zig-0.15

This skill provides Zig 0.15.x API guidance and should be used when writing or reviewing Zig code. It ensures correct usage of Zig 0.15 APIs, preventing common mistakes from using outdated 0.11/0.12/0.13/0.14 patterns. Essential for ArrayList, std.Io.Writer/Reader (Writergate), HTTP client, Ed25519, JSON, and type introspection APIs.

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Install skill "zig-0.15" with this command: npx skills add zigcc/skills/zigcc-skills-zig-0-15

Zig 0.15.x Programming Guide

Version Scope: This skill is pinned to Zig 0.15.x (specifically 0.15.2). For master/nightly builds, APIs may differ. Always check official docs for your version.

This skill ensures correct Zig 0.15.x API usage. Many LLMs have outdated Zig knowledge (0.11-0.14), causing compilation errors.

Official Documentation (0.15.2):

Community Resources (0.15.x):

Production Zig Codebases (learn from real-world projects):

Learning Resources (All 0.15.x Compatible):

Mitchell Hashimoto's Zig Libraries (Ghostty author, high quality):

Compiler/Toolchain:

AI/ML:

Blockchain/Ethereum:

Ecosystem Index:

For Other Versions:

Critical API Changes in Zig 0.15

ArrayList (BREAKING)

All mutating methods now require explicit allocator parameter:

// ❌ WRONG (0.13 and earlier)
var list = std.ArrayList(T).init(allocator);
try list.append(item);
try list.appendSlice(items);
_ = try list.addOne();
_ = try list.toOwnedSlice();

// ✅ CORRECT (0.15+)
var list = try std.ArrayList(T).initCapacity(allocator, 16);
defer list.deinit(allocator);
try list.append(allocator, item);
try list.appendSlice(allocator, items);
_ = try list.addOne(allocator);
_ = try list.toOwnedSlice(allocator);

// AssumeCapacity variants do NOT need allocator
list.appendAssumeCapacity(item);
Method0.130.15+
appendtry list.append(item)try list.append(allocator, item)
appendSlicetry list.appendSlice(items)try list.appendSlice(allocator, items)
addOnetry list.addOne()try list.addOne(allocator)
ensureTotalCapacitytry list.ensureTotalCapacity(n)try list.ensureTotalCapacity(allocator, n)
toOwnedSlicetry list.toOwnedSlice()try list.toOwnedSlice(allocator)
deinitlist.deinit()list.deinit(allocator)

HashMap

Managed (stores allocator internally):

var map = std.StringHashMap(V).init(allocator);
defer map.deinit();
try map.put(key, value);  // No allocator needed

Unmanaged (requires allocator for each operation):

var map = std.StringHashMapUnmanaged(V){};
defer map.deinit(allocator);
try map.put(allocator, key, value);  // Allocator required

Writergate: New std.Io.Writer and std.Io.Reader (MAJOR REWRITE)

Zig 0.15 introduces completely new I/O interfaces. All old std.io readers/writers are deprecated.

Key Changes

  1. Non-generic: New interfaces are concrete types, not anytype
  2. Buffer in interface: User provides buffer, implementation decides minimum size
  3. Ring buffer based: More efficient peek and streaming operations
  4. Precise error sets: No more anyerror propagation

New stdout Pattern

// ❌ WRONG (0.14 and earlier)
const stdout = std.io.getStdOut().writer();
try stdout.print("Hello\n", .{});

// ✅ CORRECT (0.15+)
var stdout_buffer: [1024]u8 = undefined;
var stdout_writer = std.fs.File.stdout().writer(&stdout_buffer);
const stdout: *std.Io.Writer = &stdout_writer.interface;

try stdout.print("Hello\n", .{});
try stdout.flush();  // Don't forget to flush!

Adapter for Migration

If you have old-style writers and need new interface:

fn useOldWriter(old_writer: anytype) !void {
    var adapter = old_writer.adaptToNewApi(&.{});
    const w: *std.Io.Writer = &adapter.new_interface;
    try w.print("{s}", .{"example"});
}

New Reader API

// Reading lines with delimiter
while (reader.takeDelimiterExclusive('\n')) |line| {
    // process line
} else |err| switch (err) {
    error.EndOfStream => {},
    error.StreamTooLong => return err,
    error.ReadFailed => return err,
}

HTTP Client (MAJOR REWRITE)

Zig 0.15.2 has both fetch() (high-level) and request() (low-level) APIs:

// ✅ CORRECT: High-level fetch() API (Zig 0.15.2)
var client: std.http.Client = .{ .allocator = allocator };
defer client.deinit();

const result = try client.fetch(.{
    .location = .{ .url = "https://example.com/api" },
    .method = .GET,
});
// result.status contains the HTTP status

