src/lib_package.c

   1 /*
   2 ** Package library.
   3 ** Copyright (C) 2005-2012 Mike Pall. See Copyright Notice in luajit.h
   4 **
   5 ** Major portions taken verbatim or adapted from the Lua interpreter.
   6 ** Copyright (C) 1994-2011 Lua.org, PUC-Rio. See Copyright Notice in lua.h
   7 */
   8
   9 #define lib_package_c
  10 #define LUA_LIB
  11
  12 #include "lua.h"
  13 #include "lauxlib.h"
  14 #include "lualib.h"
  15
  16 #include "lj_obj.h"
  17 #include "lj_err.h"
  18 #include "lj_lib.h"
  19
  20 /* ------------------------------------------------------------------------ */
  21
  22 /* Error codes for ll_loadfunc. */
  23 #define PACKAGE_ERR_LIB         1
  24 #define PACKAGE_ERR_FUNC        2
  25 #define PACKAGE_ERR_LOAD        3
  26
  27 /* Redefined in platform specific part. */
  28 #define PACKAGE_LIB_FAIL        "open"
  29 #define setprogdir(L)           ((void)0)
  30
  31 /* Symbol name prefixes. */
  32 #define SYMPREFIX_CF            "luaopen_%s"
  33 #define SYMPREFIX_BC            "luaJIT_BC_%s"
  34
  35 #if LJ_TARGET_DLOPEN
  36
  37 #include <dlfcn.h>
  38
  39 static void ll_unloadlib(void *lib)
  40 {
  41   dlclose(lib);
  42 }
  43
  44 static void *ll_load(lua_State *L, const char *path)
  45 {
  46   void *lib = dlopen(path, RTLD_NOW);
  47   if (lib == NULL) lua_pushstring(L, dlerror());
  48   return lib;
  49 }
  50
  51 static lua_CFunction ll_sym(lua_State *L, void *lib, const char *sym)
  52 {
  53   lua_CFunction f = (lua_CFunction)dlsym(lib, sym);
  54   if (f == NULL) lua_pushstring(L, dlerror());
  55   return f;
  56 }
  57
  58 static const char *ll_bcsym(void *lib, const char *sym)
  59 {
  60 #if defined(RTLD_DEFAULT)
  61   if (lib == NULL) lib = RTLD_DEFAULT;
  62 #elif LJ_TARGET_OSX || LJ_TARGET_BSD
  63   if (lib == NULL) lib = (void *)(intptr_t)-2;
  64 #endif
  65   return (const char *)dlsym(lib, sym);
  66 }
  67
  68 #elif LJ_TARGET_WINDOWS
  69
  70 #define WIN32_LEAN_AND_MEAN
  71 #ifndef WINVER
  72 #define WINVER 0x0500
  73 #endif
  74 #include <windows.h>
  75
  76 #ifndef GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS
  77 #define GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS  4
  78 #define GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT  2
  79 BOOL WINAPI GetModuleHandleExA(DWORD, LPCSTR, HMODULE*);
  80 #endif
  81
  82 #undef setprogdir
  83
  84 static void setprogdir(lua_State *L)
  85 {
  86   char buff[MAX_PATH + 1];
  87   char *lb;
  88   DWORD nsize = sizeof(buff);
  89   DWORD n = GetModuleFileNameA(NULL, buff, nsize);
  90   if (n == 0 || n == nsize || (lb = strrchr(buff, '\\')) == NULL) {
  91     luaL_error(L, "unable to get ModuleFileName");
  92   } else {
  93     *lb = '\0';
  94     luaL_gsub(L, lua_tostring(L, -1), LUA_EXECDIR, buff);
  95     lua_remove(L, -2);  /* remove original string */
  96   }
  97 }
  98
  99 static void pusherror(lua_State *L)
 100 {
 101   DWORD error = GetLastError();
 102   char buffer[128];
 103   if (FormatMessageA(FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_FROM_SYSTEM,
 104       NULL, error, 0, buffer, sizeof(buffer), NULL))
 105     lua_pushstring(L, buffer);
 106   else
 107     lua_pushfstring(L, "system error %d\n", error);
 108 }
 109
 110 static void ll_unloadlib(void *lib)
 111 {
 112   FreeLibrary((HINSTANCE)lib);
 113 }
 114
 115 static void *ll_load(lua_State *L, const char *path)
 116 {
 117   HINSTANCE lib = LoadLibraryA(path);
 118   if (lib == NULL) pusherror(L);
 119   return lib;
