Include a C library inside a no hello-world Zig library

I am doing a side project and maybe this may be not a good first step, but
I am looking to include a C library to interact with a USB device in order
to build an easy-to-use cross-platform zig library.

So, I am considering to switch for this project from Rust to zib because I think
for this kind of job, zig is a good alternative to rust, but I find difficult.

BTW my current architecture is hosted on github at and looks like the following

   - hidapi
   - libusb
- src
  - main.zig
  - hwi
    - device.zig
- build.zig

My build.zig looks like

const std = @import("std");

// Although this function looks imperative, note that its job is to
// declaratively construct a build graph that will be executed by an external
// runner.
pub fn build(b: *std.Build) void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});

    // Standard optimization options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
    // set a preferred release mode, allowing the user to decide how to optimize.
    const optimize = b.standardOptimizeOption(.{});

    const lib = b.addStaticLibrary(.{
        .name = "unified-hwi",
        // In this case the main source file is merely a path, however, in more
        // complicated build scripts, this could be a generated file.
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    lib.addCSourceFile(.{ .file = std.Build.LazyPath.relative("./external/hidapi/libusb/hid.c"), .flags = &[_][]const u8{"-std=c99"} });

    // This declares intent for the library to be installed into the standard
    // location when the user invokes the "install" step (the default step when
    // running `zig build`).

    // Creates a step for unit testing. This only builds the test executable
    // but does not run it.
    const main_tests = b.addTest(.{
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    main_tests.addCSourceFile(.{ .file = std.Build.LazyPath.relative("./external/hidapi/libusb/hid.c"), .flags = &[_][]const u8{"-std=c99"} });

    const run_main_tests = b.addRunArtifact(main_tests);

    // This creates a build step. It will be visible in the `zig build --help` menu,
    // and can be selected like this: `zig build test`
    // This will evaluate the `test` step rather than the default, which is "install".
    const test_step = b.step("test", "Run library tests");

When I will go to build the library

➜  unified-hwi git:(macros/api) nix develop
[vincent@vincent-arch unified-hwi]$ make
zig fmt .
zig build --verbose-cimport
zig test src/main.zig
src/hw/cold_card.zig:4:13: error: C import failed
const hid = @cImport({
src/hw/cold_card.zig:4:13: note: libc headers not available; compilation does not link against libc
referenced by:
    ColdCardUSB: src/hw/cold_card.zig:32:14
    ColdCardUSB: src/hw/cold_card.zig:25:21
    remaining reference traces hidden; use '-freference-trace' to see all reference traces
/home/vincent/Github/unified-hwi/zig-cache/o/d7b010b333c576d588250325510d6e84/cimport.h:2:10: error: 'hid.h' file not found
#include <hid.h>
error: Recipe `default` failed on line 3 with exit code 1
[vincent@vincent-arch unified-hwi]$ 

I am not able to understand what kind of path cInclude want, and why in this case is not able to find it?

I think I have done all what the guide tell to include

What I am missing?

I think you have to run zig build test so the tests will use your build.zig. I believe zig test alone doesn’t use build.zig.

Mh same error also with the zigbuild

I am not able to understand what kind of path the @cInclude want, or maybe I have something
wrong with my