ADDED THREAD ! Minor changes on other libs.

To communicate with a thread, use sockets on localhost, this should work.
Or use the return code, or the "last error", but that's crappy.
For the return code, just `return <number>`; only works with integers.

source/audio.c

@@ -887,7 +887,9 @@ int luaopen_audio_lib(lua_State *L) {
 }
 
 void load_audio_lib(lua_State *L) {
-	isAudioInitialized = !ndspInit(); // ndspInit returns 0 in case of success
+	if (!isAudioInitialized) {
+		isAudioInitialized = !ndspInit(); // ndspInit returns 0 in case of success
+	}
 
 	luaL_requiref(L, "ctr.audio", luaopen_audio_lib, false);
 }

source/ctr.c

@@ -114,6 +114,13 @@ The `ctr.mic` module.
 */
 void load_mic_lib(lua_State *L);
 
+/***
+The `ctr.thread` module.
+@table thread
+@see ctr.thread
+*/
+void load_thread_lib(lua_State *L);
+
 /***
 Return whether or not the program should continue.
 @function run
@@ -171,6 +178,7 @@ struct { char *name; void (*load)(lua_State *L); void (*unload)(lua_State *L); }
 	{ "audio",  load_audio_lib,  unload_audio_lib },
 	{ "apt",    load_apt_lib,    NULL             },
 	{ "mic",    load_mic_lib,    NULL             },
+	{ "thread", load_thread_lib, NULL             },
 	{ NULL, NULL }
 };
 

source/fs.c

@@ -14,6 +14,8 @@ The `fs` module.
 #include <lua.h>
 #include <lauxlib.h>
 
+bool isFsInitialized = false;
+
 Handle *fsuHandle;
 FS_Archive sdmcArchive;
 #ifdef ROMFS
@@ -211,17 +213,20 @@ int luaopen_fs_lib(lua_State *L) {
 }
 
 void load_fs_lib(lua_State *L) {
-	fsInit();
+	if (!isFsInitialized) {
+		fsInit();
 
-	fsuHandle = fsGetSessionHandle();
+		fsuHandle = fsGetSessionHandle();
-	FSUSER_Initialize(*fsuHandle);
+		FSUSER_Initialize(*fsuHandle);
 
-	sdmcArchive = (FS_Archive){ARCHIVE_SDMC, fsMakePath(PATH_EMPTY, "")};
+		sdmcArchive = (FS_Archive){ARCHIVE_SDMC, fsMakePath(PATH_EMPTY, "")};
-	FSUSER_OpenArchive(&sdmcArchive);
+		FSUSER_OpenArchive(&sdmcArchive);
-	#ifdef ROMFS
+		#ifdef ROMFS
-	romfsArchive = (FS_Archive){ARCHIVE_ROMFS, fsMakePath(PATH_EMPTY, "")};
+		romfsArchive = (FS_Archive){ARCHIVE_ROMFS, fsMakePath(PATH_EMPTY, "")};
-	FSUSER_OpenArchive(&romfsArchive);
+		FSUSER_OpenArchive(&romfsArchive);
-	#endif
+		#endif
+		isFsInitialized = true;
+	}
 	
 	luaL_requiref(L, "ctr.fs", luaopen_fs_lib, false);
 }

source/gfx.c

@@ -456,8 +456,10 @@ int luaopen_gfx_lib(lua_State *L) {
 }
 
 void load_gfx_lib(lua_State *L) {
-	sf2d_init();
+	if (!isGfxInitialized) {
-	sftd_init();
+		sf2d_init();
+		sftd_init();
+	}
 
 	isGfxInitialized = true;
 

source/httpc.c

@@ -13,6 +13,8 @@ The `httpc` module.
 #include <lapi.h>
 #include <lauxlib.h>
 
+bool isHttpcInitialized = false;
+
 /***
 Create a HTTP Context.
 @function context
@@ -205,7 +207,10 @@ int luaopen_httpc_lib(lua_State *L) {
 }
 
 void load_httpc_lib(lua_State *L) {
-	httpcInit();
+	if (!isHttpcInitialized) {
+		httpcInit();
+		isHttpcInitialized = true;
+	}
 	
