--- Comment #12 from runipg at broadcom dot com 2010-09-03 21:12 ---
Subject: Re: Bug with anonymous unions and bit-fields
Okay, I guess I was confused by "struct or union" semantics. Thanks!
jakub at gcc dot gnu dot org wrote:
> --- Comment #11 from jakub at gcc dot gnu dot org
--- Comment #11 from jakub at gcc dot gnu dot org 2010-09-03 20:53 ---
I don't see anything confusing about it. If you have:
union { int a, b, c; } u;
u.a overlaps u.b and u.c as well, and the same applies to bitfields. union
isn't struct, see ISO C99 6.7.2.1/5. The standard is clear
--- Comment #10 from runipg at broadcom dot com 2010-09-03 19:19 ---
Subject: Re: Bug with anonymous unions and bit-fields
Your suggestion works:
struct bfc {
union {
struct {
unsigned int a : 1,
b : 4;
};
--- Comment #9 from runipg at broadcom dot com 2010-09-03 14:45 ---
Subject: Re: Bug with anonymous unions and bit-fields
Thank you so much. You can close this bug if you wish.
-Runip
On 03-Sep-2010, at 3:47 AM, paolo dot carlini at oracle dot com
wrote:
>
>
> --- Comment #8
--- Comment #8 from paolo dot carlini at oracle dot com 2010-09-03 10:46
---
If you look at the actual Standard, both alignment and allocation of bit-fields
are implementation defined. Thus, as far as I can see, at best we are talking
about non-portable implementation defined behavior.
--- Comment #7 from runipg at broadcom dot com 2010-09-03 03:31 ---
Subject: Re: Bug with anonymous unions and bit-fields
Wow, So there is a diff inside and outside a struct?
This is very counter-intuitive but I am to accept your explanation if that's
what the language says.
Thank
--- Comment #6 from pinskia at gcc dot gnu dot org 2010-09-03 01:13 ---
You can use a GCC extension of anonymous structs:
struct bfa {
union {
struct {
unsigned int a : 1,
b : 4;
};
unsigned int data;
};
};
To ge
--- Comment #5 from pinskia at gcc dot gnu dot org 2010-09-03 01:10 ---
union {
unsigned int a : 1,
b : 4;
unsigned int data;
};
This is an union of three elements each over lapping, that is a:1 overlaps with
b:4 and data. So this is
--- Comment #4 from paolo dot carlini at oracle dot com 2010-09-03 01:09
---
Fair enough, but first blush I also don't see any text in the C++ Standard
guaranteeing the behavior you want, wondered if you actually can get it with
other compilers, maybe as implementation defined. Somebody
--- Comment #3 from runipg at broadcom dot com 2010-09-03 01:03 ---
Subject: Re: Bug with anonymous unions and bit-fields
That was fast and interesting that two other compilers behave the same.
Unfortunately I don't have access to any other compiler. I am simply
befuddled by the beh
--- Comment #2 from paolo dot carlini at oracle dot com 2010-09-03 00:02
---
Without having seriously looked into your code, I note that two completely
different, closed source compilers (ICC and SunStudio) leads to the same
behavior as GCC at runtime. Does your code actually "work" (be
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