zig-build-system

name

zig-build-system

description

Zig build system skill for multi-file Zig projects. Use when writing or debugging build.zig files, adding executables or libraries, integrating C source files, configuring build-time options, running tests with zig build test, or managing build.zig.zon package manifests. Activates on queries about build.zig, b.addExecutable, addCSourceFiles, b.option, zig build, build.zig.zon, or Zig package management.

Zig Build System

Purpose

Guide agents through writing build.zig files: executables, libraries, C source integration, build options, test configuration, and build.zig.zon package manifests.

Triggers

• "How do I set up a build.zig file?"
• "How do I add a C library to a Zig project?"
• "How do I define build-time options in Zig?"
• "How do I run Zig tests with zig build test?"
• "What is build.zig.zon and how do I use it?"
• "How do I add a Zig package dependency?"

Workflow

1. Project initialization

# Initialize a new project
mkdir myproject && cd myproject
zig init          # creates src/main.zig and build.zig

# Build
zig build

# Run
zig build run

# Test
zig build test

2. build.zig structure

const std = @import("std");

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

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

    // Install step (zig build → copies to zig-out/bin/)
    b.installArtifact(exe);

    // Run step (zig build run)
    const run_cmd = b.addRunArtifact(exe);
    run_cmd.step.dependOn(b.getInstallStep());
    if (b.args) |args| {
        run_cmd.addArgs(args);
    }
    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);

    // Test step (zig build test)
    const unit_tests = b.addTest(.{
        .root_source_file = b.path("src/main.zig"),
        .target = target,
        .optimize = optimize,
    });
    const run_unit_tests = b.addRunArtifact(unit_tests);
    const test_step = b.step("test", "Run unit tests");
    test_step.dependOn(&run_unit_tests.step);
}

3. Libraries

// Static library
const lib = b.addStaticLibrary(.{
    .name = "mylib",
    .root_source_file = b.path("src/mylib.zig"),
    .target = target,
    .optimize = optimize,
});
b.installArtifact(lib);

// Shared library
const shared_lib = b.addSharedLibrary(.{
    .name = "mylib",
    .root_source_file = b.path("src/mylib.zig"),
    .target = target,
    .optimize = optimize,
    .version = .{ .major = 1, .minor = 0, .patch = 0 },
});
b.installArtifact(shared_lib);

// Link library into executable
exe.linkLibrary(lib);

4. Adding C source files

// Single C file
exe.addCSourceFile(.{
    .file = b.path("src/legacy.c"),
    .flags = &.{ "-std=c11", "-Wall", "-Wextra" },
});

// Multiple C files
exe.addCSourceFiles(.{
    .files = &.{
        "src/a.c",
        "src/b.c",
        "src/c.c",
    },
    .flags = &.{ "-std=c11", "-O2" },
});

// Include directories
exe.addIncludePath(b.path("include/"));
exe.addIncludePath(.{ .cwd_relative = "/usr/local/include" });

// System libraries
exe.linkSystemLibrary("curl");
exe.linkSystemLibrary("ssl");
exe.linkLibC();  // link libc (required if calling C stdlib)

5. Build-time options

pub fn build(b: *std.Build) void {
    // Boolean option
    const enable_logging = b.option(
        bool,
        "logging",
        "Enable debug logging",
    ) orelse false;

    // Enum option
    const Backend = enum { opengl, vulkan, software };
    const backend = b.option(
        Backend,
        "backend",
        "Rendering backend",
    ) orelse .opengl;

    // Integer option
    const max_connections = b.option(
        u32,
        "max-connections",
        "Maximum concurrent connections",
    ) orelse 64;

    // Pass to Zig code as compile-time constant
    const options = b.addOptions();
    options.addOption(bool, "enable_logging", enable_logging);
    options.addOption(Backend, "backend", backend);
    options.addOption(u32, "max_connections", max_connections);

    exe.root_module.addOptions("build_options", options);
}

In Zig source:

const build_options = @import("build_options");

pub fn main() void {
    if (build_options.enable_logging) {
        std.debug.print("Logging enabled\n", .{});
    }
}

# Pass options on command line
zig build -Dlogging=true -Dbackend=vulkan -Dmax-connections=256

6. Module system

// Create a module (reusable across targets)
const mymodule = b.addModule("mymodule", .{
    .root_source_file = b.path("src/mymodule.zig"),
});

// Use module in executable
exe.root_module.addImport("mymodule", mymodule);

// Share module between exe and tests
const utils = b.addModule("utils", .{
    .root_source_file = b.path("src/utils.zig"),
});
exe.root_module.addImport("utils", utils);
unit_tests.root_module.addImport("utils", utils);

In Zig source:

const utils = @import("utils");
const mymodule = @import("mymodule");

7. Package management with build.zig.zon

// build.zig.zon
.{
    .name = "myapp",
    .version = "0.1.0",
    .minimum_zig_version = "0.13.0",

    .dependencies = .{
        .zig_clap = .{
            .url = "https://github.com/Hejsil/zig-clap/archive/refs/tags/0.9.1.tar.gz",
            .hash = "1220...",  // Run zig build to get the hash
        },
        .known_folders = .{
            .url = "https://github.com/ziglibs/known-folders/archive/refs/heads/master.tar.gz",
            .hash = "1220...",
        },
    },

    .paths = .{
        "build.zig",
        "build.zig.zon",
        "src",
        "LICENSE",
        "README.md",
    },
}

// build.zig — use the dependency
const clap_dep = b.dependency("zig_clap", .{
    .target = target,
    .optimize = optimize,
});
exe.root_module.addImport("clap", clap_dep.module("clap"));

# Fetch dependencies (creates zig-cache/packages/)
zig build    # auto-fetches on first run

# Zig will print the hash if missing — copy it into build.zig.zon

8. Custom build steps

// Code generation step
const gen_step = b.addSystemCommand(&.{
    "python3", "scripts/gen.py", "--output", "src/generated.zig",
});
exe.step.dependOn(&gen_step.step);

// Custom install step
const install_config = b.addInstallFile(
    b.path("config/default.toml"),
    "share/myapp/config.toml",
);
b.getInstallStep().dependOn(&install_config.step);

For advanced build.zig patterns, see references/build-zig-patterns.md.

Related skills

• Use skills/zig/zig-compiler for single-file builds and compiler flags
• Use skills/zig/zig-cinterop for C library integration in build.zig
• Use skills/zig/zig-cross for cross-compilation in build.zig
• Use skills/build-systems/cmake when embedding Zig into a CMake project