// ✅ CORRECT: Low-level request/response API (Zig 0.15.2)
var client: std.http.Client = .{ .allocator = allocator };
defer client.deinit();

const uri = try std.Uri.parse("https://example.com/api");

// Create request with client.request() (NOT client.open!)
var req = try client.request(.POST, uri, .{
    .extra_headers = &.{
        .{ .name = "Content-Type", .value = "application/json" },
    },
});
defer req.deinit();

// Send body (use @constCast for const slices)
try req.sendBodyComplete(@constCast("{\"key\": \"value\"}"));

// Receive response
var redirect_buf: [4096]u8 = undefined;
var response = try req.receiveHead(&redirect_buf);

// Check status
const status = @intFromEnum(response.head.status);
if (status >= 200 and status < 300) {
    // Read response body using std.Io.Reader
    var body_reader = response.reader(&redirect_buf);
    const body = try body_reader.allocRemaining(allocator, std.Io.Limit.limited(1024 * 1024));
    defer allocator.free(body);
}

Key API functions (verified in Zig 0.15.2):

  • client.request(method, uri, options) → Request
  • client.fetch(options) → FetchResult
  • req.sendBodyComplete(body) - sends body and flushes
  • req.sendBodiless() - for GET requests without body
  • req.receiveHead(buffer) → Response
  • response.reader(buffer) → *std.Io.Reader
  • reader.allocRemaining(allocator, limit) → []u8

Base64 Encoding

// ❌ WRONG (0.13)
const encoder = std.base64.standard;
const encoded = encoder.encode(&buf, data);

// ✅ CORRECT (0.15+)
const encoder = std.base64.standard.Encoder;
const encoded = encoder.encode(&buf, data);

Ed25519 Cryptography (MAJOR CHANGES)

Key types are now structs, not raw byte arrays:

const Ed25519 = std.crypto.sign.Ed25519;

// ❌ WRONG (0.13 - SecretKey was [32]u8)
const secret: [32]u8 = ...;
const kp = Ed25519.KeyPair.fromSecretKey(secret);

// ✅ CORRECT (0.15+ - SecretKey is struct with 64 bytes)
// From 32-byte seed (deterministic):
const seed: [32]u8 = ...;
const kp = try Ed25519.KeyPair.generateDeterministic(seed);

// From 64-byte secret key:
var secret_bytes: [64]u8 = ...;
const secret_key = try Ed25519.SecretKey.fromBytes(secret_bytes);
const kp = try Ed25519.KeyPair.fromSecretKey(secret_key);

// Get public key bytes:
const pubkey_bytes: [32]u8 = kp.public_key.toBytes();

// Get seed:
const seed: [32]u8 = kp.secret_key.seed();

Signature changes:

// ❌ WRONG (0.13 - fromBytes returned error union)
const sig = try Ed25519.Signature.fromBytes(bytes);

// ✅ CORRECT (0.15+ - fromBytes does NOT return error)
const sig = Ed25519.Signature.fromBytes(bytes);

Type Introspection Enums (Case Change)

// ❌ WRONG (0.13 - PascalCase)
if (@typeInfo(T) == .Slice) { ... }
if (@typeInfo(T) == .Pointer) { ... }
if (@typeInfo(T) == .Struct) { ... }

// ✅ CORRECT (0.15+ - lowercase/escaped)
if (@typeInfo(T) == .slice) { ... }
if (@typeInfo(T) == .pointer) { ... }
if (@typeInfo(T) == .@"struct") { ... }
if (@typeInfo(T) == .@"enum") { ... }
if (@typeInfo(T) == .@"union") { ... }
if (@typeInfo(T) == .array) { ... }
if (@typeInfo(T) == .optional) { ... }

Custom Format Functions

// ❌ WRONG (0.13 - used {} format specifier)
pub fn format(
    self: Self,
    comptime fmt: []const u8,
    options: std.fmt.FormatOptions,
    writer: anytype,
) !void {
    _ = fmt;
    _ = options;
    try writer.writeAll("...");
}
// Usage: std.fmt.bufPrint(&buf, "{}", .{value});

// ✅ CORRECT (0.15+ - use {f} format specifier)
pub fn format(self: Self, writer: anytype) !void {
    _ = self;
    try writer.writeAll("...");
}
// Usage: std.fmt.bufPrint(&buf, "{f}", .{value});

JSON Parsing and Serialization

const MyStruct = struct {
    name: []const u8,
    value: u32,
};

// ✅ CORRECT: Parsing (0.15+)
const json_str =
    \\{"name": "test", "value": 42}
;
const parsed = try std.json.parseFromSlice(MyStruct, allocator, json_str, .{});
defer parsed.deinit();
const data = parsed.value;

// ✅ CORRECT: Serialization (0.15.2 - writer-based API)
// Note: There is NO stringifyAlloc in 0.15.2!

