What does this assembly language code mean?

Question

I am a student and just started studying assembly language. To understand it better I just wrote a short in C and converted it to assembly language. Surprisingly I didn\'t under

Answer 1

For me, intels syntax is easier to read, learning how to generate intels syntax is handy for understanding C programs better;

gcc -S -masm=intel file.c

In windows your C program becomes;

    .file   "file.c"
    .intel_syntax noprefix
    .def    ___main;    .scl    2;  .type   32; .endef
    .section .rdata,"dr"
LC0:
    .ascii "%d\0"
    .text
    .globl  _main
    .def    _main;  .scl    2;  .type   32; .endef
_main:
LFB13:
    .cfi_startproc
    push    ebp
    .cfi_def_cfa_offset 8
    .cfi_offset 5, -8
    mov ebp, esp
    .cfi_def_cfa_register 5
    and esp, -16
    sub esp, 32
    call    ___main
    mov DWORD PTR [esp+28], 4
    mov eax, DWORD PTR [esp+28]
    mov DWORD PTR [esp+4], eax
    mov DWORD PTR [esp], OFFSET FLAT:LC0
    call    _printf
    mov eax, 0
    leave
    .cfi_restore 5
    .cfi_def_cfa 4, 4
    ret
    .cfi_endproc
LFE13:
    .ident  "GCC: (rev2, Built by MinGW-builds project) 4.8.1"
    .def    _printf;    .scl    2;  .type   32; .endef

(the compiler options should be the same on ubuntu as in windows)

Apart from the psychotic labels, this is more like the assembly i read about in text books..

Here is a way of looking at it;

    call    ___main

    mov DWORD PTR [esp+28], 4  
    mov eax, DWORD PTR [esp+28]              ; int n = 4;

    mov DWORD PTR [esp+4], eax 
    mov DWORD PTR [esp], OFFSET FLAT:LC0
    call    _printf                          ; printf("%d",n);

    mov eax, 0
    leave                                    ; return 0;