attribute set datatype

[Ruslan Nabioullin]

Hello,

What is the reason that the integral datatype used as an attribute set 
is signed in functions and macros consuming or returning the set? 
Obviously signedness is less elegant and leads to nonintuitive behavior 
when right-shifting.

Furthermore, why is the datatype different in attribute definitions 
(unsigned)?  That essentially means that two different datatypes are 
used for the same intended datatype; although C is weakly-typed, 
compilers may emit a warning, such as in:

unsigned int msg_attributes;
...
msg_attributes = color_available &&
        init_pair(MSG_COLOR_PAIR, MSG_TEXT_COLOR, COLOR_BLACK) != ERR
        ? COLOR_PAIR(MSG_COLOR_PAIR) : A_NORMAL;
...

-Ruslan