C Module Support

C modules are supported in LDE projects via build scripts.

The process is simple: compile your C source into a shared library and place it inside your package’s output directory (target/<name>/). lde adds an entry to your package.cpath which resolves shared libraries the same way it resolves Lua files in your target directory — so the library is required like any other module in your package.

Example

This example builds a module named socket.core for a package named socket. The library lands at target/socket/core.so (or .dll on Windows), so require("socket.core") finds it.

local build = require("lde-build")

-- src/ is copied into the output directory before the script runs, so the
-- source is available at build.outDir .. "/socket.c". build:cc resolves
-- paths from the package directory, so prefix arguments with build.outDir.
local ext = jit.os == "Windows" and "dll" or "so"

build:cc({
	"-shared", "-fPIC",
	"-o", build.outDir .. "/core." .. ext,
	build.outDir .. "/socket.c"
})

The exported symbol must match the require name: require("socket.core") looks for luaopen_socket_core. The example declares only the Lua C API functions it uses, so it compiles without LuaJIT headers on the machine. Larger modules usually #include "lua.h" and arrange for the headers themselves — for example by fetching them with build:fetch or driving a full build system with build:sh.

#include <stddef.h>

typedef struct lua_State lua_State;
typedef int (*lua_CFunction)(lua_State *L);

extern void lua_pushstring(lua_State *L, const char *s);

int luaopen_socket_core(lua_State *L) {
	lua_pushstring(L, "Hello from C!");
	return 1;
}

local socket = require("socket.core")
print("Here's the output: ", socket)
-- Here's the output: Hello from C!

Support for compiled applications

This also works for projects compiled with lde compile by scanning and saving any shared libraries from target into the binary, and extracting them into a temporary directory at runtime.

They are then resolved via a package.preload lookup on require(), same as lua files.

They do not require lua on the user’s system on Windows, macOS, or Linux, as the binary created exports the LuaJIT symbols from LDE.

Distributing as a Library

This all runs at the build time when someone installs your library, so you should make your build script smart enough to build on multiple platforms and ideally depend on as little as possible.