The alignment and total size of the struct are platform and compiler specific. You cannot not expect straightforward and predictable answers here. Compiler can always have some special idea. For example:
struct B
{
unsigned b0: 1; // +1 bit
unsigned char c; // +8 bits
unsigned b1: 1; // +1 bit
};
Compiler can merge fields b0 and b1 into one integer and may not. It is up to compiler. Some compilers have command line keys that control this, some compilers not. Other example:
struct B
{
unsigned short c, d, e;
};
It is up to compiler to pack/not pack the fields of this struct (asuming 32 bit platform). Layout of the struct can differ between DEBUG and RELEASE builds.
I would recommend using only the following pattern:
struct B
{
unsigned b0: 1;
unsigned b1: 7;
unsigned b2: 2;
};
When you have sequence of bit fields that share the same type, compiler will put them into one int. Otherwise various aspects can kick in. Also take into account that in a big project you write piece of code and somebody else will write and rewrite the makefile; move your code from one dll into another. At this point compiler flags will be set and changed. 99% chance that those people will have no idea of alignment requirements for your struct. They will not even open your file ever.
