Multiple variable declaration/assigment in C switch() statement yield an error in the executable

[Harm-Paas]

/* --------------------------------------------------------------------------
 * Arduino compiler error :
 *  Multiple inline variable declarations/assigments in a C switch statement
 *  yield an error in the executable.
 *  After multiple variable declarations in the switch() construct
 *  the rest of the switch statement case entries become unreachable.
 * 
 * Compiler version : Arduino IDE 1.8.15
 * O.S. Windows10
 *
 * 2021-07-25 Harm Paas PA0HPG
 */

void pickchoice(char MyChoice) {
   char Cmd ;

   Cmd = MyChoice;
   
   switch(Cmd) {
   case 'A':
     int var1 = 1;        // Signed variables in switch() 
     Serial.println(var1);
     //...stmts...
   break;
   case 'B':
     int var2 = 2;
     Serial.println(var2);
   // ...stmts...
   break;
   case 'C':
     int var3 = 3;
     Serial.println(var3);
     // ...stmts...
   break;
   } // end switch
}
//   -----------------------------------------------------------------------
//   Correct version of the same function:
void correctpickchoice(char MyChoice) {
   char Cmd ;
   int var1 = 10 ; // Do not declare/assign variables in the switch
   int var2 = 20 ;
   int var3 = 30 ; 

   Cmd = MyChoice;
   
   switch(Cmd) {
   case 'A':
     var1 = 10;
     Serial.println(var1);
     //...stmts...
   break;
   case 'B':
     var2 = 20;
     Serial.println(var2);
     // ...stmts...
   break;
   case 'C':
     var3 = 30;
     Serial.println(var3);
   // ...stmts...
   break;
   } // end switch
}
//   -----------------------------------------------------------------------

void setup(){
  Serial.begin(9600);
}

void loop() {

  Serial.println("Executable error with multiple variable declarations in switch()");
  Serial.println("Wrong version:");
  pickchoice('A');
  pickchoice('B');
  pickchoice('C');

  Serial.println("Corrected version of the declaration :");
  
  correctpickchoice('A');
  correctpickchoice('B');
  correctpickchoice('C');

  while(true);
}

[per1234]

Hi @Harm-Paas. Thanks for taking the time to submit an issue.

I see we already have a prior issue report about this at #10154

It's best to have only a single issue per subject so we can consolidate all relevant discussion to one place, so I'll go ahead and close this in favor of the other.

If you would like assistance with your code, please post on the Arduino Forum. We can definitely help you out over there:
https://forum.arduino.cc/c/using-arduino/programming-questions/20