// Method 1: Using std.json.Stringify with Allocating writer
var out: std.Io.Writer.Allocating = .init(allocator);
defer out.deinit();
var stringify: std.json.Stringify = .{
    .writer = &out.writer,
    .options = .{},
};
try stringify.write(data);
const json_output = out.written();

// Method 2: Using std.fmt with json.fmt wrapper
const formatted = try std.fmt.allocPrint(allocator, "{f}", .{std.json.fmt(data, .{})});
defer allocator.free(formatted);

// Method 3: To fixed buffer
var buf: [1024]u8 = undefined;
var fbs = std.io.fixedBufferStream(&buf);
var writer = fbs.writer();
var stringify2: std.json.Stringify = .{
    .writer = &writer.adaptToNewApi(&.{}).new_interface,
    .options = .{},
};
try stringify2.write(data);
const output = fbs.getWritten();

Memory/Formatting

// Allocating format
const formatted = try std.fmt.allocPrint(allocator, "value: {d}", .{42});
defer allocator.free(formatted);

// Non-allocating format
var buffer: [256]u8 = undefined;
const result = try std.fmt.bufPrint(&buffer, "value: {d}", .{42});

Common Error Messages and Fixes

ErrorCauseFix
expected 2 argument(s), found 1ArrayList method missing allocatorAdd allocator as first argument
no field or member function named 'encode'Using std.base64.standard.encodeUse std.base64.standard.Encoder.encode
no field or member function named 'open'Using old HTTP APIUse client.request() or client.fetch()
expected type 'SecretKey', found '[32]u8'Ed25519 SecretKey is now structUse generateDeterministic(seed)
expected error union type, found 'Signature'Signature.fromBytes doesn't return errorRemove try
enum has no member named 'Slice'@typeInfo enum case changedUse lowercase .slice
no field named 'root_source_file'Old build.zig APIUse root_module = b.createModule(...)

Verification Workflow

After writing Zig code:

  1. Run zig build to check for compilation errors
  2. If errors match patterns above, apply the 0.15 fix
  3. Run zig build test to verify functionality
  4. Use zig build -Doptimize=ReleaseFast test to catch UB

Build System (build.zig) Changes (MAJOR REWRITE)

Official Guide: https://ziglang.org/learn/build-system/

Executable Creation

// ❌ WRONG (0.14 and earlier)
const exe = b.addExecutable(.{
    .name = "hello",
    .root_source_file = .{ .path = "src/main.zig" },
    .target = target,
    .optimize = optimize,
});

// ✅ CORRECT (0.15+)
const exe = b.addExecutable(.{
    .name = "hello",
    .root_module = b.createModule(.{
        .root_source_file = b.path("src/main.zig"),
        .target = target,
        .optimize = optimize,
    }),
});

Library Creation

// ❌ WRONG (0.14 - addSharedLibrary/addStaticLibrary)
const lib = b.addSharedLibrary(.{
    .name = "mylib",
    .root_source_file = .{ .path = "src/lib.zig" },
});

// ✅ CORRECT (0.15+ - unified addLibrary with linkage)
const lib = b.addLibrary(.{
    .name = "mylib",
    .linkage = .dynamic,  // or .static
    .root_module = b.createModule(.{
        .root_source_file = b.path("src/lib.zig"),
        .target = target,
        .optimize = optimize,
    }),
});

Path Handling

// ❌ WRONG (0.14 - .path field)
.root_source_file = .{ .path = "src/main.zig" },

// ✅ CORRECT (0.15+ - use b.path())
.root_source_file = b.path("src/main.zig"),

Module Dependencies

// ❌ WRONG (0.14)
exe.addModule("sdk", sdk_module);

// ✅ CORRECT (0.15+)
exe.root_module.addImport("sdk", sdk_module);

Target Options

// ❌ WRONG (0.14)
const target = b.standardTargetOptions(.{});
// then use target directly

// ✅ CORRECT (0.15+)
const target = b.standardTargetOptions(.{});
const optimize = b.standardOptimizeOption(.{});

const exe = b.addExecutable(.{
    .name = "app",
    .root_module = b.createModule(.{
        .root_source_file = b.path("src/main.zig"),
        .target = target,      // pass to createModule
        .optimize = optimize,  // pass to createModule
    }),
});

Testing

// ✅ CORRECT (0.15+)
const unit_tests = b.addTest(.{
    .root_module = b.createModule(.{
        .root_source_file = b.path("src/main.zig"),
        .target = b.graph.host,  // use b.graph.host for native target
    }),
});

const run_unit_tests = b.addRunArtifact(unit_tests);
const test_step = b.step("test", "Run unit tests");
test_step.dependOn(&run_unit_tests.step);

Complete build.zig Example

const std = @import("std");

pub fn build(b: *std.Build) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});

    const exe = b.addExecutable(.{
        .name = "hello",
        .root_module = b.createModule(.{
            .root_source_file = b.path("src/main.zig"),
            .target = target,
            .optimize = optimize,
        }),
    });

    b.installArtifact(exe);

    const run_exe = b.addRunArtifact(exe);
    const run_step = b.step("run", "Run the application");
    run_step.dependOn(&run_exe.step);
}

std.mem Patterns

Memory Operations

// Copy memory
@memcpy(dest, src);  // Same as std.mem.copyForwards

// Set memory
@memset(buffer, 0);  // Zero-fill

// Compare memory
const equal = std.mem.eql(u8, slice1, slice2);

// Find in slice
const index = std.mem.indexOf(u8, haystack, needle);

Alignment

// Check alignment
const is_aligned = std.mem.isAligned(@intFromPtr(ptr), @alignOf(T));

// Align pointer
const aligned = std.mem.alignPointer(ptr, @alignOf(T));

std.io Patterns

Fixed Buffer Stream

var buf: [1024]u8 = undefined;
var fbs = std.io.fixedBufferStream(&buf);
const writer = fbs.writer();

try writer.writeAll("Hello");
try writer.print(" {d}", .{42});

const written = fbs.getWritten();  // "Hello 42"

Counting Writer

var counting = std.io.countingWriter(underlying_writer);
try counting.writer().writeAll("test");
const bytes_written = counting.bytes_written;  // 4

Testing Patterns

Testing Allocator (Detects Leaks)

test "no memory leaks" {
    const allocator = std.testing.allocator;  // Auto-detects leaks
    
    const data = try allocator.alloc(u8, 100);
    defer allocator.free(data);  // MUST free or test fails
    
    // ... test code ...
}

Assertions

test "assertions" {
    try std.testing.expect(condition);              // Boolean
    try std.testing.expectEqual(expected, actual);  // Equality
    try std.testing.expectEqualSlices(u8, expected, actual);  // Slices
    try std.testing.expectError(error.SomeError, result);     // Error
    try std.testing.expectEqualStrings("hello", str);         // Strings
}

Comptime Patterns

Type Reflection

fn serialize(comptime T: type, value: T) ![]u8 {
    const info = @typeInfo(T);
    
    switch (info) {
        .int => |i| {
            // Handle integer
            const byte_count = @divExact(i.bits, 8);
            // ...
        },
        .@"struct" => |s| {
            // Handle struct
            inline for (s.fields) |field| {
                // Process each field
                const field_value = @field(value, field.name);
                // ...
            }
        },
        else => @compileError("Unsupported type"),
    }
}

Optional Type Handling

fn getInner(comptime T: type) type {
    const info = @typeInfo(T);
    if (info == .optional) {
        return info.optional.child;
    }
    return T;
}

Pointer and Slice Patterns

Slice to Many-Item Pointer

const slice: []u8 = buffer[0..10];
const ptr: [*]u8 = slice.ptr;

Creating Slices

// From array
const arr = [_]u8{ 1, 2, 3, 4, 5 };
const slice = arr[1..4];  // [2, 3, 4]

// From pointer + length
const slice = ptr[0..len];

Sentinel-Terminated Slices

// Null-terminated string
const str: [:0]const u8 = "hello";
const c_str: [*:0]const u8 = str.ptr;

// Get length without sentinel
const len = str.len;  // 5, not including null

Language Changes

usingnamespace Removed

The usingnamespace keyword has been completely removed in Zig 0.15.

// ❌ WRONG (removed in 0.15)
pub usingnamespace @import("other.zig");

// ✅ CORRECT - explicit re-exports
pub const foo = @import("other.zig").foo;
pub const bar = @import("other.zig").bar;

// ✅ CORRECT - namespace via field
pub const other = @import("other.zig");
// Usage: other.foo, other.bar

Migration for mixins: Use zero-bit fields with @fieldParentPtr:

// ❌ OLD mixin pattern
pub const Foo = struct {
    count: u32 = 0,
    pub usingnamespace CounterMixin(Foo);
};

// ✅ NEW mixin pattern (0.15+)
pub fn CounterMixin(comptime T: type) type {
    return struct {
        pub fn increment(m: *@This()) void {
            const x: *T = @alignCast(@fieldParentPtr("counter", m));
            x.count += 1;
        }
    };
}

pub const Foo = struct {
    count: u32 = 0,
    counter: CounterMixin(Foo) = .{},  // zero-bit field
};
// Usage: foo.counter.increment()

async/await Keywords Removed

The async, await, and @frameSize have been removed. Async functionality will be provided via the standard library's new I/O interface.

