Cheat Engine

Frouk · Posted: Mon May 30, 2022 1:18 am Post subject: Call vtbl function

So i tried to call function from virtual table, it crashes for me, am i doing something wrong?
So the virtual table is having a lot of functions like fix, teleport, blow and etc.
Virtual table is pointing to the class of vehicle function(for car its CAutomobile::Fix, for bike CBike::Fix and etc.)

Dark Byte · Posted: Mon May 30, 2022 1:57 am Post subject:

very likely you're doing it wrong yes

Called it from the wrong thread?
Gave the wrong parameters?
Used the wrong calling convention?

Frouk · Posted: Mon May 30, 2022 2:21 am Post subject:

all function that in vtbl are having only one parameter(vehicle *this) where vehicle represents the type of it
i'm calling the function as default

Dark Byte · Posted: Mon May 30, 2022 2:25 am Post subject:

is the target 32-bit ?
and is addr correct?
and are you sure it's __cdecl ? (If it's 32-bit, the function ends with a ret. If it ends with ret 4 , it's stdcall )

Frouk · Posted: Mon May 30, 2022 2:39 am Post subject:

yes target is 32 bit
and its virtual table addr will change corresponding to a vehicle type
i'm doing this to "fix" vehicle

Dark Byte · Posted: Mon May 30, 2022 5:08 am Post subject:

check if the function you're calling assumes ECX is filled in, or if it takes it from the stack each time

else try

Frouk · Posted: Mon May 30, 2022 5:20 am Post subject:

i'll try it

Frouk · Posted: Thu Jun 02, 2022 6:03 am Post subject:

It works, thank you

EDIT:

How is execute method works?
Also is that possible to call an empty function(no parameters) with executeMethod?

Dark Byte · Posted: Thu Jun 02, 2022 9:41 am Post subject:

https://github.com/cheat-engine/cheat-engine/blob/6237bee483ae7610c033b671f40370b61a4e7478/Cheat%20Engine/bin/celua.txt#L472

the example I gave is the version where you give no parameters . To add parameters add them to the call of executeMethod