RetroArch crashes when any joystick direction is pressed, EmulationStation fine.

[The_Next_Guy]

I am writing an input driver for my device that talks to a pico to relay button presses and analog readings. I am having issues with RetroArch crashing on axis input, giving a not so detailed Floating Point Exception in /dev/shm/runcommand.log, or not recognizing DPAD input if I change it to button presses. Here is my relevant code for the driver. Everything responds in EmulationStation just fine, just RetroArch crashes. here are the relevant sections of my code:

void ControllerManager::setup_uinput_device(int joystick_id) {
    struct uinput_setup usetup;
    int fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (fd < 0) {
        perror("Unable to open /dev/uinput");
        exit(EXIT_FAILURE);
    }

    ioctl(fd, UI_SET_EVBIT, EV_KEY);
    ioctl(fd, UI_SET_KEYBIT, BTN_A);
    ioctl(fd, UI_SET_KEYBIT, BTN_B);
    ioctl(fd, UI_SET_KEYBIT, BTN_X);
    ioctl(fd, UI_SET_KEYBIT, BTN_Y);
    ioctl(fd, UI_SET_KEYBIT, BTN_START);
    ioctl(fd, UI_SET_KEYBIT, BTN_SELECT);
    ioctl(fd, UI_SET_KEYBIT, BTN_TL);
    ioctl(fd, UI_SET_KEYBIT, BTN_TR);

    ioctl(fd, UI_SET_EVBIT, EV_ABS);
    ioctl(fd, UI_SET_ABSBIT, ABS_X);
    ioctl(fd, UI_SET_ABSBIT, ABS_Y);

    memset(&usetup, 0, sizeof(usetup));
    usetup.id.bustype = BUS_USB;
    usetup.id.vendor = 0x5348; // Sample Vendor
    usetup.id.product = 0x0100 + joystick_id; // Unique product ID for each joystick
    snprintf(usetup.name, UINPUT_MAX_NAME_SIZE, "Xemplar PicoTroller %d", joystick_id);

    ioctl(fd, UI_DEV_SETUP, &usetup);
    ioctl(fd, UI_DEV_CREATE);

    fds[fd_count++] = fd;
}

void ControllerManager::monitorJoystick(byte controller_index, byte button_count, const byte* button_values, byte axis_count, const int16_t* axis_values) {
	if(controller_index < 0 || controller_index > fd_count) return; // Invalid controller index
	if(controller_index == 0){
		pluggedIn = (button_values[0] & 0x01) > 0;
		bool isFan = (button_values[0] & 0x02) > 0;
		if(isFan){
		  fanValue = axis_values[0];
		} else {
		  batteryValue = axis_values[0];
		}
		return;
	}
	controller_index--;
	
	if(controllers[controller_index].button_count < button_count){
		controllers[controller_index].button_count = button_count;
		controllers[controller_index].axis_count = axis_count;
	}
	for(int i = 0; i < button_count; i++){
		byte byte_index = i / 8;
        byte bit_index = i % 8;
        byte button_state = (button_values[byte_index] >> bit_index) & 1;
			
		controllers[controller_index].button_states[i] = button_state == 1;
	}
	for (byte i = 0; i < axis_count; ++i) {
        controllers[controller_index].axis[i].x = axis_values[i * 2];
        controllers[controller_index].axis[i].y = axis_values[i * 2 + 1];
    }
	
	if(checkSpecial(controller_index)) return;
	
	controller_index++;
	emulateJoystick(controller_index, button_count, button_values, axis_count, axis_values);
}

void ControllerManager::emulateJoystick(byte controller_index, byte button_count, const byte* button_values, byte axis_count, const int16_t* axis_values) {
    int fd = fds[controller_index - 1]; // Convert to 0-based index
    sendEvent(fd, EV_SYN, SYN_REPORT, 0);

    for (byte i = 0; i < button_count; ++i) {
		int code;
        switch (i + 1) {
            case 1: code = BTN_A; break;
            case 2: code = BTN_B; break;
            case 3: code = BTN_X; break;
            case 4: code = BTN_Y; break;
            case 5: code = BTN_START; break;
            case 6: code = BTN_SELECT; break;
            case 7: code = BTN_TL; break;
            case 8: code = BTN_TR; break;
            default: continue;
        }
        sendEvent(fd, EV_KEY, code, controllers[controller_index - 1].button_states[i]);
    }
	
    sendEvent(fd, EV_SYN, SYN_REPORT, 0);
	
	sendEvent(fd, EV_ABS, ABS_X, controllers[controller_index - 1].axis[0].x);
    sendEvent(fd, EV_ABS, ABS_Y, controllers[controller_index - 1].axis[0].y);

    sendEvent(fd, EV_SYN, SYN_REPORT, 0);

    if (DEBUG) {
        std::cout << "\rAxes: ";
        for (byte i = 0; i < axis_count * 2; ++i) {
            std::cout << std::setw(3) << static_cast<int>(i) << ":" << std::setw(6) << controllers[controller_index - 1].axis[i].x << " " << controllers[controller_index - 1].axis[i].y << " ";
        }
        std::cout << "Buttons: ";
        for (byte i = 0; i < button_count; ++i) {
            std::cout << std::setw(2) << static_cast<int>(i) << ":" << (controllers[controller_index - 1].button_states[i] ? "on " : "off ");
        }
        std::cout << std::flush;
		if(!ONE_LINE) std::cout << std::endl;
    }
}

[mitu]

RetroPie just packages RetroArch - you may want to report to the upstream project. You should add a way to reproduce the issue without relying on a specific device, so that any developer familiar with RetroArch's input system may be able to analyze and maybe fix your issue.