Recursion while `onExpanderChange`

Development
1

I’m trying to create a module with a main module and then expander modules.

On the left side of the chain, I always want a Main module, with the possibility of adding any number of Expander Modules.

I have this code to notice the main module that the new expander was added or removed, and therefore to collect all expanders into a std::map<moduleName, std::vector<Module*>> structure.

This is code in Expander Module to propagate this message to Main Module.

/** NLMmk3_DrumSequencerExpander.cpp *//
	void onExpanderChange(const ExpanderChangeEvent& e) override {
		if (e.side == 0 || e.side == 1) {
			DEBUG("ON EXPANDER CHANGE side left/right");
			Module* module = getLeftExpander().module;


			while  (module != nullptr) {
				
				if (module->getModel() == modelNLMmk3) {
					// set the newly needed value
					bool* value = (bool*) module->getRightExpander().producerMessage;
					*value = true;

					// no need to request flip, it will be done by the main module
					module->getRightExpander().requestMessageFlip();
					return;
				}
				module = module->getLeftExpander().module;
			}
		} 	
	}

And this is the code in main module to handle given collection of Expander Modules

/** NLMmk3_MainModule.cpp *//
void collectAllExpanders()
    {
        setExpandersConnectedLights(0.f);
        DEBUG("Clearing expanders");
        printAllExpanders();
        this->expanders = {};

        DEBUG("Collecting expanders:");
                Module *module = getRightExpander().module;
        while (module != nullptr) {
            if (allowedSubmodules.find(module->model) != allowedSubmodules.end()) {

                float colorParam = module->getParam(0).getValue();
                DEBUG("\tFound expander: %s with color <%d>", module->model->name.c_str(), (int)colorParam); //g
                
                if (this->expanders.find(module->getModel()) == this->expanders.end()) {
                    this->expanders[module->getModel()] = {};
                }
                this->expanders[module->getModel()].push_back(module);
            }
            module = module->getRightExpander().module;
        }
        setExpandersConnectedLights(1.f);
    }

The problem I have is when I switch two modules that are next to each other, I get this message:

969 debug src/NLMmk3_DrumSequencerExpander.cpp:46 onExpanderChange] on module with COLOR -536870912
[10.969 debug src/NLMmk3_DrumSequencerExpander.cpp:45 onExpanderChange] 
[10.969 debug src/NLMmk3_DrumSequencerExpander.cpp:46 onExpanderChange] on module with COLOR -1073741824
[10.969 debug src/NLMmk3_DrumSequencerExpander.cpp:45 onExpanderChange] 
[10.969 debug src/NLMmk3_DrumSequencerExpander.cpp:46 onExpanderChange] on module with COLOR -536870912
[10.969 debug src/NLMmk3_DrumSequencerExpander.cpp:45 onExpanderChange] 
[10.969 debug src/NLMmk3_DrumSequencerExpander.cpp:46 onExpanderChange] on module with COLOR -1073741824

Therefore, somehow, I get into infinite loop in while loop on Expander::onExpanderChange, and I just can’t understand why.

Additionally I’m adding the GitHub repo link.

2

Maybe @DaveVenom had a similar problem here:

3

I gave it a try and grabbed your sources on GitHub.

First I only looked at the module NLMmk3 because the expander module crashed Rack in the module browser. So in the plugin.json I set "hidden": true, for the Expander module.

I didn’t find any infinite loop but Rack crashed at line 66 in nl/renderer.cpp when calling output->sendMessage(msg);

Maybe the MIDI-out-port isn’t set, but your module has no way to set the MIDI-out-port (or may I have overlooked something).

I used Rack version 2.5.2