Zig Cross

Zig Cross-Compilation

Purpose

Guide agents through Zig's built-in cross-compilation: target triple selection, CPU feature targeting, zig cc for cross-compiling C projects, embedded bare-metal targets, and WASM output — all without requiring a system cross-toolchain.

Triggers

• "How do I cross-compile a Zig program for ARM?"
• "How do I build Zig for a different OS?"
• "How do I use Zig to cross-compile C code for another platform?"
• "How do I build Zig for embedded/bare-metal?"
• "How do I target WebAssembly with Zig?"
• "What Zig target triple do I use for Raspberry Pi?"

Workflow

1. Zig's native cross-compilation

Zig has cross-compilation built in — no cross-toolchain, no Docker, no sysroot needed for pure Zig code:

# List all supported targets
zig targets | python3 -c "import sys,json; d=json.load(sys.stdin); [print(t) for t in d['libc']]"

# Build for a specific target
zig build-exe src/main.zig -target aarch64-linux-gnu -O ReleaseFast

# With build system (pass target as option)
zig build -Dtarget=aarch64-linux-gnu -Doptimize=ReleaseFast

# Cross-compile for Windows from Linux/macOS
zig build-exe src/main.zig -target x86_64-windows-gnu

# Cross-compile for macOS from Linux (requires macOS SDK)
zig build-exe src/main.zig -target aarch64-macos-none

2. Common target triples

3. CPU feature targeting

# Native CPU (auto-detect, only for native builds)
zig build-exe src/main.zig -mcpu native

# Baseline for architecture (most compatible)
zig build-exe src/main.zig -target x86_64-linux-gnu -mcpu baseline

# x86-64 with AVX2
zig build-exe src/main.zig -target x86_64-linux-gnu -mcpu x86_64+avx2+bmi2

# Raspberry Pi 4 (Cortex-A72)
zig build-exe src/main.zig -target aarch64-linux-gnu -mcpu cortex_a72

# Cortex-M4 with FPU
zig build-exe src/main.zig \
    -target thumbv7em-freestanding-eabihf \
    -mcpu cortex_m4+vfp4

# List CPU features for a target
zig targets | python3 -c "
import sys,json
d=json.load(sys.stdin)
for c in d['cpus']:
    if 'cortex' in c['name']:
        print(c['name'])
"

4. zig cc for C cross-compilation

zig cc cross-compiles C without a system cross-toolchain:

# Cross-compile C for ARM64 Linux
zig cc -target aarch64-linux-gnu -O2 -o myapp-arm64 main.c

# Cross-compile C for Windows
zig cc -target x86_64-windows-gnu main.c -o myapp.exe

# Cross-compile C with static musl linking
zig cc -target x86_64-linux-musl -static main.c -o myapp-static

# Use in Makefile for all platforms
CC_LINUX_AMD64 = zig cc -target x86_64-linux-gnu
CC_LINUX_ARM64 = zig cc -target aarch64-linux-gnu
CC_WINDOWS     = zig cc -target x86_64-windows-gnu

5. Build system cross-compilation

// build.zig — cross-build all targets
pub fn build(b: *std.Build) void {
    const targets = [_]std.Target.Query{
        .{ .cpu_arch = .x86_64, .os_tag = .linux, .abi = .gnu },
        .{ .cpu_arch = .aarch64, .os_tag = .linux, .abi = .gnu },
        .{ .cpu_arch = .x86_64, .os_tag = .windows, .abi = .gnu },
        .{ .cpu_arch = .aarch64, .os_tag = .macos },
    };

    for (targets) |t| {
        const target = b.resolveTargetQuery(t);
        const exe = b.addExecutable(.{
            .name = b.fmt("myapp-{s}", .{@tagName(t.cpu_arch.?)}),
            .root_source_file = b.path("src/main.zig"),
            .target = target,
            .optimize = .ReleaseFast,
        });
        b.installArtifact(exe);
    }
}

