How to solve C++ runtime error: 'pointer is pointing to deallocated memory'?

How to solve C runtime error: 'pointer is pointing to deallocated memory'

Introduction
C is a powerful programming language, but when using it When running, you often encounter some runtime errors. One of them is 'pointer is pointing to deallocated memory'. This error often causes the program to crash or produce unpredictable results. To avoid this mistake, this article will introduce some common workarounds and provide corresponding code examples.

1. Understand the cause of the problem
Before solving the problem, we first need to understand the cause of this error. When we release the memory pointed to by a pointer, the pointer still retains its original address. This means that although the memory has been freed, the pointer still points to that memory address. When we try to use this pointer, the 'pointer is pointing to deallocated memory' error occurs.

2. Use smart pointers
Smart pointers are an important feature in C, which can help us manage memory and avoid some common mistakes. Using smart pointers can effectively solve the 'pointer is pointing to deallocated memory' problem. The following is a sample code:

#include <memory>

int main() {
    std::shared_ptr<int> ptr = std::make_shared<int>(10);
    ptr.reset(); // 释放指针所指向的内存

    // 使用智能指针时，它会自动判断指针是否有效
    if (ptr) {
        // 这里的代码不会执行，因为指针已经被释放
        *ptr = 20;
    }

    return 0;
}

In this sample code, we use std::shared_ptr to allocate a dynamic memory, and pass reset after use The function frees the memory. After using a smart pointer, the pointer will automatically determine whether the memory has been released, thus avoiding incorrect use.

3. Avoid null pointer access
Another way to solve the 'pointer is pointing to deallocated memory' problem is to avoid null pointer access. The following is a sample code:

int main() {
    int* ptr = new int(10);
    delete ptr; // 释放指针所指向的内存

    // 检查指针是否为空
    if (ptr != nullptr) {
        // 这里的代码不会执行，因为指针已经被释放
        *ptr = 20;
    }

    return 0;
}

In this sample code, we use an if statement to check whether the pointer is null after releasing the memory pointed to by the pointer. In this way, we can avoid accessing the null pointer and thus avoid errors.

4. Correctly release pointers
In C, we usually use delete or delete[] to release dynamically allocated memory. If we forget to release the pointer, we may get the 'pointer is pointing to deallocated memory' error. Here is a sample code:

int main() {
    int* ptr = new int(10);
    // 忘记释放指针

    // 这里的代码会出现错误，因为指针未释放
    *ptr = 20;

    return 0;
}

In this sample code, we allocate a dynamic memory and forget to release it before the end of the program. As a result, errors will occur when using pointers in programs. To avoid this, we should always remember to release the pointer, using delete or delete[].

Conclusion
The 'pointer is pointing to deallocated memory' error is one of the common runtime errors in C. To solve this problem, we can use smart pointers to manage memory, avoid null pointer accesses, and always release pointers correctly. By following these methods and checking the code carefully, we can effectively avoid this error from happening.

I hope the methods and sample code introduced in this article can help you better solve the 'pointer is pointing to deallocated memory' error and write a more stable and reliable C program.

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