Xmake Scripting

Xmake Scripting, import, and Native Modules

xmake.lua is Lua, but "writing Lua" in xmake means working inside the script domain — hook bodies like on_load, on_build, after_build, on_install, on_run, on_test, or standalone modules loaded through import(). This skill covers how to write, organize, and load that code, including native (C/C++) Lua modules.

If you are looking for the description/script domain boundary and style rules, see xmake-style. This skill picks up once you are inside a script.

1. Where scripts live

Three idiomatic forms, from inline to fully external:

Inline (short logic)

target("app")
    set_kind("binary")
    add_files("src/*.cpp")
    after_build(function (target)
        os.cp(target:targetfile(), "$(buildir)/dist/")
    end)

Fine for anything under ~15 lines.

External file under modules/

target("app")
    on_load("modules.app.load")
    on_install("modules.app.install")

With a tree:

xmake.lua
modules/
  app/
    load.lua
    install.lua

Each external script file uses the module convention (see below) — no return, a main function is the entry point.

Standalone reusable module imported with import()

xmake.lua
scripts/
  codegen.lua
  utils.lua

-- inside some on_load / on_build
import("scripts.codegen")
codegen.generate(target)

2. The module convention

Xmake does not use Lua's native require / return pattern. Module files follow xmake's own convention:

-- scripts/foo.lua

-- private: prefixed with underscore, not exported
function _helper(x)
    return x * 2
end

-- public: any top-level function without leading underscore
function add(a, b)
    return _helper(a) + b
end

function greet(name)
    print("hello, %s!", name)
end

-- optional: `main` is the module's callable entry point
function main(a, b)
    return add(a, b)
end

Imported:

import("scripts.foo")

foo.add(1, 2)           -- public function
foo.greet("ruki")       -- public function
foo(1, 2)               -- calls main()
-- foo._helper(1)       -- ERROR: underscore-prefixed is private

Equivalent one-shot: import("scripts.foo")(1, 2).

Rules:

• No return at the end of the file.
• Top-level functions without _ prefix are public.
• Top-level functions with _ prefix are private.
• main(...) is optional; if present, calling the imported table invokes it.

3. import() — loading modules

import("core.base.option")            -- built-in xmake module
import("core.project.project")
import("lib.detect.find_tool")
import("scripts.foo")                 -- local module at ./scripts/foo.lua

Resolution order:

1. Current script directory (relative to the file doing the import).
2. xmake's built-in extension class libraries under $(programdir)/modules/ and $(programdir)/core/.
3. Any directories added with add_moduledirs(...).

Options

import("core.platform.platform", {alias = "p"})            -- rename to avoid conflicts
import("scripts.foo",             {rootdir = "/abs/path"}) -- import from elsewhere
import("scripts.foo",             {try = true})            -- return nil on failure
import("scripts.foo",             {anonymous = true})      -- don't pollute scope
import("scripts.base",            {inherit = true})        -- merge into current module

• alias — bind the module to a different local name. Critical when two modules share a base name.
• rootdir — import from an absolute directory, useful for shared tool libraries.
• try — don't throw if the module doesn't exist; return nil instead.
• anonymous — don't create a top-level local; return the import object and let the caller bind it.
• inherit — copy all public functions into the calling module (module-level inheritance).

4. Frequently imported xmake core modules

Example — find a tool and shell out through it:

on_build(function (target)
    import("lib.detect.find_tool")
    import("core.base.option")

    local protoc = assert(find_tool("protoc"), "protoc not found")
    os.vrunv(protoc.program, {"--cpp_out=" .. target:autogendir(), "proto/msg.proto"})
end)

5. Target/config APIs from inside a hook

Inside on_load(function (target) ... end) the target argument gives you a target instance:

target:name()
target:kind()
target:targetfile()          -- full path of the built file
target:sourcefiles()         -- list of source files
target:installdir()
target:pkg("fmt")            -- get a package instance bound to the target
target:add("links", "pthread")
target:add("defines", "DEBUG", {public = true})
target:set("kind", "binary")
target:get("includedirs")
target:values("cxflags")

target:add / target:set / target:get are the script-domain equivalents of add_* / set_* / the raw config.

6. Built-in modules you can use in scripts

All of these are pre-imported in the script domain — no import(...) needed:

• os — cross-platform os.cp, os.mv, os.rm, os.mkdir, os.exists, os.exec, os.vrunv, os.iorunv, os.getenv, os.mtime, os.tmpdir, os.host, os.arch.
• io — io.readfile, io.writefile, io.open, io.lines, io.gsub.
• path — path.join, path.filename, path.basename, path.extension, path.directory, path.absolute, path.relative, path.translate.
• table — xmake-extended: table.concat, table.contains, table.insert, table.unique, table.join, table.copy.
• string — xmake-extended: string.split, string.trim, string.startswith, string.endswith.
• hash — hash.md5, hash.sha1, hash.sha256, hash.xxh64.
• print / cprint / vprint / printf / cprintf — xmake's logging. cprint supports ${color} tags; vprint only prints in -v mode.
• raise — throw an error. Inside cli.bisect or on_test, a raised error marks the step bad.
• try ... catch ... finally — structured error handling, xmake's Lua-level equivalent.
• winos / linuxos / macos — host-specific helpers.

