translate-c

Active contributors: vexu, andrewrk

Purpose

zig translate-c converts a C source file or .c-style translation unit into Zig. The work is split between Aro (the bundled C frontend, see aro) and lib/compiler/translate-c/, which walks Aro's AST and emits Zig.

Directory layout

lib/compiler/translate-c/
└── ...                 # AST-to-Zig lowering for every Aro node kind

The driver entry point is src/main.zig's cmdTranslateC (and friends), which builds an Aro translation unit, runs the lowering, and prints the resulting Zig source.

What gets translated

zig translate-c aims to produce compilable Zig from any preprocessed C input:

• Type declarations (struct, union, enum, typedef).
• Function declarations and definitions.
• Macros (constant #defines become Zig consts; function-like macros are lowered when feasible).
• Statements and expressions (with the usual caveats for unrepresentable patterns).
• C-style bitfields, anonymous fields, flexible arrays.

When a construct cannot be translated (e.g. some macros, certain preprocessor abuses, GCC extensions), the generator emits @compileError or skips the symbol with a comment, matching the behavior of @cImport.

How it integrates

• Standalone: zig translate-c foo.c > foo.zig.
• From within Zig: @cImport({ @cInclude("foo.h"); }) runs the same path internally and returns a Zig namespace.
• From the build system: lib/std/Build/Step/TranslateC.zig exposes a Step.TranslateC.

Tests

zig build test-translate-c exercises a fixture set under test/cases.zig's translate-c slice. Each fixture pairs a C input with the expected Zig output.

Key source files

File	Purpose
lib/compiler/translate-c/	The translator.
lib/compiler/aro/	The C frontend it consumes.
lib/std/Build/Step/TranslateC.zig	The build step.
src/main.zig (cmdTranslateC)	CLI dispatch.

See aro for the upstream C frontend.