lost Interrupts for Digital Pin and attached ISR function

Hi,
I have a Push Button with pullup connected to digital in pin. I'm reading from digital Pin having attached an IRQ routing
attachInterrupt(digitalPinToInterrupt(pin), IRQ_ForPin, CHANGE)
In the Interrupt routing I read the value of the pin
value = DigitalReal(pin)

My problem is, that sometimes the value read is not the value of the pin. So there was a PIN change, but no further call to the ISR routine. Thats why I call this a lost interrupt.

Looking at the IRQ handling shows, that IRQ routing is called before interrupt is cleared. So pin may change after I read and before IRQ is cleared. Thats seems to be the problem. I fixed by clearing IRQ after call attached function.

After doing this change, this issue is gone:

From WInterrupts.c:
void EIC_Handler(void)
{
[...]
{
if ((EIC->INTFLAG.reg & ISRlist[i]) != 0)
{
// interted here by me
// Clear the interrupt
EIC->INTFLAG.reg = ISRlist[i];

// Call the callback function
ISRcallback[i]();

// commented out here by me
// Clear the interrupt
// EIC->INTFLAG.reg = ISRlist[i];
}
}
}

I can not see any advantage of clearing IRQ after calling the attached function. So I assume, that is a bug.

What are your thoughts?
Can this be fixed?

Thanks and best regards
Achim

Start by reading WInterrupts.c, focusing on EIC_Handler and the attachInterrupt path described in the issue. Compare the interrupt-flag clearing order around ISRcallback[i] and verify the behavior with a CHANGE-triggered digital pin; done means the interrupt handling no longer loses a subsequent pin change.

Written by the indexing model from the issue text.