Question

我一直在尝试用C ++实现动态数组，并且在指针引用方面遇到了一些麻烦。

使用以下代码，我遇到了分段错误。

如果我使用数组和大小作为全局变量，则应用程序可以正常工作。我知道我能做到，但我想知道为什么它不起作用。我想我正在丢失指针数组指针引用，但我不知道如何在方法中保留它。

我不想使用像vector这样的STL容器。

感谢您的帮助。

void addElement(int newElement, unsigned int * array, int& size ){
    /* create a temp array in order to copy the contents from the current array
    * it is needed because we want to increase the size of the array */
    unsigned int* temp = new unsigned int[size + 1];

   // copy all the data from array to temp
   for (int x=0; x < size; x++){
       *(temp + x) = array[x];
   }

   // add the new element
   *(temp + size) = newElement;

   size++;

   // release the memory from the temp array
   delete [] array;

   // the temp array turn into the temp array, that contains all the elements
   array = temp;

}

int main(){

    unsigned int * array;
    int size;

    addElement(1, array, size);
    addElement(2, array, size);
    addElement(3, array, size);
    cout << array[1];
    return 1;

}

Answer 1

array = temp;在您通过unsigned int* array而不是unsigned int*&array

时没有做到您期望的事情

用

替换原型

void addElement(int newElement, unsigned int*& array, int& size )

此外，您应该初始化变量：

unsigned int* array = nullptr;
int size = 0;

并删除main中的array：

delete [] array;

Answer 2

你没有初始化指针数组和变量size。所以程序有未定义的行为

此功能也必须声明为

void addElement(int newElement, unsigned int * & array, int& size );

或

int * addElement(int newElement, unsigned int * array, int& size );

否则main中定义的ponter将不会更改。

例如

int * addElement(int newElement, unsigned int * array, int& size ){
    /* create a temp array in order to copy the contents from the current array
    * it is needed because we want to increase the size of the array */
    unsigned int* temp = new unsigned int[size + 1];

   // copy all the data from array to temp
   for (int x=0; x < size; x++){
       *(temp + x) = array[x];
   }

   // add the new element
   *(temp + size) = newElement;

   size++;

   // release the memory from the temp array
   delete [] array;

   // the temp array turn into the temp array, that contains all the elements
   return temp;
}

int main(){

    unsigned int * array = NULL;
    int size = 0;

    array = addElement(1, array, size);
    array = addElement(2, array, size);
    array = addElement(3, array, size);
    cout << array[1];

    delete [] array;

    return 1;

}

或者

void addElement(int newElement, unsigned int * &array, int& size ){
    /* create a temp array in order to copy the contents from the current array
    * it is needed because we want to increase the size of the array */
    unsigned int* temp = new unsigned int[size + 1];

   // copy all the data from array to temp
   for (int x=0; x < size; x++){
       *(temp + x) = array[x];
   }

   // add the new element
   *(temp + size) = newElement;

   size++;

   // release the memory from the temp array
   delete [] array;

   // the temp array turn into the temp array, that contains all the elements
   array = temp;

}

int main(){

    unsigned int * array = NULL;
    int size = 0;

    addElement(1, array, size);
    addElement(2, array, size);
    addElement(3, array, size);
    cout << array[1];

    delete [] array;

    return 1;

}

考虑到在标头std::copy中声明的标准算法std::copy_n和<algorithm>可以在函数中使用而不是循环。例如

std::copy_n( array, size, temp );

或

std::copy( array, array + size, temp );

C ++ - 分段错误 - 动态数组

2 个答案: