# Zig Best Practices

> Use when reading or writing Zig files (.zig, build.zig, build.zig.zon).

- Skill: `tomevault-io/zig-best-practices` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/zig-best-practices`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/zig-best-practices/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/zig-best-practices

---


# Zig Best Practices

Follows type-first, functional, and error handling patterns from CLAUDE.md. This skill covers Zig-specific idioms only.

## Type System Patterns

**Tagged unions for mutually exclusive states** — prevents invalid combinations that a struct with multiple nullable fields would allow:
```zig
const RequestState = union(enum) {
    idle,
    loading,
    success: []const u8,
    failure: anyerror,
};
```

**Explicit error sets** — documents exactly what can fail; `anyerror` hides failure modes:
```zig
const ParseError = error{ InvalidSyntax, UnexpectedToken, EndOfInput };
fn parse(input: []const u8) ParseError!Ast { ... }
```

**Distinct types for domain IDs** — compiler prevents mixing up different ID types:
```zig
const UserId = enum(u64) { _ };
const OrderId = enum(u64) { _ };
```

**Comptime validation** — catch invalid configurations at compile time, not runtime:
```zig
fn Buffer(comptime size: usize) type {
    if (size == 0) @compileError("buffer size must be greater than 0");
    return struct { data: [size]u8 = undefined, len: usize = 0 };
}
```

## Memory Management

- Pass allocators explicitly to every function that allocates; no global allocator state.
- Place `defer resource.deinit()` immediately after acquisition — keeps cleanup co-located with creation.
- Use `errdefer` for cleanup on error paths; `defer` for unconditional cleanup.
- Use arena allocators for batch/temporary work; they free everything at once.
- Use `std.testing.allocator` in tests — reports leaks with stack traces.

```zig
fn createResource(allocator: std.mem.Allocator) !*Resource {
    const resource = try allocator.create(Resource);
    errdefer allocator.destroy(resource);  // runs only on error
    resource.* = try initializeResource();
    return resource;
}
```

## Key Conventions

- Prefer `const` over `var`; prefer slices over raw pointers.
- Prefer `comptime T: type` over `anytype`; explicit types produce clearer errors. Use `anytype` only for genuinely polymorphic cases (callbacks, `std.debug.print`-style).
- Exhaustive `switch`: include an `else` returning an error or `unreachable` for truly impossible cases.
- Use `std.log.scoped(.module_name)` for namespaced logging; define a module-level `const log` constant.
- Larger cohesive files are idiomatic — tests alongside implementation, comptime generics at file scope.

## Advanced Topics

- **Generic containers** (queues, stacks, trees): See [GENERICS.md](GENERICS.md)
- **C library interop** (raylib, SDL, curl): See [C-INTEROP.md](C-INTEROP.md)
- **Debugging memory leaks** (GPA, stack traces): See [DEBUGGING.md](DEBUGGING.md)

## Tooling

**zigdoc** — browse std library and dependency docs:
```bash
zigdoc std.mem.Allocator   # std lib symbol
zigdoc vaxis.Window        # project dependency
zigdoc @init               # create AGENTS.md with API patterns
```

**ziglint** — static analysis with `.ziglint.zon` config:
```bash
ziglint                    # lint current directory
ziglint --ignore Z001      # suppress specific rule
```

## References

- Language Reference: https://ziglang.org/documentation/0.15.2/
- Standard Library: https://ziglang.org/documentation/0.15.2/std/
- Zig Guide: https://zig.guide/

---
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<!-- tomevault:4.0:skill_md:2026-04-11 -->