Memory management of C++ function return value types

In C, the memory management of function return values ​​varies by type: Basic type: stored directly in the stack space of the function without explicit release. Pointer type: Points to an object in heap memory and needs to be explicitly released before the function returns to avoid memory leaks. Reference type: just an alias to another object, no additional memory management required. Object type: The constructor is called when returning and the object is copied to the stack space. The original object in the heap space needs to be explicitly released through the destructor before the function returns to prevent memory leaks.

C Memory management of function return value types

In C, memory management of function return values ​​is crucial to prevent memory leaks and access exceptions . Depending on the return value type, memory management is done differently.

Basic types

Basic types (such as int, float) are stored in the stack space of the function. When the function completes execution, the stack space will be released, so there is no need to explicitly release the return value space. For example:

int get_number() {
  return 42;
}

Pointers and references

Pointer and reference types point to the address of an object in the heap space, and their values ​​are stored in the stack space of the function. If a function needs to allocate new memory for a pointer or reference type, that memory must be explicitly freed before the function returns. Otherwise, a memory leak will result.

Pointer:

int* get_array() {
  int* arr = new int[10]; // 分配堆内存
  // ... 使用 arr ...
  return arr; // 返回指针
}

int main() {
  int* arr = get_array();
  // ... 使用 arr ...

  delete[] arr; // 释放堆内存
  return 0;
}

Reference:

Since a reference is just an alias to another object, no additional Memory management.

Object

If the function returns an object, the object's constructor will be called and the object will be copied to the caller's stack space. When the function completes execution, the stack space is released, but the original object and any allocated memory remain in the heap space. To prevent memory leaks, functions must explicitly free the heap space by calling the destructor before returning the object.

struct MyObject {
  MyObject() = default;
  ~MyObject() {
    // 释放堆内存
  }
};

MyObject get_object() {
  return MyObject(); // 调用构造函数并复制对象
}

int main() {
  MyObject obj = get_object();
  // ... 使用 obj ...

  // 不需要显式释放 obj，因为析构函数会在 obj 销毁时被自动调用
  return 0;
}

Practical case

Creating and releasing dynamic arrays:

int* create_array(int size) {
  int* arr = new int[size]; // 分配堆内存
  // ... 使用 arr ...
  return arr;
}

int main() {
  int* arr = create_array(10);
  // ... 使用 arr ...

  delete[] arr; // 释放堆内存
  return 0;
}

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