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* [Bug libc/10355] New: cabs(z) == nan if z = inf + j * nan
@ 2009-07-01 9:55 cournape at gmail dot com
2009-10-30 6:29 ` [Bug libc/10355] " drepper at redhat dot com
0 siblings, 1 reply; 3+ messages in thread
From: cournape at gmail dot com @ 2009-07-01 9:55 UTC (permalink / raw)
To: glibc-bugs
Hi,
I came across the following when using cabs and the glibc:
#define _ISOC99_SOURCE
#include <complex.h>
#include <stdio.h>
#include <math.h>
int main(void)
{
complex z;
double x, y;
x = INFINITY;
y = NAN;
z = x + I * y;
printf("%f\n", cabs(z));
printf("%f\n", hypot(x, y));
return 0;
}
This prints:
nan
inf
I believe that cabs behavior is incorrect in this case if I read the C99
standard correctly (Section G 6.6 from the committee draft of september 2007):
"
Each of the functions cabs and carg is specified by a formula in terms of a real
function (whose special cases are covered in annex F):
cabs(x + iy) = hypot(x, y)
carg(x + iy) = atan2(y, x)
"
glibc version: 2.8
gcc version: 4.3.2
--
Summary: cabs(z) == nan if z = inf + j * nan
Product: glibc
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: libc
AssignedTo: drepper at redhat dot com
ReportedBy: cournape at gmail dot com
CC: glibc-bugs at sources dot redhat dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=10355
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* [Bug libc/10355] cabs(z) == nan if z = inf + j * nan
2009-07-01 9:55 [Bug libc/10355] New: cabs(z) == nan if z = inf + j * nan cournape at gmail dot com
@ 2009-10-30 6:29 ` drepper at redhat dot com
0 siblings, 0 replies; 3+ messages in thread
From: drepper at redhat dot com @ 2009-10-30 6:29 UTC (permalink / raw)
To: glibc-bugs
------- Additional Comments From drepper at redhat dot com 2009-10-30 06:29 -------
Have you even looked at the variable z? It's value is (NaN,Nan), not (Inf,NaN).
If you'd use correct code to initialize the variable it would work as expected.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |INVALID
http://sourceware.org/bugzilla/show_bug.cgi?id=10355
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* [Bug libc/10355] cabs(z) == nan if z = inf + j * nan
[not found] <bug-10355-131@http.sourceware.org/bugzilla/>
@ 2014-07-01 7:53 ` fweimer at redhat dot com
0 siblings, 0 replies; 3+ messages in thread
From: fweimer at redhat dot com @ 2014-07-01 7:53 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10355
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Flags| |security-
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-- links below jump to the message on this page --
2009-07-01 9:55 [Bug libc/10355] New: cabs(z) == nan if z = inf + j * nan cournape at gmail dot com
2009-10-30 6:29 ` [Bug libc/10355] " drepper at redhat dot com
[not found] <bug-10355-131@http.sourceware.org/bugzilla/>
2014-07-01 7:53 ` fweimer at redhat dot com
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