＞第 19 章 汇编与C之间的关系＞main函数和启动例程

    最后那里，“注意，如果声明一个函数的返回值类型是int，函数中每个分支控制流程必须写return语句指定返回值，如果缺了return则返回值不确定（想想这是为什么）”。请问宋老师这是为什么呢？我想不明白哦！

因为返回值是通过eax传的。

Mr. Song,

May I ask you a question? Why can't I see calling exit() in or the similar thing int $0x80 in _start routine? 

All I see in _sart is:
push   $0x80483c4                        
call   80482c4 <__libc_start_main@plt>   
hlt                                     
nop 					
nop

Where is exit? I'm confused!
Thanks in advance!

That must be in the libc routine __libc_start_main. I think I have given enough hint for you to come up with this inference.

First of all, thanks to you for your patience. 

I find  U exit@@GLIBC_2.0 symbol in executable file if I use C.

How can I find _exit() symbol if I use assemble?

I have another question: how do you know which obj file a function lies in? such as exit() is in libc, and how do you know where _exit() is in?

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