Rule 4-5-1 prohibits 'b1 |= b2;' ?

[mishak]

Remember that any non-zero value will be considered as 'true' within a logical context, which can lead to surprises:

Code:

a = 0x01u;   // This is logically 'true'
b = 0x10u;   // This is logically 'true'

if ( a &  b )   // Result of bit-wise 'and' is 'false'
if ( a && b )   // Result of logical 'and' is true

Rule 4-5-1 helps to enforce a consistent use of boolean types, helping to allowing defects to be detected.