WorkerThreadPool max thread count set to 0 produces index error and crash at start

[smix8]

Tested versions

Godot 4.5beta1

System information

Windows 10

Issue description

If WorkerThreadPool max thread count is set to 0 in the ProjectSettings it causes index errors at game start followed by a crash.

Expected would be that it would set itself to at least 1 thread as default as it does with all platforms that do not support threads.

Steps to reproduce

Set WorkerThreadPool max thread count to 0 in the ProjectSettings.

Minimal reproduction project (MRP)

N/A

[WinnerWind]

I'll be looking into this, but since my C++ skills are very weak, I'll keep you posted whether or not I am able to do this or not.

Ideally the user shouldn't be allowed to set threads to 0, but I'll need to study the codebase to figure out what is going on.

EDIT: Just looked at ProjectSettings, and seeing the existence of -1, I think threads being 0 should be completely disallowed.

[bs-mwoerner]

Ideally the user shouldn't be allowed to set threads to 0, but I'll need to study the codebase to figure out what is going on.

Maybe both prevent entering 0 into the UI and add a safeguard to the code in case the setting is set by other means (editing the settings file)?

This should be where the thread pool is initialized:

godot/core/object/worker_thread_pool.cpp

Lines 778 to 792 in 242b8ff

	void WorkerThreadPool::init(int p_thread_count, float p_low_priority_task_ratio) {
	ERR_FAIL_COND(threads.size() > 0);
	runlevel = RUNLEVEL_NORMAL;
	if (p_thread_count < 0) {
	p_thread_count = OS::get_singleton()->get_default_thread_pool_size();
	}
	max_low_priority_threads = CLAMP(p_thread_count * p_low_priority_task_ratio, 1, p_thread_count - 1);
	print_verbose(vformat("WorkerThreadPool: %d threads, %d max low-priority.", p_thread_count, max_low_priority_threads));
	threads.resize(p_thread_count);

I suppose you could change this to p_thread_count <= 0, so that 0 also uses the default value. Alternatively, you could check p_thread_count for 0 and either change it to 1 or error out at this point.

[WinnerWind]

Oh, thanks for taking a look at the code!
I was about to say the same thing as well, both prevent the GUI from being set to 0 (running a game at 0 threads, even if it does something completely different, makes no sense and is in my opinion bad UX)