Importing C

Zig can parse C headers directly. There is no binding generator and no intermediate .zig file to maintain.

const c = @cImport({
    @cDefine("_GNU_SOURCE", {});
    @cInclude("stdio.h");
    @cInclude("string.h");
});

pub fn main(init: std.process.Init) !void {
    _ = init;
    _ = c.printf("hello from C\n");
    const len = c.strlen("abc");
    ...
}

Everything the header declares appears as a member of c.

Telling the build where to look

exe.linkLibC();
exe.addIncludePath(b.path("vendor/include"));
exe.linkSystemLibrary("sqlite3");

Or compile the C yourself. Zig includes a C compiler, so vendoring a dependency’s sources is a reasonable option:

exe.addCSourceFile(.{ .file = b.path("vendor/thing.c"), .flags = &.{"-std=c99"} });

What translates and what does not

Types, functions, and simple #define constants translate cleanly. Function-like macros do not: they are C syntax, not C semantics, and Zig cannot always give them meaning. When one matters, reimplement it in Zig; zig translate-c shows you what the automatic translation produced, which is a useful starting point.

Strings

C strings are [*c]const u8 and null-terminated. Zig string literals are already null-terminated, so passing one to C needs no conversion. Coming back, std.mem.span(ptr) recovers a slice by scanning for the terminator.

Why this page has no Run button

Unlike every other chapter here, this one shows no runnable snippet: @cImport needs real C headers and a libc for the target, and the wasm sandbox these pages execute in has neither. The code above is illustrative rather than CI-verified, the only page in this guide of which that is true.