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1. Products and Versions Concerned
    C compiler package for the M32C series* (M3T-NC308WA)
      V.5.00 Release 1 through V.5.40 Release 00

    C compiler package for the M16C series** (M3T-NC30WA)
      V.5.10 Release 1 through V.5.40 Release 00A

     * The M32C series is the generic name of the M32C/80, and M16C/80
       series.
    ** The M16C series is the generic name of the M16C/60, /30, /20, /10, 
       /Tiny and R8C/Tiny series.

2. Description
   If a write to and a read from a bit field are made before and after 
   calling a function respectively, the value of the bit field may become 
   incorrect.

3. Conditions
   This problem may occur if the following conditions are all satisfied:
   (1) Any of the optimizing options -O[1-5],-OR, and -OS is selected.
   (2) A bit field is used whose storage class is auto.
   (3) The bit field in (2) is not qualified to be volatile.
   (4) A write is made to the bit field in (2).
   (5) The program performs either of the following after the write in (4):
       (a) A call is made to the function that takes the address of the 
           structure containing the bit field in (2) as its argument.
       (b) A call is made to a function immediately after the address of 
           the structure containing the bit field in (2) is assigned to 
           another variable.
   (6) The value of the bit field in (2) is changed within either of the 
       functions in (5)-(a) and (5)-(b).
   (7) The bit field in (2) is accessed after a call is made to either 
       of the functions in (5)-(a) and (5)-(b)

   Example:
   ------------------------------------------------------------------------
    struct tag{       // Conditions (2) and (3)
        unsigned char b0:1;
        unsigned char b1:1;
        unsigned char b2:1;
        unsigned char b3:1;
        unsigned char b4:1;
        unsigned char b5:1;
    };

    main()
    {
        struct tag bit2;

        bit2.b1 = 1;     // Condition (4)
        func(&bit);      // Condition (5)-(a)

        if(bit2.b1==1)   // Condition (7)
        sub();
    }
   ------------------------------------------------------------------------

4. Workaround
   Place a dummy asm function between a write to the bit field and a call 
   to the function involved.
   ------------------------------------------------------------------------
    . . . . . . . . . . . . . . . . . . . .
    main()
    {
        struct tag bit2;

        bit2.b1 = 1;
        asm();      // Place asm function
        func(&bit); 
     . . . . . . . . . . . . . . . . . . . .
   ------------------------------------------------------------------------

5. Schedule of Fixing the Problem
   This problem has already been resolved in the following versions of the 
   products concerned:
    - C compiler package for the M32C series (M3T-NC308WA) V.5.41 Release 00
    - C compiler package for the M16C series (M3T-NC30WA) V.5.42 Release 00
   So use these or later versions.