lkml.org 
[lkml]   [2002]   [Sep]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] warnkill trivia 2/2
>    From: Tomas Szepe <szepe@pinerecords.com>
> Date: Sun, 1 Sep 2002 14:10:53 +0200
>
> > Let's keep the sparc atomic_read() how it is so more bugs
> > like this can be found.
>
> I don't know, though... scratching my head here -- Is GCC actually
> able to distinguish between 'const int *a' and 'int const *a'?
>
> No I don't mean this in a "C" sense, I mean conceptually that marking
> an object const which has members which are volatile and updated
> asynchronously makes zero sense.

True.

I've been playing a bit with how gcc handles the const qualifiers
and made an interesting discovery:

Trying to compile

typedef int *p_int;
void a(const p_int t) { *t = 0; }
void b(const p_int t) { t = (int *) 0; }
void c(const int *t) { *t = 0; }
void d(const int *t) { t = (int *) 0; }
void e(int const *t) { *t = 0; }
void f(int const *t) { t = (int *) 0; }

will give 'assignment of read-only location' warnings for
b(), c() and e(), i.e. it's impossible to have a constant
pointer to a non-constant value w/o using a qualified
typedef.

W/o a typedef, gcc seems unable to tell the difference
between 'const int *' and 'int const *' altogether. In case
one needs a constant pointer to a constant value, something
like this should do:

typedef const int *p_int;
void f(const p_int a);

Usable? I don't quite think so.

T.
-
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 13:22    [W:0.055 / U:11.788 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site