From: Robert Lipe <robertlipe@usa.net>
To: greened@eecs.umich.edu, egcs@egcs.cygnus.com
Subject: Re: egcs and bitfields
Date: Wed, 31 Mar 1999 23:46:00 -0000 [thread overview]
Message-ID: <19990311174029.T1570@rjlhome.sco.com> (raw)
Message-ID: <19990331234600.kYSdwpS-26VXVzMCs9ZztqLkfuDHk-Co8BknmmN2LWI@z> (raw)
In-Reply-To: <199903112300.AAA19947@mira.isdn.cs.tu-berlin.de>
> struct baz { unsigned int a:2, b:4, c:32;} y;
>
> void foo()
> {
> y.c = 0x56789;
> }
>
> int main()
> {
> unsigned int *b;
> bzero(&y,sizeof(y));
> foo();
> b=&y;
> printf("%x %x\n",b[0],b[1]);
> }
>
> Is this the case you are talking about? Now, you claim that the SysV
> ABI requires y.c to be at offset 4, right? (this is a claim I can't
> verify since I don't have that specification)
"System V ABI" is too vague for purposes of this discussion. Do you
refer to the iBCS2 spec or the SVR4 ABI? I don't know that they differ
in this regard, but it isn't an unreasonable question before tearing
into large books.
> Anyway, when I run the program on i586-pc-linux-gnu, with
> egcs-2.93.11, I get as output
>
> 0 56789
>
> From your explanation, I understand that this result is
> ABI-compliant. So where is the problem?
I fed this example into the following compilers on a system V/386 host:
SCO OpenServer /bin/cc
UDK cc (essentially the SVR4 ABI)
EGCS 1.1.1
Intel's optimizing compiler
It produced identical output on all of them.
I think (but am no authority) that Linux uses substantially the SVR4 ABI
but it does have some deviations.
RJL
next prev parent reply other threads:[~1999-03-31 23:46 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-03-11 14:33 David A. Greene
[not found] ` < 36E844B2.8DAEFAAF@eecs.umich.edu >
1999-03-11 15:14 ` Martin v. Loewis
[not found] ` < 199903112300.AAA19947@mira.isdn.cs.tu-berlin.de >
1999-03-11 15:41 ` Robert Lipe [this message]
1999-03-31 23:46 ` Robert Lipe
1999-03-12 7:16 ` David A. Greene
[not found] ` < 36E92F61.5951621@eecs.umich.edu >
1999-03-12 8:48 ` Robert Lipe
[not found] ` < 19990312104540.D1570@rjlhome.sco.com >
1999-03-12 9:41 ` Doug Semler
[not found] ` < 199903121741.JAA24401@vortex.seaspace.com >
1999-03-12 9:59 ` Robert Lipe
1999-03-31 23:46 ` Robert Lipe
1999-03-12 13:26 ` Martin v. Loewis
[not found] ` < 199903122118.WAA00520@mira.isdn.cs.tu-berlin.de >
1999-03-12 13:52 ` Doug Semler
1999-03-31 23:46 ` Doug Semler
1999-03-31 23:46 ` Martin v. Loewis
1999-03-31 23:46 ` Doug Semler
1999-03-31 23:46 ` Robert Lipe
1999-03-12 9:27 ` Martin v. Loewis
1999-03-12 10:47 ` David A. Greene
1999-03-31 23:46 ` David A. Greene
1999-03-31 23:46 ` Martin v. Loewis
1999-03-31 23:46 ` David A. Greene
1999-03-31 23:46 ` Martin v. Loewis
1999-03-31 23:46 ` David A. Greene
1999-03-12 7:20 David A. Greene
1999-03-31 23:46 ` David A. Greene
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