When ESP changes

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l4m2

Joined: 15 Jan 2015
Posts: 674

l4m2 08 Jan 2016, 16:12

Code:

; example of simplified Windows programming using complex macro features
include 'win32ax.inc' ; you can simply switch between win32ax, win32wx, win64ax and win64wx here
.code
    start:
        push    string1
        invoke  MessageBox,HWND_DESKTOP,dword [esp+8],invoke GetCommandLine,MB_OK
        invoke  ExitProcess,0
    string1:
        db 'Hello!'
.end start

Here if you use

Code:

invoke  MessageBox,HWND_DESKTOP,dword [esp],invoke GetCommandLine,MB_OK

it won't work as expected (I got the name of the .exe file). Is it possible to make it automatically change [esp] to [esp+8] when two values are pushed?

08 Jan 2016, 16:12

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 08 Jan 2016, 16:50

You could try to apply a modification to macros this way:

Code:

include 'win32ax.inc'

macro pushd value {
        pushd value
        offset@stack = offset@stack + 4
}

macro invoke statement& {
        define esp (esp+offset@stack)
        offset@stack = 0
        invoke statement
        restore esp
}

.code
    start:
        push    string1
        invoke  MessageBox,HWND_DESKTOP,dword [esp],invoke GetCommandLine,MB_OK
        invoke  ExitProcess,0
    string1:
        db 'Hello!',0
.end start

But this only adds a layer of processing to the outermost "invoke" - if you wanted to make it work correctly inside a nested statements too, you'd have to modify the allow_nesting macro in win32ax.inc and store/restore the stack offsets at every level of nesting.

08 Jan 2016, 16:50

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