Common errors in reference and pointer parameters in C++ functions

Common mistakes between reference parameters and pointer parameters are: reference parameters must be initialized to valid variables and cannot be changed in type, and pointer parameters must point to valid variables and cannot be released repeatedly. Additionally, pointer parameters can access uninitialized pointers and dereference unpointed variables, while reference parameters cannot point to temporary variables.

#Common mistakes in reference parameters and pointer parameters in C functions

Reference parameters

Definition of reference parameters

A reference parameter is like an ordinary variable, but it is an alias for another variable. This means that any modifications to the reference parameter will be reflected in the variable it refers to.

Syntax:

void function(T& reference_parameter);

Common mistakes with reference parameters

• Using uninitialized reference parameters:The reference parameter must be initialized to a valid variable. Otherwise, the program will segfault.
• Modify the type of reference parameters: Reference parameters cannot change the type of the variable they reference. For example, you cannot change a reference int parameter to a reference float parameter.
• Point reference parameters to temporary variables: Reference parameters cannot point to temporary variables because temporary variables will be destroyed when the function returns.

Pointer parameters

Definition of pointer parameters

Pointer parameters point to the memory address of another variable. Through a pointer, the variable pointed to can be modified.

Syntax:

void function(T* pointer_parameter);

Common mistakes with pointer parameters

• Accessing uninitialized pointers:Pointer parameters must be initialized to a valid address . Otherwise, the program will segfault.
• Dereference a pointer to a variable not pointed to: The pointer must point to a valid variable. Otherwise, dereferencing will cause a segfault.
• Repeated release of pointers: Once the variable pointed to by the pointer is no longer needed, the pointer should be released. Otherwise, a memory leak will result.

Practical case

The following example demonstrates the correct usage of reference parameters and pointer parameters:

#include <iostream>

void swap(int& a, int& b) {
    int temp = a;
    a = b;
    b = temp;
}

void swapPointers(int* a, int* b) {
    int* temp = a;
    a = b;
    b = temp;
}

int main() {
    int x = 10;
    int y = 20;

    // 调用引用参数函数
    swap(x, y);
    std::cout << "x: " << x << ", y: " << y << std::endl;  // 输出：x: 20, y: 10

    int* px = &x;
    int* py = &y;

    // 调用指针参数函数
    swapPointers(px, py);
    std::cout << "*px: " << *px << ", *py: " << *py << std::endl;  // 输出：*px: 20, *py: 10
}

In this example:

## The
• #swap function uses reference parameters and correctly swaps the values ​​​​of x and y. The
• swapPointers function uses pointer parameters and correctly swaps the values ​​of the variables pointed to by px and py.

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