 120 }
 121
 122 static lua_CFunction ll_sym(lua_State *L, void *lib, const char *sym)
 123 {
 124   lua_CFunction f = (lua_CFunction)GetProcAddress((HINSTANCE)lib, sym);
 125   if (f == NULL) pusherror(L);
 126   return f;
 127 }
 128
 129 static const char *ll_bcsym(void *lib, const char *sym)
 130 {
 131   if (lib) {
 132     return (const char *)GetProcAddress((HINSTANCE)lib, sym);
 133   } else {
 134     HINSTANCE h = GetModuleHandleA(NULL);
 135     const char *p = (const char *)GetProcAddress(h, sym);
 136     if (p == NULL && GetModuleHandleExA(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS|GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
 137                                         (const char *)ll_bcsym, &h))
 138       p = (const char *)GetProcAddress(h, sym);
 139     return p;
 140   }
 141 }
 142
 143 #else
 144
 145 #undef PACKAGE_LIB_FAIL
 146 #define PACKAGE_LIB_FAIL        "absent"
 147
 148 #define DLMSG   "dynamic libraries not enabled; no support for target OS"
 149
 150 static void ll_unloadlib(void *lib)
 151 {
 152   (void)lib;
 153 }
 154
 155 static void *ll_load(lua_State *L, const char *path)
 156 {
 157   (void)path;
 158   lua_pushliteral(L, DLMSG);
 159   return NULL;
 160 }
 161
 162 static lua_CFunction ll_sym(lua_State *L, void *lib, const char *sym)
 163 {
 164   (void)lib; (void)sym;
 165   lua_pushliteral(L, DLMSG);
 166   return NULL;
 167 }
 168
 169 static const char *ll_bcsym(void *lib, const char *sym)
 170 {
 171   (void)lib; (void)sym;
 172   return NULL;
 173 }
 174
 175 #endif
 176
 177 /* ------------------------------------------------------------------------ */
 178
 179 static void **ll_register(lua_State *L, const char *path)
 180 {
 181   void **plib;
 182   lua_pushfstring(L, "LOADLIB: %s", path);
 183   lua_gettable(L, LUA_REGISTRYINDEX);  /* check library in registry? */
 184   if (!lua_isnil(L, -1)) {  /* is there an entry? */
 185     plib = (void **)lua_touserdata(L, -1);
 186   } else {  /* no entry yet; create one */
 187     lua_pop(L, 1);
 188     plib = (void **)lua_newuserdata(L, sizeof(void *));
 189     *plib = NULL;
 190     luaL_getmetatable(L, "_LOADLIB");
 191     lua_setmetatable(L, -2);
 192     lua_pushfstring(L, "LOADLIB: %s", path);
 193     lua_pushvalue(L, -2);
 194     lua_settable(L, LUA_REGISTRYINDEX);
 195   }
 196   return plib;
 197 }
 198
 199 static const char *mksymname(lua_State *L, const char *modname,
 200                              const char *prefix)
 201 {
 202   const char *funcname;
 203   const char *mark = strchr(modname, *LUA_IGMARK);
 204   if (mark) modname = mark + 1;
 205   funcname = luaL_gsub(L, modname, ".", "_");
 206   funcname = lua_pushfstring(L, prefix, funcname);
 207   lua_remove(L, -2);  /* remove 'gsub' result */
 208   return funcname;
 209 }
 210
 211 static int ll_loadfunc(lua_State *L, const char *path, const char *name, int r)
 212 {
 213   void **reg = ll_register(L, path);
 214   if (*reg == NULL) *reg = ll_load(L, path);
 215   if (*reg == NULL) {
 216     return PACKAGE_ERR_LIB;  /* unable to load library */
 217   } else {
 218     const char *sym = r ? name : mksymname(L, name, SYMPREFIX_CF);
 219     lua_CFunction f = ll_sym(L, *reg, sym);
 220     if (f) {
 221       lua_pushcfunction(L, f);
 222       return 0;
 223     }
 224     if (!r) {
 225       const char *bcdata = ll_bcsym(*reg, mksymname(L, name, SYMPREFIX_BC));
 226       lua_pop(L, 1);
 227       if (bcdata) {
 228         if (luaL_loadbuffer(L, bcdata, ~(size_t)0, name) != 0)
