Targets

A "target" in Zig is a (cpu, os, abi, ofmt) tuple plus a feature set. Every part of the compiler routes off this descriptor.

The descriptor

lib/std/Target.zig (~116 KB) defines:

• Cpu.Arch — the architecture enum.
• Cpu.Model and Cpu.Feature — CPU model + feature bits.
• Os.Tag, Os.Version* — OS plus version range.
• Abi — gnu/musl/macho/eabi/etc.
• ObjectFormat — elf, macho, coff, wasm, c, spirv, hex, raw, plan9.

Per-architecture feature tables live in lib/std/Target/<arch>.zig. They are generated from LLVM's tablegen by tools/update_cpu_features.zig.

Triple parsing

lib/std/zig/target.zig parses <arch>-<os>-<abi> triples and resolves them against lib/std/Target.zig. zig targets (src/print_targets.zig) prints the full enumerable space.

Capability gating in the compiler

src/target.zig carries the per-target capability table the compiler uses:

• Which backends are available (useLlvm, useNonLlvmBackend).
• Whether the in-tree linker supports the format.
• Calling-convention flavors.
• C ABI quirks.

src/codegen.zig reads this table to dispatch to the right backend. lib/std/zig/LibCDirs.zig reads it (indirectly via Target) to pick the bundled libc tree.

CPU feature sets

A Cpu is Model + Set(Feature). -mcpu=baseline+feature1-feature2 modifies the base model. The compiler:

• Resolves the model name against lib/std/Target/<arch>.zig.
• Applies +feature / -feature deltas.
• Validates required combinations.
• Forwards the resolved set to the chosen backend.

What zig env prints

target_arch_subarch_endian: ...
target_os_abi_dynamic_linker: ...
target_dynamic_linker: ...
zig_lib_dir: ...
zig_global_cache_dir: ...

(Exact keys vary by version; see src/print_env.zig.)

Cross-references

• Cross compilation for the user-facing story.
• Code generation backends for backend coverage.
• Bundled libraries for the libc/libcxx selection.