Q63054: Case Lost in Complex Switch Statement in C 6.00

Article: Q63054
Product(s): See article
Version(s): 6.00   | 6.00
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | buglist6.00 | mspl13_c
Last Modified: 25-JUL-1990

Under certain circumstances, a case may be lost in a complex switch
statement under default optimizations with Microsoft C version 6.00.

The following code demonstrates the problem by losing track of case
30. To work around the problem, disable optimizations or add /Os via
the command-line switches or through the use of the optimize pragma.

Sample Code
-----------

#include <stdio.h>

int cm_lockup( void ) ;

int main( void )
{
   int j;

   switch( 30 )
   {
      case 7:
      case 43:
          j = 1;

      case 8:
          ++j;

      case 35:
          ++j;

      case 137:
          break;

      case 33:
      case 39:
          j = 3;
          break;

      case 30:           // this case is missed
          j = 4;
          break;

      case 12:
          j = 5;
          break;

      case 11:
      case 32:
          j = 6;
          break;

      case 10:
          j = 7;
          break;

      case 2:
          j = 8;
          break;

      case 37:
          j = 9;
          break;

      case 6:
          j = 10;
          break;

      case 13:
          break;

      case 44:
          j = 11;
          break;

      case 41:
          j = 12;
          break;

      case 42:
          j = 13;
          break;

      default:
          cm_lockup();
          break;
   }
   return j;
}

int cm_lockup( )
{
   printf( "bad" );
   return 1;
}

Microsoft has confirmed this to be a problem with C version 6.00. We
are researching this problem and will post new information here as it
becomes available.

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