 229           return PACKAGE_ERR_LOAD;
 230         return 0;
 231       }
 232     }
 233     return PACKAGE_ERR_FUNC;  /* unable to find function */
 234   }
 235 }
 236
 237 static int lj_cf_package_loadlib(lua_State *L)
 238 {
 239   const char *path = luaL_checkstring(L, 1);
 240   const char *init = luaL_checkstring(L, 2);
 241   int st = ll_loadfunc(L, path, init, 1);
 242   if (st == 0) {  /* no errors? */
 243     return 1;  /* return the loaded function */
 244   } else {  /* error; error message is on stack top */
 245     lua_pushnil(L);
 246     lua_insert(L, -2);
 247     lua_pushstring(L, (st == PACKAGE_ERR_LIB) ?  PACKAGE_LIB_FAIL : "init");
 248     return 3;  /* return nil, error message, and where */
 249   }
 250 }
 251
 252 static int lj_cf_package_unloadlib(lua_State *L)
 253 {
 254   void **lib = (void **)luaL_checkudata(L, 1, "_LOADLIB");
 255   if (*lib) ll_unloadlib(*lib);
 256   *lib = NULL;  /* mark library as closed */
 257   return 0;
 258 }
 259
 260 /* ------------------------------------------------------------------------ */
 261
 262 static int readable(const char *filename)
 263 {
 264   FILE *f = fopen(filename, "r");  /* try to open file */
 265   if (f == NULL) return 0;  /* open failed */
 266   fclose(f);
 267   return 1;
 268 }
 269
 270 static const char *pushnexttemplate(lua_State *L, const char *path)
 271 {
 272   const char *l;
 273   while (*path == *LUA_PATHSEP) path++;  /* skip separators */
 274   if (*path == '\0') return NULL;  /* no more templates */
 275   l = strchr(path, *LUA_PATHSEP);  /* find next separator */
 276   if (l == NULL) l = path + strlen(path);
 277   lua_pushlstring(L, path, (size_t)(l - path));  /* template */
 278   return l;
 279 }
 280
 281 static const char *searchpath (lua_State *L, const char *name,
 282                                const char *path, const char *sep,
 283                                const char *dirsep)
 284 {
 285   luaL_Buffer msg;  /* to build error message */
 286   luaL_buffinit(L, &msg);
 287   if (*sep != '\0')  /* non-empty separator? */
 288     name = luaL_gsub(L, name, sep, dirsep);  /* replace it by 'dirsep' */
 289   while ((path = pushnexttemplate(L, path)) != NULL) {
 290     const char *filename = luaL_gsub(L, lua_tostring(L, -1),
 291                                      LUA_PATH_MARK, name);
 292     lua_remove(L, -2);  /* remove path template */
 293     if (readable(filename))  /* does file exist and is readable? */
 294       return filename;  /* return that file name */
 295     lua_pushfstring(L, "\n\tno file " LUA_QS, filename);
 296     lua_remove(L, -2);  /* remove file name */
 297     luaL_addvalue(&msg);  /* concatenate error msg. entry */
 298   }
 299   luaL_pushresult(&msg);  /* create error message */
 300   return NULL;  /* not found */
 301 }
 302
 303 static int lj_cf_package_searchpath(lua_State *L)
 304 {
 305   const char *f = searchpath(L, luaL_checkstring(L, 1),
 306                                 luaL_checkstring(L, 2),
 307                                 luaL_optstring(L, 3, "."),
 308                                 luaL_optstring(L, 4, LUA_DIRSEP));
 309   if (f != NULL) {
 310     return 1;
 311   } else {  /* error message is on top of the stack */
 312     lua_pushnil(L);
 313     lua_insert(L, -2);
 314     return 2;  /* return nil + error message */
 315   }
 316 }
 317
 318 static const char *findfile(lua_State *L, const char *name,
 319                             const char *pname)
 320 {
