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* [Bug c/19138] New: double complex / inf gives nan instead of 0
@ 2004-12-23 14:35 dmitri at unm dot edu
2004-12-23 14:41 ` [Bug middle-end/19138] " pinskia at gcc dot gnu dot org
` (9 more replies)
0 siblings, 10 replies; 11+ messages in thread
From: dmitri at unm dot edu @ 2004-12-23 14:35 UTC (permalink / raw)
To: gcc-bugs
The following program gives "nan nan" output instead of expected "0 0"
#include <stdio.h>
_Complex double a, r;
double b = 1.0 / 0.0;
int
main (void)
{
__real__ a = 1.0;
__imag__ a = -1.0;
r = a / b;
printf ("%f %f\n", __real__ r, __imag__ r);
return 0;
}
As alois.schloegl@tugraz.at pointed out
<<<<
Prof. W .Kahan mentions in his "Lecture Notes on the Status of IEEE
754" p.10
http://www.cs.berkeley.edu/~wkahan/ieee754status/IEEE754.PDF
"when (0+3i)/inf is turned naively into (0+3i)*(inf-i)/(inf^2+0^2) it
generates
a NaN instead of the expected 0."
>>>>
This may be of some relevance here.
--
Summary: double complex / inf gives nan instead of 0
Product: gcc
Version: 3.2.2
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: dmitri at unm dot edu
CC: gcc-bugs at gcc dot gnu dot org,jakub at redhat dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
@ 2004-12-23 14:41 ` pinskia at gcc dot gnu dot org
2004-12-23 14:43 ` dmitri at unm dot edu
` (8 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-12-23 14:41 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-12-23 14:41 -------
I don't see anything wrong with this.
--
What |Removed |Added
----------------------------------------------------------------------------
Component|c |middle-end
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
2004-12-23 14:41 ` [Bug middle-end/19138] " pinskia at gcc dot gnu dot org
@ 2004-12-23 14:43 ` dmitri at unm dot edu
2004-12-23 15:18 ` dmitri at unm dot edu
` (7 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: dmitri at unm dot edu @ 2004-12-23 14:43 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From dmitri at unm dot edu 2004-12-23 14:43 -------
I do not understand. "nan" is not "0". That seems to be the problem.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
2004-12-23 14:41 ` [Bug middle-end/19138] " pinskia at gcc dot gnu dot org
2004-12-23 14:43 ` dmitri at unm dot edu
@ 2004-12-23 15:18 ` dmitri at unm dot edu
2004-12-23 15:50 ` joseph at codesourcery dot com
` (6 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: dmitri at unm dot edu @ 2004-12-23 15:18 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From dmitri at unm dot edu 2004-12-23 15:18 -------
I noticed that my attempt to do multiple selection of gcc version did not quite
work. I see this bug with gcc 3.2.2, 3.3.3 and as late as 3.4.3 20041212 (Red
Hat 3.4.3-10).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
` (2 preceding siblings ...)
2004-12-23 15:18 ` dmitri at unm dot edu
@ 2004-12-23 15:50 ` joseph at codesourcery dot com
2004-12-23 17:14 ` bangerth at dealii dot org
` (5 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: joseph at codesourcery dot com @ 2004-12-23 15:50 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From joseph at codesourcery dot com 2004-12-23 15:50 -------
Subject: Re: New: double complex / inf gives nan instead of 0
On Thu, 23 Dec 2004, dmitri at unm dot edu wrote:
> The following program gives "nan nan" output instead of expected "0 0"
It would have been helpful to point to C99 G.5.1 paragraph 4 third bullet
point as the source of your expectation. We don't yet implement the C99
requirements for complex numbers (either the normative ones, or the
non-normative ones in Annex G), though it would be useful to do so.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
` (3 preceding siblings ...)
2004-12-23 15:50 ` joseph at codesourcery dot com
@ 2004-12-23 17:14 ` bangerth at dealii dot org
2004-12-23 19:20 ` pcarlini at suse dot de
` (4 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: bangerth at dealii dot org @ 2004-12-23 17:14 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From bangerth at dealii dot org 2004-12-23 17:14 -------
Joseph's comment points to the exact right place. The result should be zero.
