The relationship between C++ function parameter passing method and memory management

C Function parameter passing method affects memory management: value passing creates a copy without affecting external variables, reference passing directly modifies external variables without additional memory allocation, pointer passing accesses external variables through pointers and requires manual allocation and release of memory.

#The relationship between function parameter passing method and memory management

In C, function parameters can be passed by reference, pointer or value. The choice of delivery method is critical to memory management.

Value passing

When function parameters are passed by value, what is actually passed in is a copy of the variable. Modifications to the copy within the function will not affect external variables. This method is simple and safe, but less efficient because it requires copying data.

void swap(int a, int b) {
  // 交换 a 和 b 的副本
  int temp = a;
  a = b;
  b = temp;
}

int main() {
  int x = 1, y = 2;
  swap(x, y);  // 传入副本
  // x 和 y 仍然为 1 和 2
}

Passing by reference

When function parameters are passed by reference, what is actually passed in is the reference of the variable. Modifications to references inside a function will directly affect external variables. This approach is efficient, but requires careful management of references to avoid dangling references or wild pointer errors.

void swap(int& a, int& b) {
  // 交换 a 和 b 的引用
  int temp = a;
  a = b;
  b = temp;
}

int main() {
  int x = 1, y = 2;
  swap(x, y);  // 传入引用
  // x 和 y 现在交换为 2 和 1
}

Pointer passing

When function parameters are passed through pointers, what is actually passed in is the pointer of the variable address. External variables can be accessed and modified through pointers inside the function. This method is efficient, but requires allocating and releasing memory, which is more complicated.

void swap(int* a, int* b) {
  // 交换 a 和 b 的指针
  int temp = *a;
  *a = *b;
  *b = temp;
}

int main() {
  int x = 1, y = 2;
  swap(&x, &y);  // 传入指针
  // x 和 y 现在交换为 2 和 1
}

Memory management

• Value transfer: A temporary variable is created inside the function to store the parameters. The variable is destroyed after the function returns and does not cause memory loss. leakage.
• Pass by reference: Directly access external variables within the function, no additional memory allocation is created, and there is no risk of memory leaks.
• Pointer passing: Accessing variables through pointers inside the function requires manual allocation and release of memory. Improper management may lead to memory leaks.

Practical case

Case: Implement a function to exchange two integers through pointers.

Code:

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

Usage:

int main() {
  int x = 1, y = 2;
  swap(&x, &y);  // 传入指针
  // x 和 y 现在交换为 2 和 1
}

In this case, the function exchanges two integers through pointers, This avoids copying of values ​​and improves efficiency. At the same time, memory management is the responsibility of the caller and requires manual allocation and release of memory.

The above is the detailed content of The relationship between C++ function parameter passing method and memory management. For more information, please follow other related articles on the PHP Chinese website!