 321   const char *path;
 322   lua_getfield(L, LUA_ENVIRONINDEX, pname);
 323   path = lua_tostring(L, -1);
 324   if (path == NULL)
 325     luaL_error(L, LUA_QL("package.%s") " must be a string", pname);
 326   return searchpath(L, name, path, ".", LUA_DIRSEP);
 327 }
 328
 329 static void loaderror(lua_State *L, const char *filename)
 330 {
 331   luaL_error(L, "error loading module " LUA_QS " from file " LUA_QS ":\n\t%s",
 332              lua_tostring(L, 1), filename, lua_tostring(L, -1));
 333 }
 334
 335 static int lj_cf_package_loader_lua(lua_State *L)
 336 {
 337   const char *filename;
 338   const char *name = luaL_checkstring(L, 1);
 339   filename = findfile(L, name, "path");
 340   if (filename == NULL) return 1;  /* library not found in this path */
 341   if (luaL_loadfile(L, filename) != 0)
 342     loaderror(L, filename);
 343   return 1;  /* library loaded successfully */
 344 }
 345
 346 static int lj_cf_package_loader_c(lua_State *L)
 347 {
 348   const char *name = luaL_checkstring(L, 1);
 349   const char *filename = findfile(L, name, "cpath");
 350   if (filename == NULL) return 1;  /* library not found in this path */
 351   if (ll_loadfunc(L, filename, name, 0) != 0)
 352     loaderror(L, filename);
 353   return 1;  /* library loaded successfully */
 354 }
 355
 356 static int lj_cf_package_loader_croot(lua_State *L)
 357 {
 358   const char *filename;
 359   const char *name = luaL_checkstring(L, 1);
 360   const char *p = strchr(name, '.');
 361   int st;
 362   if (p == NULL) return 0;  /* is root */
 363   lua_pushlstring(L, name, (size_t)(p - name));
 364   filename = findfile(L, lua_tostring(L, -1), "cpath");
 365   if (filename == NULL) return 1;  /* root not found */
 366   if ((st = ll_loadfunc(L, filename, name, 0)) != 0) {
 367     if (st != PACKAGE_ERR_FUNC) loaderror(L, filename);  /* real error */
 368     lua_pushfstring(L, "\n\tno module " LUA_QS " in file " LUA_QS,
 369                     name, filename);
 370     return 1;  /* function not found */
 371   }
 372   return 1;
 373 }
 374
 375 static int lj_cf_package_loader_preload(lua_State *L)
 376 {
 377   const char *name = luaL_checkstring(L, 1);
 378   lua_getfield(L, LUA_ENVIRONINDEX, "preload");
 379   if (!lua_istable(L, -1))
 380     luaL_error(L, LUA_QL("package.preload") " must be a table");
 381   lua_getfield(L, -1, name);
 382   if (lua_isnil(L, -1)) {  /* Not found? */
 383     const char *bcname = mksymname(L, name, SYMPREFIX_BC);
 384     const char *bcdata = ll_bcsym(NULL, bcname);
 385     if (bcdata == NULL || luaL_loadbuffer(L, bcdata, ~(size_t)0, name) != 0)
 386       lua_pushfstring(L, "\n\tno field package.preload['%s']", name);
 387   }
 388   return 1;
 389 }
 390
 391 /* ------------------------------------------------------------------------ */
 392
 393 static const int sentinel_ = 0;
 394 #define sentinel        ((void *)&sentinel_)
 395
 396 static int lj_cf_package_require(lua_State *L)
 397 {
 398   const char *name = luaL_checkstring(L, 1);
 399   int i;
 400   lua_settop(L, 1);  /* _LOADED table will be at index 2 */
 401   lua_getfield(L, LUA_REGISTRYINDEX, "_LOADED");
 402   lua_getfield(L, 2, name);
 403   if (lua_toboolean(L, -1)) {  /* is it there? */
 404     if (lua_touserdata(L, -1) == sentinel)  /* check loops */
 405       luaL_error(L, "loop or previous error loading module " LUA_QS, name);
 406     return 1;  /* package is already loaded */
 407   }
 408   /* else must load it; iterate over available loaders */
