[Bug c/46090] 16 bit uint16_t puts non-zero in highest bits when shifting

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46090

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-10-20 
13:34:31 UTC ---
Because that's what the C standard says, under the rules for integer promotions