From: Joel Brobecker <brobecker@adacore.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: gdb-patches@sourceware.org
Subject: Re: [RFA/doco] Fix gdb.Field attributes documentation for enum types.
Date: Mon, 30 Dec 2013 02:57:00 -0000 [thread overview]
Message-ID: <20131230025715.GA6055@adacore.com> (raw)
In-Reply-To: <83vby92vo5.fsf@gnu.org>
> > @table @code
> > @item bitpos
> > This attribute is not available for @code{enum} or @code{static}
> > -(as in C@t{++} or Java) fields. The value is the bit position of
> > -the field.
> > +(as in C@t{++} or Java) fields. The value is the position, counting
> > +in bits, from the start of the containing type.
>
> Thanks, this is clear.
Thanks. I just pushed the commit.
> I'm curious: why are the bit units useful? Field offsets are
> generally counted in bytes, not bits.
It's normally true that fields are byte-aligned. But the containing
structures can also be packed, in which case the fields no longer
start at byte offsets. You need bit-precision to determine their
location. Some example in the GDB code bases are, I think, struct
symbol, where some of the fields are packed together to fit within
the same word, without regard to byte boundaries (avoiding unused
"holes").
--
Joel
prev parent reply other threads:[~2013-12-30 2:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-23 7:23 Joel Brobecker
2013-12-23 16:15 ` Eli Zaretskii
2013-12-28 3:30 ` Joel Brobecker
2013-12-28 9:05 ` Eli Zaretskii
2013-12-30 2:57 ` Joel Brobecker [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20131230025715.GA6055@adacore.com \
--to=brobecker@adacore.com \
--cc=eliz@gnu.org \
--cc=gdb-patches@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox