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* c++/8209: Failure to detect negative bit-field size (!)
@ 2002-10-13 2:06 wwieser
0 siblings, 0 replies; 3+ messages in thread
From: wwieser @ 2002-10-13 2:06 UTC (permalink / raw)
To: gcc-gnats
>Number: 8209
>Category: c++
>Synopsis: Failure to detect negative bit-field size (!)
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: accepts-illegal
>Submitter-Id: net
>Arrival-Date: Sun Oct 13 02:06:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: wwieser@gmx.de
>Release: 3.2.1 20021007 (prerelease) and many more
>Organization:
>Environment:
linux-elf
>Description:
The bug was verified to be still present in yesterday's
CVS (Oct 12):
If you compile the following code:
struct A
{
int : (-1);
};
you get the (correct) _error_
negative width in bit-field `A::<anonymous>'
Now, if you compile
struct A
{
int : (sizeof(int)-5);
};
then you just get the _warning_
warning: width of `A::<anonymous>' exceeds its type
which is incorrect.
As a result, sizeof(A) turns out to be 536870912
(500Mb).
>How-To-Repeat:
Just compile the four-liner above.
>Fix:
Should be fairly trivial, but I don't know.
>Release-Note:
>Audit-Trail:
>Unformatted:
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: c++/8209: Failure to detect negative bit-field size (!)
@ 2002-10-13 2:57 nathan
0 siblings, 0 replies; 3+ messages in thread
From: nathan @ 2002-10-13 2:57 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, nobody, wwieser
Synopsis: Failure to detect negative bit-field size (!)
State-Changed-From-To: open->closed
State-Changed-By: nathan
State-Changed-When: Sun Oct 13 02:57:42 2002
State-Changed-Why:
not a bug. sizeof (int) -5 has unsigned type.
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8209
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: c++/8209: Failure to detect negative bit-field size (!)
@ 2002-10-13 8:26 Tim Prince
0 siblings, 0 replies; 3+ messages in thread
From: Tim Prince @ 2002-10-13 8:26 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR c++/8209; it has been noted by GNATS.
From: Tim Prince <tprince@computer.org>
To: wwieser@gmx.de, gcc-gnats@gcc.gnu.org
Cc:
Subject: Re: c++/8209: Failure to detect negative bit-field size (!)
Date: Sun, 13 Oct 2002 08:18:24 -0700
On Sunday 13 October 2002 02:01, wwieser@gmx.de wrote:
> If you compile the following code:
> struct A
> {
> int : (-1);
> };
> you get the (correct) _error_
> negative width in bit-field `A::<anonymous>'
>
> Now, if you compile
> struct A
> {
> int : (sizeof(int)-5);
> };
> then you just get the _warning_
> warning: width of `A::<anonymous>' exceeds its type
> which is incorrect.
>
> As a result, sizeof(A) turns out to be 536870912
> (500Mb).
>
>
It looks like your headers might make size_t an unsigned type, but you
haven't showed that. Here's what my gcc installation has to say in <gc.h>:
/* The ANSI standard suggests that size_t and ptr_diff_t might be */
/* better choices. But those appear to have incorrect definitions */
/* on may systems. Notably "typedef int size_t" seems to be both */
/* frequent and WRONG. */
Maybe the author's failure to check spelling reduces his/her credibility, but
you can see there is a documented opinion on this subject.
As I read the info page, if you wanted warnings from -Wconversion, should
size_t be defined in accordance with the above prejudices, you should get
them with
sizeof(int) +(-5).
--
Tim Prince
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2002-10-13 15:26 UTC | newest]
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2002-10-13 2:06 c++/8209: Failure to detect negative bit-field size (!) wwieser
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