I write empty programs to annoy the hell out of stackoverflow coders, NOT. I am just exploring the gnu toolchain.

Now the following might be too deep for me, but to continuie the empty program saga I have started to examine the output of the C compiler, the stuff GNU as consumes.

    gcc version 4.4.0 (TDM-1 mingw32)


*test.c:*

    int main()
    {
        return 0;
    }


*gcc -S test.c*

    	.file	&quot;test.c&quot;
    	.def	___main;	.scl	2;	.type	32;	.endef
    	.text
    .globl _main
    	.def	_main;	.scl	2;	.type	32;	.endef
    _main:
    	pushl	%ebp
    	movl	%esp, %ebp
    	andl	$-16, %esp
    	call	___main
    	movl	$0, %eax
    	leave
    	ret 

Can you explain what happens here? Here is my effort to understand it. I have used the `as` manual and my minimal x86 ASM knowledge:

 - `.file &quot;test.c&quot;` is the directive for the logical filename.
 -  `.def`: according to the docs *&quot;Begin defining debugging information for a symbol name&quot;*. What is a symbol (a function name/variable?) and what kind of debugging information?
 - `.scl`: docs say *&quot;Storage class may flag whether a symbol is static or external&quot;*. Is this the same *static* and *external* I know from C? And what is that &#39;2&#39;?
 - `.type`: stores the parameter *&quot;as the type attribute of a symbol table entry&quot;*, I have no clue.
 - `.endef`: no problem.
 - `.text`: Now this is problematic, it seems to be something called section and I have read that its the place for code, but the docs didn&#39;t tell me too much.
 - `.globl` *&quot;makes the symbol visible to ld.&quot;*, the manual is quite clear on this.
 - `_main:` This might be the starting address (?) for my main function
 - `pushl_`: A long (32bit) push, which places EBP on the stack
 - `movl`: 32-bit move. Pseudo-C: `EBP = ESP;`
 - `andl`: Logical AND. Pseudo-C: `ESP = -16 &amp; ESP`, I don&#39;t really see whats the point of this.
 - `call`: Pushes the IP to the stack (so the called procedure can find its way back) and continues where `__main` is. (what is __main?)
 - `movl`: this zero must be the constant I return at the end of my code. The MOV places this zero into EAX.
 - `leave`: restores stack after an ENTER instruction (?). Why?
 - `ret`: goes back to the instruction address that is saved on the stack

**Thank you for your help!**

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GCC's assembly output of an empty program on x86, win32