lkml.org 
[lkml]   [2001]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: sizeof problem in kernel modules
On Sat, 23 Jun 2001, Richard B. Johnson wrote:

> On Sun, 24 Jun 2001, Keith Owens wrote:
>
> > On Sat, 23 Jun 2001 21:56:06 -0400 (EDT),
> > "Richard B. Johnson" <root@chaos.analogic.com> wrote:
> > >FYI, structures are designed to be accessed only by their member-names.
> > >Therefore, the compiler is free to put members at any offset. In fact,
> > >members, other than the first, don't even have to be in the order
> > >written!
> >
> > Bzzt! I don't know where people get these ideas from. Extracts from
> > the C9X draft.
> >
> > A structure type describes a sequentially allocated nonempty set of
> > member objects (and, in certain circumstances, an incomplete array),
> > each of which has an optionally specified name and possibly distinct
> > type.
> >
> > When two pointers are compared ... If the objects pointed to are
> > members of the same aggregate object, pointers to structure members
> > declared later compare greater than pointers to members declared
> > earlier in the structure.
> >
> > Two objects may be adjacent in memory because they are adjacent
> > elements of a larger array or adjacent members of a structure with no
> > padding between them,
> >
> > As discussed in 6.2.5, a structure is a type consisting of a sequence
> > of members, whose storage is allocated in an ordered sequence,
> >
> > Within a structure object, the non-bit-field members and the units
> > in which bit-fields reside have addresses that increase in the order
> > in which they are declared
> >
> > C requires that members of a structure be defined in ascending address
> > order as specified by the programmer. The compiler may not reorder
> > structure fields, although bitfields are a special case.
> >
>
> Previous to the "Draft" "Proposal" of C98, there were no such
> requirements. And so-called ANSI -C specifically declined to
> define any order within structures.

Maybe Ansi didn't but K&R certainly did

Frank

>
>
> Cheers,
> Dick Johnson
>
> Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).
>
> "Memory is like gasoline. You use it up when you are running. Of
> course you get it all back when you reboot..."; Actual explanation
> obtained from the Micro$oft help desk.
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>

HI! I'm a .signature virus! cp me into your .signature file to help me spread!

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:55    [W:0.099 / U:38.000 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site