[Python-Dev] PEP 7: Adding anonymous union / struct

Inada Naoki songofacandy at gmail.com
Wed Apr 17 07:47:29 EDT 2019

On Wed, Apr 17, 2019 at 8:27 PM Victor Stinner <vstinner at redhat.com> wrote:
> AIX is somehow supported and uses xlc compiler: does xlc support this
> C11 feature?

I find Language Reference for v11.1 (2010/4/13)

I find "anonymous union" in p73.

I can not find language reference for versions older than v11.1.
And I can not find "anonymous struct" in v11.1 too.

Maybe, we should consider only anonymous union?

> Do you want to use it in Python 3.8 and newer only?


In case of bpo-27987, Python 3.6 and 3.7 uses named union
for PyGC_Head.  So changing dummy from "double" to "long double"
is enough.

In case of Python 3.8, I removed dummy from PyGC_Head and
stop using named union because it is (implicitly) aligned by two
words (16byte on 64bit, 8byte on 32bit platform) already.

But we can align it more explicitly by using anonymous union,
without adding many `.gc.` again.


Inada Naoki  <songofacandy at gmail.com>

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