1const std = @import("std");
2
3// Although this function looks imperative, it does not perform the build
4// directly and instead it mutates the build graph (`b`) that will be then
5// executed by an external runner. The functions in `std.Build` implement a DSL
6// for defining build steps and express dependencies between them, allowing the
7// build runner to parallelize the build automatically (and the cache system to
8// know when a step doesn't need to be re-run).
9pub fn build(b: *std.Build) void {
10 // Standard target options allow the person running `zig build` to choose
11 // what target to build for. Here we do not override the defaults, which
12 // means any target is allowed, and the default is native. Other options
13 // for restricting supported target set are available.
14 const target = b.standardTargetOptions(.{});
15 // Standard optimization options allow the person running `zig build` to select
16 // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
17 // set a preferred release mode, allowing the user to decide how to optimize.
18 const optimize = b.standardOptimizeOption(.{});
19 // It's also possible to define more custom flags to toggle optional features
20 // of this build script using `b.option()`. All defined flags (including
21 // target and optimize options) will be listed when running `zig build --help`
22 // in this directory.
23
24 // This creates a module, which represents a collection of source files alongside
25 // some compilation options, such as optimization mode and linked system libraries.
26 // Zig modules are the preferred way of making Zig code available to consumers.
27 // addModule defines a module that we intend to make available for importing
28 // to our consumers. We must give it a name because a Zig package can expose
29 // multiple modules and consumers will need to be able to specify which
30 // module they want to access.
31 const mod = b.addModule("_NAME", .{
32 // The root source file is the "entry point" of this module. Users of
33 // this module will only be able to access public declarations contained
34 // in this file, which means that if you have declarations that you
35 // intend to expose to consumers that were defined in other files part
36 // of this module, you will have to make sure to re-export them from
37 // the root file.
38 .root_source_file = b.path("src/root.zig"),
39 // Later on we'll use this module as the root module of a test executable
40 // which requires us to specify a target.
41 .target = target,
42 });
43
44 // Here we define an executable. An executable needs to have a root module
45 // which needs to expose a `main` function. While we could add a main function
46 // to the module defined above, it's sometimes preferable to split business
47 // logic and the CLI into two separate modules.
48 //
49 // If your goal is to create a Zig library for others to use, consider if
50 // it might benefit from also exposing a CLI tool. A parser library for a
51 // data serialization format could also bundle a CLI syntax checker, for example.
52 //
53 // If instead your goal is to create an executable, consider if users might
54 // be interested in also being able to embed the core functionality of your
55 // program in their own executable in order to avoid the overhead involved in
56 // subprocessing your CLI tool.
57 //
58 // If neither case applies to you, feel free to delete the declaration you
59 // don't need and to put everything under a single module.
60 const exe = b.addExecutable(.{
61 .name = "_NAME",
62 .root_module = b.createModule(.{
63 // b.createModule defines a new module just like b.addModule but,
64 // unlike b.addModule, it does not expose the module to consumers of
65 // this package, which is why in this case we don't have to give it a name.
66 .root_source_file = b.path("src/main.zig"),
67 // Target and optimization levels must be explicitly wired in when
68 // defining an executable or library (in the root module), and you
69 // can also hardcode a specific target for an executable or library
70 // definition if desireable (e.g. firmware for embedded devices).
71 .target = target,
72 .optimize = optimize,
73 // List of modules available for import in source files part of the
74 // root module.
75 .imports = &.{
76 // Here "_NAME" is the name you will use in your source code to
77 // import this module (e.g. `@import("_NAME")`). The name is
78 // repeated because you are allowed to rename your imports, which
79 // can be extremely useful in case of collisions (which can happen
80 // importing modules from different packages).
81 .{ .name = "_NAME", .module = mod },
82 },
83 }),
84 });
85
86 // This declares intent for the executable to be installed into the
87 // install prefix when running `zig build` (i.e. when executing the default
88 // step). By default the install prefix is `zig-out/` but can be overridden
89 // by passing `--prefix` or `-p`.
90 b.installArtifact(exe);
91
92 // This creates a top level step. Top level steps have a name and can be
93 // invoked by name when running `zig build` (e.g. `zig build run`).
94 // This will evaluate the `run` step rather than the default step.
95 // For a top level step to actually do something, it must depend on other
96 // steps (e.g. a Run step, as we will see in a moment).
97 const run_step = b.step("run", "Run the app");
98
99 // This creates a RunArtifact step in the build graph. A RunArtifact step
100 // invokes an executable compiled by Zig. Steps will only be executed by the
101 // runner if invoked directly by the user (in the case of top level steps)
102 // or if another step depends on it, so it's up to you to define when and
103 // how this Run step will be executed. In our case we want to run it when
104 // the user runs `zig build run`, so we create a dependency link.
105 const run_cmd = b.addRunArtifact(exe);
106 run_step.dependOn(&run_cmd.step);
107
108 // By making the run step depend on the default step, it will be run from the
109 // installation directory rather than directly from within the cache directory.
110 run_cmd.step.dependOn(b.getInstallStep());
111
112 // This allows the user to pass arguments to the application in the build
113 // command itself, like this: `zig build run -- arg1 arg2 etc`
114 run_cmd.addPassthruArgs();
115
116 // Creates an executable that will run `test` blocks from the provided module.
117 // Here `mod` needs to define a target, which is why earlier we made sure to
118 // set the releative field.
119 const mod_tests = b.addTest(.{
120 .root_module = mod,
121 });
122
123 // A run step that will run the test executable.
124 const run_mod_tests = b.addRunArtifact(mod_tests);
125
126 // Creates an executable that will run `test` blocks from the executable's
127 // root module. Note that test executables only test one module at a time,
128 // hence why we have to create two separate ones.
129 const exe_tests = b.addTest(.{
130 .root_module = exe.root_module,
131 });
132
133 // A run step that will run the second test executable.
134 const run_exe_tests = b.addRunArtifact(exe_tests);
135
136 // A top level step for running all tests. dependOn can be called multiple
137 // times and since the two run steps do not depend on one another, this will
138 // make the two of them run in parallel.
139 const test_step = b.step("test", "Run tests");
140 test_step.dependOn(&run_mod_tests.step);
141 test_step.dependOn(&run_exe_tests.step);
142
143 // Just like flags, top level steps are also listed in the `--help` menu.
144 //
145 // The Zig build system is entirely implemented in userland, which means
146 // that it cannot hook into private compiler APIs. All compilation work
147 // orchestrated by the build system will result in other Zig compiler
148 // subcommands being invoked with the right flags defined. You can observe
149 // these invocations when one fails (or you pass a flag to increase
150 // verbosity) to validate assumptions and diagnose problems.
151 //
152 // Lastly, the Zig build system is relatively simple and self-contained,
153 // and reading its source code will allow you to master it.
154}