What's the diffrence between __libc_start_main and __libc_start_call_main?

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>
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There is NO WARRANTY, to the extent permitted by law.
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<https://www.gnu.org/software/gdb/bugs/>.
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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.