From: Segher Boessenkool <segher@koffie.nl>
To: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>
Cc: gcc@gcc.gnu.org
Subject: Re: long long bit-fields
Date: Mon, 31 Mar 2003 08:46:00 -0000 [thread overview]
Message-ID: <3E87B155.3020408@koffie.nl> (raw)
In-Reply-To: <87of3taur5.fsf@student.uni-tuebingen.de>
Falk Hueffner wrote:
> Hi,
>
> PR c/6346, middle-end/7018 and target/9620 deal with long long
> bit-fields. I guess part of the confusion comes from the fact that the
> C standard doesn't specify how they should behave (at least I couldn't
> find it). So what is the following program supposed to print?
>
> #include <stdio.h>
>
> int
> main(int argc, char *argv[]){
> struct {
> unsigned long long ull31a: 31;
> unsigned long long ull31b: 31;
> } x;
> x.ull31a = -1;
> x.ull31b = 1;
>
> printf("%016llx %016llx %016llx\n",
> (x.ull31a << 48) >> 48,
> (x.ull31a << 16),
> (x.ull31b << 48));
> }
>
> Candidates are:
>
> ffffffffffffffff ffffffffffff0000 0000000000010000 (gcc)
Correct (the integer promotions promote an unsigned integer
bit-field to a signed integer, if it fits).
> ffffffffffffffff 00007fffffff0000 0001000000000000 (Compaq C)
Not correct.
> 000000000000ffff 00007fffffff0000 0001000000000000 (g++)
> 0000000000000000 ffffffffffff0000 0000000000000000 (Compaq C++)
Don't know about C++, sorry.
Segher
next prev parent reply other threads:[~2003-03-31 5:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-30 19:14 Falk Hueffner
2003-03-31 8:46 ` Segher Boessenkool [this message]
2003-03-31 9:22 ` Falk Hueffner
2003-04-01 0:11 ` Segher Boessenkool
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=3E87B155.3020408@koffie.nl \
--to=segher@koffie.nl \
--cc=falk.hueffner@student.uni-tuebingen.de \
--cc=gcc@gcc.gnu.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;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).