zig cc and the C/C++ toolchain

Purpose

zig is a drop-in C/C++ toolchain. The relevant sub-commands all come from src/main.zig:

ar               Use Zig as a drop-in archiver
cc               Use Zig as a drop-in C compiler
c++              Use Zig as a drop-in C++ compiler
dlltool          Use Zig as a drop-in dlltool.exe
lib              Use Zig as a drop-in lib.exe
ranlib           Use Zig as a drop-in ranlib
objcopy          Use Zig as a drop-in objcopy
rc               Use Zig as a drop-in rc.exe

This page is about how zig cc, zig c++, zig ar/lib/ranlib, zig dlltool, and zig rc are wired together.

How zig cc works

zig cc accepts the clang command line. The flow is:

1. src/main.zig recognizes the sub-command and invokes the bundled clang driver via src/zig_clang_driver.cpp.
2. The driver translates the clang invocation into a Compilation.Config (e.g. -c foo.c becomes a single-file compile to object).
3. Compilation.create runs the compile through clang's frontend (src/zig_clang_cc1_main.cpp or src/zig_clang_cc1as_main.cpp for assembly), producing an object via LLVM.
4. Linking goes through src/link/Lld.zig (LLD) or, in the future, the in-tree linker for the target format.
5. Include paths are resolved from lib/include/ (clang resource), lib/libc/include/, and the libc flavor matching the target.

zig c++ is the same path with C++ on; lib/libcxx/, lib/libcxxabi/, and lib/libunwind/ get linked when needed.

Archiver and shim sub-commands

Sub-command	Backed by
zig ar	src/zig_llvm-ar.cpp (LLVM's llvm-ar repurposed).
zig ranlib	Same llvm-ar codepath.
zig lib	Same llvm-ar codepath in lib-mode.
zig dlltool	Bundled LLVM dlltool glue.
zig objcopy	lib/compiler/objcopy.zig (Zig native). See objcopy.
zig rc	lib/compiler/resinator/. See resinator.

Cross-compilation

The same machinery that powers Zig cross-compilation (see Cross compilation) backs zig cc -target ...:

• Bundled headers under lib/libc/<flavor>/ and lib/libc/include/ provide the system headers.
• lib/compiler_rt/ provides libcalls (replacing libgcc.a).
• lib/libcxx/ etc. provide the C++ runtime when needed.
• src/link/Lld.zig invokes LLD with the right per-target flags.

Caching

zig cc caches per translation unit through std.Build.Cache. A subsequent compile with the same inputs is a cache hit, returning the existing object.

Tests

• test/c_abi/ — C ABI conformance tests across architectures.
• test/cases.zig — translate-c tests exercise C parsing/preprocessing.
• test/standalone/ — projects that consume zig cc end-to-end.

Key source files

File	Purpose
src/main.zig	Sub-command dispatch.
src/zig_clang_driver.cpp	Clang driver glue.
src/zig_clang_cc1_main.cpp	Clang cc1 (compile) main.
src/zig_clang_cc1as_main.cpp	Clang cc1as (assemble) main.
src/zig_llvm.cpp, src/zig_llvm.h	LLVM glue (codegen, opt).
src/zig_llvm-ar.cpp	llvm-ar for zig ar/ranlib/lib.
src/link/Lld.zig	LLD invocation.
lib/compiler/objcopy.zig, lib/compiler/resinator/	Native Zig toolchain components.
lib/libc/, lib/libcxx/, lib/libcxxabi/, lib/libunwind/, lib/include/, lib/compiler_rt/	Bundled runtime trees.