 	luaL_requiref(L, "ctr.httpc", luaopen_httpc_lib, false);
 }

source/thread.c

@@ -0,0 +1,160 @@
+/***
+The `thread` module.
+@module ctr.thread
+@usage local thread = require("ctr.thread")
+*/
+
+#include <lua.h>
+#include <lauxlib.h>
+#include <lualib.h>
+
+#include <3ds/types.h>
+#include <3ds/thread.h>
+#include <3ds/services/apt.h>	
+
+#include <malloc.h>
+#include <string.h>
+
+void load_ctr_lib(lua_State *L);
+
+typedef struct {
+	Thread thread;
+	const char *code;
+	char *error;
+} thread_userdata;
+
+void entryPoint(void *thread) {
+	lua_State *T = luaL_newstate();
+	luaL_openlibs(T);
+	load_ctr_lib(T);
+	
+	if (luaL_dostring(T, ((thread_userdata*)thread)->code)) {
+		const char* lerror = luaL_checkstring(T, -1);
+		((thread_userdata*)thread)->error = malloc(strlen(lerror)+1);
+		strcpy(((thread_userdata*)thread)->error, lerror);
+	}
+	
+	int exitCode = 0;
+	if (lua_isinteger(T, -1)) {
+		exitCode = lua_tointeger(T, -1);
+	}
+	lua_close(T);
+	threadExit(exitCode);
+}
+
+// module
+/***
+Set the maximum CPU time allocated to threads on CPU #1.
+@function setCpuLimit
+@tparam number time in percents.
+*/
+static int thread_setCpuLimit(lua_State *L) {
+	u32 percent = luaL_checkinteger(L, 1);
+	APT_SetAppCpuTimeLimit(percent);
+	
+	return 0;
+}
+
+/***
+Start a new thread.
+@function start
+@tparam string code Lua code to load in the new thread. May not work with dumped functions.
+@tparam[opt=0] number cpu must be >= 0 and < 2 for 3ds or < 4 for new3ds
+@tparam[opt=0x27] number priority must be > 0x18 and < 0x3f; the lower is higher.
+@tparam[opt=0x100000] number stacksize size of the stack, increase it in case of OoM
+@treturn thread a new thread object
+*/
+static int thread_start(lua_State *L) {
+	const char* code = luaL_checkstring(L, 1);
+	s32 processor = luaL_optinteger(L, 2, 0);
+	s32 priority = luaL_optinteger(L, 3, 0x27);
+	size_t stackSize = luaL_optinteger(L, 4, 0x100000);
+	
+	thread_userdata *thread = lua_newuserdata(L, sizeof(thread_userdata*));
+	luaL_getmetatable(L, "LThread");
+	lua_setmetatable(L, -2);
+	
+	thread->code = code;
+	thread->error = NULL;
+	thread->thread = threadCreate(entryPoint, thread, stackSize, priority, processor, true);
+	
+	return 1;
+}
+
+/***
+Wait for a thread to finish.
+@function :join
+@tparam[opt=2^32-1] number timeout in ns
+@treturn number exit code
+@treturn string last error, or nil
+*/
+static int thread_join(lua_State *L) {
+	thread_userdata *thread = luaL_checkudata(L, 1, "LThread");
+	u64 timeout = luaL_optinteger(L, 2, 4294967295);
+	
+	threadJoin(thread->thread, timeout);
+	
+	lua_pushinteger(L, threadGetExitCode(thread->thread));
+	if (thread->error != NULL) {
+		lua_pushstring(L, thread->error);
+		return 2;
+	}
+	return 1;
+}
+
+/***
+Return the last error of a thread.
+@function :lastError
+@treturn string last error, or nil
+*/
+static int thread_lastError(lua_State *L) {
+	thread_userdata *thread = luaL_checkudata(L, 1, "LThread");
+	
+	if (thread->error == NULL) {
+		lua_pushnil(L);
+	} else {
+		lua_pushstring(L, thread->error);
+	}
+	return 1;
+}
+
+/***
+Destroy a finished thread.
+@function :destroy
+*/
+static int thread_destroy(lua_State *L) {
+	thread_userdata *thread = luaL_checkudata(L, 1, "LThread");
+	
+	threadFree(thread->thread);
+	free(thread->error);
+	
+	return 0;
+}
+
+static const struct luaL_Reg thread_lib[] = {
+	{"start", thread_start},
+	{"setCpuLimit", thread_setCpuLimit},
+	{NULL, NULL}
+};
+
+static const struct luaL_Reg thread_methods[] = {
+	{"join", thread_join},
+	{"lastError", thread_lastError},
+	{"destroy", thread_destroy},
+	{"__gc", thread_destroy},
+	{NULL, NULL}
+};
+
+int luaopen_thread_lib(lua_State *L) {
+	luaL_newmetatable(L, "LThread");
+	lua_pushvalue(L, -1);
+	lua_setfield(L, -2, "__index");
+	luaL_setfuncs(L, thread_methods, 0);
+	
+	luaL_newlib(L, thread_lib);
+	return 1;
+}
+
+void load_thread_lib(lua_State *L) {
+	luaL_requiref(L, "ctr.thread", luaopen_thread_lib, 0);
+}