I'm new to the assembly world and I study converting code in C to better understand the logic. I use objconv to do the conversion and I use Windows. I converted the following C code:
#include <stdio.h>
int main()
{
int vector[5] = {2, 6, 8, 9, 4};
int aux = 0;
for(int i = 0; i < 5; i++)
{
aux = aux + vector[i];
}
printf("The summation of array is: %d", aux);
}
The generated assembly code was:
global _main:
extern _printf
extern ___main
SECTION .text
.text: ; Local function
_main:
push ebp
mov ebp, esp
and esp, 0FFFFFFF0H
sub esp, 48
call ___main
mov dword [esp+14H], 2
mov dword [esp+18H], 6
mov dword [esp+1CH], 8
mov dword [esp+20H], 9
mov dword [esp+24H], 4
mov dword [esp+2CH], 0
mov dword [esp+28H], 0
jmp ?_002
?_001: mov eax, dword [esp+28H]
mov eax, dword [esp+eax*4+14H]
add dword [esp+2CH], eax
add dword [esp+28H], 1
?_002: cmp dword [esp+28H], 4
jle ?_001
mov eax, dword [esp+2CH]
mov dword [esp+4H], eax
mov dword [esp], ?_003
call _printf
mov eax, 0
leave
ret
nop
SECTION .data
SECTION .bss
SECTION .rdata
?_003: ; byte
db 54H, 68H, 65H, 20H, 73H, 75H, 6DH, 6DH ; 0000 _ The summ
db 61H, 74H, 69H, 6FH, 6EH, 20H, 6FH, 66H ; 0008 _ ation of
db 20H, 61H, 72H, 72H, 61H, 79H, 20H, 69H ; 0010 _ array i
db 73H, 3AH, 20H, 25H, 64H, 00H, 00H, 00H ; 0018 _ s: %d...
As you can see, C's printf is representing the assembly at label ?_003. What exactly would all this data be? Is it possible to simplify this output?
The hexadecimal block at the label ?_003 is just the representation of the C string
"The summation of array is: %d"
You can see an ASCII translation on the right side after the comment char ;: the number is the relative address, the underscore a delimiter, and the chars are part of the string.
db 54H, 68H, 65H, 20H, 73H, 75H, 6DH, 6DH ; 0000 _ The summ
db 61H, 74H, 69H, 6FH, 6EH, 20H, 6FH, 66H ; 0008 _ ation of
db 20H, 61H, 72H, 72H, 61H, 79H, 20H, 69H ; 0010 _ array i
db 73H, 3AH, 20H, 25H, 64H, 00H, 00H, 00H ; 0018 _ s: %d...
An equivalent in (NASM) assembly that isn't created automatically (like by objconv) would be
outStr: db "The summation of array is: %d",0