 409   lua_getfield(L, LUA_ENVIRONINDEX, "loaders");
 410   if (!lua_istable(L, -1))
 411     luaL_error(L, LUA_QL("package.loaders") " must be a table");
 412   lua_pushliteral(L, "");  /* error message accumulator */
 413   for (i = 1; ; i++) {
 414     lua_rawgeti(L, -2, i);  /* get a loader */
 415     if (lua_isnil(L, -1))
 416       luaL_error(L, "module " LUA_QS " not found:%s",
 417                  name, lua_tostring(L, -2));
 418     lua_pushstring(L, name);
 419     lua_call(L, 1, 1);  /* call it */
 420     if (lua_isfunction(L, -1))  /* did it find module? */
 421       break;  /* module loaded successfully */
 422     else if (lua_isstring(L, -1))  /* loader returned error message? */
 423       lua_concat(L, 2);  /* accumulate it */
 424     else
 425       lua_pop(L, 1);
 426   }
 427   lua_pushlightuserdata(L, sentinel);
 428   lua_setfield(L, 2, name);  /* _LOADED[name] = sentinel */
 429   lua_pushstring(L, name);  /* pass name as argument to module */
 430   lua_call(L, 1, 1);  /* run loaded module */
 431   if (!lua_isnil(L, -1))  /* non-nil return? */
 432     lua_setfield(L, 2, name);  /* _LOADED[name] = returned value */
 433   lua_getfield(L, 2, name);
 434   if (lua_touserdata(L, -1) == sentinel) {   /* module did not set a value? */
 435     lua_pushboolean(L, 1);  /* use true as result */
 436     lua_pushvalue(L, -1);  /* extra copy to be returned */
 437     lua_setfield(L, 2, name);  /* _LOADED[name] = true */
 438   }
 439   lj_lib_checkfpu(L);
 440   return 1;
 441 }
 442
 443 /* ------------------------------------------------------------------------ */
 444
 445 static void setfenv(lua_State *L)
 446 {
 447   lua_Debug ar;
 448   if (lua_getstack(L, 1, &ar) == 0 ||
 449       lua_getinfo(L, "f", &ar) == 0 ||  /* get calling function */
 450       lua_iscfunction(L, -1))
 451     luaL_error(L, LUA_QL("module") " not called from a Lua function");
 452   lua_pushvalue(L, -2);
 453   lua_setfenv(L, -2);
 454   lua_pop(L, 1);
 455 }
 456
 457 static void dooptions(lua_State *L, int n)
 458 {
 459   int i;
 460   for (i = 2; i <= n; i++) {
 461     lua_pushvalue(L, i);  /* get option (a function) */
 462     lua_pushvalue(L, -2);  /* module */
 463     lua_call(L, 1, 0);
 464   }
 465 }
 466
 467 static void modinit(lua_State *L, const char *modname)
 468 {
 469   const char *dot;
 470   lua_pushvalue(L, -1);
 471   lua_setfield(L, -2, "_M");  /* module._M = module */
 472   lua_pushstring(L, modname);
 473   lua_setfield(L, -2, "_NAME");
 474   dot = strrchr(modname, '.');  /* look for last dot in module name */
 475   if (dot == NULL) dot = modname; else dot++;
 476   /* set _PACKAGE as package name (full module name minus last part) */
 477   lua_pushlstring(L, modname, (size_t)(dot - modname));
 478   lua_setfield(L, -2, "_PACKAGE");
 479 }
 480
 481 static int lj_cf_package_module(lua_State *L)
 482 {
 483   const char *modname = luaL_checkstring(L, 1);
 484   int loaded = lua_gettop(L) + 1;  /* index of _LOADED table */
 485   lua_getfield(L, LUA_REGISTRYINDEX, "_LOADED");
 486   lua_getfield(L, loaded, modname);  /* get _LOADED[modname] */
 487   if (!lua_istable(L, -1)) {  /* not found? */
 488     lua_pop(L, 1);  /* remove previous result */
 489     /* try global variable (and create one if it does not exist) */
 490     if (luaL_findtable(L, LUA_GLOBALSINDEX, modname, 1) != NULL)
 491       lj_err_callerv(L, LJ_ERR_BADMODN, modname);
 492     lua_pushvalue(L, -1);
 493     lua_setfield(L, loaded, modname);  /* _LOADED[modname] = new table */
