Undefined Reference

ofmrew

I am trying to create column-major matrix, but of the constructors gives an undefined reference, but I cannot see the problem. I found similar code in woboq for QMatrix4x4.
I am using Win11 and mingw. Thanks.

#include "mymatrix3d.h"

MyMatrix3D::MyMatrix3D(){}
MyMatrix3D::MyMatrix3D(
        qreal m11,qreal m12,qreal m13,qreal m14,
        qreal m21,qreal m22,qreal m23,qreal m24,
        qreal m31,qreal m32,qreal m33,qreal m34,
        qreal m41,qreal m42,qreal m43,qreal m44){
    e[0][0]=m11;
    e[0][1]=m12;
    e[0][2]=m13;
    e[0][3]=m14;
    e[1][0]=m21;
    e[1][1]=m22;
    e[1][2]=m23;
    e[1][3]=m24;
    e[2][0]=m31;
    e[2][1]=m32;
    e[2][2]=m33;
    e[2][3]=m34;
    e[3][0]=m41;
    e[3][1]=m42;
    e[3][2]=m43;
    e[3][3]=m44;
}
MyMatrix3D::MyMatrix3D(qreal *elements[]){
    for(int row=0; row<4; row++) {
        for(int col=0; col<4; col++) {
            e[row][col]=*elements[row*8 + col];};};
}

#ifndef MYMATRIX3D_H
#define MYMATRIX3D_H
#include <QtMath>
#include <QDebug>
#include <QDebugStateSaver>
#include "mypoint3d.h"

class MyMatrix3D
{
public:
MyMatrix3D();
MyMatrix3D(qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal, qreal);
MyMatrix3D(qreal *elements[]);
qreal e[4][4];
qreal row1[4];
qreal row2[4];
qreal row3[4];
};

#endif // MYMATRIX3D_H

Christian Ehrlicher

And you really compile mymatrix3d.cpp in your project? I would guess no.

ofmrew

Yes. I should have added that it is third constructor that gives the problem.

I get :
D:\QtPrograms\build-3DModeling-Desktop_Qt_6_2_0_MinGW_64_bit-Debug..\3DModeling\mainwindow.cpp:14: error: undefined reference to MyMatrix3D::MyMatrix3D(double (*) [4])' debug/mainwindow.o: In functionMainWindow::MainWindow(QWidget*)':
D:\QtPrograms\build-3DModeling-Desktop_Qt_6_2_0_MinGW_64_bit-Debug/../3DModeling/mainwindow.cpp:14: undefined reference to `MyMatrix3D::MyMatrix3D(double (*) [4])'

Christian Ehrlicher

How do you call it? Why do you need this ctor at all? Pass a properly aligned std::array so you don't have to make sure it's length is correct.

ofmrew

Long story, but the short version is: 1. QMatrix4x4 uses floats and I want qreals because I want to do modeling and not just graphics. 2. Looking ahead when OpenGL will be replaced by renders which will culling will be done on the CPU side. 3. I want to incorporate intrinsics to improve performance.

What can I do to gather the information to help solve this problem.

How does it differ from what I found in qmatrix4x4.cpp, namely:

QMatrix4x4::QMatrix4x4(const float *values)
{
    for (int row = 0; row < 4; ++row)
        for (int col = 0; col < 4; ++col)
            m[col][row] = values[row * 4 + col];
    flagBits = General;
}

Any help will be greatly appreciated, thanks.

Christian Ehrlicher

The QMatrix ctor takes a pointer to a float, you pass a pointer to a pointer of a float. Both are very problematic because none of them has the chance to check the size of the values.

JonB

@ofmrew said in Undefined Reference:

How does it differ from what I found in qmatrix4x4.cpp, namely:

MyMatrix3D(qreal *elements[])

is not the same level of indirection as

QMatrix4x4(const float *values)

Humour me: if you declared yours as qreal **elements (or qreal *elements if that is what you really intend) that might make the linker error go away?

ofmrew

My mistake. If you note the second constructor does what I want: get a two dimensional array of [row ][column] that will allow me to construct a contiguous array of qreals. White the final constructor I was trying to make it less verbose. Some other languages allow something like x[0][:] to return and array with the first row of x[][].

Also, I will note that I have watching on but I do not get a notification unless I click no the icon, before a number, representing the number of notifications, would appear on the icon.