Note that this only applies if both are in the same block. Just like in C++, it is perfectly legal to have the same variable name in two different nested scopes.
The original implementation just printed a mostly information-free message and then went on as if nothing has happened, making it ridiculously easy to write broken code and release it. Changed it to:
* Any VMAbortException will now terminate the game session and go back to the console.
* It will also print a VM stack trace with all open functions, including source file and line numbers pointing to the problem spots. For this the relevant information had to be added to the VMScriptFunction class.
An interesting effect here was that just throwing the exception object increased the VM's Exec function's stack size from 900 bytes to 70kb, because the compiler allocates a separate local buffer for every single instance of the exception object.
The obvious solution was to put this part into a subfunction so that it won't pollute the Exec function's own stack frame. Interesting side effect of this: Exec's stack requirement went down from 900 bytes to 600 bytes. This is still on the high side but already a lot better.
- fixed PARAM_ACTION_PROLOGUE to assign correct types to the implicit pointers. It gave the actual class to the wrong one, which until now did not matter because all functions were using 'Actor', regardless of actual class association.
- fixed the definition of IceChunk and removed some redundant code here. Since A_FreezeDeathChunks already calls SetState, which in turn calls the state's action function, there is no need to call it again explicitly.
- throw a useful exception when a VM abort occurs, the simple enum was incapable of reporting anything more than the barest minimum, which at least for array index out of bounds errors was insufficient.
The current exception mechanism is still insufficient. It really has to report a proper crash location and print a stack trace to the maximum extent possible. Instead it just prints a message and happily goes on. This is not a good solution.
Although this already helps a lot with the messed up code generated for comparisons it's not really a solution for this - it still needs a proper implementation to generate efficient code.
- fixed: When replacing a tentative class, the pointers in the morph objects were not replaced. Instead of adding more ReplaceClassRef methods I chose to integrate this part into the PointerSubstitution mechanism and delete ReplaceClassRef entirely. The code had some oversights anyway that would have caused problems, now that non-actors can be created.
It is utterly pointless to require every function that wants to make a VM call to allocate a new stack first. The allocation overhead doubles the time to set up the call.
With one stack, previously allocated memory can be reused. The only important thing is, if this ever gets used in a multithreaded environment to have the stack being declared as thread_local, although for ZDoom this is of no consequence.
- eliminated all cases where native code was calling other native code through the VM interface. After scriptifying the game code, only 5 places were left which were quickly eliminated. This was mostly to ensure that the native VM function parameters do not need to be propagated further than absolutely necessary.
