Using host libthread_db library "/lib/libthread_db.so.1".
(gdb) start
Breakpoint 1 at 0x4004bc
Starting program: /home/*user*/thunk 
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
0x00000000004004bc in main ()
(gdb) disassemble
Dump of assembler code for function main:
0x00000000004004b8 <main+0>:	push   %rbp
0x00000000004004b9 <main+1>:	mov    %rsp,%rbp
0x00000000004004bc <main+4>:	mov    (%rsp),%rbx
0x00000000004004c0 <main+8>:	retq   
0x00000000004004c1 <main+9>:	leaveq 
0x00000000004004c2 <main+10>:	retq   
End of assembler dump.
(gdb) x main+4
0x4004bc <main+4>:	0x241c8b48
(gdb) x main+8
0x4004c0 <main+8>:	0x90c3c9c3
(gdb) quit

----

#include <stdio.h>

int main(void) {
  __asm__("mov (%rsp),%rbx");
  __asm__("ret");
}