22.9 Structures, Unions, Enumerations and Bit-Fields

Implementation-Defined Behavior for Structures, Unions, Enumerations and Bit-Fields is covered in sections A.6.3.9 and G.3.9 of the ANSI C Standard.

What are the results if a member of a union object is accessed using a member of a different type? (ISO 6.3.2.3)

No conversions are applied.

Describe the padding and alignment of members of structures? (ISO 6.5.2.1)

Chars are byte-aligned. All other objects are word-aligned.

What is the equivalent type for a plain int bitfield? (ISO 6.5.2.1)

User defined. By default, signed int bitfield. May be made an unsigned int bitfield using a command line option.

What is the order of allocation of bit-fields within an int? (ISO 6.5.2.1)

Bits are allocated from least-significant to most-significant.

Can a bit-field straddle a storage-unit boundary? (ISO 6.5.2.1)

Yes.

Which integer type has been chosen to represent the values of an enumeration type? (ISO 6.5.2.2)

int.