C OR '|' operator

Question

I have an statement in a C program by someone else in this format int variable |= functioncall(parameter); I don't understand the use of OR '|' sign in that statement. Can any one please explain what does it do with the assignment operator. I am guessing bitwise OR and then assign.

Answer 1

|= is the bitwise OR assignment operator. Basically, a |= b means a = a | b.

Please check this Wikipedia article for a list of all such compound assignment operators.

For here, the exact meaning of the whole statement someVar |= functioncall(parameter); is:

1. Compute the return value of functioncall(parameter) and then,
2. Do bitwise OR on the return value and the original value of someVar,
3. And finally assign the result of the bitwise OR to someVar.