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From: prj@po.cwru.edu (Paul Jarc)
Cc: guile-devel@gnu.org, Marius Vollmer <mvo@zagadka.de>
Subject: Re: The relationship between SCM and scm_t_bits.
Date: Fri, 21 May 2004 16:30:01 -0400	[thread overview]
Message-ID: <m34qq9frq8.fsf@multivac.cwru.edu> (raw)
In-Reply-To: <40AE5A80.9050809@dirk-herrmanns-seiten.de> (Dirk Herrmann's message of "Fri, 21 May 2004 21:37:36 +0200")

Dirk Herrmann <dirk@dirk-herrmanns-seiten.de> wrote:
> As long as it is just a cell, we check the bits. Only if we know its
> a pair, we dare to access it as a pair of SCM values.

But according to the C standard, we shouldn't dare to access it as
scm_t_bits either.  unsigned char is the only universally safe
aliasing access type.

If it wouldn't be too much trouble to access the type bits through
unsigned char, then we could store SCM values on the heap and work
with pointers to SCM (even if only for reading, not writing).  We
would use the type bits to decide whether to access a given word/cell
as SCM or scm_t_bits.  (It'd be nice for smobs if void* could be
another option there.)  That would conform to the C standard.


paul


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  reply	other threads:[~2004-05-21 20:30 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-05-03 15:06 The relationship between SCM and scm_t_bits Marius Vollmer
2004-05-03 16:10 ` Marius Vollmer
2004-05-03 16:21 ` Paul Jarc
2004-05-04 13:53 ` Marius Vollmer
2004-05-04 17:16   ` Paul Jarc
2004-05-04 17:49     ` Marius Vollmer
2004-05-04 18:35       ` Paul Jarc
2004-05-05 10:00         ` Marius Vollmer
2004-05-05 14:58           ` Paul Jarc
2004-05-10 13:42 ` Marius Vollmer
2004-05-15  7:31 ` Dirk Herrmann
2004-05-17 18:09   ` Marius Vollmer
2004-05-15 15:00 ` Dirk Herrmann
2004-05-15 16:42   ` Dirk Herrmann
2004-05-17 19:22   ` Marius Vollmer
2004-05-17 20:17     ` Paul Jarc
2004-05-21 19:37     ` Dirk Herrmann
2004-05-21 20:30       ` Paul Jarc [this message]
2004-05-22  6:48         ` Dirk Herrmann
2004-05-23 15:03           ` Paul Jarc
2004-08-09 21:09           ` Marius Vollmer
2004-08-20 19:17             ` Dirk Herrmann
2004-08-21 16:16               ` Marius Vollmer
2004-10-03  9:09                 ` Dirk Herrmann
2004-10-04 14:12                   ` Marius Vollmer

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