# Build all targets
zig build
# Creates: zig-out/bin/myapp-x86_64, myapp-aarch64, myapp-x86_64.exe, myapp-aarch64

6. Embedded (bare-metal) targets

# Cortex-M4 with FPU (STM32F4xx)
zig build-exe src/main.zig \
    -target thumbv7em-freestanding-eabihf \
    -mcpu cortex_m4+vfp4 \
    -O ReleaseSmall \
    --script linker.ld

// src/main.zig — bare metal entry point
const std = @import("std");

// Custom panic handler for embedded (no OS)
pub fn panic(msg: []const u8, _: ?*std.builtin.StackTrace, _: ?usize) noreturn {
    // Toggle LED or halt
    while (true) {}
}

// Entry point (matches linker script)
export fn _start() void {
    main() catch |err| {
        _ = err;
        while (true) {}
    };
}

fn main() !void {
    // Hardware initialization...
}

7. WebAssembly

# WASM freestanding (browser)
zig build-exe src/main.zig \
    -target wasm32-freestanding \
    -O ReleaseSmall \
    --export=init \
    --export=update \
    -fno-entry

# WASM WASI (wasmtime, wasmer)
zig build-exe src/main.zig \
    -target wasm32-wasi \
    -O ReleaseSafe
wasmtime myapp.wasm

# Optimize WASM size
wasm-opt -Oz myapp.wasm -o myapp.opt.wasm

For target triple reference and embedded linker script setup, see references/zig-target-triples.md.

Related skills

• Use skills/zig/zig-compiler for single-file compilation flags
• Use skills/zig/zig-build-system for multi-target build.zig configuration
• Use skills/compilers/cross-gcc for system cross-toolchain setup when needed
• Use skills/rust/rust-cross for Rust's cross-compilation approach comparison

Zig Target Triples Reference

Triple Format

<cpu_arch>-<os>-<abi>

• cpu_arch: x86_64, aarch64, arm, thumb, thumbv6m, thumbv7m, thumbv7em, thumbv8m, riscv32, riscv64, mips, mipsel, wasm32, wasm64, ...
• os: linux, windows, macos, ios, freebsd, netbsd, openbsd, dragonfly, solaris, freestanding, wasi, other
• abi: none, gnu, gnueabi, gnueabihf, musl, musleabi, musleabihf, eabi, eabihf, msvc, android, ...

Linux Targets

Windows Targets

macOS / iOS Targets

Note: Cross-compiling to macOS requires the macOS SDK.

Embedded (Freestanding) Targets

ARM Cortex-M

ARM Cortex-A (freestanding)

RISC-V

Other

WASM Targets

CPU Feature Strings

# x86_64 common features
x86_64                     # baseline (SSE2 only)
x86_64+sse4.2              # SSE 4.2
x86_64+avx                 # AVX (Sandy Bridge)
x86_64+avx2+bmi+bmi2       # AVX2 (Haswell)
x86_64+avx512f             # AVX-512 Foundation
x86_64v2                   # x86-64-v2 microarch level
x86_64v3                   # x86-64-v3 (AVX2, BMI2)

# ARM64 common CPUs
cortex_a53                  # Pi 3, many phones
cortex_a72                  # Pi 4
cortex_a76                  # Snapdragon 855+
apple_m1                    # Apple M1
neoverse_n1                 # AWS Graviton2

# ARM Cortex-M CPUs
cortex_m0                   # Cortex-M0
cortex_m0plus               # Cortex-M0+
cortex_m3                   # Cortex-M3
cortex_m4                   # Cortex-M4 (no FPU)
cortex_m4+vfp4              # Cortex-M4 with FPU
cortex_m7+vfp5_d16          # Cortex-M7 with FPU
cortex_m33                  # Cortex-M33
cortex_m33+vfp5_d16         # Cortex-M33 with FPU

# RISC-V extensions
riscv32i                    # Base integer
riscv32im                   # + Multiply
riscv32imc                  # + Compressed
riscv32imac                 # + Atomics + Compressed
riscv64gc                   # 64-bit general