20220831-zig-pointer-cheatsheet.md

Zig pointer types cheatsheet

Hello (Zig) World!

since I'm still not automatically remembering all the various combinatorial possibilities of different types of pointers, slices, constness and optionals, I've finally taken the plunge and created a little cheatsheet for quick reference. It's not exhaustive, but should cover most real world cases... nobody said it'd be easy! :)

const Cheatsheet = struct {
    /// single u8 value
    a: u8,
    /// single optional u8 value
    b: ?u8,
    /// array of 2 u8 values
    c: [2]u8,
    /// zero-terminated array of 2 u8 values
    d: [2:0]u8,
    /// slice of u8 values
    e: []u8,
    /// slice of optional u8 values
    f: []?u8,
    /// optional slice of u8 values
    g: ?[]u8,
    /// pointer to u8 value
    h: *u8,
    /// pointer to optional u8 value
    i: *?u8,
    /// optional pointer to u8 value
    j: ?*u8,
    /// pointer to immutable u8 value
    k: *const u8,
    /// pointer to immutable optional u8 value
    l: *const ?u8,
    /// optional pointer to immutable u8 value
    m: ?*const u8,
    /// pointer to multiple u8 values
    n: [*]u8,
    /// pointer to multiple zero-terminated u8 values
    o: [*:0]u8,
    /// array of 2 u8 pointers
    p: [2]*u8,
    /// pointer to array of 2 u8 values
    q: *[2]u8,
    /// pointer to zero-terminated array of 2 u8 values
    r: *[2:0]u8,
    /// pointer to immutable array of 2 u8 values
    s: *const [2]u8,
    /// pointer to slice of immutable u8 values
    t: *[]const u8,
    /// slice of pointers to u8 values
    u: []*u8,
    /// slice of pointers to immutable u8 values
    v: []*const u8,
    /// pointer to slice of pointers to immutable optional u8 values
    w: *[]*const ?u8,
};

Extern struct limitations

In extern structs optionals can only be used if in pointer-like form (but not directly for optional values), i.e. the following cases are all fine:

• ?*u8
• *?u8
• *const ?u8
• ?*const u8
• []?u8
• []const ?u8

On the other hand, a plain ?u8 field isn't allowed in extern structs...