target/4899: error in val=sin(arg) on arm-plattform

[alexander dot kuchler at pruftechnik dot com]

>Number:         4899
>Category:       target
>Synopsis:       error in val=sin(arg) on arm-plattform
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Nov 19 05:36:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Alexander Kuchler
>Release:        gcc version 2.95.2 19991030 (2.95.3 prerelease/franzo)
>Organization:
>Environment:
# GNU Make version 3.79.1, by Richard Stallman and Roland McGrath.
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# Finished Make data base on Mon Nov 19 13:06:02 2001
>Description:
Value of val=sin(arg) is jumping from 0.78.. to -0.77.. at arg=Pi/4 when running on arm-processor after crosscompiling from i386 to arm. The jump is repeating every Pi/2. The error does not happen with the same code on i386.

The error is the same with C(math.h) and C++(cmath).
>How-To-Repeat:
compile attached file with arm-linux-gcc and run it with gdb. watch "sinus" at "nLoop=51" to "nLoop=52"
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="main.cpp"
Content-Disposition: inline; filename="main.cpp"

/***************************************************************************
                          main.cpp  -  description
                             -------------------
    begin                : Mon Nov 19 2001
    copyright            : (C) 2001 by 
    email                : 
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#include <cmath>
#include <iostream>

const float Pi=3.14f;
const int nSamples=4096;
const float Freq=10.0f;

int main(void)
{
    double sinus[nSamples];
    int nLoop=0;

    for (nLoop=0; nLoop<nSamples; nLoop++)
    {
        sinus[nLoop]=sin(2.0f*Pi*Freq/nSamples*nLoop);
    }
    cout << sinus[51] << endl;
    cout << sinus[52] << endl;
    return(0);
}