The function return

 
Stack during Subroutine Call

 

基本知识： http://www.cs.virginia.edu/~evans/cs216/guides/x86.html

#include <iostream>
using namespace std;

/*Function to return struct */
struct A
{
   int ma;
   int mb;
   int mc;
   int md;
   int me;
};

struct A fun(void)
{
     struct A a1;
     a1.ma = 1;
     a1.mb = 2;
     a1.mc = 3;
     a1.md = 4;
     a1.me = 5;
     return a1;
}

//the asm codestruct A fun(void){00411370 push ebp 00411371 mov ebp,esp //设定函数栈起始地址00411373 sub esp,54h //预留空间给局部变量00411376 push ebx 00411377 push esi 00411378 push edi struct A a1; a1.ma = 1;00411379 mov dword ptr [a1],1 a1.mb = 2;00411380 mov dword ptr [ebp-10h],2 a1.mc = 3;00411387 mov dword ptr [ebp-0Ch],3 a1.md = 4;0041138E mov dword ptr [ebp-8],4 a1.me = 5;00411395 mov dword ptr [ebp-4],5 return a1;//以下部分代码，将a1 拷贝到 ebp+8指定地址的一块区域里0041139C mov eax,dword ptr [ebp+8]0041139F mov ecx,dword ptr [a1]004113A2 mov dword ptr [eax],ecx004113A4 mov edx,dword ptr [ebp-10h]004113A7 mov dword ptr [eax+4],edx004113AA mov ecx,dword ptr [ebp-0Ch]004113AD mov dword ptr [eax+8],ecx004113B0 mov edx,dword ptr [ebp-8]004113B3 mov dword ptr [eax+0Ch],edx004113B6 mov ecx,dword ptr [ebp-4]004113B9 mov dword ptr [eax+10h],ecx//设定返回值放置的地址004113BC mov eax,dword ptr [ebp+8]}//函数返回 弹出栈004113BF pop edi 004113C0 pop esi 004113C1 pop ebx 004113C2 mov esp,ebp004113C4 pop ebp 004113C5 ret

class B
{
    public:
       B() { cout << "hello"<<endl;}
       B(B& b) { i = b.i;cout << "hello"<<endl;}k
       ~B() {cout << "bye" <<endl;}
       int i;
};

/*Function to return class */
B fun2(void)
{
   B b;
   b.i = 1;
   return b;
  
}

B fun2(void){004113E0 push ebp //设定函数栈起始地址（也称基址） 004113E1 mov ebp,esp 004113E3 push 0FFFFFFFFh 004113E5 push offset __ehhandler$?fun2@@YA?AVB@@XZ (413A91h) 004113EA mov eax,dword ptr fs:[00000000h] 004113F0 push eax 004113F1 mov dword ptr fs:[0],esp //预留局部变量地址004113F8 sub esp,48h 004113FB push ebx 004113FC push esi 004113FD push edi //不知道这个ebp-54h这个变量是干什么用的。004113FE mov dword ptr [ebp-54h],0 B b;//压入this 指针，调用构造函数。00411405 lea ecx,[b] 00411408 call B::B (4110C8h) 0041140D mov dword ptr [ebp-4],1 b.i = 1;//给i 赋值1 00411414 mov dword ptr [b],1 return b;//在调用函数栈上创建一个临时对象//ebp+8存放着临时对象的起始地址//并调用拷贝构造函数0041141B lea eax,[b] 0041141E push eax 0041141F mov ecx,dword ptr [ebp+8] 00411422 call B::B (4111B8h) 00411427 mov ecx,dword ptr [ebp-54h] 0041142A or ecx,1 0041142D mov dword ptr [ebp-54h],ecx 00411430 mov byte ptr [ebp-4],0 //调用b 的析构函数00411434 lea ecx,[b] 00411437 call B::~B (411113h) 0041143C mov eax,dword ptr [ebp+8] }0041143F mov ecx,dword ptr [ebp-0Ch] 00411442 mov dword ptr fs:[0],ecx 00411449 pop edi 0041144A pop esi 0041144B pop ebx 0041144C mov esp,ebp 0041144E pop ebp 0041144F ret 

int main(int argc,char *agrv[])
{
    //test the struct return
    struct A a2;
    a2 = fun();
   
    //test class return and initialize the class variable
    B b2= fun2();
   
    //test class return and assign the class variable
    B b3;
    b3 = fun2();
   
    return 0;
   
}