// ❌ REMOVED - no async/await keywords
async fn fetchData() ![]u8 { ... }
const result = await fetchData();

// ✅ Use std.Io interfaces or threads instead

Arithmetic on undefined

Operations on undefined that could trigger illegal behavior now cause compile errors:

const a: u32 = 0;
const b: u32 = undefined;

// ❌ COMPILE ERROR in 0.15+
_ = a + b;  // error: use of undefined value here causes illegal behavior

Lossy Integer to Float Coercion

Compile error if integer cannot be precisely represented:

// ❌ COMPILE ERROR in 0.15+
const val: f32 = 123_456_789;  // error: cannot represent precisely

// ✅ CORRECT - opt-in to floating-point rounding
const val: f32 = 123_456_789.0;

Extended References (This Skill)

详细的 API 参考和迁移指南请查阅以下文档：

文档路径内容
标准库 API 详解references/stdlib-api-reference.mdArrayList、HashMap、HTTP Client、Ed25519、Base64、JSON、@typeInfo、std.fmt 等完整 API 参考
迁移模式指南references/migration-patterns.md从 0.13/0.14 迁移到 0.15 的详细对照，包括 Writergate、ArrayList、Build System 等
生产级代码库references/production-codebases.mdSig（Solana）、ZML（AI）、Zeam（Ethereum）、Bun、Tigerbeetle 等项目学习指南，以及 0.15.x 兼容库列表
版本策略VERSIONING.md版本兼容性说明和更新策略

快速查阅建议

  • 编写 HTTP 请求？ → 查看 references/stdlib-api-reference.md 的 std.http.Client 部分
  • ArrayList 报错？ → 查看 references/migration-patterns.md 的 ArrayList Migration 部分
  • 学习最佳实践？ → 查看 references/production-codebases.md 中的 Sig 项目（Solana 验证器）
  • 寻找第三方库？ → 查看 references/production-codebases.md 的 Smaller Learning Projects 表格

References

Official Documentation (0.15.2):

Community Resources (0.15.x):

Cookbook Recipe Categories (all tested on 0.15.x):

  • File System: read files, mmap, iterate directories
  • Cryptography: SHA-256, PBKDF2, Argon2
  • Network: TCP/UDP client/server
  • Web: HTTP GET/POST, HTTP server
  • Concurrency: threads, shared data, thread pools
  • Encoding: JSON, ZON, base64
  • Database: SQLite, PostgreSQL, MySQL

Production Zig Codebases (learn from real-world projects):

ProjectURLLearn From
Sighttps://github.com/Syndica/sigSolana validator in Zig - most relevant for this SDK!
Zeamhttps://github.com/blockblaz/zeamEthereum client in Zig - blockchain patterns
Bunhttps://github.com/oven-sh/bunJS runtime, async I/O, FFI, build system
Tigerbeetlehttps://github.com/tigerbeetle/tigerbeetleFinancial DB, deterministic execution, testing
Machhttps://github.com/hexops/machGame engine, graphics, memory management
Ghosttyhttps://github.com/ghostty-org/ghosttyTerminal emulator, cross-platform, GPU rendering
Zig Algorithmshttps://github.com/TheAlgorithms/ZigData structures, algorithms, idiomatic Zig

Key Sections in Release Notes:

Source Code & Development:

Version Compatibility Notes

This skill targets Zig 0.15.x. If you're using a different version:

VersionDocumentationNotes
0.15.xThis skillCurrent stable, solana-zig uses 0.15.2
0.14.xhttps://ziglang.org/documentation/0.14.1/Old build.zig API, old std.io
0.13.xhttps://ziglang.org/documentation/0.13.0/ArrayList without allocator param
masterhttps://ziglang.org/documentation/master/Unstable, APIs may change daily

How to check your Zig version:

zig version
# or for this project:
./solana-zig/zig version

When APIs differ from this skill:

  1. Check your actual Zig version
  2. Consult version-specific documentation
  3. Use compiler errors as guidance - Zig has excellent error messages

Source Transparency

This detail page is rendered from real SKILL.md content. Trust labels are metadata-based hints, not a safety guarantee.

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