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

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

Introduction:
C is a powerful programming language, but you may encounter various runtime errors when writing code. One of the common errors is the "invalid pointer" error. This error message indicates that there is a pointer to an invalid memory address in the code. This article explains how to resolve this error and provides relevant code examples.

What is an invalid pointer?
In C, a pointer is a variable that holds the memory address of a variable. Pointers can point to variables of any type, including integer, floating point, character, etc. The 'invalid pointer' error occurs when a pointer points to an invalid memory address. This situation usually occurs in the following three situations:

1. The pointer is not initialized or is NULL: When a pointer is not initialized correctly, or is assigned a value of NULL, it will point to an invalid address.

int* p;
*p = 10;

2. The pointer has been deleted or freed: When delete or free is used to release the memory pointed to by a pointer, the pointer becomes an invalid pointer.

int* p = new int;
delete p;
*p = 10;

3. The pointer exceeds the range of the memory it points to: When a pointer is incremented or decremented beyond the range of the memory it points to, it points to an invalid address.

int arr[5] = {1, 2, 3, 4, 5};
int* p = &arr[0];

p = p + 10;
*p = 10;

How to solve 'invalid pointer' error?
In order to solve the 'invalid pointer' error, we need to follow the following steps:

1. Initialize the pointer and ensure that it points to a valid memory address: Before using the pointer, first make sure that the pointer has been correctly Initialized and pointing to a valid memory address. You can assign a valid address to the pointer, or initialize it to NULL.

int* p1 = new int;
*p1 = 10;

int* p2 = nullptr;
p2 = new int;
*p2 = 20;

2. Avoid repeatedly releasing the memory pointed to by the pointer: When deleting the memory pointed to by the pointer, we only need to call delete or free when it is no longer needed. Make sure to release memory only once to prevent invalid pointers.

int* p = new int;
*p = 10;
delete p;
p = nullptr;

// 之后不要再使用指针p

3. Don’t let pointers exceed the range of the memory they point to: When using pointers to increment and decrement memory, make sure not to exceed the range of the memory they point to. You can use conditionals to prevent pointers from going out of scope.

int arr[5] = {1, 2, 3, 4, 5};
int* p = &arr[0];

if (p < &arr[5]) {
    p = p + 10; // 避免指针超出范围
    *p = 10;
}

Conclusion:
'invalid pointer' is one of the common runtime errors in C, which means that there is a pointer to an invalid memory address in the code. To resolve this error, we should properly initialize the pointer and ensure that it points to a valid memory address, avoid repeatedly releasing the memory pointed to by the pointer, and avoid letting the pointer exceed the scope of the memory it points to.

By following the above steps, we can better manage pointers and reduce the occurrence of 'invalid pointer' errors. When writing and debugging code, paying close attention to the use of pointers can help us detect and solve such errors early and improve the quality and robustness of the code.

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