Cheat Engine

[cheat_me]

When CE executes a cheat script with [ENABLE] / [DISABLE] sections, it overwrites machine instructions in the process memory. But does CE pauses the process during this overwrite? Because I am having a non persistent crash in a game at the moment the cheat is DISABLED. If the process is not paused, the game may try to execute that part of code which CE has not yet finished writing to. And therefore the code will be in a wrong state.

[Profound_Darkness]

I was having something similar...

I don't actually know how CE does things, I suspect that it (somehow) keeps an eye on execution and if your memory isn't being executed CE will allow the dealloc (finishes disabling the cheat).

On the other hand it could just be coincidence that crashes aren't more common... The game, ideally, spends most of it's time outside of your code/injection area so if your code is taking longer to run and/or the sequence you overwrite with injection is executed FREQUENTLY the odds go up for a crash.

I had some code execution (call) to another script's memory that if I were in that other script/memory the return could (usually did) crash since the return pointed to null memory.

The first thing I tried, MUCH simpler, was to globalalloc... well most of the memory I was using. Same for memory with variables (symbols) that might need to get passed around. I didn't really like this...

I ended up writing a Lua script that was executed in the disable section. It wrote a 1 into memory (variable) that the asm code had access to and the lua code would sleep (blocking, repeat until) while waiting for that value to go to 0.

In the asm code at the end of any and all call chains or jumps I set the value of that variable to 0 (always).

Works like a charm.

If you end up going this route, error() in Lua will prevent the cheat from disabling. I mention this as it's a good idea to give up waiting after a while (due to bug in code or game is being debugged) otherwise CE will end up stuck (and it sucks if you haven't saved recently ).

There could be some other possibilities for the crash, from my limited experience, but I don't know what was the cause exactly in those cases.

Edit:
Went ahead and posted an example of what I'm doing in Lua, it might have some bugs still...

I've tweaked the code from my original to operate entirely within a single script instead of spread out over multiple scripts... This is tweaked to be for just one script but it doesn't take much to make it work for multiple scripts/variables...

I didn't test the code as it is here...

(I was quite sleepy when I stripped out some elements, one of which was key, if someone else uses the code, this has the aspect added back in, not tested).

[Dark Byte]

aa scripts are written as blocks in the order they appear(while a block is written the game is locked/paused)

if the jump to newmem is above the newmem block, then first the jmp will be written, and a while later newmem will be filled.
That means that if you don't want to crash, put the implementation of newmem first (just like the code injection example)

[cheat_me]

The crash occurs not when I enable but rather when I DISABLE the cheat. The code looks like this