Colascione
2018-02-12 20:37         ` Paul Eggert
2018-02-12 22:18     ` Richard Stallman
2018-02-12 22:18     ` Richard Stallman

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