C++ memory-safe programming practices: avoid memory leaks and illegal access

C is a powerful programming language, but its nature of pointers and arrays makes memory management and memory safety more complex. This article will describe how to avoid memory leaks and illegal access problems in C and provide some best practice suggestions.

1. The problem of memory leaks

A memory leak means that the memory allocated during the running of the program is not released correctly, causing the memory space to be occupied all the time, eventually leading to system performance degradation or crash. In C, memory leaks are common because programmers need to manually allocate and free memory.

To address the problem of memory leaks, we can take the following measures to solve it:

1. Use smart pointers

A smart pointer is a special type of pointer, and its overloading With the operator, the memory pointed to by the pointer can be automatically managed without the need to manually release the memory. Two types of smart pointers were introduced in the C 11 standard:

• unique_ptr: There can only be one smart pointer pointing to a piece of memory. The pointer cannot be copied or moved. It is generally used to transfer pointer ownership.
• shared_ptr: Multiple smart pointers can point to the same memory, using reference counting to achieve intelligent management of memory.

2. Use RAII technology

RAII (Resource Acquisition Is Initialization) technology is a commonly used memory safety programming technology in C. Its basic idea is that during the life cycle of the object , uses resource application to obtain the required memory, and automatically releases all resources at the end of the object's life cycle, thereby ensuring that resources are released correctly.

For example, you can use std::vector to manage the memory of a dynamic array, and it will automatically release the requested memory in its destructor.

3. Avoid manual release of memory

For manually allocated memory, it must be ensured that it can be released correctly at any time in the program. However, in practice, you will find that manually releasing memory is very error-prone. Therefore, try to avoid manually allocating and releasing memory, and it is recommended to use smart pointers or RAII technology to manage memory.

2. The problem of illegal access

Illegal access means that the program attempts to access an unallocated or released memory area. This situation will cause the program to crash or undefined behavior. In C, due to the existence of pointers, illegal access is very easy to occur.

To address the problem of illegal access, we can take the following measures to solve it:

1. Avoid null pointers

Before using a pointer, you should always check whether the pointer is null. Otherwise, serious problems will occur when accessing pointers.

For example, before deleting the object corresponding to the pointer, you should check whether the pointer is null:

if(ptr != NULL)
{

delete ptr;
ptr = NULL;

}

2. Use constant reference

Using constant reference to pass parameters can ensure that the parameters passed in will not be modified in the function. This is an effective method to prevent illegal access.

For example, when passing the address of the same object in different functions, you can use a constant reference:

void func1(const MyClass& obj)
{

// 只读操作

}

void func2(const MyClass& obj)
{

// 只读操作

}

3. Use boundary check

Use boundary check to verify whether the program crosses the boundary access memory. The STL library in C provides safe containers with bounds checking, such as std::vector, std::deque, std::array, etc.

For example, when using std::vector in STL, you can use the at() function to perform boundary checking:

std::vector vec{1, 2, 3 };

try {

int val = vec.at(10); // 越界异常

} catch (std::out_of_range& ex) {

// 处理越界异常

}

Summary

Memory leak and illegal access are common problems in C, but we can take some measures to solve these problems. Using smart pointers and RAII technology to manage memory can effectively avoid the risk of memory leaks. When using pointers to access memory, null pointers and illegal access should be avoided, which can be achieved through techniques such as constant references and bounds checking. When writing code, we should develop good programming habits to ensure code memory safety and make the program more stable and robust.

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