Hello,
I have written a simple Hello World program.
#include <stdio.h>
int main() {
printf("Hello World");
return 0;
}
I wanted to understand how the relocatable object file and
executable file look like.
The object file corresponding to the main function is
0000000000000000 <main>:
0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: bf 00 00 00 00 mov $0x0,%edi
9: b8 00 00 00 00 mov $0x0,%eax
e: e8 00 00 00 00 callq 13 <main+0x13>
13: b8 00 00 00 00 mov $0x0,%eax
18: c9 leaveq
19: c3 retq
Here the function call for printf is callq 13. One thing i don't understand is why is it 13. That means call the function at adresss 13, right??. 13 has the next instruction, right?? Please explain me what does this mean??
The
executable code corresponding to main is
00000000004004cc <main>:
4004cc: 55 push %rbp
4004cd: 48 89 e5 mov %rsp,%rbp
4004d0: bf dc 05 40 00 mov $0x4005dc,%edi
4004d5: b8 00 00 00 00 mov $0x0,%eax
4004da: e8 e1 fe ff ff callq 4003c0 <printf@plt>
4004df: b8 00 00 00 00 mov $0x0,%eax
4004e4: c9 leaveq
4004e5: c3 retq
Here it is callq 4003c0. But the binary instruction is e8 e1 fe ff ff. There is nothing that corresponds to 4003c0. What is that i am getting wrong?
Thanks.
Bala
