How to solve C++ runtime error: 'invalid pointer assignment'?

How to solve C runtime error: 'invalid pointer assignment'

In the process of C programming, we often encounter various runtime errors. One of the common errors is the 'invalid pointer assignment' error, which can crash the program and cause unpredictable behavior. This article will introduce the cause and solution of this error, and provide some code examples to help readers understand better.

1. Cause of error
   The 'invalid pointer assignment' error usually occurs when trying to assign a pointer to the wrong type or an invalid address. This may be due to the following reasons:

• Pointer is not initialized: Before using a pointer, we must initialize it first. If a pointer is uninitialized, its value is undefined and assigning it to another pointer or variable may result in an 'invalid pointer assignment' error.
• Pointer type error: Different pointer types occupy different numbers of bytes in memory. If we try to assign a pointer to an incompatible pointer type, the 'invalid pointer assignment' error will occur.
• Continue to use after releasing the pointer: If we release the memory pointed to by a pointer and then continue to use the pointer for access, the 'invalid pointer assignment' error will occur.

2. Solution
   In order to solve the 'invalid pointer assignment' error, we can take the following steps:

• Initialize the pointer: Always initialize a pointer before using it. Can be initialized using nullptr or a pointer to a valid memory address.
• Check pointer type: Make sure the pointer is assigned to a pointer variable of the correct type. Casting can be done if needed.
• Avoid repeated release: After releasing the memory pointed to by the pointer, ensure that the pointer is no longer used for access. Pointers can be set to nullptr to avoid accidental reuse.

Here are some sample codes to help readers better understand the ways to solve the 'invalid pointer assignment' error:

// 示例 1: 未初始化指针
int* ptr; // 未初始化的指针
*ptr = 10; // 试图将值赋给未初始化的指针
// 解决方法：
int* ptr = nullptr; // 初始化指针
*ptr = 10; // 现在指针已经初始化，可以正确赋值

// 示例 2: 指针类型错误
int* intPtr;
char* charPtr = (char*)intPtr; // 将int指针赋值给char指针
// 解决方法：
int* intPtr;
char* charPtr = reinterpret_cast<char*>(intPtr); // 使用强制类型转换

// 示例 3: 释放指针后继续使用
int* ptr = new int;
delete ptr;
int value = *ptr; // 试图访问已经释放的内存
// 解决方法：
int* ptr = new int;
delete ptr;
ptr = nullptr; // 设置指针为nullptr，避免继续使用

By understanding the causes and reasons of the 'invalid pointer assignment' error Solutions, combined with the above sample code, we can better handle and troubleshoot similar errors, and improve the quality and reliability of the code during the programming process.

To summarize, the key to solving the 'invalid pointer assignment' error is to pay attention to the initialization, type matching and release of the pointer and no longer use it. Developing good programming habits can help us avoid such errors. I hope this article can help readers solve the 'invalid pointer assignment' error in C.

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