zig: use a c library from a dependency

The zig community is large, but the number of native zig libraries is still growing. However, you can easily import any C library into your zig project.

Step 1: Fetch and Install the C Library

First install the c library, we will use cJSON as an example.

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zig fetch --save=cjson https://github.com/DaveGamble/cJSON/archive/refs/heads/master.zip

Step 2: Modify build.zig to Include the C Library

Now we need to adjust build.zig to import the library to our executable:

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// ...
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const cjsonDep = b.dependency("cjson", .{});
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exe.addIncludePath(cjsonDep.path(""));
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exe.linkLibC();
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exe.addCSourceFiles(.{
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    .root = .{
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        .dependency = .{
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            .dependency = cjsonDep,
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            .sub_path = "",
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        },
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    },
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    .files = &[_][]const u8{
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        "cJSON.c",
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    },
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});
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// ...

Step 3: Use the C Library in Your zig Application

Now, you can access the public API of cJSON in your zig application.

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const c = @cImport({
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    @cInclude("cJSON.h");
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});
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const value = c.cJSON_Parse(
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    "{ \"name\": \"Patrick\" }",
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);
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defer std.c.free(value);
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const name = c.cJSON_GetObjectItemCaseSensitive(
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    value,
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    "name",
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);
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defer std.c.free(name);
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if (c.cJSON_IsString(name) == 1) {
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    const str: [:0]u8 = std.mem.span(name.*.valuestring);
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    std.debug.print(
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        "name = {s}, len = {d}\n",
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        .{
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            str,
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            str.len,
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        },
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    );
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}

Output:

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> zig build run
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name = Patrick, len = 7

With this approach, you can easily extend your Zig applications using the vast ecosystem of C libraries, like cJSON. This flexibility allows you to bridge the gap between Zig and C seamlessly.

Source Code

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