Code crashing in a struct

[CreativeRobotics]

EDIT - Damn it, I meant Switch, not Struct ...
I can't tell if this is an issue with code, a compiler optimisation bug or something else so I thought I would ask here.
I've been trying to use the Microchip DALI1 control gear stack on Arduino with MegaTinyCore (DALI is a lighting control system for commercial buildings). I downloaded it as a demo project using AtmelSTART and then extracted all the stack files, and put them in an src folder in a sketch. I renamed all the .c files to .cpp, and added an include Ardhino.h to the file called DALI_top.h and them rearranged the code that would have been in main, to be in the sketch.

It compiles - yipee!

When I run it on an attiny1616 it will crash shortly after starting. I traced the crash to a case statement in the function that handles fading.

I can't see anything wrong with the code that would cause it to crash here so I tried removing the entire switch statement and replacing it with a series of if else conditions and now the code compiles and runs, I can send it commands from a DALI controller and it will respond correctly.

If I recompile it for an attiny3217 the code will crash. I can't work out where ...

What I can't get my head around is why it is crashing when I use a device that just has extra pins and memory, or why the switch statement was causing a crash on the first device - its Microchips official software stack and it reportedly works fine so I don't understand why it goes wrong when I compile with megaTinyCore, particuarly why its failing in a switch statement.

I was hoping some more technically skilled programmers might point me to where the problem could be:
Is it a compiler optimisation issue?
Is it because I did something naughty trying to get the c code to work with c++?
Is it something else I failed to understand entirely?

[MX682X]

I don't know why, but gcc can't handle variable initialisation inside the switch case. If you want to initialize a Variable inside a case, you'll need to do that insida a scope, aka curly braces. Is there any initialisation in the swich case?

[CreativeRobotics]

Thanks for replying. I can't see anything wrong in the struct, but as noted above, its Microchips own code and is supposed to compile with their toolchains so its a bit of a puzzle. What I have found is that the code I have at the moment (with the problematic switch statement changed to if/else) will work fine on the attiny1616 and 1617, but will crash on 3216 and 3217 devices.

Given that (I think) the devices are identical apart from memory, I was wondering if there was anything different in the way code was compiled for the different memory size - any different optimisation settings ...?

I've pasted the code below where the crash was happening. This was the code before I changed ot to use if/else.

void dali_command_fade_ms_tick(void)
{
	uint8_t  temp_level, temp0, temp1;
	uint16_t temp_val0, temp_val1;
	uint32_t temp_fade_step;
	uint32_t temp_long_level;

	/* Using this a lot here, use local parameter to save code space */
	temp_fade_step  = fade_step;
	temp_level      = dali.level;
	temp_long_level = dali.long_level;

	if (power_on_flag == true) {
		if (power_on_time > 0) {
			power_on_time--;
		}
	}

	if (current_fade_time > 0) {
		current_fade_time--;
	}

	if (w15min_waiting_time > 0) {
		w15min_waiting_time--;
	}

	if (w10s_identify_time > 0) {
		w10s_identify_time--;
	}

	if (dapc_sequence == true) {
		if (dapc_sequence_time > 0) {
			dapc_sequence_time--;
		} else {
			dapc_sequence                  = false;
			dali_ram.variable.target_level = temp_level;
			update_flag |= VAR_UPDATE;
			fade_direction = FADE_STOP;
		}
	}

	if (dali_hal_get_dali_input_level() == 0) {
		if (interface_fail_time == (uint16_t)FAIL_TIME) {
			interface_fail_flag = true;
			interface_fail_time++;
		} else if (interface_fail_time < (uint16_t)FAIL_TIME) {
			interface_fail_time++;
		}
	} else {
		interface_fail_time = 0;
	}

	switch (fade_direction) {
	case FADE_IDLE:
		break;

	case FADE_STOP:
		need_fade = false;
		status_information &= ~FADE_RUNNING;
		fade_direction = FADE_IDLE;
		if (temp_level != 0) {
			last_active_level = temp_level;
		}
		break;

	/* Fade using int_fadetime. Actually running this as a fade rate
	 * (inv_int_fadetime_val), not directly timed. */
	case FADE_TIME_UP:
		/* Rounding errors may then cause slight changes in fade time,
		 * but the target level will still be the correct one. */
		if (temp_level < dali_ram.variable.target_level) {
			/* Increase level */
			if ((0xFE000000 - temp_long_level) <= temp_fade_step) {
				/* max level 254 */
				temp_long_level = 0xFE000000;
			} else {
				temp_long_level = temp_long_level + temp_fade_step;
			}
		} else {
			/* Turn off fading when done. */
			fade_direction = FADE_STOP;
		}
		break;

	/* Fade using int_fadetime.This fades down, but does not turn off the
	 * lamp. It will stop at minimum level. */
	case FADE_TIME_DOWN:
		if (temp_level >= dali_ram.variable.target_level) {
			/* decrease level */
			if (temp_long_level <= temp_fade_step) {
				temp_long_level = 0;
				/* Turn off as level is 0 now */
				fade_direction = FADE_STOP;
			} else {
				temp_long_level = temp_long_level - temp_fade_step;
			}
		} else {
			temp_long_level = (uint32_t)(dali_ram.variable.target_level) << 24;
			/* Turn off fading when done. */
			fade_direction = FADE_STOP;
		}
		break;

