Discuss the underlying implementation of C++ function memory allocation and destruction

C The underlying implementation of function memory allocation and destruction is as follows: Memory allocation: Call the new operator to allocate stack frames on the stack and store local variables and function call information. Memory destruction: When the function returns, release the stack frame and its stored local variables; call the delete operator to release the memory allocated by new.

The underlying implementation of C function memory allocation and destruction

Memory allocation

When a function is called, it requires a stack frame to Store its local variables and function call information. A stack frame is an area of ​​memory allocated on the stack when a function is called.

In C, memory is allocated by the new operator. new The operator returns a pointer to the allocated memory.

int* p = new int;  // 分配一个 int 变量

Memory destruction

When a function returns, its stack frame is released. This also releases local variables stored in the stack frame.

Memory in C is released by the delete operator. The delete operator releases the memory allocated by new.

delete p;  // 释放之前分配的 int 变量

Practical example

Consider the following code snippet:

void foo() {
  int* p = new int;
  *p = 10;
  return;
}

int main() {
  foo();
  return 0;
}

In this example, the foo function allocates an int variable and set its value to 10. When the foo function returns, the memory pointed to by p will be released.

However, the memory pointed to by p is not released in the main function. This can cause memory leaks.

In order to solve this problem, you can call the delete operator in the main function to release the memory pointed to by p.

int main() {
  foo();
  delete p;  // 释放 foo() 中分配的内存
  return 0;
}

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