Q48724: Incorrect Evaluation When Type Casting in while and for Loops

Article: Q48724
Product(s): See article
Version(s): 1.01 2.00 2.01
Operating System(s): MS-DOS
Keyword(s): ENDUSER | S_QuickASM buglist1.01 buglist2.00 | mspl13_c
Last Modified: 10-OCT-1989

The resulting value is incorrectly evaluated when you type cast an
integer to a float (or double) in "for" loops and "while" loops in
QuickC Versions 1.01 and 2.00 and QuickAssembler Version 2.01.

The problem does not occur in the initialization expression, only
in the conditional test expression and the increment expression.
Workarounds include using a temporary variable and simplifying the
assignment expression.

Microsoft has confirmed this to be a problem with QuickC Versions 1.01
and 2.00 and QuickAssembler Version 2.01 (buglist2.01). We are
researching this problem and will post new information as it becomes
available.

The following program demonstrates the problem. Note that the problem
also exists if you replace references to "float" by "double".

#include <stdio.h>
void main(void)
{
   float var;
   float temp;

   var = (float)1;               /* do-while statement:            */
   do                            /* all casts work correctly       */
     var += (float)2;
   while (var <= (float)5);
   printf ("var = %12f, expected 7.000000\n", var);

   var = (float)1;               /* while statement:                */
   while (var <= (float)5)       /* this cast works incorrectly     */
     var += (float)2;            /* this cast works correctly       */
   printf ("var = %12f, expected 7.000000\n", var);

   for                           /* for statement:                  */
       (var = (float)1;          /* this cast works correctly       */
        var <= (float)5;         /* this cast works incorrectly     */
        var += (float)2)         /* this cast and/or the assignment */
                                 /* works incorrectly               */
            continue;
   printf("var = %12f, expected 7.000000\n", var);

/* Workarounds for the while- and for-loops:                        */

   var = (float)1;               /* while statement:                */
   temp = (float)5;              /* this cast works correctly       */
   while (var <= temp)           /* use a non-cast float here       */
     var += (float)2;            /* this cast works correctly       */
   printf ("var = %12f, expected 7.000000\n", var);

   for                           /* for statement:                  */
       (var = (float)1;          /* this cast works correctly       */
        var <= (float)5;
        var = var + (float)2)    /* use a different assignment      */
            continue;
   printf("var = %12f, expected 7.000000\n", var);
}

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