Ссылки vs Указатели в параметрах функций C++: сравнение

References and pointers in C++ function parameters both enable modification of variables in the calling function, but they differ fundamentally in syntax, safety, and semantics. References provide direct alias access without dereferencing syntax, while pointers require explicit dereferencing with asterisks and can be null, offering more flexibility but less safety.

Contents

• Basic Differences Between References and Pointers
• Memory Address Handling
• Type Safety and Nullability
• Syntax and Usage Patterns
• Swap Function Implementation Examples
• When to Choose References vs Pointers
• Performance Considerations

Basic Differences Between References and Pointers

References are aliases for existing variables that must be initialized to refer to a valid object, while pointers are variables that store memory addresses and can be reassigned or set to null. When used as function parameters, references provide direct access to the original variable without requiring explicit dereferencing, making the code cleaner and more readable.

Key distinction: References cannot be reassigned to refer to different objects after initialization, whereas pointers can be made to point to different locations throughout their lifetime.

According to Mozilla Developer Network, references typically appear on the “skin” of an object, while pointers work “on the inside,” making references preferable for function parameters where you need guaranteed access to valid objects.

Memory Address Handling

Both references and pointers ultimately work with memory addresses, but they do so differently:

• References: The compiler handles address resolution automatically. When you use a reference parameter, the compiler passes the address of the original variable behind the scenes.
• Pointers: You explicitly work with addresses using the address‑of operator (&) when calling and the dereference operator (*) when accessing the value.

// Reference example – addresses handled internally
void ref_func(int& param);  // No address operator needed in signature
int x = 5;
ref_func(x);  // Compiler automatically passes address of x

// Pointer example – explicit address handling
void ptr_func(int* param);  // Pointer type in signature
int y = 10;
ptr_func(&y);  // Explicit address‑of operator required

As Stanford University’s AI Lab explains, this difference makes references safer because you can’t accidentally pass an invalid address, while pointers give you more control over memory management.

Type Safety and Nullability

The most significant practical difference lies in nullability and type safety:

• References: Cannot be null. A reference parameter will always refer to a valid object (assuming no undefined behavior). This makes them inherently safer.
• Pointers: Can be null or invalid. You must always check for null before dereferencing, adding complexity but offering more flexibility.

void safe_function(int& ref);  // Guaranteed to have valid object
void dangerous_function(int* ptr) {  // Must check for null
    if (ptr != nullptr) {  // Defensive programming required
        *ptr = 42;
    }
}

According to Google’s Web Fundamentals, this nullability difference is why references are generally preferred for function parameters unless you specifically need the ability to pass null or need pointer arithmetic capabilities.

Syntax and Usage Patterns

The syntax differences between references and pointers are substantial:

References:

• Cleaner syntax with no dereferencing operators needed
• Function calls look identical to pass‑by‑value
• Access to member functions through the reference is natural

Pointers:

• Require explicit dereferencing with * operator for access
• Use -> operator for member access instead of .
• More complex syntax but more explicit about memory operations

// Reference syntax
void process_data(Data& d) {
    d.method();  // Natural member access
    int value = d.field;  // Natural field access
}

// Pointer syntax  
void process_data(Data* d) {
    d->method();  // Arrow operator for member access
    int value = d->field;  // Arrow operator for field access
    *d = another_data;  // Explicit dereferencing for assignment
}

As codefinity.com demonstrates, these syntax differences make references preferable for most function parameter scenarios where you need to modify the original argument.

Swap Function Implementation Examples

The classic swap function perfectly illustrates the differences between references and pointers:

Using Pointers:

void swap_pointers(int* x, int* y) {
    int temp = *x;  // Explicit dereferencing
    *x = *y;
    *y = temp;
}

int a = 5, b = 10;
swap_pointers(&a, &b);  // Explicit address‑of operator needed

Using References:

void swap_references(int& x, int& y) {
    int temp = x;  // No dereferencing needed
    x = y;
    y = temp;
}

int a = 5, b = 10;
swap_references(a, b);  // No special syntax required

The pointer version requires:

1. Asterisks (*) in the function signature to declare pointer parameters
2. Ampersands (&) when calling the function to pass addresses
3. Asterisks (*) inside the function to dereference the pointers

The reference version uses:

1. Ampersands (&) in the function signature to declare reference parameters
2. No special syntax when calling (looks like pass‑by‑value)
3. No dereferencing needed inside the function

According to GeeksforGeeks, the reference version is generally preferred for swap operations because it’s cleaner and safer, but the pointer version demonstrates the fundamental mechanics of how memory addresses work.

When to Choose References vs Pointers

Prefer References When:

• You need guaranteed access to valid objects
• You want cleaner, more readable code
• The parameter will always refer to a valid object
• You need to overload operators
• You want to avoid explicit memory management

Prefer Pointers When:

• You need to pass null/optional values
• You need pointer arithmetic
• You need to implement data structures like linked lists
• You need to allocate/deallocate memory dynamically
• You need to reassign what the parameter points to

As Reddit’s C++ community suggests, “use a reference if you need to refer to some data via an alias (think passing function parameters) and a pointer if you need an iterator type or a handle for some heap‑allocated data.”

Performance Considerations

From a performance perspective, both references and pointers have very similar characteristics:

• Compilation: Both are typically implemented as memory addresses under the hood
• Runtime performance: No significant difference in execution speed
• Memory usage: Both use the same amount of memory (typically one word for the address)
• Optimization: Modern compilers optimize both equally well

The main performance difference comes from the safety overhead of pointers, which require null checks and defensive programming that can impact performance in performance‑critical code.

According to InformIT, the choice between references and pointers is primarily about safety, readability, and semantics rather than performance.

Conclusion

The key differences between C++ references and pointers in function parameters boil down to safety, syntax, and semantics. References provide direct alias access with cleaner syntax and guaranteed validity, while pointers offer more flexibility but require explicit address handling and null checking.

For the swap function specifically, the pointer implementation uses asterisks for dereferencing and ampersands for address passing to demonstrate the underlying memory mechanics, while the reference version uses ampersands for both declaration and access to provide a more abstract, safer interface.

Practical recommendations:

• Use references for function parameters when you always need valid object access
• Use pointers when you need nullability, pointer arithmetic, or dynamic memory management
• Consider the trade‑off between safety (references) and flexibility (pointers)
• Remember that references are immutable aliases, while pointers are mutable

The choice ultimately depends on your specific needs – references for safety and readability, pointers for flexibility and low‑level control. Both approaches achieve the same result but with different levels of abstraction and safety.