C++ Question on variable declaration within switch statement

1

I have a switch statement with 6 cases. I wanted to declare some variables within case 5 that would only be used in case 5. The following did NOT work:

case 5:  
      int tempDegF = static_cast<int>(rtcDS3231.getTemperature()*1.8+32);
      int startingY = map(tempDegF, -10, 110, 46, 21); 
break;
case 6:
break;

but this did

case 5: 
      int tempDegF;
      int startingY;
      tempDegF = static_cast<int>(rtcDS3231.getTemperature()*1.8+32);
      startingY = map(tempDegF, -10, 110, 46, 21); 
break;
case 6:
break;

and this did as well

case 5:  
      int tempDegF = static_cast<int>(rtcDS3231.getTemperature()*1.8+32);
      int startingY = map(tempDegF, -10, 110, 46, 21); 
break;
// with case 5 as the final case in the switch statement

why is this?

2

Good question, that would be a good question towards https://stackoverflow.com/.

The one thing I can say is that in order to avoid these problems, create a new scope by using {} and create and use the variables in there, or declare the variables outside the switch statement, in the function body above. So

would work perfectly too.

3

This explains it in detail:

This also explains why it works in the last case (case 5).

4

I see. Thank you guys for that explanation. This is a nuance I was unaware of.

Fish