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* [Bug c/18666] New: Conversion of floating point into bit-fields
@ 2004-11-25 0:32 jakub at gcc dot gnu dot org
2004-11-25 0:52 ` [Bug c/18666] " joseph at codesourcery dot com
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: jakub at gcc dot gnu dot org @ 2004-11-25 0:32 UTC (permalink / raw)
To: gcc-bugs
Is
/* { dg-do run } */
/* { dg-options "-std=c99 -pedantic-errors } */
struct A { unsigned int i : 1; } a;
extern void abort (void);
int
main (void)
{
a.i = 16.0;
if (a.i != 0)
abort ();
return 0;
}
a valid test or not? This worked with 3.4.x and earlier, but doesn't any
longer. The question is mainly if the type of a.i for the 6.3.1.4/1 purposes
is unsigned int (in this case it would be well-defined, 16 is representable
in unsigned int and storing 16 into unsigned int i : 1 bitfield is defined),
or if the type is integer type with precision 1.
--
Summary: Conversion of floating point into bit-fields
Product: gcc
Version: 4.0.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jakub at gcc dot gnu dot org
CC: aoliva at redhat dot com,gcc-bugs at gcc dot gnu dot
org,joseph at codesourcery dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18666
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/18666] Conversion of floating point into bit-fields
2004-11-25 0:32 [Bug c/18666] New: Conversion of floating point into bit-fields jakub at gcc dot gnu dot org
@ 2004-11-25 0:52 ` joseph at codesourcery dot com
2004-12-02 13:41 ` [Bug c/18666] [4.0 Regression] " pinskia at gcc dot gnu dot org
2004-12-23 20:25 ` aoliva at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: joseph at codesourcery dot com @ 2004-11-25 0:52 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From joseph at codesourcery dot com 2004-11-25 00:52 -------
Subject: Re: New: Conversion of floating point into bit-fields
On Thu, 25 Nov 2004, jakub at gcc dot gnu dot org wrote:
> a valid test or not? This worked with 3.4.x and earlier, but doesn't any
> longer. The question is mainly if the type of a.i for the 6.3.1.4/1 purposes
> is unsigned int (in this case it would be well-defined, 16 is representable
> in unsigned int and storing 16 into unsigned int i : 1 bitfield is defined),
> or if the type is integer type with precision 1.
There are at least three DRs affirming that the type is unsigned:1, i.e. a
type with precision 1.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18666
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/18666] [4.0 Regression] Conversion of floating point into bit-fields
2004-11-25 0:32 [Bug c/18666] New: Conversion of floating point into bit-fields jakub at gcc dot gnu dot org
2004-11-25 0:52 ` [Bug c/18666] " joseph at codesourcery dot com
@ 2004-12-02 13:41 ` pinskia at gcc dot gnu dot org
2004-12-23 20:25 ` aoliva at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-12-02 13:41 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-12-02 13:41 -------
Reading comment #1, seems to me that the test is correct but still don't know for sure since it worked
differently on 3.4 and before, I am marking as a regression.
--
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Summary|Conversion of floating point|[4.0 Regression] Conversion
|into bit-fields |of floating point into bit-
| |fields
Target Milestone|--- |4.0.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18666
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/18666] [4.0 Regression] Conversion of floating point into bit-fields
2004-11-25 0:32 [Bug c/18666] New: Conversion of floating point into bit-fields jakub at gcc dot gnu dot org
2004-11-25 0:52 ` [Bug c/18666] " joseph at codesourcery dot com
2004-12-02 13:41 ` [Bug c/18666] [4.0 Regression] " pinskia at gcc dot gnu dot org
@ 2004-12-23 20:25 ` aoliva at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: aoliva at gcc dot gnu dot org @ 2004-12-23 20:25 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From aoliva at gcc dot gnu dot org 2004-12-23 20:25 -------
http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_120.html seems to be pretty
clear on this matter: the type of the bit-field is informally unsigned int :1,
so the conversion invokes undefined behavior per 6.3.1.4/#1.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18666
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2004-12-23 20:25 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2004-11-25 0:32 [Bug c/18666] New: Conversion of floating point into bit-fields jakub at gcc dot gnu dot org
2004-11-25 0:52 ` [Bug c/18666] " joseph at codesourcery dot com
2004-12-02 13:41 ` [Bug c/18666] [4.0 Regression] " pinskia at gcc dot gnu dot org
2004-12-23 20:25 ` aoliva at gcc dot gnu dot org
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