Creating stack references dynamicly

[DoomyD]

Out of curiosity: I wondered if there is a way to create a symbolic stack reference without using the LOCAL directive - I usually do so manualy when working with structures: I use the [reg + <struct.item>] \ lea reg,[reg + <struct>] , but I believe a macro could be more efficiant here. For an elaboration: I want to do so from the middle of a procedure, as I find it easier to work with.
Any ideas?

[Mark Jones]

May I ask, how would this be (different/better/more useful) than just using LOCAL?

[DoomyD]

For an example, VirtualProtectEx requires a pointer to a variable to set with the old access protection, which I don't use. Creating a local for that task is simply not not that useful in my opinion. The following is my choise for this API:

Code Select Expand

push 0
invoke VirtualProtectEx, hProcess, lpAdress, dwSize, flNewProtect, esp ;esp < esp = the new variable
add esp, 4
.
.
.Another example would be Process32First\Next:

Code Select Expand

invoke CreateToolHelp32Snapshot, <dwFlags>, <th32ProcessID>
.if (eax)
  push eax ;<<<<
  invoke Process32First, [esp+4], <LPPROCESSENTRY32> ;<[esp+4] = snapshot handle
  .repeat
    ...
    invoke Process32Next, [esp+4], <LPPROCESSENTRY32>
  .until (!eax)
  call CloseHandle
.endifAs you can see, its not hard to work with a single dword, but what I want to do, is to create the PROCESSENTRY32 dynamicly(sub\add esp, sizeof PROCESSENTRY32 ), as my procedure might be a bit large and I want to keep it close to the code that uses it. In addition, when the Process32First\Next section of the code is conditional, a local directive could result as useless.

[jj2007]

as my procedure might be a bit large and I want to keep it close to the code that uses it

If you use the stack, it doesn't make a difference if the LOCAL is declared on top or close to your code. Unless, of course, you decide to make the code section writeable and to put the variable really close:

Code Select Expand

include \masm32\include\masm32rt.inc

.data?
f2sConW dw 0

.code
start:
; int 3 ; set a breakpoint in OllyDbg if you want to see what ml does
jmp @F
MyStruc:
dd 100, 200, 300, 400
@@:
mov edx, offset MyStruc

mov eax, [edx]
pushad
invoke MessageBox, 0, str$(eax), chr$("Test 1"), MB_OK
popad

mov eax, [edx+4]
pushad
invoke MessageBox, 0, str$(eax), chr$("Test 2"), MB_OK
popad

exit
end start