--- name: zig-knowledge-patch description: "Zig changes since training cutoff (latest: 0.14.0) \u2014 labeled switch, decl literals, @branchHint, DebugAllocator, unmanaged containers, root_module build API. Load before working with Zig." license: MIT version: "0.14.0" metadata: author: Nevaberry --- # Zig Knowledge Patch Claude's baseline knowledge covers Zig through 0.12.x. This skill provides breaking changes and new features in 0.13.0 and 0.14.0. ## Breaking Changes Quick Reference | Version | Change | Impact | Details | |---------|--------|--------|---------| | 0.13.0 | `ComptimeStringMap` -> `StaticStringMap` | API rename + new init pattern | [stdlib-changes](references/stdlib-changes.md) | | 0.13.0 | `zig-cache` -> `.zig-cache` | Update .gitignore | [stdlib-changes](references/stdlib-changes.md) | | 0.13.0 | `std.Progress` rework | Pass `Node` by value, new init API | [stdlib-changes](references/stdlib-changes.md) | | 0.14.0 | `std.builtin.Type` fields lowercased | `.Int` -> `.int`, `.Struct` -> `.@"struct"` | [language-changes](references/language-changes.md) | | 0.14.0 | `@setCold` removed | Use `@branchHint(.cold)` | [language-changes](references/language-changes.md) | | 0.14.0 | `@fence` removed | Use stronger atomic orderings | [language-changes](references/language-changes.md) | | 0.14.0 | `@export` takes pointer | Add `&` operator | [language-changes](references/language-changes.md) | | 0.14.0 | `CallingConvention` overhauled | Tagged union, `.C` -> `.c` | [language-changes](references/language-changes.md) | | 0.14.0 | Anonymous struct types removed | Tuples unified, structural equivalence | [language-changes](references/language-changes.md) | | 0.14.0 | `GeneralPurposeAllocator` -> `DebugAllocator` | New init pattern | [stdlib-changes](references/stdlib-changes.md) | | 0.14.0 | `ArrayList` deprecated | Use `ArrayListUnmanaged`, pass allocator | [stdlib-changes](references/stdlib-changes.md) | | 0.14.0 | `std.mem.page_size` removed | Use `std.heap.pageSize()` | [stdlib-changes](references/stdlib-changes.md) | | 0.14.0 | Build API: `root_module` | `addExecutable` takes `root_module` | [build-system](references/build-system.md) | | 0.14.0 | Package hash format changed | New format includes name/version/fingerprint | [build-system](references/build-system.md) | ## New Language Features (0.14.0) ### Labeled Switch Switch statements can be labeled and targeted by `continue` for state machines: ```zig foo: switch (@as(u8, 1)) { 1 => continue :foo 2, // jump to case 2 2 => continue :foo 3, 3 => return, else => unreachable, } ``` Generates optimized branch prediction code. Also supports `break` from labeled switch. ### Decl Literals `.foo` syntax resolves to declarations on the target type (not just enum variants): ```zig const S = struct { x: u32, const default: S = .{ .x = 123 }; fn init(val: u32) S { return .{ .x = val + 1 }; } }; const a: S = .default; // S.default const b: S = .init(100); // S.init(100) ``` **Key pattern**: Unmanaged containers use `.empty` instead of `.{}`: ```zig var list: std.ArrayListUnmanaged(u32) = .empty; foo: std.ArrayListUnmanaged(u32) = .empty, // as struct field default ``` Fields and declarations in the same container cannot share names. ### @branchHint Replaces `@setCold`. Must be first statement in block: ```zig @branchHint(.unlikely); // .none, .likely, .unlikely, .cold, .unpredictable ``` ### @FieldType Builtin ```zig comptime assert(@FieldType(MyStruct, "field_name") == u32); ``` ### @splat for Arrays ```zig var pixels: [W][H]Rgba = @splat(@splat(.black)); ``` See [references/language-changes.md](references/language-changes.md) for full details. ## Standard Library (0.14.0) ### Allocator Changes ```zig // DebugAllocator (replaces GeneralPurposeAllocator) var debug_allocator: std.heap.DebugAllocator(.{}) = .init; const gpa = debug_allocator.allocator(); defer _ = debug_allocator.deinit(); // SmpAllocator (for ReleaseFast, competitive with glibc) const allocator = std.heap.smp_allocator; ``` New `remap` on Allocator.VTable enables relocation during resize (uses `mremap` on Linux). ### Unmanaged Containers (managed versions deprecated) ```zig var list: std.ArrayListUnmanaged(i32) = .empty; defer list.deinit(gpa); try list.append(gpa, 1234); // allocator passed to methods ``` Same for `ArrayHashMapUnmanaged`. `popOrNull` renamed to `pop`. ### ZON Support Runtime: `std.zon.parse.fromSlice(T, allocator, zon_bytes, .{})`. Compile-time: `const cfg: Config = @import("config.zon");`. ### Runtime Page Size `std.heap.pageSize()` (runtime, memoized). Comptime bounds: `page_size_min`, `page_size_max`. See [references/stdlib-changes.md](references/stdlib-changes.md) for full details. ## Build System (0.14.0) ### File System Watching ```bash zig build --watch # rebuilds on source changes zig build --watch --debounce 100 # custom debounce (default 50ms) ``` ### Module-First API ```zig const mod = b.createModule(.{ .root_source_file = b.path("src/main.zig"), .target = target, .optimize = optimize, }); const exe = b.addExecutable(.{ .name = "hello", .root_module = mod }); // Reuse same module for tests: const tests = b.addTest(.{ .name = "hello-test", .root_module = mod }); ``` ### Incremental Compilation (opt-in) ```bash zig build -Dno-bin -fincremental --watch # fast error-checking loop ``` ### x86 Backend 98% behavior test pass rate. Select with `-fno-llvm`. Expected default for debug mode in 0.15.0. See [references/build-system.md](references/build-system.md) for full details. ## Major Deprecation Removals (0.14.0) Now compile errors: `std.mem.tokenize` (use `tokenizeAny`/`tokenizeSequence`/`tokenizeScalar`), `std.mem.split` (use `splitSequence`/`splitAny`/`splitScalar`), `std.rand` (use `std.Random`), `std.TailQueue` (use `std.DoublyLinkedList`), `std.zig.CrossTarget` (use `std.Target.Query`), `std.fs.MAX_PATH_BYTES` (use `max_path_bytes`). ## Reference Files | File | Contents | |------|----------| | [language-changes.md](references/language-changes.md) | Labeled switch, decl literals, @branchHint, @fence removal, CallingConvention, type field renames, packed struct changes, tuple unification | | [stdlib-changes.md](references/stdlib-changes.md) | DebugAllocator, SmpAllocator, remap API, unmanaged containers, ZON, runtime page size, StaticStringMap, Progress rework, deprecations | | [build-system.md](references/build-system.md) | --watch, root_module API, addLibrary, package hash format, incremental compilation, fuzzer, WriteFile/RemoveDir changes |