switch in C … confused by freeform text.

I was surprised just now to learn (or relearn) a new variant of the C switch syntax looking at code today that I didn’t write (or I am particularly senile today).

I’d always written my case conditions in a scope, and had the break (if any) in that scope like so:

#include <stdio.h>

int main( int argc, char ** argv )
{
   switch (argc)
   {
      case 0:
      {
         printf( "can't get here: argc: %d\n", argc ) ;
         break ;
      }

      case 1:
      {
         printf( "1: argc: %d\n", argc ) ;
         break ;
      }

      default:
      {
         printf( "2: argc: %d\n", argc ) ;
      }
   }

   return 0 ;
}

hotel80:/vbs/engn/sqe> cc t.c
hotel80:/vbs/engn/sqe> a.out
1: argc: 1
hotel80:/vbs/engn/sqe> a.out 1
2: argc: 2
hotel80:/vbs/engn/sqe> a.out 1 blah
2: argc: 3

For some reason today I appear to have thought that the syntax HAD to be like:

case CONDITION:
STATEMENT_OR_SCOPE
case CONDITION:
STATEMENT_OR_SCOPE
...

Where STATEMENT_OR_SCOPE if it is a scope can contain an optional break. So today when I saw code like:

   switch (argc)
   {
      case 0:
      {
         printf( "can't get here: argc: %d\n", argc ) ;
      }
      break ;

      case 1:
      {
         printf( "1: argc: %d\n", argc ) ;
      }
      break ;

I thought … “how can that possibly work?” Can you ever get to case 1? Turns out the answer is yes, which makes sense in retrospect since the statements after a case don’t have to be in a scope.

Since I’ve put my breaks and everything else in the scope following the case for so many years and never deviating from that practice I got confused when I saw otherwise.

If the code had been written:

   switch (argc)
   {
      case 0:

         printf( "can't get here: argc: %d\n", argc ) ;
         break ;

      case 1:

         printf( "1: argc: %d\n", argc ) ;
         break ;

… I don’t think I would have gotten confused (ie. if you are going to use a scope for your case statements doesn’t it make sense to put the break in there too?) It’s funny how much a little deviation from convention makes a difference in understanding program flow.

Personally it seems to me that a scope following a case really ought to be mandatory. It’s a tiny bit more typing, but I think the clarity is worth it. I’m probably getting spoiled by perl, where the scope is mandatory.