.p2align 2 (ASM)

I was looking at some ASM code for some of my programs using the 'gcc -S' option to generate it and I noticed a few things that I have NO IDEA what they do, why they are there and if they have any effect on my programs.

Here is a list:

Code:

---

;at the begining
.text
    .align 4

.p2align 2 ;what's this?!

;and I used to know what these were but I forgot

leave ;I think this does popl %ebp to get the original base pointer
ret ;and does this jump to where the program was called or after it or what, I forgot...

---

Any help would be appreciated, im not too concerned about the last two commands but more or less the aligns, what are they, and are they important, I would imagine they are relatively significant because they are there to begin with.


EDIT:

And another question in ASM:
I can't seem to figure out why I continually get a seg-fault for this prog:

Code:

---


.lor:
        .string "Hello, World!\n"

.text
        .align 4
.globl main
main:
        pushl %ebp
        movl %esp, %ebp
        movl $10, %ebx
LOOP:
        cmpl $0, %ebx
        jne NE
        jmp GO
NE:
        pushl $.lor
        call printf
        popl %eax
        decl %ebx
        jmp LOOP
GO:
        movl $0, %eax
        leave
        ret

---

Any explanations of just how things work at all could help, thanks.

-LC

please never mind. I fixed the ASM probelm and I figured out what all that stuff meant, but I can't delete the thread. ::shrug::

The solution was:

Code:

---

NE:
        subl $4, %esp
        pushl $.lor
        call printf
        addl $4, %esp
        decl %ebx
        jmp LOOP

---

Note it will leave a little bit of memory free at the end about 40 bytes, but its better and easier (maybe not faster) because the leave command automatically moves the esp and ebp back to where they were.

a better fix might be:

Code:

---

NE:
        pushl $.lor
        call printf
        addl $4, %esp
        decl %ebx
        jmp LOOP

---

-LC