Create FFI union type

Creates a union type where all fields share the same memory location. The union's size is the size of its largest member.

Usage

ffi_union(..., .pack = NULL)

Arguments

...

Named FFIType objects representing union fields

.pack

Integer packing alignment (1, 2, 4, 8, or 16). When specified, the union's alignment is reduced to min(natural_alignment, .pack). This affects placement when the union is used as a struct member. Default NULL uses natural alignment.

Value

UnionType object

Examples

# Normal union
U <- ffi_union(c = ffi_char(), i = ffi_int())

# Packed union (alignment = 1)
PackedU <- ffi_union(c = ffi_char(), i = ffi_int(), .pack = 1)

# Packed union in a struct - offset of next field is affected
S <- ffi_struct(u = PackedU, after = ffi_char())

# Note: Packed unions cannot be passed by value to C functions.
# Use pointers instead.