具有数组属性的类的 C++ 复制构造函数

问：

我正在创建一个矩阵模板，在编写复制构造函数时遇到了问题。虽然数据似乎是从构造函数中正确复制的，但返回到主程序的对象没有正确的值（看起来像它指向不同的内存地址）。在我尝试调试它时，我尝试创建一个极简主义示例，但奇怪的是，这并没有产生相同的错误。我感觉这个问题要么超出了我对 C++ 的理解......或者是由我不知何故错过的错别字引起的。谁能发现我做错了什么？

matlib.h

#ifndef MATLIB_H
#define MATLIB_H
#include <iostream>

    namespace matlib{
        template <typename T>
        struct Matrix {
                unsigned int rows;   //number of rows
                unsigned int cols;   //number of columns
                unsigned int length; //number of elements
                T data[];                  //contents of matrix
    
                /* Constructors */
                Matrix(unsigned int m, unsigned int n) : rows(m), cols(n) {
                    length = m*n;
                    T data[m*n];
                    //::std::cout << "Hello from the null constructor!" << ::std::endl;
                    //::std::cout << "rows = " << rows << ", cols = " << cols << ", length = " << length << ::std::endl;
                }
                
                Matrix(const Matrix<T> &mat) {
                    rows = mat.rows;
                    cols = mat.cols;
                    length = mat.length;
                    T data[mat.length];
                    ::std::cout << "Hello from the copy constructor!" << ::std::endl;                
                    for (int i = 0; i < length; ++i) {
                        data[i] = mat.data[i];
                        ::std::cout << "data[" << i << "] = " << data[i] << ", mat.data[" << i << "] = " << mat.data[i] << ::std::endl;
                    }
                } 
    
                //Single element indexing and assigment
                T& operator() (int i, int j) {
                    return data[ i*this->cols + j ];
                }
    
                T& operator() (unsigned int i, unsigned int j) {
                    return data[ i*this->cols + j ];
                }
    
                //Single element indexing and assigment
                T& operator() (int i) {
                    return data[i];
                }
    
                T& operator() (unsigned int i) {
                    return data[i];
                } 
    
                
        };
    
    }
    
    #endif

testscript.cpp

#include <iostream>
#include "matlib.h"

int main() {
    float arr[7] = {4, 1, 6, 6, 8, 4, 2};
    matlib::Matrix<float> mat1(1,7);

    //Assign values and print
    std::cout << "mat1 = ";
    for (int i = 0; i < mat1.length; ++i) {
        mat1(i) = arr[i];
        std::cout << mat1(i) << " ";
    }
    std::cout << "\n" << std::endl;

    //Copy the object
    matlib::Matrix<float> mat2 = mat1;

    //Print the copied values
    std::cout << "mat2 = ";
    for (int i = 0; i < mat2.length; ++i) {
        std::cout << mat2(i) << " ";
    }
    std::cout << std::endl;

    return 0;
}

控制台输出：

mat1 = 4 1 6 6 8 4 2 

Hello from the copy constructor!
data[0] = 4, mat.data[0] = 4
data[1] = 1, mat.data[1] = 1
data[2] = 6, mat.data[2] = 6
data[3] = 6, mat.data[3] = 6
data[4] = 8, mat.data[4] = 8
data[5] = 4, mat.data[5] = 4
data[6] = 2, mat.data[6] = 2
mat2 = 9.80909e-45 1.4013e-45 9.80909e-45 9.80909e-45 4 1 6 

我相信很多人会建议涉及“std：：vector”的解决方案，尽管这主要是考虑 HPC 的学习练习。一旦这更发达，我可能会添加绑定检查。