• State Not Answered
  • Locked Locked
  • Replies 4 replies
  • Subscribers 22 subscribers
  • Views 3427 views
  • Users 0 members are here
Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Avoiding macro using 32 bits shift warning

HenkvW

Hi,

I use below macro
#define SFRX(Sfr,Msk) (Sfr=((Sfr & (~ ((Msk)>>8)) ) |(Msk)))
to simply both Set and Reset specified bits in some register.

If I write SFRX ( MyReg , 0x0100 ) this macro clears bit 0.
If I write SFRX ( MyReg , 0x0002 ) this macro set bit 1.
If I write SFRX ( MyReg , 0x0102 ) this macro clears bit 0 and sets bit 1 in one go whithout affecting other bits.

Now I would like to use this macro for a 32-bits system:
#define SREG(Reg,Msk) (Sfr=((Sfr & (~ ((Msk)>>32)) ) |(Msk)))

Although the compiler warns that shifting is too long it works fine.
(main.c(56): warning: #63-D: shift count is too large)

My question is: how do I prevent this warning to occur?

Thanks

Henk

Parents
  • 0 in reply to HenkvW

    The disadvantage is of course that the code is very hard to read, since the code performs a very non-intuitive operation.

    Why not instead create (assuming that one motor may need multiple bits):

    MaskAndSet(MOTOR_LEFT_MASK|MOTOR_RIGHT_MASK,MOTOR_LEFT_ON|MOTOR_RIGHT_OFF);


    or if each motor only have one bit:

    MotorsOffOn(MOTOR_RIGHT,MOTOR_LEFT);


    Your SFRX #define does not give any indication what it does - at best it looks like it performs a set operation, i.e. Sfr = Msk.

    In the general case, you can't just assume that the preprocessor is able to process data of twice the register size. Let's say you have a 64-bit processor where int and long are both 64 bits - why should the preprocessor then support 128-bit integers? Or a 32-bit processor may have 32-bit int and long - why should it have 64-bit support in the preprocessor?

Reply
  • 0 in reply to HenkvW

    The disadvantage is of course that the code is very hard to read, since the code performs a very non-intuitive operation.

    Why not instead create (assuming that one motor may need multiple bits):

    MaskAndSet(MOTOR_LEFT_MASK|MOTOR_RIGHT_MASK,MOTOR_LEFT_ON|MOTOR_RIGHT_OFF);


    or if each motor only have one bit:

    MotorsOffOn(MOTOR_RIGHT,MOTOR_LEFT);


    Your SFRX #define does not give any indication what it does - at best it looks like it performs a set operation, i.e. Sfr = Msk.

    In the general case, you can't just assume that the preprocessor is able to process data of twice the register size. Let's say you have a 64-bit processor where int and long are both 64 bits - why should the preprocessor then support 128-bit integers? Or a 32-bit processor may have 32-bit int and long - why should it have 64-bit support in the preprocessor?

Children
No data