One 、 Concept

register ：CPU The variables in the

cpu There are many registers in the , Register for access

The process of function call will generate a stack ,

esp: Top register

ebp: Bottom of stack register

Two 、 Function call procedure

1. Parameter stack

Parameter stack ：（c Language ）

Four byte stack ：

#include<stdio.h>
int fun(int a, int b)
{
	int c = 0;
	return c = a + b;
}
int main()
{
	int a = 10;
	int b = 5;
	int c = fun(a,b);
	printf("%d", c);
	return 0;
}

        fun(a,b)

        4 Byte parameter stack （ The order ： From right to left ）

        fun(a,b); First b Again a

        The way ： Using registers push Into the

Eight character section into the stack ：

#include<stdio.h>
struct Node
{
	int _1;
	int _2;
};
int fun(struct Node a, struct Node b)
{
	int c = 20;
	return c;
}
int main()
{
	struct Node a = { 10,20 };
	struct Node b = { 30,40 };
	fun(a, b);
	return 0;
}

 8 Byte parameter stack ：

The order ：    From right to left

The way         Using registers push Into the

12 Byte parameter stack

 12 byte （ Greater than 8 byte ） Parameter stack ：

The order ： From right to left

The way ： First, open up enough space for this parameter at the top of the stack , Then copy the data in

c++ Parameters in the stack

c++ As long as it is a custom type , No matter how many bytes , All adopt the method of opening up space first , The way of assignment after

2. Function stack frame

Put the instruction address of the next line of the caller's function on the stack

Put the bottom register of the caller's function on the stack

Give Way ebp = esp

Give Way esp = esp -***

Stack other used registers ,

Write all the newly opened stack frame space as cccc cccc

 

3. Function return value

c In language

4 Byte return value

The way ： Put the return value into the register and bring it back to

 8 Byte return value

The way ： Put the return value in two registers , Bring back

 

12 byte （ Greater than 8 byte ） Return value

The way ：

After the function parameters are stacked , Stack the address on a caller's stack frame ( Near the top of the stack )

When the return value returns , Write the return data to the caller's address that was previously stacked

After returning , The data will be taken from this address

c++ in

Byte return value mode ：

The custom types are based on the stack caller address

4. Function stack exit

Check the current function stack frame

Take the thread protected register out of the stack

Give Way esp=ebp
ebp= pop
Restore the address of the next instruction line

Remove parameters
 

notes ： The function call procedure in this paper depends on c Language default calling convention   _cdecl

There are other calling methods , Such as ：_stdcall , _fastcall