	/* Fade using int_fadetime.This fades down, and will turn off the lamp
	 * if the level gets that low. */
	case FADE_TIME_DOWN_OFF:
		if (temp_level >= dali_ram.variable.minimum_level) {
			/* decrease level */
			if (temp_long_level <= temp_fade_step) {
				temp_long_level = 0;
			} else {
				if (fade_step == 0) { // Here check fade_step
					/* If these is no need to step, turn off the lamp directly*/
					status_information &= ~LAMP_ON;
					temp_long_level = 0;
					fade_direction  = FADE_STOP;
				} else {
					temp_long_level = temp_long_level - fade_step;
				}
			}
		} else {
			/* Once we have reached minimum level, turn off the lamp */
			status_information &= ~LAMP_ON;
			temp_long_level = 0;
			fade_direction  = FADE_STOP;
		}
		break;

	/* Fade using fade_rate (flash_fade_rate_val). */
	case FADE_RATE_UP:
		if (temp_level >= dali_ram.variable.maximum_level) {
			/* Fade terminates until fade expires */
			if (current_fade_time == 0) {
				temp_level                     = dali_ram.variable.maximum_level;
				temp_long_level                = (uint32_t)temp_level << 24;
				dali_ram.variable.target_level = temp_level;
				update_flag |= VAR_UPDATE;
				status_information |= LIMIT_ERROR;
				/* Turn off fading when done. */
				fade_direction = FADE_STOP;
			}
		} else {
			temp_long_level = temp_long_level + temp_fade_step;
			if (current_fade_time == 0) {
				/* Done fading */
				status_information &= ~LIMIT_ERROR;
				dali_ram.variable.target_level = temp_level;
				update_flag |= VAR_UPDATE;
				/* Turn off fading when done. */
				fade_direction = FADE_STOP;
			}
		}
		break;

	/* Fade using fade_rate (flash_fade_rate_val). Does not turn off
	 * the lamp. */
	case FADE_RATE_DOWN:
		if (temp_level < dali_ram.variable.minimum_level) {
			/* Fade terminates until fade expires */
			if (current_fade_time == 0) {
				temp_level                     = dali_ram.variable.minimum_level;
				temp_long_level                = (uint32_t)temp_level << 24;
				dali_ram.variable.target_level = temp_level;
				update_flag |= VAR_UPDATE;
				status_information |= LIMIT_ERROR;
				/* Turn off fading when done. */
				fade_direction = FADE_STOP;
			}
		} else {
			temp_long_level = temp_long_level - temp_fade_step;
			if (current_fade_time == 0) {
				/* Done fading */
				status_information &= ~LIMIT_ERROR;
				dali_ram.variable.target_level = temp_level;
				update_flag |= VAR_UPDATE;
				/* Turn off fading when done. */
				fade_direction = FADE_STOP;
			}
		}
		break;

	/* Identification fade in initialisation state */
	case FADE_DIRECT_IDENTIFICATION:
		temp_long_level = (uint32_t)temp_level << 24;
		/* Use physical max/min level temporarily */
		if (recall_level_flag == MIN_LEVEL_FLAG) {
			temp_level = POWER_MIN;
		} else {
			temp_level = POWER_MAX;
		}
		dali_cmd_set_pwm_output(temp_level);
		status_information &= ~FADE_RUNNING;
		fade_direction = FADE_IDLE;
		if (temp_level != 0) {
			if (interface_fail_flag == false) {
				last_active_level = temp_level;
			}
			if (!(status_information & LAMP_FAILURE)) {
				status_information |= LAMP_ON;
			}
		} else {
			status_information &= ~LAMP_ON;
		}
		/* Clear interface fail flag after fade if there is one */
		interface_fail_flag = false;
		break;
	/* Output directly */
	case FADE_DIRECT:
		dali_cmd_set_pwm_output(temp_level);
		temp_long_level = (uint32_t)temp_level << 24;
		status_information &= ~FADE_RUNNING;
		fade_direction = FADE_IDLE;
		if (temp_level != 0) {
			if (interface_fail_flag == false) {
				last_active_level = temp_level;
			}
			if (!(status_information & LAMP_FAILURE)) {
				status_information |= LAMP_ON;
			}
		} else {
			status_information &= ~LAMP_ON;
		}
		/* Clear interface fail flag after fade if there is one */
		interface_fail_flag = false;
		break;

	case FADE_BETWEEN_MINLEVEL_AND_OFF:
		if (fade_time_off_and_minlevel > 0) {
			fade_time_off_and_minlevel--;
		} else {
			dali.level     = dali_ram.variable.target_level;
			fade_direction = FADE_DIRECT;
		}
		break;

	default:
		break;
	}

	if (need_fade == true) {
		/* Current dali level */
		temp0 = temp_long_level >> 24;
		/* First 8 bit of the dali level fraction */
		temp1     = temp_long_level >> 16;
		temp_val0 = dali_cmd_read_pwm_value(temp0);
		/* Linear interpolation between two dali steps. Difference
		 * between two steps is maximum 110 in PWM output. */
		temp_val1 = ((dali_cmd_read_pwm_value(temp0 + 1) - dali_cmd_read_pwm_value(temp0)) * temp1) >> 8;

		dali_hal_update_pwm_output(temp_val0 + temp_val1);
	}

	dali.long_level = temp_long_level;
}