Full reference lives under xmake/core/base/ and xmake/core/sandbox/modules/ in the xmake source.

7. Shell-outs: pick the right os.*

Prefer *v forms (list args) over string forms — no shell quoting surprises. Prefer vrunv inside build hooks so -v controls visibility.

8. Custom tasks — callable from the CLI

Wrap a module into a task and it becomes xmake <taskname>:

task("hello")
    set_menu {
        usage = "xmake hello [options]",
        description = "Say hello",
        options = {
            {"n", "name", "kv", "world", "name to greet"}
        }
    }
    on_run(function ()
        import("core.base.option")
        cprint("${bright green}hello, %s!${clear}", option.get("name"))
    end)

xmake hello --name=ruki

Option kind: "k" (flag), "kv" (key-value), "vs" (values list). See xmake-plugins for more.

9. Native modules (C/C++ Lua modules)

When Lua is too slow (heavy hash/parse/math), or when you want to reuse an existing C library, drop into a native module. Xmake builds it automatically and loads it via import() just like a Lua module.

Two flavors:

• Shared (module.shared) — a .so/.dll/.dylib loaded into the xmake process. Fastest; exposes Lua C API.
• Binary (module.binary) — an executable spawned per call. Simpler, cross-platform, but slower.

Shared native module

Directory layout:

xmake.lua
modules/
  foo/
    xmake.lua            # builds the module
    foo.c                # native source

Module xmake.lua:

-- modules/foo/xmake.lua
add_rules("mode.debug", "mode.release")

target("foo")
    add_rules("module.shared")
    add_files("foo.c")

Native source:

// modules/foo/foo.c
#include <xmi.h>   // xmake's lua include shim — prefer over <lua.h>

static int c_add(lua_State* lua) {
    int a = lua_tointeger(lua, 1);
    int b = lua_tointeger(lua, 2);
    lua_pushinteger(lua, a + b);
    return 1;
}

static int c_sub(lua_State* lua) {
    int a = lua_tointeger(lua, 1);
    int b = lua_tointeger(lua, 2);
    lua_pushinteger(lua, a - b);
    return 1;
}

int luaopen(foo, lua_State* lua) {
    static const luaL_Reg funcs[] = {
        {"add", c_add},
        {"sub", c_sub},
        {NULL, NULL}
    };
    lua_newtable(lua);
    luaL_setfuncs(lua, funcs, 0);
    return 1;
}

Key points:

• Include xmi.h, not lua.h/luaconf.h directly — it papers over Lua vs LuaJIT differences.
• Xmake's main binary already exports the full Lua C API — no Lua dependency needed in your module.
• luaopen(<name>, lua_State*) is the entry point; xmake calls it when the module is imported.

Binary native module

modules/bar/
  xmake.lua
  bar.cpp

// modules/bar/bar.cpp
#include <cstdio>
#include <cstdlib>
int main(int argc, char** argv) {
    int a = atoi(argv[1]);
    int b = atoi(argv[2]);
    printf("%d", a + b);
    return 0;
}

-- modules/bar/xmake.lua
target("add")
    add_rules("module.binary")
    add_files("bar.cpp")

The module protocol: xmake spawns the binary with the args, reads stdout for the return value. No Lua API involved.

Consuming the module

-- ./xmake.lua
add_moduledirs("modules")           -- tell xmake where to look

target("app")
    set_kind("phony")
    on_load(function (target)
        import("foo", {always_build = true})
        import("bar")
        print("foo.add(1,1) = %s", foo.add(1, 1))
        print("foo.sub(1,1) = %s", foo.sub(1, 1))
        print("bar.add(1,1) = %s", bar.add(1, 1))
    end)

• add_moduledirs(dir) registers a directory as an additional module root. Modules inside are built automatically on first import.
• {always_build = true} makes xmake re-check the module sources on every run — essential while iterating. Drop it in production for faster startup.

When to use which

Reference project in the xmake source: tests/projects/other/native_module_cjson.

10. Common pitfalls

• Forgetting that description domain is parsed multiple times. print / os.iorun / network calls at the top level run on every parse. Move them into on_load.
• Using require instead of import. Xmake's module convention is not standard Lua. require will sometimes work but skips xmake's sandbox, resolution order, and privacy rules. Always import.
• Returning from a module file. Unnecessary — xmake collects top-level function definitions automatically. A trailing return M confuses the loader.
• Private _foo called externally. foo._helper(x) from outside the module fails. Expose a public wrapper or drop the underscore.
• Native module rebuild not triggering. Without {always_build = true}, xmake only builds the module once. Add it during development.
• Native module including lua.h directly. Works until you hit a LuaJIT-only build; use <xmi.h> for portability.
• Shelling out with os.exec("cmd " .. user_input). String-form is shell-parsed. Use os.execv(program, {args...}) to avoid injection and quoting bugs.

When to branch out

• Where scripts live vs. description-domain rules → xmake-style
• Writing a CLI subcommand (task/plugin) → xmake-plugins
• Writing a rule (lifecycle hook tied to a file extension) → xmake-rules
• Debugging script behavior (-vD, tracebacks, EmmyLua) → xmake-troubleshooting, xmake-dev