return ( void )( fl = 0.f );
That is rather unusual code. Casting an expression to
void is usually done to suppress a compiler-warning -- it's an idiom that tells the compiler "yes, I know I am throwing this expression's value away -- but I'm doing it deliberately, so you don't need to warn me about it".
What is unusual there is that the author decided to do that in a
return statement. It would have been clearer (and logically equivalent) to write
fl = 0.0f; return;
instead. The only thing I can think of is that the function used to return a value, and perhaps the author thought he might someday want to change it to return a value again, and would therefore try to keep the code-style looking similar to that of a value-returning function? (If so, it seems a bit "too clever" to me)