__libc_start_main 和 __libc_start_call_main 有什么区别？

Question

I came to know about the __libc_start_main function. I have been thinking that __libc_start_main call the main function like this , but when I checked ret of main function of my own program, it is the address of __libc_start_call_main. What's the diffrence between __libc_start_main and __libc_start_call_main?

source code of my program, test.c

#include <stdio.h>

int main(void) 
{
    puts("Sunghyeon Lee");
}

gdb output:

──(kali㉿kali)-[~]
└─$ gdb test   
GNU gdb (Debian 12.1-3) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

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Reading symbols from test...
(No debugging symbols found in test)
(gdb) b *main
Breakpoint 1 at 0x1139
(gdb) r
Starting program: /home/kali/test 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, 0x0000555555555139 in main ()
(gdb) x/a $rsp
0x7fffffffdec8: 0x7ffff7dd920a <__libc_start_call_main+122>

Thank you for your help!

I have searched about the diffrence between __libc_start_main and __ibc_start_call_main, I have never found the explanation about it.

Answer 1

I have never found the explanation about it.

Take a look at the commit which created __libc_start_call_main .

Effectively a chunk of __libc_start_main was split out into a separate routine.