4.9 Structures, unions, enumerations, and bit-fields

• Whether a “plain” int bit-field is treated as a signed int bit-field or as an unsigned int bit-field (6.7.2, 6.7.2.1).
• Allowable bit-field types other than _Bool, signed int, and unsigned int (6.7.2.1).
• Whether a bit-field can straddle a storage-unit boundary (6.7.2.1).
• The order of allocation of bit-fields within a unit (6.7.2.1).
• The alignment of non-bit-field members of structures (6.7.2.1).
• The integer type compatible with each enumerated type (6.7.2.2).