Question

I have a series of classes that are going to require many boolean fields, somewhere between 4-10. I’d like to not have to use a byte for each boolean. I’ve been looking into bit field structs, something like:

struct BooleanBitFields
    {
        bool b1:1;
        bool b2:1;
        bool b3:1;
        bool b4:1;
        bool b5:1;
        bool b6:1;
    };

But after doing some research I see a lot of people saying that this can cause inefficient memory access and not be worth the memory savings. I’m wondering what the best method for this situation is. Should I use bit fields, or use a char with bit masking (and’s and or
s) to store 8bits? If the second solution is it better to bit shift or use logic?

If anyone could comment as to what method they would use and why it would really help me decide which route I should go down.

Thanks in advance!

Answer 1

With the large address spaces on desktop boxes, an array of 32/64-bit booleans may seem wasteful, and indeed it is, but most developers don’t care, (me included). On RAM-restricted embedded controllers, or when accessing hardware in drivers, then sure, use bitfields, otherwise..

One other issue, apart from R/W ease/speed, is that a 32- or 64-bit boolean is thread-safer than one bit in the middle that has to be manipulated by multiple logical operations.