 494   }
 495   /* check whether table already has a _NAME field */
 496   lua_getfield(L, -1, "_NAME");
 497   if (!lua_isnil(L, -1)) {  /* is table an initialized module? */
 498     lua_pop(L, 1);
 499   } else {  /* no; initialize it */
 500     lua_pop(L, 1);
 501     modinit(L, modname);
 502   }
 503   lua_pushvalue(L, -1);
 504   setfenv(L);
 505   dooptions(L, loaded - 1);
 506   return 0;
 507 }
 508
 509 static int lj_cf_package_seeall(lua_State *L)
 510 {
 511   luaL_checktype(L, 1, LUA_TTABLE);
 512   if (!lua_getmetatable(L, 1)) {
 513     lua_createtable(L, 0, 1); /* create new metatable */
 514     lua_pushvalue(L, -1);
 515     lua_setmetatable(L, 1);
 516   }
 517   lua_pushvalue(L, LUA_GLOBALSINDEX);
 518   lua_setfield(L, -2, "__index");  /* mt.__index = _G */
 519   return 0;
 520 }
 521
 522 /* ------------------------------------------------------------------------ */
 523
 524 #define AUXMARK         "\1"
 525
 526 static void setpath(lua_State *L, const char *fieldname, const char *envname,
 527                     const char *def, int noenv)
 528 {
 529 #if LJ_TARGET_CONSOLE
 530   const char *path = NULL;
 531   UNUSED(envname);
 532 #else
 533   const char *path = getenv(envname);
 534 #endif
 535   if (path == NULL || noenv) {
 536     lua_pushstring(L, def);
 537   } else {
 538     path = luaL_gsub(L, path, LUA_PATHSEP LUA_PATHSEP,
 539                               LUA_PATHSEP AUXMARK LUA_PATHSEP);
 540     luaL_gsub(L, path, AUXMARK, def);
 541     lua_remove(L, -2);
 542   }
 543   setprogdir(L);
 544   lua_setfield(L, -2, fieldname);
 545 }
 546
 547 static const luaL_Reg package_lib[] = {
 548   { "loadlib",  lj_cf_package_loadlib },
 549   { "searchpath",  lj_cf_package_searchpath },
 550   { "seeall",   lj_cf_package_seeall },
 551   { NULL, NULL }
 552 };
 553
 554 static const luaL_Reg package_global[] = {
 555   { "module",   lj_cf_package_module },
 556   { "require",  lj_cf_package_require },
 557   { NULL, NULL }
 558 };
 559
 560 static const lua_CFunction package_loaders[] =
 561 {
 562   lj_cf_package_loader_preload,
 563   lj_cf_package_loader_lua,
 564   lj_cf_package_loader_c,
 565   lj_cf_package_loader_croot,
 566   NULL
 567 };
 568
 569 LUALIB_API int luaopen_package(lua_State *L)
 570 {
 571   int i;
 572   int noenv;
 573   luaL_newmetatable(L, "_LOADLIB");
 574   lj_lib_pushcf(L, lj_cf_package_unloadlib, 1);
 575   lua_setfield(L, -2, "__gc");
 576   luaL_register(L, LUA_LOADLIBNAME, package_lib);
 577   lua_pushvalue(L, -1);
 578   lua_replace(L, LUA_ENVIRONINDEX);
 579   lua_createtable(L, sizeof(package_loaders)/sizeof(package_loaders[0])-1, 0);
 580   for (i = 0; package_loaders[i] != NULL; i++) {
 581     lj_lib_pushcf(L, package_loaders[i], 1);
 582     lua_rawseti(L, -2, i+1);
 583   }
 584   lua_setfield(L, -2, "loaders");
 585   lua_getfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
 586   noenv = lua_toboolean(L, -1);
 587   lua_pop(L, 1);
 588   setpath(L, "path", LUA_PATH, LUA_PATH_DEFAULT, noenv);
 589   setpath(L, "cpath", LUA_CPATH, LUA_CPATH_DEFAULT, noenv);
 590   lua_pushliteral(L, LUA_PATH_CONFIG);
 591   lua_setfield(L, -2, "config");
 592   luaL_findtable(L, LUA_REGISTRYINDEX, "_LOADED", 16);
 593   lua_setfield(L, -2, "loaded");
 594   luaL_findtable(L, LUA_REGISTRYINDEX, "_PRELOAD", 4);
 595   lua_setfield(L, -2, "preload");
 596   lua_pushvalue(L, LUA_GLOBALSINDEX);
 597   luaL_register(L, NULL, package_global);
 598   lua_pop(L, 1);
 599   return 1;
 600 }
 601