Confirmed with gcc 3.3 and mainline.
W.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Known to fail| |3.3.1 4.0.0
Last reconfirmed|0000-00-00 00:00:00 |2004-12-23 17:14:40
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
` (4 preceding siblings ...)
2004-12-23 17:14 ` bangerth at dealii dot org
@ 2004-12-23 19:20 ` pcarlini at suse dot de
2004-12-23 23:06 ` bangerth at dealii dot org
` (3 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: pcarlini at suse dot de @ 2004-12-23 19:20 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pcarlini at suse dot de 2004-12-23 19:20 -------
I'm tempted to mark this as duplicate of middle-end/18902, which I will try to
(partially) fix after 4.0 branches. Ok with everyone?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
` (5 preceding siblings ...)
2004-12-23 19:20 ` pcarlini at suse dot de
@ 2004-12-23 23:06 ` bangerth at dealii dot org
2004-12-23 23:17 ` pcarlini at suse dot de
` (2 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: bangerth at dealii dot org @ 2004-12-23 23:06 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From bangerth at dealii dot org 2004-12-23 23:06 -------
This PR only covers a special case of the other PR, so I would be tempted
to keep both open and if the other one is fixed checked whether this also
covers the special case discussed here. I'm not sure whether this special
case here immediately follows from fixing PR 18902.
W.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
` (6 preceding siblings ...)
2004-12-23 23:06 ` bangerth at dealii dot org
@ 2004-12-23 23:17 ` pcarlini at suse dot de
2004-12-23 23:19 ` bangerth at dealii dot org
2004-12-23 23:22 ` pcarlini at suse dot de
9 siblings, 0 replies; 11+ messages in thread
From: pcarlini at suse dot de @ 2004-12-23 23:17 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pcarlini at suse dot de 2004-12-23 23:17 -------
> I'm not sure whether this special
> case here immediately follows from fixing PR 18902.
It does, indeed, this one is a *really* a special case: have a look to the test
case that I have attached to 18902 (and verified fixed by a preliminary patch ;)
But, if we want to keep both open, it's ok with me!
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
` (7 preceding siblings ...)
2004-12-23 23:17 ` pcarlini at suse dot de
@ 2004-12-23 23:19 ` bangerth at dealii dot org
2004-12-23 23:22 ` pcarlini at suse dot de
9 siblings, 0 replies; 11+ messages in thread
From: bangerth at dealii dot org @ 2004-12-23 23:19 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From bangerth at dealii dot org 2004-12-23 23:19 -------
I'll be happy to defer to your superior technical knowledge :-)
W.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/19138] double complex / inf gives nan instead of 0
2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
` (8 preceding siblings ...)
2004-12-23 23:19 ` bangerth at dealii dot org
@ 2004-12-23 23:22 ` pcarlini at suse dot de
9 siblings, 0 replies; 11+ messages in thread
From: pcarlini at suse dot de @ 2004-12-23 23:22 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pcarlini at suse dot de 2004-12-23 23:22 -------
Ok ;) Then, let's close this one.
*** This bug has been marked as a duplicate of 18902 ***
--
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |DUPLICATE
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19138
^ permalink raw reply [flat|nested] 11+ messages in thread
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2004-12-23 14:35 [Bug c/19138] New: double complex / inf gives nan instead of 0 dmitri at unm dot edu
2004-12-23 14:41 ` [Bug middle-end/19138] " pinskia at gcc dot gnu dot org
2004-12-23 14:43 ` dmitri at unm dot edu
2004-12-23 15:18 ` dmitri at unm dot edu
2004-12-23 15:50 ` joseph at codesourcery dot com
2004-12-23 17:14 ` bangerth at dealii dot org
2004-12-23 19:20 ` pcarlini at suse dot de
2004-12-23 23:06 ` bangerth at dealii dot org
2004-12-23 23:17 ` pcarlini at suse dot de
2004-12-23 23:19 ` bangerth at dealii dot org
2004-12-23 23:22 ` pcarlini at suse dot de
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