Cannot convert double to QString

[maxpower]

I am running Qt 4.2.2 on FreeBSD 4.8 with gcc 3.4.6. I am working with dollar amounts in doubles but I cannot properly convert these doubles into QStrings for display in a QLabel. As a test I compiled the following very simple code:

#include <QtCore>
int main () {
        double doublevar = 42.84;
 
        qDebug() << QString::number(doublevar); 
}

#include <QtCore>
int main () {
        double doublevar = 42.84;

        qDebug() << QString::number(doublevar); 
}

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Which outputs "-0" to the terminal. What could be causing this? The same code in this simple program runs fine on my Linux and Windows boxes. If I use a QVariant as below:

#include <QtCore>
int main () {
        double doublevar = 42.84;
 
        QVariant var(doublevar);
        qDebug() << var.toString(); 
}

#include <QtCore>
int main () {
        double doublevar = 42.84;

        QVariant var(doublevar);
        qDebug() << var.toString(); 
}

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The output is "-0.00000000005965e+224". Again, what could be wrong?

Thanks
mAx

[wysota]

This indeed is strange. The output you experience could be caused by mixups caused by incompatibility between your machine (CPU and OS) and the Qt library, but I think that in this cause nothing should run at all. What is the result of the following?

double  d = 42.84;
qDebug() << d;

double  d = 42.84;
qDebug() << d;

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[maxpower]

This

#include <QtCore>
int main () {
        double d = 42.84;
        qDebug() << d; 
}

#include <QtCore>
int main () {
        double d = 42.84;
        qDebug() << d; 
}

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still gives "-0"

Thanks
mAx

[gfunk]

What compiler options do you use, maybe there are some special switches for double floating point (64-bit)?

[maxpower]

I have not edited the default settings that Qt defaulted to. Here is what is given during a make:

g++34 -c -pipe -O2 -Wall -W -pthread -D_THREAD_SAFE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I../../../local/Trolltech/Qt-4.2.2/mkspecs/freebsd-g++34 -I. -I../../../local/Trolltech/Qt-4.2.2/include/QtCore -I../../../local/Trolltech/Qt-4.2.2/include/QtCore -I../../../local/Trolltech/Qt-4.2.2/include/QtGui -I../../../local/Trolltech/Qt-4.2.2/include/QtGui -I../../../local/Trolltech/Qt-4.2.2/include -I. -I. -I. -I../../../local/include -o foo.o foo.cpp

Thanks
mAx

[wysota]

And this one?

printf("%lf\n", 42.84);

printf("%lf\n", 42.84);

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[maxpower]

That gives: 42.840000

[wysota]

Did you compile Qt yourself or do you use some precompiled package? What exact architecture do you have? x86?

[maxpower]

Yes it is x86 and I did compile Qt myself as I could only find Qt 3 for FreeBSD 4.8 in package format.

Thanks
mAx

[yuzr]

Some ARM installations have floating point implementations that are not fully IEEE-compliant. In Qt/Embedded 3.3.x, this causes QString::number(double) and related functions to give incorrect results. A fix for this was introduced in Qt 3.3.2: defining the macro QT_QLOCALE_USES_FCVT will make Qt use system library code instead, i.e:

./configure -embedded arm -DQT_QLOCALE_USES_FCVT ...

i am in the face of this problem,i have added the macro,but it doesn't work.