How do I configure laura be used with custom C/C++ extensions?

[MichaelBonnet]

Say I had something like this main.c:

#include <stdio.h>
#include <stdlib.h>
#include "lua5.4/lua.h"
#include "lua5.4/lauxlib.h"
#include "lua5.4/lualib.h"

// compile : gcc main.c -o custom_lua_app -I/usr/include/lua5.4 -llua5.4 -lm -ldl
// run     : ./custom_lua_app script1.lua

/**
 * sumLua: Expects two numbers on the stack; returns their sum.
 * Stack layout (top at the right):
 *   1: number
 *   2: number
 */
static int sumLua(lua_State* L) {
    // Check we have 2 arguments
    int nArgs = lua_gettop(L);
    if(nArgs != 2) {
        return luaL_error(L, "sumLua expects exactly 2 arguments!");
    }

    // Get arguments (both should be numbers)
    if(!lua_isnumber(L, 1) || !lua_isnumber(L, 2)) {
        return luaL_error(L, "sumLua expects numbers!");
    }

    double a = lua_tonumber(L, 1);
    double b = lua_tonumber(L, 2);

    // Compute sum
    double result = a + b;

    // Push result onto the Lua stack
    lua_pushnumber(L, result);

    // Return 1 value to Lua
    return 1;
}

int main(int argc, char** argv) {
    // Create Lua state
    lua_State* L = luaL_newstate();

    // Open standard libraries
    luaL_openlibs(L);

    // Register functions
    lua_register(L, "sumLua", sumLua);

    // Check if the user passed a script name
    if(argc < 2) {
        printf("Usage: %s <Lua script>\n", argv[0]);
        lua_close(L);
        return 1;
    }

    // Load and run the Lua script
    if(luaL_loadfile(L, argv[1]) || lua_pcall(L, 0, 0, 0)) {
        fprintf(stderr, "Error: %s\n", lua_tostring(L, -1));
        // lua_pop(L, 1); // remove error message
        lua_close(L);
        return 1;
    }

    // Clean up and close Lua
    lua_close(L);
    return 0;
}

with script1.lua:

-- script1.lua

-- Call sumLua, which is defined in C
local x = 10
local y = 25
local s = sumLua(x, y)
print("Lua: The sum of ", x, " and ", y, " is ", s)

How might I configure Laura such that I can unit test the Lua use of available custom C functions?

[dknight]

If you compile your code as shared module, of course it is possible to test C functions from laura. I would suggest you to move your sumLua function to library.

sumLua.c

#include <stdio.h>
#include <stdlib.h>
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

// compile : gcc main.c -o custom_lua_app -I/usr/include/lua5.4 -llua5.4 -lm -ldl
// run     : ./custom_lua_app script1.lua

/**
 * sumLua: Expects two numbers on the stack; returns their sum.
 * Stack layout (top at the right):
 *   1: number
 *   2: number
 */
static int c_sumLua(lua_State* L) {
    // Check we have 2 arguments
    int nArgs = lua_gettop(L);
    if(nArgs != 2) {
        return luaL_error(L, "sumLua expects exactly 2 arguments!");
    }

    // Get arguments (both should be numbers)
    if(!lua_isnumber(L, 1) || !lua_isnumber(L, 2)) {
        return luaL_error(L, "sumLua expects numbers!");
    }

    double a = lua_tonumber(L, 1);
    double b = lua_tonumber(L, 2);

    // Compute sum
    double result = a + b;

    // Push result onto the Lua stack
    lua_pushnumber(L, result);

    // Return 1 value to Lua
    return 1;
}


static const luaL_Reg my_funtions[] = {
    {"sumLua", c_sumLua},
    {NULL, NULL}
};

int luaopen_sumLua(lua_State *L) {
    luaL_newlib(L, my_funtions);
    return 1;
}

After compile it, for example with gcc: gcc -shared -fPIC -o sumLua.so sumLua.c -llua -lm -ldl
Or DLL if you are on Windows.

Now you will get your shared module sumLua.so and you can use it your script.

script1.lua

local sumLua = require("sumLua").sumLua
-- Call sumLua, which is defined in C
local x = 10
local y = 25
local s = sumLua(x, y)
print("Lua: The sum of ", x, " and ", y, " is ", s)

Next write your test

script1_test.lua

local laura = require("laura")
local describe = laura.describe
local it = laura.it
local expect = laura.expect
local mod = require("sumLua")

describe("test issue 1", function()
	it("should sum the values", function()
		local sum = mod.sumLua(12, 30)
		expect(sum).toEqual(42)
	end)
end)

Run laura and OK

laura
test issue 1
        [passing] should sum the values (667μs)

SUMMARY
1 of 1 passing
0 failing
0 skipping

time: ~895μs / mem: 321.63KB @ 2025-04-15 18:21:59
pass

In your approach where ./custom_lua_app script1.lua it is barely possible, or at least I have no idea how to do this.