Cheat Engine

[DepressedCE]

Hello,
I'm trying to create a little c++ that would replicate something in the DS3 Cheat engine table.

I have code that allows me to grab the process id and the modules (similar to what is done in the DS3 table) but what I'm confused about is how the program would invoke a function in the DS3 program.

I have the process id and modules address etc, I can use things to write to memory but it seems I can't find a tutorial I understand that kinda explains a way to invoke the function that is being invoked by Cheat Engine.
Here is the ASM of the cheat:

[OldCheatEngineUser]

[DepressedCE]

Is there anything describing the pros and cons of the two approaches?

Isn't it what Cheat engine does?
Can you provide some links to some materials I would need to review to try any of the two ways?

Thank you

[OldCheatEngineUser]

i never called a function externally, the code setup required to call a function externally have lot of overhead.

and lets be clear its not a real call, its made by creating a remote thread in your target process.

you will have to change thread context to setup some registers used by the function, you also need to edit thread's stack to pass arguments to that function as well as the return address so the thread returns to the system and get destroyed.

you cant get a return value, its waste of resources; creating 100 threads isnt anywhere near good or OK.

as for dll injection, its much simpler all you need to do is to pass arguments and determine whether its cdecl or stdcall.
you can get the returned value when you call it internally, its much faster and safer.
you can also hook that function and alter it behavior.

an example on how to call a function from C code (internally):
typedef void(__cdecl *_MyFuncCall)(int arg1, int arg2); /* prototype */
_MyFuncCall MyFuncCall = (_MyFuncCall)0x12345678; /* instance of the function plus assigning the instance to an address */
MyFuncCall(1, 2); /* call it */

or if you wish you may use:
void MyFuncCall(int arg1, int arg2)
{
__asm{
push arg2 // valid in 32-bit process, invalid in 64-bit
push arg1 // as calling conventions are different
call 0x12345678
add esp, 8 // you dont need this line if its stdcall
}
}

side note:
visual studio no longer support inline assembly for 64-bit processes.