Union individual bits of bitfield

You can accomplish this in C by using a union of two structures (as well as your raw member). In one structure, put one of the two bit-fields you wish to overlay and all the other bit-fields. In the other structure, put the other bit-field you wish to overlay and anonymous fields to replicate the layout of the first structure.

struct OAMAttribute0 { union { u16 raw; struct { u16 ypos : 8; // 0-255 u16 rotation_scaling: 1; // 0=off, 1=on u16 double_size : 1; // when rotation/scaling used u16 mode : 2; // 0=normal, 1=semi-transparent, 2=obj window, 3=prohibited u16 mosaic : 1; // 0=off, 1=on u16 colors : 1; // 0=16/16, 1=256/1 u16 shape : 2; // 0=square, 1=horizontal, 2=vertical, 3=prohibited }; struct { u16 : 8; u16 : 1; u16 obj_disable : 1; // 0=normal, 1=not displayed u16 : 2; u16 : 1; u16 : 1; u16 : 2; }; }; };

The C++ standard does not provide for anonymous structures, but some compilers may support it.

This is not to say it is a good idea.

What you want isn't possible. A union or struct type has to be at least 1 bytes in length.

The closest thing you can do is use a #define to alias one field as the other.