neg esi

[Camel]

Code Select Expand

.text:6F6721BB                 lea     esi, [eax+9]
.text:6F6721BE                 neg     esi
.text:6F6721C0                 xor     ebx, ebx
.text:6F6721C2                 and     esi, 3Fh

If I am not mistaken, the first line should set esi to the offset (eax+9). What, then, is the point of inverting a pointer?

[iago]

eax isnt' necessarely a pointer.  Using a lea is an optimized way of adding 2 variables and storing them somewhere else.

It's basically, esi = ~(eax + 9);

[Camel]

Ah, thanks.

[edit]

Code Select Expand

.text:6F6721F9                 lea     esp, [esp+0]
Uh, esp = esp + 0?

[iago]

yes, actually.. that load the address of [esp] into esp .. I don't know why it would do that, unless I was horribly mistaken

[Camel]

Well, I should say esp = &(*(esp+0));

[Skywing]

yes, actually.. that load the address of [esp] into esp .. I don't know why it would do that, unless I was horribly mistaken

That is a fairly common "large nop" when the compiler has a specific amount of bytes it wants to fill with do-nothing code with as minimal of a performance impact as possible.  Typical reasons for this are aligning a code segment that the compiler thinks will be used a good deal.